## Exciting engineering challenges with great prizes

Show off your skills and solve real design problems

# Airplane Bearing Bracket Challenge

Optimize Airplane Bearing Bracket Design

With new advances in additive manufacturing (AM), there is an opportunity for old design geometry to be optimized for weight and strength. AM allows for the creation of complicated but desired geometries that were once unable to be fabricated via conventional methods. The bearing bracket is a common component on control surfaces of various aircraft that provides a great platform for applying AM. As a dynamic component that interfaces with moving parts, the bearing bracket has to conform to a certain geometrical envelope as well as being able to sustain large loading forces in various directions. Redesigning the bracket for AM could provide significant weight savings and help reduce fuel consumption of airplanes.

### Design Considerations

The objective of this challenge is to redesign the bearing bracket in such a way that its topology and shape are optimized for minimizing weight while fitting in the target envelope and meeting the technical requirements. The bracket is intended to be additively manufactured and the design shall also minimize and/or eliminate the need for support structures. The submitted designs will be evaluated via FEA and ranked based on their strength-to-weight ratio. The top five designs will be fabricated via additive manufacturing and tested. The winners will be selected based on mechanical performance and on the cost associated with the additional manufacturing operations to remove support structures.

Requirements:

 The design must fit entirely within target envelope described in the specifications.

 Design material: 15-5PH per AMS5862:
o Elastic Modulus (E) = 29,000 KSI = 200,000 MPa = 200 GPa
o Poisson Ratio (ν) = 0.27
o Yield Stress (σ_y) = 145 KSI = 1000 MPA
o Density (ρ) = 0.283 lb/in^3 = 7833 kg/m^3
o Material is assumed to be linear elastic

 Minimum geometric feature: 0.025 in.

 Minimum wall thickness: 0.045 in.

 Parts shall be optimized for minimum weight with the following boundary and loading conditions:
- Base support: The part is bolted against a mating plate of high stiffness
- Bolts interface: The parts is fastened with four #10-32 high strength tension rated bolts as indicated in the specifications
- Bearing interface: The part is loaded through a high stiffness spherical bearing with three load cases:
1. A load of 1,250 lbf applied horizontally
2. A load of 1,875 lbf applied 45 degrees from the horizontal
3. A load of 2,500 lbf applied vertically

 Parts are intended to be additively manufactured via a laser/powder bed system. Please indicate the intended printing direction/orientation in your submission.

As the entries will be fabricated and tested, the Finalists will be announced by March 18th, 6 weeks from the end of the challenge in order to allow time for testing.

### Requirements

• STEP
• Any render or image files (jpeg, png, etc)
• Any calculations or considerations
• A schematic or sketch showing the desired printing direction

• Technical requirements:

Must fulfill design considerations stated above.

• Judging criteria:

Judging criteria will be based on achievement of accomplishing criteria listed above, including:
Weight
Strength
Cost (ease of manufacturing, minimal/no support structure required)

### Rules

• SUBMITTING AN ENTRY
Only entries uploaded to GrabCAD through the "Submit entry" button on this Challenge page will be considered an entry. Only public entries are eligible.

We encourage teams to use GrabCAD Workbench for developing their entries.

Entries are automatically given the tag "airplanebearingbracket" when uploading to GrabCAD. Please do not edit or delete this tag. Only entries with valid tag will participate in the Challenge.

• AWARDING THE WINNERS The sum of the Awards is the total gross amount of the reward. The awarded participant is solely liable for the payment of all taxes, duties and other similar measures if imposed on the reward pursuant to the legislation of the country of his/her residence, domicile, citizenship, workplace, or any other criterion of similar nature. Only 1 award per person. All judging decisions are final.   All winners will be contacted by the GrabCAD staff to get their contact information and any other information needed to get the prize to them. Payment of cash awards is made through PayPal. All team awards will be transferred to the member who entered the Challenge.   We will release the finalists before the announcement of the winners to give the Community an opportunity to share their favorites in the comments, discuss concerns, and allow time for any testing or analysis by the Jury. The Jury will take the feedback into consideration when picking the winners.   Winning designs will be chosen based on the Rules and Requirements. - Entry deadline is February 7, 2016 (11:59pm UTC). - The finalists will be announced by March 18, 2016. - The winners will be announced by March 30, 2016.   Void where prohibited.

• SPEC REFINEMENT We want to make sure that you have all of the information that you need to tackle the challenge. As such, in the first week of a challenge we may refine the specifications or offer clarifications based on member feedback. Please ask any questions that you have!

### Prizes

\$3,000 in prizes for top 3 places!

1st Prize

\$1,500

2nd Prize

\$1,000

3rd Prize

\$500

The jury consists of experts from Alcoa and GrabCAD.

Alcoa Fastening Systems & Rings, a business unit of Alcoa, is a leading worldwide designer and manufacturer of fastening systems and rings, including specialty fasteners, fluid fittings, assembly components, installation systems, and seamless rings for aerospace and industrial applications. Headquartered in Torrance, California, the company has approximately 8,700 employees at 39 manufacturing and distribution/logistics locations in 13 countries. A global leader in lightweight metals technology, engineering and manufacturing, Alcoa innovates multi-material solutions that advance our world. Our technologies enhance transportation, from automotive and commercial transport to air and space travel, and improve industrial and consumer electronics products. We enable smart buildings, sustainable food and beverage packaging, high-performance defense vehicles across air, land and sea, deeper oil and gas drilling and more efficient power generation. We pioneered the aluminum industry over 125 years ago, and today, our more than 60,000 people in 30 countries deliver value-add products made of titanium, nickel and aluminum, and produce best-in-class bauxite, alumina and primary aluminum products.

• ### steff evans over 6 years ago

Hi. Is there a STEP file or other dimension set available to define the target envelope? Nothing seems to be given in the specification? Thanks.

• ### RPM over 6 years ago

Hello,

There is no Step file available for the download and neither are the dimensions mentioned for the envelope. It would be great if we are provided with the envelope size and the Dimensions for the part in the pdf?

Thank you.
RPM Teja

• ### steff evans over 6 years ago

Also, do you have a set of displacement constraint/desired stiffness, and a desired safety factor for the material and bolts? Thanks.

• ### Wil Hamilton over 6 years ago

Is there a preferred format for any calculations/considerations/notes that go along with the design? Word/Powerpoint/excel etc.?
What is the best way to indicate print direction?

• ### Wudhidham Prachumsri over 6 years ago

Hi Wil, for the calculations/considerations/notes, any format that is clear and can be understood without searching through lots of data would be fine. For the print direction, please indicate the base plane or face (i.e. the plane/face that will be sitting flat on the build plate); note that the base plane does not need to be an existing face of the part/envelope but can be a plane that you create.

• ### Wudhidham Prachumsri over 6 years ago

@Nicolas Please ignore the"Cut-extrude" body and do a complete redesign within the volume of "cut-revolve". The "cut-extrude" body was an example we were toying around with. We will upload an updated packet with the correct step file that only has one component soon. Sorry about the confusion

• ### Steve Trutanich over 6 years ago

Are there any dimensional constraints other than the obvious? Must any space be saved above the base or under the arm?

• ### Ben Ewing over 6 years ago

Jason, we just updated the file. See if you have any luck now.

• ### Wudhidham Prachumsri over 6 years ago

@Steve, The part just has to fit within the envelope given by the step file. No part of the design should extend beyond the envelope given. I hope that answered your question.

• ### Ben Ewing over 6 years ago

To try to combat the issue with opening in NX, we added a different version of STEP (203 rather than 214) as well as IGES and STL versions. Sorry for the difficulty!

• ### Ben Ewing over 6 years ago

Great to hear, Jason!

• ### Angel Alexandrov over 6 years ago

So as far as I understand the outer surface and dimensions of the part should be absolutelly the same as the template STEP file , and we have to use the AM capabilities to lighten the existing part, and we aren't allowed to thicken or change the dimensions in any plane of the template model?

• ### Wudhidham Prachumsri over 6 years ago

@Angel, the outer surface and dimensions of the part DO NOT need to be exactly the same as the template, but they do need to STAY WITHIN the outer surfaces of the template. Hope that makes sense!

• ### Angel Alexandrov over 6 years ago

Yes, thank you.

• ### Ray over 6 years ago

Could you provide a picture of the current bracket in use? I'd like to get a better idea of the intended use of this bracket. If you can't provide a picture how bout a little more detailed description of what this bracket actually does and what attaches through the bearing.

• ### John over 6 years ago

I note that loads are provided but not deflection limits, from my first analysis the material will yield a long way without reaching max stress levels. I can't believe that is correct.

• ### Doug Davey over 6 years ago

I would like to know what the clearance area for the flap itself are.

• ### Wudhidham Prachumsri over 6 years ago

@Ray The original bracket was used on the landing gear doors and attaches between the door itself and a hinge or actuator. I hope that helps.

• ### Wudhidham Prachumsri over 6 years ago

@Steff Evans @John, We currently have no deflection limits on the design as long as the stress levels are under the specified material yield strength. As for the safety factor of the material, the value has already been absorbed in the specified loading conditions (i.e. if it can withstand those loads at a safety factor of 1, that is fine). The bolts are assumed to be much stronger than the part and is not a point of failure so they can be assumed as rigid members.

• ### Tommy Tosser over 6 years ago

Inches and pounds? Are we building a boat to sail to discover the 'new world'?

• ### Handily1 over 6 years ago

What is the Make and Part Number of the Spherical Bearing?

• ### Handily1 over 6 years ago

1. Are we to be concerned with temperate and environmental conditions?
2. Are we to assume that there are no side loads?

• ### Wudhidham Prachumsri over 6 years ago

@A A You do not need to worry about the environmental conditions. Yes, assume no side loads, use only the loads specified

• ### Tom Martin over 6 years ago

Hi, is there factor of safety and stiffness requirements? if yes, what is acceptable?

• ### Wudhidham Prachumsri over 6 years ago

@Tom Martin The factor of safety is already built into the load cases specified, therefore if the design can handle those loads, you should be fine. I will get back to you on the stiffness requirements, we are looking into that.

• ### Wudhidham Prachumsri over 6 years ago

Note that the files given are in units of inches. The width of the part envelope is 1.500 in. which you can use as a reference value when importing into your CAD/FEA software. If you were to import it into analysis software such as Abaqus, you would have to keep the units of the loading consistent (lbf not newtons) or you may need to scale the parts to fit the default units.

• ### Handily1 over 6 years ago

Any information on the spherical bearing (MFG & Part Number)

• ### Wudhidham Prachumsri over 6 years ago

@Handily1 I just sent new files into GrabCAD which includes the spherical bearings, I hope they get uploaded soon. Please check back. It is a high strength hardened aerospace spec steel bearing so apply the appropriate material properties or you can assume the bearing to be a rigid member also.

• ### Ben Ewing over 6 years ago

The files should now be updated with the bearings!

• ### Kamen Rusev over 6 years ago

there will be 500 entries is my guess :)

• ### René over 6 years ago

Now the pdf with the illustrations seems to be missing in the specification download.

• ### Nic over 6 years ago

Could we please get a basic diagram showing the load vectors. Depending on how I import the model, y-axis up etc, makes the loading description ambiguous. Thanks.

• ### Wudhidham Prachumsri over 6 years ago

@Rene @Nic Sorry about the confusion, we updated the files and failed to upload the specification file that used to be there. GrabCAD should upload them soon.

• ### Steve Trutanich over 6 years ago

I'm thinking that a pattern such as a honeycomb, with space, will be the target

• ### shankar gonti over 6 years ago

What you given in specification of cad file is not opening properly can you provide proper cad dimensions. I can work on this project .tanke you

• ### Doug Davey over 6 years ago

Does anyone know if the is a solidworks material as needed in this challenge

• ### ruben_s over 6 years ago

From STEP file, the spherical radius of bearing is 7.95 mm.
From the Alcoa Bearing Bracket specs.pdf, the spherical bearing with .3125in in diameter

• ### shankar gonti over 6 years ago

i am waiting for proper dimensions, any one help me

• ### Rodrigo Pinheiro over 6 years ago

Hi everyone!

I'm glad to see so many questions and comments. Thank you all for the feedback.
Some of the schematics provided are missing from the specification. We will update the documentation as soon as possible.

The dimensions on the STEP file are in inches.
The bearing diameter is indeed .3215 inches exactly (or 7.9375 mm).
It might be a surprise to some of the participants, but most of the hardware for commercial aerospace products is specified in imperial units (inches, lbf, KSI, etc.), as are the material properties on the MMPDS.

The STEP file defines the working ENVELOPE for the part, meaning that the final design MUST fit completely inside of it.

The printing direction can be provided in any orientation related to the part envelope, any geometrical entity provided on the STEP file can be used as a reference from where the print orientation can be derived. A long as it is unequivocally defined, it will work. Feel free to be creative.

The vertical load is pointing down, perpendicularly towards the base (the base is where the fastener holes are).
The horizontal load is pointing away from the part, parallel to the base, on the symmetry plane.
The inclined load is pointing down and away, aligned with a direction that makes 45deg with the base plane.

Hope that helps.

My kindest regards to all participants.

• ### Steve Trutanich over 6 years ago

Realistically, you can say the bearing is less important. More important is how you
Set the parameters for the stress simulation. Am I wrong Rodrigo?

• ### Clint K Campbell over 6 years ago

Would it be possible for you to define the load directions from the center extremities of the bearing in the STEP file?

• ### Rodrigo Pinheiro over 6 years ago

Hi Steve Trutanich,

The main challenge is to optimize the bracket that holds the bearing for light weight, under the giving loading conditions. Also, incorporate the additive manufacturing aspects to the design, in such a way that the final product can be printed properly and economically. All together, this can be very challenging. And in this case, the bearing element is standard and not part of the challenge per se.

Hope that helps.

Regards,
Rodrigo

• ### Doug Davey over 6 years ago

Please confirm the dimension of the drawing at Flap bracket pdf

• ### Nic over 6 years ago

I have a question regarding the bearing. The CAD files provided show the spherical bearing as a separate body to the bracket, but it seems the bearing annulus is part of the bracket and hence envelope. Would the complete bearing not be press fit into the the bracket as a separate component, thus making the bracket body envelope smaller in this area?

Please say if my question is unclear.

• ### shankar gonti over 6 years ago

@doug Davey I download that u gave pdf is it correct values

• ### Nicolas Marc over 6 years ago

Hi,
Could we have a PDF file with the different directions of load applications?
Best regards.

• ### Doug Davey over 6 years ago

@shankar gonti Thats what I am asking them to check

• ### Ernesto Chavez over 6 years ago

For some reason SolidWorks doesn't want to the SLDPRT file in the specs download. I have no issues opening the provided IGES and STEP files, but I keep getting an error trying to open the SLDPRT. Anyone else encounter a similar issue?

• ### Pouya Hosseinzadeh over 6 years ago

Hi.
Where is listed as related dimensions to design ??
or original model ??

• ### Fahad Rafi over 6 years ago

all loads applied at once or one be one?

• ### A. Anderl over 6 years ago

@alcoaTeam
I added a new material to my library with following properties: Tensile Strength, Yield: 145 Kpi; Modulus of Elasticity: 29000 Ksi; Poisson: 0.12.

Apparently, the supplied part FAILS under 1250 lbf applied horizontally (along with the cylindrical shape of bearing)

Should we go forward with current definitions? Should we apply the horizontal force perpendiculary to the cilindrical face of bearing?

Thanks.

• ### Serge Mikhaylevski over 6 years ago

http://www.rolledalloys.com/alloys/stainless-steels/15-5/en/
It's correct data? Poisson's Ratio is very important parameter.
Condition "H 1075" or Yield Strength 145Ksi too?

• ### Serge Mikhaylevski over 6 years ago

2,500 lbf = 2500lbf = 11120N
It's correct?
Sorry for my metric mind :)

• ### Catalin over 6 years ago

I think it would be much easy if you give us all the material data needed, or material file for Solidworks.

• ### P.J.Russell over 6 years ago

Catalin is right, I think we need more material specifications.

• ### Doug Davey over 6 years ago

Material in this format will help a lot

Elastic Modulus 31183113.6 psi
Poisson's Ratio 0.28 N/A
Shear Modulus 11457981.28 psi
Mass Density 0.27818 lb/in^3
Tensile Strength 123282.08 psi
Compressive Strength psi
Yield Strength 101526.42 psi
Thermal Expansion Coefficient 6.111111111e-006 /ºF
Thermal Conductivity 0.000187247 Btu/(in·sec·ºF)
Specific Heat 0.105092 Btu/(lb·ºF)
Material Damping Ratio N/A

• ### Rodrigo Pinheiro over 6 years ago

Dear All,

As mentioned, we will update the description and specification documents with more details on loading and material properties as soon as possible. Meanwhile, here are some comments:

Horizontal load is 1,250 lbf = 1250 lbf = 5560 N
Inclined load is 1,875 lbf = 1875 lbf = 8340 N
Vertical load is 2,500 lbf = 2500 lbf = 11120 N

The material:
Elastic modulus E = 29,000 KSI = 200000 MPa = 200 GPa
Poisson ratio nu = 0.27
Yield stress Fty = 145 KSI = 1000 MPa
Density rho = 0.283 lb/in^3 = 7833 Kg/m^3 = 7.83e-9 ton/mm^3
Material is to be assumed linear elastic.

If you are running an analysis using the envelope geometry provided and the correct material and loading, the part should not reach yield in any of the load cases.
Note that the STEP file geometry is in inches, and as a reference the width of the envelope geometry is 1.50 in = 38.10 mm.

Hope that helps.

Good Luck!

• ### A. Anderl over 6 years ago

"If you are running an analysis using the envelope geometry provided and the correct material and loading, the part should not reach yield in any of the load cases"
Sorry, but the model fails if loaded horizontally with 1250 lbf. (Doesn't fail under vertical and inclined loads)

• ### Rodrigo Pinheiro over 6 years ago

Hi A. Anderl,

We would like to confirm:
"If you are running an analysis using the envelope geometry provided and the correct material and loading, the part should not reach yield in any of the load cases"

Regards,
Rodrigo

• ### Wudhidham Prachumsri over 6 years ago

@Doug Davey The pdf you have posted has the correct dimensions. Thank you

• ### Wudhidham Prachumsri over 6 years ago

@Ernesto Chavez, the provided sldprt file is created in Solidworks 2015-2016. It will not open in any older version of Solidworks. If you are running an older Solidworks version, you would have to use the attached step or iges files

• ### Wudhidham Prachumsri over 6 years ago

Hi All,
Please remember to include a sketch or schematic of some kind to show the desired printing direction of this part. Thank you.

• ### A. Anderl over 6 years ago

@Rodrigo

Alcoa Bracket

Regards,
Anderl

• ### Wudhidham Prachumsri over 6 years ago

@A. Anderl the entry you posted shows a load condition that we did not specified and is not required. Please check the specifications PDF again. There should be no loading perpendicular to the bearing, all loading on the bearing are in the radial directions (45 degrees, horizontal, and vertical).

• ### A. Anderl over 6 years ago

@W
Thank you.
Specifications PDF? No such document in "Original" folder under "Download specifications" button... ??

• ### Wudhidham Prachumsri over 6 years ago

@A. Anderl, the specifications PDF I am referring to is "Alcoa Bearing Bracket Specs"

• ### A. Anderl over 6 years ago

@Wudhidham Prachumsri
All right now. Thanks
Regards,
Anderl

• ### J. F. Gomez over 6 years ago

@ AFSR Staff: Can we assume the locations of the four bolts to be flexible or are we to keep them the same as in the envelope model?

• ### Rodrigo Pinheiro over 6 years ago

Hi J F Gomez,
The bolt pattern is fixed and can't be changed.
Regards,
Rodrigo

• ### ruben_s over 6 years ago

Why do you include parts of ball bearing in the model, if it will not participate neither in FEM analysis nor in geometry optimization?

• ### Rodrigo Pinheiro over 6 years ago

@rsahak
The bearing element is there for those who want to include it as a way to apply load through multi-body contact and perhaps capture its influence on the surrounding geometry.
Also, feel free to include more realistic boundary conditions, as a non-rigid support plate, fasteners and the influence of preload. It is up to you!
Kindest Regards,
Rodrigo

• ### ruben_s over 6 years ago

Very hard burden for CPU. Is it possible to exclude bearing at all and apply force directly on bracket? Thanks.

• ### Rodrigo Pinheiro over 6 years ago

@rsahak
It certainly is! The challenge is to optimize the bracket. Feel free to do it in the way that works best for you.
Good Luck!

Regards,
Rodrigo

• ### Steve Trutanich over 6 years ago

Lowest factor of safety is 1.056 on the original part

• ### Manolo Valenzuela over 6 years ago

Just to confirm:
1- The geometry max limits are given for the original CAD part files, any other minimum distances are allowed, Right? (except for features 0.025 and thickness 0.045)
2- When FEA, any max PSI x,y,z limit to avoid?. Or should we take the YoungM as the limit?

• ### hoho(Jaja) hehe over 6 years ago

Does all the loads are applied at once or separate?

• ### Rodrigo Pinheiro over 6 years ago

Hi Steve Trutanich,

The "safety factor" and other reliability factors are already incorporated on the loading conditions and the material limit provided.

Regards,
Rodrigo

• ### Rodrigo Pinheiro over 6 years ago

Hi "hoho hehe",

Each load case is to be applied separately.
Regards,
Rodrigo

• ### Rodrigo Pinheiro over 6 years ago

Hi Manolo Valenzuela,

One can use the Yield stress of 145 KSI (1000MPa) as the limit.

Regards,
Rodrigo

• ### Kamen Rusev over 6 years ago

I can't open the file...Anyone with SolidWorks 2014 or lower to share with me?

• ### Todd Balls over 6 years ago

Hi Kamen Rusev,
You will have to import one of the other file types. The SolidWorks file was made in 2015. Sorry about the inconvenience.
Regards, Todd

• ### Manolo Valenzuela over 6 years ago

Kamer / Todd and anyone else who are using a closed parametric CAD.
You must TRY A DIRECT DESIGN CAD !!!

• ### Allan Bowers over 6 years ago

Hi can I submit more than one design? Do I have to include the FEA as haven't taught myself how to use the Simulation SW yet!!

• ### DJEMALI LOGBI over 6 years ago

bonjour,
besoin la fiche technique de ce produit en français.

• ### Wudhidham Prachumsri over 6 years ago

Hi @Allan Bowers Bowers,
You can go ahead and submit as many designs you would like! FEA would be a great supplement to your design submission so please try your best to include some sort of analysis.
Regards,

• ### Wudhidham Prachumsri over 6 years ago

Hi Djemali Tahler,
Unfortunately we are unable to accommodate that request to translate the design specification to French.
Regards,

• ### Doug Davey over 6 years ago

@ Wudhidham Prachumsri
What amount of "displacement" is aloud for or will be acceptable

• ### Krasimir Asenov over 6 years ago

@Wudhidham Prachumsri,
Could you tell us what will be the exact mathematical formula for evaluating the finalists? I am asking this question because if you evaluate based on the strength-to -weight ratio then for example 100psi / 2lbs = 50 psi/lbs ratio and if 100psi / 1lbs = 100psi/lbs, then the higher ratio (100 psi/lbs) will be better than the lower one, but on other hand if 100psi / 2lbs = 50psi/lbs and 80psi / 2 lbs = 40 psi/lbs then in the second case with equal weight there is less stress, so lower ratio (40 psi/lbs) is better than higher one. I think evaluating should be based on more coplicated formula.

• ### René over 6 years ago

Hello Alcoa-Team, one thing I have not fully understood yet: Do you want to additively manufacture the component including the outer ring of the bearing? The words "Integrated bearing" irritate me in the first illustration of the pdf.

If that is your intent I would advise against doing so. How to accurately machine the spherical face inside?

• ### René over 6 years ago

Just read this comment from Rodrigo further up. Question is answered then.
"And in this case, the bearing element is standard and not part of the challenge per se."

• ### farzad over 6 years ago

This was a question for me, should the bearing not be included in analysis? is it standard or can we differ the diameter?

• ### Steve Trutanich over 6 years ago

So many great designs, I wonder if the most narrow arm will become susceptible to lateral instability.

• ### farzad over 6 years ago

not all the entries will be fabricated ,they will be analyzed @jose

• ### steff evans over 6 years ago

Can I ask whether you have any standard mesh size parameters for the FEA you plan to do? Obviously, if the chosen element size is too coarse, then the stress output won't be converged, and any resultant stress values will be under-predicted. For aerospace-standard 'converged stress' models, we would typically use a far tighter mesh requirement in areas such as fillets to ensure the output is robust. Without this, the stress distributions cannot be relied upon, and any mass saving claims are rendered highly dubious.

• ### Wudhidham Prachumsri over 6 years ago

@Doug Davey
We have no restrictions of the displacement of the part, the loading conditions given in the challenge specification has taken into account the part factor of safety and material properties. As long as the max stress levels in the part is below its yielding stress the part is okay.

@KHANTECH
The part will be evaluated based on many criteria including strength to weight, cost of manufacturing (amount of supports/powder required) and ease of printing.

The bearing size and shape is fixed. Including the bearing in the analysis will give you more accurate results.

@Jose Luis Martin Medina,
The finalist entries will be fabricated by us (Alcoa Fastening Systems and Rings) and tested in our test lab with the load conditions presented in the specification. Entrants are not required to fabricate the parts but are encouraged to run some sort of analysis to help with the design of the part.

@Steff Evans,
The parts will be analyzed by our engineers and the appropriate meshes will be applied to ensure that the simulation is as accurate as possible.

Thank you for all the comments and entries! I am glad to see so much enthusiasm and variety in designs.

• ### Angel Alexandrov over 6 years ago

Steff Evans has a point. In SW there is 10% diffenrence in results between coarsest and finest mesh

• ### steff evans over 6 years ago

Thanks for your response, @Wudhidham Prachumsri. I notice that the winner of a previous challenge which was heavily FE-centric (Autodesk Robot Gripper Arm) included a mesh-convergence study, to demonstrate a robust solution. Maybe this is the way to go with this challenge!

• ### Jonathan Brazeau over 6 years ago

@ Alcoa. Doesn't the powder act as support material as it's being laser sintered? Therefore allowing printing in any orientation?

Also, I always thought SLS wasn't structurally as strong as cast and extruded raw billet material. Doesn't the printing process leave a very different crystalline structure to the material?

• ### Robert Gorhan over 6 years ago

@jonathan height will effect print time and therefore cost. And yes, dmls isn't as strong as cast... I'm assuming Alcoa took that into consideration when giving strength limitations. (see previous posts)

• ### Jonathan Brazeau over 6 years ago

is there weakness in the layers like with plastic FDM printing?

• ### Aqil Ghaffar over 6 years ago

@Wudhidham Prachumsri: hi, i just want to know about the limmits and condition for Meshing in our FEA softwares.what are the minimum requirments for meshing?
second thing is about that bearing, i would like to ask you to uploade seperate model for bearing as i have tried to seperate that bearing but surfaces were missing in my CAD software.
one more thing, why we need to consider bearing in FEA if we are assuming it to be the ultra strong..

• ### Wudhidham Prachumsri over 6 years ago

Hi Aqil, try your best to mesh as appropriately as possible. Use sufficiently fine mesh for the more detailed areas so that you can capture the entire result. As far as the bearing goes, you may exclude the bearing entirely from the simulation; the bearing was uploaded because some of the entrants were requesting it. Utilizing the bearing in the simulation actually improves the accuracy of the simulation since the loading through the bearing will be more representative of the actual loading. Thank you.

• ### Rodrigo Pinheiro over 6 years ago

Hi Jonathan,

The material 15-5PH in its printed and heat treated state will provide static mechanical properties very close to a plate.

As for the supports, laser powder bed processes do require them for walls that make less than roughly 45 degrees in inclination in relation to the base plate (normal to the printing direction).

From one hand, combining topological and shape optimization with the constraints of metal 3D printing can be quite a challenge, but on the other hand, from what I have seen so far, some of the participants have mastered that beautifully.

Good Luck!

• ### Jonathan Brazeau over 6 years ago

So then layer orientation isn't an issue like with FDM plastic printing?....

• ### Rodrigo Pinheiro over 6 years ago

Hi Jonathan,

Note our challenge does not involve a plastic material, but a martensitic, precipitation hardening stainless steel, 15-5 PH (or AISI S15500), as per AMS5862 specification.

This material can be used for 3D metal printing, with several powder bed laser sintering technologies.

And the orientation for metal printing is quite important.

Regards,
Rodrigo

• ### farzad over 6 years ago

@Rodrigo what do you mean by : The material 15-5PH in its printed and heat treated state will provide static mechanical properties very close to a plate.

• ### Master3D over 6 years ago

I think "why don't give a real prize like: a job position in the company who is using the challenges to all the winners or at least those with the 1st,2nd and 3rd place", that is more inspiring, isn't ?

• ### Imran Mushtaq over 6 years ago

master3d your comment is full of sense great !!!!

Joining it

• ### Aqil Ghaffar over 6 years ago

@Wudhidham Prachumsri; hi, sorry to disturb you again.
i just want to ask you that either i have to follow the position of screws as given in model or i can play around with that.

• ### Rodrigo Pinheiro over 6 years ago

When 3D printing and heat treating 15-5PH powder with the proper parameters, it should produce static mechanical properties similar to the ones obtained from a plate of the same material, in H1025 condition.

Regards,
Rodrigo

• ### Rodrigo Pinheiro over 6 years ago

Hi Aqil Ghaffar,

The fastener locations are fixed and can NOT be changed.

Good Luck!

Regards,
Rodrigo

• ### Allan Bowers over 6 years ago

Please advise bolt dimensions. Most important is total length from top of head to end of threads. This is for clearance checking to ensure the bolts can be inserted into the bolt holes in my base plate. Also can the be hex head so they can be tightened with a spanner from the side rather than top down with an Allen key. Thanks

• ### farzad over 6 years ago

I'd like to ask more info, why have you replaced the bolts with BC ? shall we know the clamp load and material of the bolts ?

• ### shankar gonti over 6 years ago

Hi frindes, I am stuck with simulations of my part! Any one tell me that how to add loading conditions to the bearing @

• ### Angel Alexandrov over 6 years ago

Hello, to what angle(relative to print bed) can intended DMLS printer, print without support structures?

• ### farzad over 6 years ago

also I was wondering , where the bracket is actually placed, I think for topology optimization, it was better to know if any other region of the piece, has contact or connection to any other part or it's only connected to a main body via the bearing and the stand ? In this case it was easier to deside the shape of the regions we were going to remove

• ### SVV over 6 years ago

@Angel Alexandrov
Just a dozen comments above, Rodrigo Pinheiro wrote:
"As for the supports, laser powder bed processes do require them for walls that make less than roughly 45 degrees in inclination in relation to the base plate (normal to the printing direction)."
Hope that will help. Unfortunately they have not given the exact angle in specifications. I believe that this is one of the KEY parameters for the challenge, since the number of supports is stated as judgement criterion.

• ### Angel Alexandrov over 6 years ago

Thank you @SVV. I was asking because information ot internet for DMLS printers vaies from 25 to 50 degrees.

• ### Julian Groeli over 6 years ago

Hi there - I have a quick question about the bearing. I understand the bearing consists of a spherical ball that is fitted into a race.

Is the race intended to be 3D printed as well (current assumption) or is the race a standard off the shelf part that will be press fit or somehow assembled into the bracket?

To me it looks like the race is the stepped out diameter that is part of the CAD file provided. Thanks!

• ### Rodrigo Pinheiro over 6 years ago

Hi Julian Groeli,

The bearing race is intended as an integrated part of the bracket, and was provided in the STEP file.

Regards,
Rodrigo

• ### Rodrigo Pinheiro over 6 years ago

Dear All,

As we have passed the half-way point in our design challenge, it is a good time for some constructive feedback. In the coming days, the Alcoa team team will visit every entry and leave comments and perhaps pertinent suggestions.

Regards,
Rodrigo

• ### René over 6 years ago

Hello Rodrigo, the spherical surface of the bearing race definitely has to be reworked after DMLS. Furthermore this surface should be hardened. Are you sure that you want to additively manufacture this outer race? It is just a cheap purchase part after all. I personally would advise against it.

• ### Allan Bowers over 6 years ago

There appears to be much confusion as to the requirement for support structures and the 45 degree angle. A diagram would be useful. As they say a pic paints a thousand words. I note that on many submissions your team have commented about support structure requirements due to the print direction chosen. This seems to be whether the bracket is printed on its side or on its head or its base. As the majority of entries follow the angle of the elbow portion of the original bracket with modification to width to reduce weight is there ANY print direction that will not require support structures?? I agree with the comment about the bearing race and tolerances that must require further machining after printing for an adequate pressed interference fit, ergo does it matter about support structures required in this area. Please upload a suitable drawing of your original part, (if applicable) showing an example of where a spt structure would be needed in each plane of available print directions. I am sure this would reduce confusion and improve the designs offered. Whilst we can all use the internet for researching AM techniques there appears to be many interpretations and differences of opinion regarding spt structures. A definitive guideline from you will allow all of the designers to be on the same playing field.Thanks

• ### Wudhidham Prachumsri over 6 years ago

Hi Allan,
The comments regard the support structures are to encourage the designers to explore/improve their designs with this consideration in mind. A lot of the submitted designs have great geometry and strength but we would also like to emphasize the importance of print direction and support structures. Some designs may not have a print direction that eliminates support structures entirely, but we just want to remind the designers to try to minimize them. I will try to upload an example schematic to elaborate on the 45 degree rule for the support structures. As for the bearing race, yes those will be finished machine afterwards; the entrants should not worry so much about that portion, just know that it will be printed with the part and post machined.
Best Regards,

• ### Allan Bowers over 6 years ago

@Robert, thankyou for the link. I am not an engineer and have no knowledge of the process. I wanted to just get clarification on the advice that has been given out by the team regarding this 45 degree rule. Your link looks like it says 35 degrees, thus I reiterate my point that there appears to be many views on what can be printed without a spt structure. This is my first entry so I am trying my best to understand the requirements. Cheers

• ### Julian Groeli over 6 years ago

Hi Rodrigo & Wudhidham,
Thanks for the clarification regarding your intent for the bearing race.
Great challenge and helpful feedback overall!

• ### farzad over 6 years ago

I guess my questions were Ignored, yet I think the positioning of the piece and the modelling of the bolts are important, yet modelling them has been a memory and cpu burden on my system

• ### Angel Alexandrov over 6 years ago

From the comments I understand that creating a design without support structure is of big importance. I allways tought that the number of layers and powder used is what affects the price in powder printers. Therefore the lightest design with least ammount of powder used and the smallest size in Z axis will be cheapest. Regardles of support structures.Now I guess that removing the support structures is more costly than printing in the wrong direction.

• ### Rodrigo Pinheiro over 6 years ago

Hi René,

As it is widely known, laser/powder bed systems are not capable of producing finishes needed for a bearing, not even to properly seat a fastener.
For this bracket bearing, it will require secondary operations as machining and even lapping the bearing race.
But this is beyond the scope of this challenge.
Regards,
Rodrigo

• ### Rodrigo Pinheiro over 6 years ago

Please feel free to model the fasteners and a flexible base to support the bracket.
It is possible to deduce or estimate the general type of fasteners from the provided geometry.
At this time, the requested additional information can not be made available.
But we welcome your best effort in designing a high performance bracket bearing with the given information.
Thank you and Good Luck!
Regards,
Rodrigo

• ### Ernesto Chavez over 6 years ago

^ Rodrigo, just to confirm, is the supporting base supposed to be stiff or flexible? The specs say it's stiff but above you say it's flexible.

• ### Rodrigo Pinheiro over 6 years ago

Dear All,
Just some comments from the questions and remarks regarding 3D printing and support structures:
- The challenge does not ask for a 100% self-supported design (no supports), but does not discourage the idea either.
- 3D printing gives a lot of freedom for designing shapes and forms. But it might pose challenges when it comes to fixturing, gaging and inspecting such free-form geometries.
- When 3D printing metals, removal of support structures from free-form shapes can be a very difficult, complex, and costly task.
...
In that sense, we encourage the participants to consider additive manufacturing aspects in their concepts and designs, as stated on the "design Considerations" section of the challenge:
"The bracket is intended to be additively manufactured and the design shall also minimize and/or eliminate the need for support structures".
...
And I have to say that some of the entries have mastered the idea beautifully.
...
Thanks for all the comments, questions, and all the great concepts and designs received so far. From our side, it has been a wonderful experience for all of us involved with this design challenge.
Regards,
Rodrigo

• ### Wudhidham Prachumsri over 6 years ago

Hi Allan,
I understand that from the link that Robert provided, at minimum angle of 35 degree was specified. However, for our machine that will be printing the finalist parts, we have found that a minimum of 45 degrees for the support structure works best. I hope that addresses your question.
Regards,

• ### Rodrigo Pinheiro over 6 years ago

Hi Ernesto Chavez,
The base is to be considered "stiff", not necessarily "rigid".
One of the participants cited the that including the base stiffness (or flexibility) might be important for the design outcome. We only stated that we welcome the pursue of that train of though.
At this time more information about the matting structure can not be made available, but that should not discourage you or any participant from considering the influence of such things in your concepts and designs.
Regards,
Rodrigo

• ### Ben Ewing over 6 years ago

Hey all, just wanted to let you know that we've added a PDF to the 'Download specification' zip of support structure examples. Hope this helps!

• ### Allan Bowers over 6 years ago

@Ben Great thanks!!!

• ### Terry over 6 years ago

using this support structure requirements the View C will also require a structure under the base. Will it not?

• ### Allan Bowers over 6 years ago

Ha ha, I must be learning something. I thought that too Terry!

• ### Wudhidham Prachumsri over 6 years ago

Hi All,

I would like to apologize for the confusion regarding the PDF example recently posted, I mistakenly posted the incorrect version of the example. A new version should be posted soon which will reflect the corrections that a couple of you have pointed out; thank you for catching that by the way!

Another note regarding support structures is that a common and usually most cost effective way of removing these support structures after printing is to wire EDM the structures. This is only possible if the support structures run through the entire print width of your part (i.e. no internal supports, or nested supports inside pockets).
I am sorry about the confusion. A new PDF should be posted soon.

Regards,

• ### Azrul Amir over 6 years ago

Can anyone tell me where to put my constraint/fixture during simulation? I see some entrant fix their base and others fix their bolt hole... This is important as it affect simulation results... From what i see, if you fix the base, you can shave more weight compared to if you fix the hole... This need to be standardised...

• ### Angel Alexandrov over 6 years ago

Very good question @Azrul Amir

• ### Robert Gorhan over 6 years ago

statics would dictate that the fixed faces would be the underside of the bolt (the bottom of the bolt hole) and the bottom face of the bracket where it mounts the the "rigid plate". The reason you want to include the rigid plate face is because the material will flex around the "bolt head" face and wouldn't transfer the load to the plate as desired. try working with it in sim and watch the way the model deforms, itll make more sense.

• ### Allan Bowers over 6 years ago

Hi team I asked a week or so ago about bolt dimensions so I could check clearance on my model. Are they available please. Particularly goal length from top of bolt head to end of thread and dia of bolt head. Thanks

• ### Terry over 6 years ago

Hi Alcoa team, are you able to advise the brand and product specs for the printer that you will use to manufacture your bracket?

• ### Terry over 6 years ago

Another question, do you require the support structures to be part of the .step file or will you be adding them when you input the file to your printers?

• ### farzad over 6 years ago

Only one point , about modelling , I wish the fillets in the bearing area didn't exist, cause the one in the bearing is removeable, but the bracket one not, also it is not necessary for the FEM part

• ### Rodrigo Pinheiro over 6 years ago

Hi Allan Bowers,
The geometry provided is the part "maximum working envelope" and the holes there are provided as the mating pattern for the fasteners.
At this point, the fastener selection is not available for this application, but as a suggestion, it would be adequate to leave the fastener holes and surrounding bearing areas unchanged.
Hope that helps.
Regards,
Rodrigo

• ### Rodrigo Pinheiro over 6 years ago

Hi Terry,
The challenge only requires that the intended PART geometry is provided.
If you have a particular support structure configuration that provides advantages do the process, perhaps reducing the manufacturing costs, feel free to submit it as well. We will be glad to consider it. But that is not a requirement for your entry.
Thank you.
Regards,
Rodrigo

• ### Wudhidham Prachumsri over 6 years ago

Hi All,

As we near the end of challenge, we will start to evaluate your designs in more detail. Therefore, if any updates or changes are made to your entry please leave a comment on your entry page to notify us of the update. This will ensure that we do not miss any changes that are made over the next week or so! Thank you.

Regards,

• ### Wudhidham Prachumsri over 6 years ago

Hi All,
As I am going through all the different entries, I have found that some entries have no included any 3D solid model files (step, iges, sldprt, etc.). I understand that some of you are still working on it but please upload the files before the deadline! We will only consider entries with uploaded models.
Regards,

• ### Fábio Gabriel Lage Xavier over 6 years ago

Hi I have a small doubt about the maximum working envelope.
Our part need to fit exactly inside the provided part or there is some freedom room around it, with our part fitting inside the same "box" as the original part?

• ### Wudhidham Prachumsri over 6 years ago

Hi All,
Please make sure that your part fits ENTIRELY inside the envelope. No part of your design shall extend pass any of the surfaces given by the envelope model. So far, as we have gone through the designs submitted, many parts have failed this criteria so please make sure to update your part so that it first inside the envelope entirely.
Thank you,

• ### Ayuk over 6 years ago

Hello, is the bearing made of the same material? Thank you

• ### Ioannis Skarlatakis over 6 years ago

Hi All,

A couple of quick personal notes for this great challenge.
I see that the most of the submitted models if not all use as boundary conditions "Fixed" the bottom of the bracket.
Well... this is super simplified or idealised condition. (I didn't say wrong ...Not yet!)
Unless the jury will use the exact same conditions I strongly recommend guys to revisit your FEA.
I'm sure someone would like to share a couple of words.
I also see that most of the models have stopped the optimization very close to the yield point. This is super confident unless of course if you achieved such a great converged solution of about 3~5% .
If this is not the case there might be a big chance that you missed to capture some important stress. As a result the same model under an analysis with different Boundary Cond. and a converged solution can be found with max. stress over the yield point very very very; did I say very? well... very easily!

I understand that is beyond the scope of this challenge to give a lecture on how to conduct an FEA analysis and I also understand that from Alcoa point of you we have been given all the appropriate information for the boundary conditions. No doubt! ;D

However, I'm not sure why there wasn't any comment not even a minor one on the FEA results for each model which by definition are sensitive enough to burn down a model.
After all the aim is to optimise the weight of the bracket and without a reasonable understanding of the performed analysis any results are as good as... bananas! ;D

My point is that in the end of this challenge we might find the winning model to be 300 or 400 grms despite the complains of...
"...mine was lighter I don't understand what went wrong?..."
I am not sure if ALCOA would like to put some words together but it looks to me like there is some room for a quick response. (8 days to go)

Many thanks guys and apologies for the long text
...keep it Up!

• ### Doug Davey over 6 years ago

@Ioannis Skarlatakis.

It would have been great to see a diagram of the operational envelope of the part

Weight may be important but keeping the controls on the aircraft...... I think is more important

• ### Ioannis Skarlatakis over 6 years ago

@Doug Davey.
Everything you said is true I will not disagree with any of your comments. I am sure that they sound equally important.
Nevertheless, Fatigue can be removed from the equation with a very conservative criterion (as you mentioned they might have included this already). +Fatigue is also directly related to the finish quality of the surface, environment etc. and for this kind of material and manufacturing process you can only assume in order
to go further.
However, my point is not the FOS is the "Claim" of an optimised model based on an approximated solution.
How can you compare my model to another based on our published reports when we don't use the same B.C. it is almost like we don't use the same loading conditions. (I might exaggerate a little bit but you know what I mean) :D
I think the FEA validation line is too thin between a participant & ALCOA.
I am not saying that ALCOA didn't provide with adequate information just that there is no correlation among the submitted models so far UNLESS...
Unless ALCOA will confirm that the Boundary conditions will be used from their side will be the same as every one used so far. Then we will probably be on the same page.

In the end it might be just me taking it to deep.
Cheers! ;D

• ### Doug Davey over 6 years ago

@Ioannis Skarlatakis

It all a little academic ....... in the end our models have to be re validated by ALCOA using the same FAE state. So it is not from our FAE that they chose a model but from theirs. That makes the playing field level ......... We hope

• ### Luc Worms over 6 years ago

So, agreeing with the FEA discussion above, maybe one of the organisers can give us a little more insight in the FEA that will be used for judging: fixed bottom plane, fixed in 1 direction (perpendicular to the plane), or maybe also modelling the bottom plate and bolts and use a contact simulation.

Another question, on a completely different subject: supports a\have to be placed if the angle with the base plane is less than 45 degrees. I guess this is not applicable for a radius between 2 supports with an angle larger than 45 degrees? An example of this situation is in the last picture of the file "SupportStructureExamples_V3.pdf"

• ### Robert Gorhan over 6 years ago

@ionnis @doug Alcoa have given us the parameters to design around. stick to them and give the customer what they want. there may be a reason for nondisclosure... that and I'm sure there are at least a few aeronautic engineers on staff who will be able to handle the situation without your help. it doesn't need to make sense, it just needs to make them happy.

• ### Ioannis Skarlatakis over 6 years ago

@Robert
Thanks Robert, I appreciate your answer but it seems that you are not familiar with the process of optimization. This process has nothing to do with happiness and it has much to do with sensible assumptions. After all as an engineer you are here to bring sense by asking questions.
Many thanks again ;D

• ### Robert Gorhan over 6 years ago

@ioannis, that's not the way these challenges work. i lost to two non functional designs in the last challenges i participated in. additionally, i have plenty of experience with "optimization" as you put it... however, you have to realize that the design we produce most likely will not be put directly into production and will need to be modified to suit the development of the project.

• ### Ioannis Skarlatakis over 6 years ago

Thanks for your input Robert Good luck!

• ### Nic over 6 years ago

I've not worked with DMLS directly before and would like to ask a few questions regarding support material. Are the supports printed at the same density as the model itself? Will supports be automatically generated by the print processing software for our desired model orientation, or is it a manual process where we can model the supports ourselves? Is there any consideration in the build time and how that affects cost? Or does the cost of material far outweigh instrument time?

I know wire EDM is the preferred method of support removal and highly precise, but is limited when clearing cavities, will there be any additional grinding or particular surface finishing, say ceramic stone tumbling? I totally understand if the details are under wraps in the spirit of the challenge.

I've been working hard to get my entry together but still need to tackle some tricky 45' surfaces and push the mass as low as she'll go. Plenty of featherweight entries coming in. Much luck to all who take up the challenge.

• ### Doug Davey over 6 years ago

@Robert Gorhan
I just thought we were taking our heads out of the sand ……. Just a little

• ### Rodrigo Pinheiro over 6 years ago

Dear Nic,

- Supports are usually scanned with different laser parameters, and employ some kind of lattice or pattern.
- Support generation is a complicated matter, but is usually a combination of both automated generation and user interaction.
- Only the costs associated with removal of supports are part of the challenge. Cost modeling for Additive Manufacturing can be quite tricky and is beyond the scope of this challenge.
- As a guideline, secondary operations will be applied to the parts in order to bring them back to the intended geometry provided in the STEP file entry. The target finish on the areas where supports will be removed is the same as "as printed", so all the entries are on the same basis for comparison.
.
.
Hope that helps.
Regards,
Rodrigo

• ### Rodrigo Pinheiro over 6 years ago

Dear All,
.
.
Just a few remarks on some of the latest comments regarding modeling, FEA and optimization:
- We shared as much information as possible when it comes to the application and its boundary conditions.
- As in most contests of this kind, the interpretation of the requirements is part of the challenge. It is up to the participants to use the information in the best possible way.
- As stated in the "Design Considerations" section, the winners will be selected based on static test data. In this sense, we would like to encourage the participants to consider boundary conditions that are as "realistic" as possible to a real world application.
- As for safety factors, mechanical properties, fatigue characteristics and other characteristics that might omitted on the specifications, we would like to clarify that typical printed metal parts have a strong sensitivity to print directions, powder characteristics, laser parameters and many other factors. For the scope of this challenge, those details are not considered and only the static load cases provided will be used in the selection process.
.
.
We are glad to see so many entries and such creativity and quality.
Thank you and good luck!
Regards,
Rodrigo

• ### Luke Haylock over 6 years ago

All,
I want to take a minute to express my sincere thanks to everyone for submitting proposals to our challenge. It will be difficult to make a final selection but I wanted to comment in general about the intended use of the part and offer some a few points to consider.

Alcoa has been in the business of designing and fabricating aerospace components since the Wright Brothers first asked us to fabricate a lightweight aluminum block for their engine, so you can say that we fabricated our first aerospace part before the industry existed. Today Alcoa content represents approximately 30% of the structure of any aircraft. While we are best known for our aluminum products, today we manufacture a wide range of parts and offer a wide range of raw materials.

Each year material suppliers around the world produce 1.5 billion pounds of raw materials and parts for the aerospace industry. Likewise each year the worldwide aerospace industry produces approximately 200 million pounds of aircraft with commercial aircraft representing 50% of that. Thus at the highest level the buy-to-fly ratio for the aerospace industry is greater than 7 to 1. Stated another way 6/7 of all aerospace materials end up being scraped or recycled. This a significant cost to our society.

Some say that additive manufacturing technologies signals the beginning of a third industrial revolution. In practice metal additive manufacturing technologies are in their early stages but very few people will deny the disruptive nature of the technology and most believe that these technologies represent a step-change in the economics of aerospace production. We often joke that accounts are the ultimate aircraft designers and while weight is very important ultimately the cost to transport that weight over the life of an aircraft is the true measure design effectiveness.

Which brings me back to the challenge and why we are specifically interested in additive manufacturing process. You are designing a hinge for an aircraft landing gear door. For aircraft, the landing gear supports the aircraft when it is not flying, allowing it to take off, land, and taxi without damage. Faster aircraft usually have retractable landing gear, which folds away during flight to reduce aerodynamic drag. As an aircraft comes in for landing the landing the door is opened to deploy the landing gear.

Additive technologies are less constrained than traditional processes and design complexity is essentially free. I would encourage you to seek inspiration from nature by emulating nature's time-tested patterns and strategies. What analogs in natural structures such as trees can you study for inspiration given that complexity is essentially free with additive technologies?

Regards,
Luke Haylock

• ### Wudhidham Prachumsri over 6 years ago

Hi All,

I have noticed that some entries submitted have incorrect bolt hole spacing. Please make sure that the bolt hole spacing and dimensions are exactly the same as the given envelope. Note that the spacing between the front two bolts are not the same as the spacing between the rear two bolts.

In addition, to make it easier for us to not miss any updated entries, please send me a private message with a link to your entry page if you make any updates. That would help us out greatly. Thank you!

Regards,

• ### Andrew Rabbitt over 6 years ago

Just a question on printing - is there any minimum surface area whereby the 45° rule does not apply? For example, if in a fillet as there is on my design under some orientations, there is an area that is about 1-2mm² or so that is less than 45° to the print plane but has material surrounding it that is greater than this angle, would this need support structure?

• ### Allan Bowers over 6 years ago

Hi, I noticed that when I tried to include the bearing in my FEA it would not mesh because the bearing supplied interfered with the main body of the part. I had to run a subtract operation to make the surfaces match so that the mesh would work

• ### Dan Rudmin over 6 years ago

The spherical bearing in the model appears to be double the stated diameter of 0.3125". Which is the definitive authority, the model or the spec?

• ### René over 6 years ago

I found 2 interesting videos on YouTube, where this bracket can be seen. 4 of them are attached to each landing door.

• ### Flaviano Crespi over 6 years ago

@René, These videos are interesting because they show the constraint in the hinge and the loads applied to the base, just different of what is proposed by this challenge. @Alcoa maybe can explain why you have reversed the pattern? Thanks.

• ### Marty007 over 6 years ago

@René, thanks for finding those videos. It's always interesting to see where the parts you work on will be applied.
@Flaviano Crespi, If you draw a free body diagram, it doesn't really matter which end you consider 'fixed'. I suspect they chose to write the spec the way they did because it leaves less room for misinterpretation. If you considered the bearing point as 'fixed', then the load combinations would have had to include complicated bending moments.

That said, if these are in fact how the brackets will be used, I think the challenge specs have the vertical load backwards. If you consider the case where the door is horizontal (closed), then the weight of the door is pulling down on the 4xbolts, which would put a reactive vertical-UPWARDS force on the bearing. The spec currently has the vertical load pulling downwards.

• ### Flaviano Crespi over 6 years ago

@Marty007, I agree with the theoretical premises and I also think that the choice was dictated by need for simplicity, however, you have identified the problem about the direction of the vertical load.
In fact, given that the load was indicated down, the constraint of the base is collaborative for the object resistance, and many competitors have reduced the mounting ears to the bone, Mickey Mouse style.
In real conditions with the opposite load and deriving bending moments the minimal mounting ears would fail.

• ### Marty007 over 6 years ago

@Flaviano Crespi, Yep, if in fact the vertical load is backwards as we both suspect, then there will certainly be designs that meet this competitions design criteria, but would fail in the real world... Hopefully Alcoa reads these posts and takes a close look.

• ### Robert Gorhan over 6 years ago

@rene' after reviewing those videos im curious as to why there is such a strict build envelope... it would seem the both mounting points and the interior arc are define the limitations of the bracket.

• ### René over 6 years ago

@Flaviano Crespi and @Marty007, the time that I learned engineering mechanics is quite long ago. Yet I think, that the force directions from Alcoa are correct. Please have a look at this (messy) sketch and tell me what you think.
http://imgur.com/N3Hr7Xj
@Robert Gorhan, I don't know. I suppose there are some other parts, that could interfere.
PS: Very cool challenge! More interesting than my real job :)

• ### Marty007 over 6 years ago

@René, in your Load Case 3 diagram, do a balance of forces on the bracket. If both the door and the bearing are pulling down, what is holding the bracket up? If the door is pulling down, the bearing must be pulling up.

• ### Flaviano Crespi over 6 years ago

@René, Even for me Time passed, then I add some practical sense considerations.
In real conditions the door is hung on the bracket with the screws.
The action of weight is therefore exerted by the face of the screw against the bracket.
In the challenge conditions it is said that the bracket rests on a rigid constraint floor and it is pressed by a vertical force. The bending moment acts against the rigid constraint and the bracket is not more then hung on the screws.
This substantially changes the results of the analysis because, as has happened,many competitors have reduced the size of the ears that in reality carry the load.
All these considerations are based on the fact that the only load is a gravity. An opposing force could be a pressure that tries to implode the door in the airplane, but in this case the door would rely on the jamb as all the doors that open outward.

• ### René over 6 years ago

@Marty007, I slowly get what you mean. But that would mean, that Load Case 2 is also wrong. The load should face 45° upwards - not downwards, isn't it?

• ### Nic over 6 years ago

Hey guys, don't let the animations linked in the previous post guide you. It's possible that in this case, the body of the bracket is mounted to the fuselage and the pivot is attached at the door making the load cases supplied reasonable. Given the actual small size of this bracket envelope, it is employed in a far lighter duty than shown in the videos. We can only work to the supplied guidelines, so good luck to all challengers.

• ### Rodrigo Pinheiro over 6 years ago

Hi Everyone,

Just for clarification, our Design Challenge is focused on an specific application, with well defined conditions.

The videos that were posted here by the community, although very illustrative, don't represent our application.
Thank you.

Regards,
Rodrigo

• ### Dan Rudmin over 6 years ago

Any info yet on the 0.3125 in bearing diameter spec in the document versus the 0.625 in bearing diameter in the model? It seems like it might be a diameter/radius mixup.

• ### Wudhidham Prachumsri over 6 years ago

Hi Dan,
The 0.3125in Bearing diameter is the inner diameter(shaft diameter) of the bearing given in the envelope model which can be found in the specification files. The 0.625in dimension that you are referring to is the dimension of the outer diameter of the bearing/inner diameter of the bearing race.
Regards,

• ### Allan Bowers over 6 years ago

Hi can you let me know the deadline time in GMT please.

• ### Wudhidham Prachumsri over 6 years ago

Hi Allan, the submission deadline is February 7th, 11:59pm UTC which is the same as 11:59pm GMT.
Regards,

• ### Marty007 over 6 years ago

What support fixtures will you be using in the analysis?

I ask, because I am seeing designs that use very flimsy structures near the rear set of bolts. I downloaded and took a look at one such model recently submitted, and as I suspected, the submission had likely used a 'fixed' restraint across the support base. I ran the model on my machine with a bolted connection and virtual wall, and the stresses doubled, far exceeding the 145ksi limit (see below).
Airplane Bearing Bracket Challenge 1.0

My submission used the virtual wall/foundation bolt method, but I could likely further reduce the weight if I know you'll be using a fixed restraint on the base.

• ### Wudhidham Prachumsri over 6 years ago

Hi Marty007,
When analyzing your model, try to make the constraint conditions as realistic as possible. In this case fixing the support base is not the most realistic condition. We will go through and analyze the models with identical constraints for each entry and eliminate those that do not pass.
Regards,

• ### Lauri Link over 6 years ago

Thanks for organizing this interesting challange. Some crazy ideas here

• ### Steve Trutanich over 6 years ago

good luck selecting a winner :)

• ### Krasimir Asenov over 6 years ago

Just updated my model. Now is more suitable for printing. Please check.
Optimax

• ### Tom over 6 years ago

Glad when this challenge is no longer accepting entries; all those uploads looks exactly the same. Indeed good luck selecting a winner :)

• ### Jonas Banhos over 6 years ago

I am about to submit my entry and it says PASSED. "Coordinated Universal Time (UTC)". That is a tricky detail.

• ### René over 6 years ago

@Jonas Banhos I was also surprised, that the deadline ended 5mins too early. But I uploaded just in time.
@Alcoa, do you already know how many of those 320 entries are going to be manufactured? 10? Less?

• ### Ernesto Chavez over 6 years ago

@René, from the Design Considerations up top:
"The submitted designs will be evaluated via FEA and ranked based on their strength-to-weight ratio. The top five designs will be fabricated via additive manufacturing and tested."

• ### René over 6 years ago

Oooops! Thank you :)

• ### Wudhidham Prachumsri over 6 years ago

Hi All,

The list of finalists have already been submitted to GrabCAD. Hang tight, they should post the announcement soon!

Regards,

• ### Ben Ewing over 6 years ago

The finalists have been announced: https://grabcad.com/challenges/airplane-bearing-bracket-challenge/results! At the top of the page, you'll see an explanation of how the finalists were selected. Next, the judges will be taking an even deeper look at how the finalists stack up in respect to the Judging criteria. Winners will be announced by March 30th!

• ### Paul Berg over 6 years ago

Could the committee that did the FEA to pick the finalists show or explain in more detail how they did the analysis. The committee mentioned many people did not consider the flexibility of a bolted connection. How did they consider it?

• ### Wudhidham Prachumsri over 6 years ago

Hi Paul,

in the following weeks up to the time we announce the winners, we will be posting a brief explanation showing the FEA on all the models that we ran and how we did it. We will try to be as helpful as possible to show the way we ran our FEA.

Regards,

• ### SVV over 6 years ago

Thank you guys for making a tremendous amount of work by checking so many entries! I believe that your work would be much more useful for Grabcad community if you’ll share your judgment results. Your challenge is very different from most of challenges because you have very formal requirements and criteria, allowing to range the entries with almost no subjectivity involved. I’m sure that I’m not the only participant who want to know what exactly was wrong with his “world’s best model” :) . Hope you will provide some feedback, at least tell at what evaluation step had the model failed.

Hi Wudhidham,
Very nice contest, how much manufacture-ability influence the result of this contest? I think some winner need high cost manufacturing process and need much post processing after 3d print. (they missed 45 deg rules)
can you give me feedback on my design? (Strong and Light V-Core Design 310 grams)

• ### SVV over 6 years ago

It was also quite surprising to see so many heavy designs in the finalist list (some are above 300 grams), despite the fact that there were lots of promising models around 230-250 grams. Seems that severity of FEA conditions was very underestimated by most of participants.

• ### Paul Berg over 6 years ago

I have a suggestion to increase the number of qualified entries for future contests that are evaluated by FEA.

State in the specifications EXACTLY how the FEA will be performed. Give an example. Show what surfaces are fixed, what surfaces are loaded. If it is evaluated as part of an assembly with bolts for example.

Because it was stated in the beginning of the finalists list that " .. although many did FEA on their parts they did it wrong. The flexibility of a bolted connection wasn't taken into consideration"

The goal of the contest is to get the lightest bracket possible with as much input as volunteered.
When most of the people are designing a bracket and evaluating it wrong that's a waste of time.

I don't think the intent of the contest was to see if people could figure out how to do the FEA right given the stated mounting conditions. It's not a test ... or it shouldn't be.

I say this because I saw many good entries under .57 lbs that show their FEA results. If they knew how to do the FEA right they could tweak the designs to pass and still remain much lighter than some of the finalists that are over .75 lbs.

• ### BRO1977 over 6 years ago

This will happen in every contest, some agree and some not agree with the result. But we need to accept that the fact, jury's decision is conclusive.
Some might disappointed and some might happy. Sometimes I agree to disappointed statement person.
To unlucky participant, try for next challenge again and again.

• ### DWP over 6 years ago

For SVV, Paul Berg and a few other confused colleagues (including the amused me):
This challenge includes (at least) two hidden traps which I didn't notice at the right time:
1. The ball bearing diameter is 7.9502mm according to the model and 7.9375mm in the description. Follow the description and you fail. There is a "skin" of 12.7 µm (twelve point seven microns) that will not fit to the given envelope :)
(This applies to the metric system, I don't know what happens if using imperial units.)
2. The edge of the ball bearing cavity is rounded, not much, 50.8 µm, that's about a half of the human hair, but it's there, you don't notice it - you fail.
Now I understand your frustration, the first thing I've done was to download my own model (who knows, it might have been an upload error).
Well, it still weights 228 grams (228.39 for the sake of microns and milligrams) and it still passes all the FEA tests, at least according to my knowledge and experience.
Now that the finalists are already announced, it's hard to believe that somebody will reevaluate your work or will admit that you lost because of a small error or misunderstanding. It may have been FEA ...or not, you'll never know.
So keep your eyes wide open next time, when you may be subjected to a colour shade test :) This recommendation includes me, again, of course.

• ### DWP over 6 years ago

...BTW, for the sake of truth I'm sure that they didn't do it on purpose.

• ### Marty007 over 6 years ago

I, like likely many others, would like to better understand where my design fell short on making the short list. I had modeled the bolted connection, ran the model as an assembly with contact constraints at the bearing, and managed to slim the design down to 0.521g. The Bracket has Landed

I'm at a loss, and will likely be walking away from future Grabcad Challenges due to my experience. The inexact challenge description and lack of feedback make this a practice in frustration that's simply not worth my time. The frustrations that you're likely to hear about in the next week could have be avoided with a clearer challenge description. Just describe how you will perform the FEA!

• ### A. Anderl over 6 years ago

Congratulations to all the finalist.

• ### Allan Bowers over 6 years ago

What I find interesting is that now I have revisited my own model of 252gm is that I had the Sim set up correctly but included all the bearings parts. If I exclude these from the sim then the results are even better than what I submitted. As the models were submitted in stp format it is unlikely that any were modified. Thus models with bearing detail included perhaps were at a distinct disadvantage when put through simulation. As I was trimming my design for weight if I had not included the bearing then I would have achieved a far greater wgt/strength ratio. I think for an even playing field it would have been good if the bearing was a must have or to be exclude from the challenge. Despite this I am very happy that efforts to comment on models by the judging team is beyond the call considering the number of entries and we all should be happy for that!. What is important is GrabCADs final comment Quote in part:
"We encourage everyone following to leave a comment with their favorite or letting us know if we left a great entry out of the mix." End Quote.
This implies within the next week if there has been an omission of a good model the community can get behind it and maybe have it included in the final assessment to select the models to be printed and physically tested.
Of course I would love it if mine were in the mix and I am sure you feel the same about your own models too.

• ### Rodrigo Pinheiro over 6 years ago

Dear All,

It has been a busy time for all of us involved in evaluating the Design Challenge entries here at Alcoa Fastening Systems & Rings.
When we first considered creating this challenge, months ago, we didn’t know what to expect and were certainly overwhelmed by the great participation from the GrabCAD the community, reflected by the number of entries and also the creativity and engineering quality.

Looking back, one of our many goals with this challenge was to learn how to work within the paradigm of a design challenge and crowdsourcing design.
We posted this reasonably simple and very well defined problem, but filled with subtleties and challenges that would make it interesting for the community.

Among our biggest concerns around specifying the problem was the idea that we did not want to over-constraint or over-define the solution methodology, purposely giving freedom to the participants for interpreting the challenge and using their skills and knowledge to devise the best possible solution for a concept/design/performance/manufacturing problem.

And judging by the diversity and quality of the entries received, it was a very successful approach.

For the evaluation and selection process, we employed our typical internal methodologies for modeling bolted joints and bearing components.
We ranked the entries by mass and then modeled and run the 150 lightest ones.
It was with surprise that we saw many entries failing to meet the maximum allowed stress, especially the ones with FEA provided by the participants.

From the 10 lightest that passed our FEA screening, we selected the 5 finalists based on manufacturability by an additive process (printing difficulty, volume of supports, surface area for secondary machining.

We appreciate the contribution of all participants and are dedicating all our available resources in this evaluation process. In the next days, we will provide material describing our FEA screening method in detail, and also provide individual feedback to each of the 150 entries that were modeled.

Congratulation to the finalists! The printed components look great!

We will be in touch soon with our winners!

Kindest Regards,
Rodrigo

• ### René over 6 years ago

Thumbs up to Alcoa. For me this challenge was not about winning but rather learning new things (i.e. topology optimization & reverse engineering with SubD surfaces). If we get some insight now on how such a FEA model is supposed to be set up and a feedback for our designs - that is more than I personally hoped for. So thank you for that.

It was fun.

• ### Rizaldy over 6 years ago

Congrats to all the finalist!. Such as a great challenge.
However, I have one concern. I have checked all the 10 finalist, and found one (the last finalist) that even did not pass the FEA while it analyzed by the participant himself. His FEA result stated that the Max Stress was around 1,340 MPa but still pass as a finalist. Just wondering how the Jury analyze the model, so it can pass the simulation. Below is the link of the finalist that I mean.
ALCOA BRACKET (BRCT 12a) correction

• ### igor Nikol over 6 years ago

Dear Rizaldy!Thank’s for your attention to my model. If you make FEA without ductility you will have picks of stress in local places like sharp edges. In the real world a bearing stress could be more than ultimate tensile stress. In that places material is compressed and creep just a little so load is spread on bigger area and pick of stress gone. Than it will be like a small chamfer or fillet .

• ### Rizaldy over 6 years ago

Dear Igor. Thanks for the reply and congrats for be one of the finalist.
My concern was just wondering about the analysis process of the jury, because if you do the analysis corectly, I think that Jury's result will get almost the same result (1,000++ MPa). Ductile material will start to yield at a location when the Von Mises stress becomes equal to the stress limit of the material. If assumed that way, I think I prefer to eliminate those small-wild-stress (stress at small area that sometimes did not make any sense), because my understanding that before the part has been prototyped and tested, we need to prove it virtually through FEA. If counting on the real test (with not pass FEA result), then I think there is no point doing FEA (this was my own opinion).
I am sure that most of the participant do their best to keep the stresses under 1,000 MPa or 145 KSI, even they found small-wild-stress at very small point/portion of their design.
Once again, congrats Igor, for be one of the finalist and good luck to all participants.

• ### Handily1 over 6 years ago

@Ben and @Judging Team
I notice that there is nothing noted in the design requirement that FEA had to be used only that Alcoa would do a FEA. I also believe that the Bracket Challenge was to be a Static Load Test (i.e. P/A) and you are stating that the type of restraint entrants are using did not meet the Judging Criteria. Is it not if you state the restraints had to be connected to the bolts that this would then become a Dynamic Analysis. If so, you would have to provide supporting members of the mount base. And, the loads should have been applied to the bearing and pin shaft including what is attached to the mount shaft. In addition, the applied loads should be shown as the force on the attached part and rotated thru the rotation sweep angle. All of these would have impact to the resultant bracket stresses as mount structures are designed to dampen impact loads. Then run an analysis using a dynamic FEA program (such as Adams Kinematics,etc.). I feel the judging criteria needs to be reviewed and refrained to just the static loads to the bracket itself. At least, this was the progression we used when analyzing aircraft landing gear and wing flap brackets. This would also give entrants that were eliminated a chance to compete in the final judgement.
I also was not selected and I would like my model reassessed. I would think you would make a comment on each entrants design so they would know the reasoning for being or not being selected. This would give everyone a better grip on making a challenge, as well as helping everyone improve their knowledge base. Thank You, Ben

• ### Wudhidham Prachumsri over 6 years ago

Hi Igor and Rizaldy,

When we ran our simulation on the entry, we did not observe the behavior discussed. We incorporated a fastener to the simulation to model the bearing loads on that area as opposed to fixing the bearing surface or the bolt hole cylinder.

Regards,

• ### Allan Bowers over 6 years ago

The concerns that have been raised after the finalists were selected demonstrate how many entries were unsuccessful because they used a different analysis technique to the judges.
It seems to me that all this would have been avoided if the specification had contained a section on how the judges would conduct the FEA. Thus all entries would be designed with that in mind and a fair playing field would be established.
This would avoid any consternation after finalists have been announced. I accept the comment by Rodrigo that they wanted a spec that would not be restrictive in the design process, however being creative and thinking laterally is all in vain if the analysis technique you are using to assess your own design fails because it differs from the judges methodology.
I believe GrabCAD and the community at large would be better served if they made the spec criteria for FEA a requirement for this type of design challenge.
It may well encourage more participation. At least we will get some feedback from the judges on our own entries which is gratifying, thanks.

• ### Marty007 over 6 years ago

I reviewed the comments regarding my submission, and have grown even more disenchanted by this challenge process. The Bracket has Landed

It appears that my model failed the FEA by approximately 5%, because I modeled the support structure as rigid instead "high-stiffness". I have to ask, without a support stiffness specified in the original challenge specs, how the @#\$% are we supposed to optimize our designs?!

Given my submission weight of 236g, if details of the judging analysis had been provided, I'm certain that I could have easily modified my design to keep it under 250g. Seeing finalists that are over 300g is just a slap in the face.

The guys running FEA analyses at Alcoa must understand how pointless it is to run an FEA optimization without well defined boundary conditions. And yet, that's exactly how this challenge was specified, and then judged. If you state "high stiffness" supports, what assumption of support structure other than rigid can we possibly make?!

I spent easily 40hrs of my life on this, and to be thrown out by 5% due to poorly defined challenge specifications is pretty bruising.

A note to Alcoa and Grabcad: FEA is a very finicky analysis tool. Loads and restraints are critical in obtaining useful results. There is also a significant time component to running these types of analyses (particularly if you start working in multi-body parts with contact constraints). It's a waste of everyone's time if you do not accurately define the loads/materials/restraints/etc....

• ### SVV over 6 years ago

Marty, don't be so drastic. We all should thank Alcoa and Grabcad for this challenge. They proposed us to play and hosted this exciting event! We played but failed. Anyhow, it gave us a new experience. We were trying to hit the bull's eye by sniper riffle but guys who took machine guns won. Sometimes machine guns are more practical!

• ### igor Nikol over 6 years ago

I think ALCOA get us absolutly clear spec. " Let's design it from this material under thouse loads and this geometry in any way. It will be verified via practice test". Any FEA is modelling of the real world. Any FEA is'nt perfect. Thank's ALCOA we can veryfy our metodology.

• ### Marty007 over 6 years ago

What I am trying to convey is twofold. Because of the imprecise design specification, first, I don't believe that Alcoa has obtained the best possible design, and second, it has resulted in a negative experience for some of the participants. The first is a shame for Alcoa because they have invested at least a little real money in this competition and the best outcome for them would be to obtain the optimum design. The second is a shame for Grabcad because it is going to result in participants choosing to leave the site, reducing the commercial viability of the competition format.

• ### Angel Alexandrov over 6 years ago

I am not trying to bash the results, but just like many others I think that there are a lot of unclear specifications. First I thing that the FEA specs were not well defined especially mesh size and parameters and fixtures. Again I am not trying to bash, but some of the finalist fail fine mesh or adaptive convergence studies(on my 2013 SW simulation), especially the area around the front bolts under 2500 load.

Second I think that there should have been some allowable tolerance regarding size envelope. I highly doubt that after printing and heat treating this part will be microns correct to the CAD model, or that in it's real world application 1/10 of mm would matter.

Last, but of great importance I think that the entries for the challenge should have been hidden or at least not downloadable, because there were a lot of "last day entries" that looked a lot like just a tweaked and slightly improved versions of other people who spent nearly a month developing.

• ### Paolo Minetola over 6 years ago

First of all I want to thank Alcoa and GrabCad for this interesting challenge.
I'm glad to be among the finalists and I was surprised about that. I have partecipated to some other GrabCad challenges in the past. In several challenges, people complain and concern about plagiarism of entries that were uploaded earlier by other participants.
I agree with Angel Alexandrov and I think it should not be difficult for GrabCad to keep the submissions hidden to the community until the deadline and then reveal them all at once. It should be a blind submission procedure and up to the deadline participants should not know what the other entries are.
As concerns this specific challenge, it is very similar to the one of the GE engine bracket (https://grabcad.com/challenges/ge-jet-engine-bracket-challenge). In that case there were lots of complaints about the results (over 600 entries and just 10 prizes) as well. The winning design was not the lightest (complying with the design specifications and withstanding the loads), but the cheapest.
The FEA analysis is just the first step to assess the structural resistance of the proposed component, but keep in mind that there are additional issues related to manufacturing process planning. You should consider manufacturing and finishing costs VS. weight for the part. In this case I think Alcoa is driving the selection process correctly, as stated in the last post by Rodrigo Pinheiro"From the 10 lightest that passed our FEA screening, we selected the 5 finalists based on manufacturability by an additive process (printing difficulty, volume of supports, surface area for secondary machining)."
I would suggest people to read this interesting article by Delcam (https://www.linkedin.com/pulse/planning-preparing-producing-walking-tightrope-between-hamilton) that considers a very similar case study, i.e. an airbrake bracket. The article explains very well how manufacturability issues should be taken into account in the design of additive manufactured metal parts.
Good luck to all the finalists! I'm looking forward to the results.

• ### Ben Ewing over 6 years ago

I appreciate all of your feedback regarding the challenge criteria, finalist selection and challenge processes. We will definitely keep your thoughts in mind and discuss your suggestions for future challenges!

• ### Ben Ewing over 6 years ago

I'm also happy to announce the winners for the Alcoa Airplane Bearing Bracket challenge: https://grabcad.com/challenges/airplane-bearing-bracket-challenge/results! At the top of the results, you'll see a great explanation by Alcoa Engineer, Wudhidham Prachumsri, as to how the winners and finalists were selected. Congratulations to the winners and to all of the finalists!

• ### Ernesto Chavez over 6 years ago

I'd still like to see some detailed explanation of Alcoa's FEA screening. Congrats to the winners and finalists!

• ### SVV over 6 years ago

Warm congradulation to winners! Hope Alcoa will share the photos of printed brackets and test videos or photos!

• ### Ben Ewing over 6 years ago

Hi all, the team at Alcoa wrote a great, in depth blog article on the selection process used for this challenge. Check it out, especially if you have questions about the process: goo.gl/Gzkq8L!

• ### steff evans over 6 years ago

Hi Ben. I can't seem to get the goo.gl link to work. Can you help? Thanks.

• ### igor Nikol over 6 years ago

Nice article. Unfortunately they did not show the broken brackets to know the weaknesses on the different designs.

• ### A. Anderl over 6 years ago

Thanks for the article. I learned a bit more about analysis and industrial procedures. I found specially interesant the procedure followed for the necessary dimensional inspection of printed parts. Clearly, Alcoa has executed a rigorous and extensive analysis before selecting the winner. I personally thank this interest and effort.
Congrats to the winner!!

• ### René over 6 years ago

Some final comments from my side:

For this special application and design DMLS may only be used for prototyping. The winning design is so trivial (geometrically), that it shouldn't be hard to precision cast it.

Regarding the thermal deformations after DMLS: We usually morph the parts according to the white light scanning results to mitigate the deformation.

Anyway, good luck.

• ### NatarajBeelagi over 5 years ago

Hi. I know this challenge is over. I'm curious to learn weight optimisation so I was doing FEA analysis on original CAD. While importing CAD geometry into FEA software I used a scale factor of 25.4 since they have specified that CAD model is in Inches. Since I'm doing FE analysis in "mm", "Ton", "newton" and "second".
But FE results that I'm getting are in the range of 1 to 10 MPa for all the load cases.

Please correct me if I'm doing it wrong or please specify FE analysis method that you have followed.