Pre-Printing tips for PolyJet on GrabCAD Print

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In this tutorial, we will discuss how to optimize a 3D model in GrabCAD Print before printing it on a PolyJet 3D printer.

  1. Step 1: The 3D printing process for PJ on GCP

    The diagram below depicts the 3D printing process. 

    The following GrabCAD Print (GCP) settings can help you achieve optimal printing results:

    1. Material selection
    2. Part orientation
    3. Surface finish: Matte / Glossy
    4. Support style: (Heavy / Medium / Lite)
    5. Printing mode: High Speed / High Quality / Digital Material or High Mix


    We will explain more about each of these settings: 



  2. Step 2: Select Printing Materials

    Verify that the materials loaded into the cabinet are the ones you selected in GCP. You can also use the Get printer's loaded materials button in GCP.


    If they are not, change materials using the Change Materials option.

    From the Print Settings Menu, select Change Materials.


    A.     Select a Support material.

    B.     Add or remove materials using the buttons in the middle of the window.

    C.     GCP chooses color profiles automatically based on the materials you load. These profiles don’t need any adjustment in the vast majority of cases. If you do want to choose your own color profile, use the Color Profiles dropdown menu if you are printing an STL file. If you are printing VRML or OBJ, use the Texture Profiles dropdown menu 

  3. Step 3: Position the Part

    Automatic tray arrangement:

    GrabCAD Print can automatically arrange models for shortest printing time.


    From the Print Settings menu, select Arrange > Arrange this Tray

    Manual tray arrangement:

    You can also position parts manually to optimize other considerations, including:

    ·        the amount of Support material consumed

    ·        where Support material is applied

    ·        glossy or matte finish

    To manually adjust the model’s orientation, use the Orient dialogue box in the Print Setting menu. 

    From the Print Settings menu, select Orient.

    Manual scaling:

    For manual orientation, you will also need to scale the model yourself. When you are scaling the model, you can do uniform scaling to keep the model’s original proportions as you make it larger or smaller, or non-uniform scaling to adjust the proportions.

    From the Print Settings menu, select Scale, and then check Uniform Scaling if desired. 

    Here are some rules for optimizing manual orientation:

    A)     The X-Y-Z Rule.


    This rule considers a model's outer dimensions.


    ·        Since the print heads move back and forth along the X-axis, the printing time along this axis is relatively short, compared to printing time along the Y-axis and Z-axis. From this point of view, it is advisable to place the object's largest dimension along the X-axis.

    ·        Since the print heads measure about 2 inches (5 centimeters) on the Y-axis, models measuring less than this (on the Y-axis) are printed in one pass. From this point of view, it is advisable to place the object's intermediate dimension along the Y-axis.


    ·        Since models are built up, on the Z-axis, in 16- or 30-micron layers (according to the printing mode), it is very time-consuming to print a tall object. From this point of view, it is advisable to place the object's smallest dimension along the Z-axis.


    Compare the two orientations below and their respective build times. The first has the largest dimension along the Z-axis, while the second orientation places the largest orientation along the X-axis.

    ·        Aligning the model with the X, Y, and Z axes will also minimize or prevent stepping in the walls of the parts and other locations.

    Stepping is when you do not get smooth lines along the edges of your model because the quality is not good enough. It happens when the STL did not have a high enough resolution. Stepping is far less common in PolyJet because of its fine resolution capabilities. It can be fixed by sanding the part during post-processing. Even though stepping is minimal in PolyJet, it is always best to orient parts parallel along these axes.  

    B)     The single-pass rule

    ·        Whenever possible, keep the model contained within a single pass, preferably starting from the top left corner, to minimize print head passes. 

    This rule is especially important once you print more than one model at a time. If multiple models fit into the same printing pass, the print-time only increases by a small amount.

    Below, we printed 2 parts in one pass in 1:14 hrs. in High Speed mode – roughly 37 minutes per part. 


    In the next picture, we printed 6 parts in 1:44 hrs.; roughly 17 minutes per part. So, triple the amount of parts, but 140% the amount of time- much less than double, let alone triple.  

    This economy of scale can be especially helpful for smaller parts, especially compared to build times using other technologies.


    C) The Tall-Left Rule


    This rule considers models where one side is taller than the other, when orientated on the build tray according to other considerations.


    ·        Since the print heads move along the X-axis from left to right, taller sections on the right require the print heads to scan unnecessarily from the left until reaching them. If, on the other hand, the taller sections are positioned on the left of the build tray, the print heads only have to scan the model until printing these sections—once the lower parts have been completed. Therefore, you should position the taller side of the model, when possible, on the left.



    Three more rules, provided that the top of the model will not need Support material:


    D) Recess-Up Rule


    This rule considers models containing surface recesses. Recesses in the surface (like hollows, drill holes, etc.) should, when possible, be positioned face-up.


    E) Fine Details-Up Rule


    This rule considers models that have one side on which there are fine details (like the keypad side of a telephone).


    The side of the model containing fine details should, when possible, be positioned face-up and printed in glossy finish. This results in a smoother, clearer appearance.

    F) Avoid Support Material Rule


    This rule considers models that have large holes or hollows, open on at least one side (like a pipe or a container).


    It may be advantageous to print a model standing up, so Support material does not fill the hollow, even though printing the model lying down would be much faster.




















  4. Step 4: Choose the Surface Finish

    Surfaces can either have a rough and matte finish, or a smooth and glossy finish.

    If you want to use the same surface finish for all the models on the tray, you can set it as your default surface finish from the Preferences tab.

    Go to File > Preferences> PolyJet. 

    Choose your default surface finish and select Save.

    If you prefer to choose a different surface finish for each model, you can also select it from the print settings menu.

    From the Print Settings menu, select the Finish dropdown menu.

     


    Ultimately, any part of a model requiring Support material will have a matte finish and any parts without Support material will have a glossy finish. Each finish has its pros and cons, so you need to decide which finish to use on a case-by-case basis. Use the table below. 



    The following model was printed used a matte surface finish.


    In the case below, a glossy surface finish was selected. However, to support the undercuts, Support material was added around the bottom of the model and this resulted in a matte surface finish. 










  5. Step 5: Choose the Support Grid Style

    Adjust the strength of the structure formed with the Support material. This adjustment is useful when producing either large/massive models or small/delicate models. For most purposes, the default setting provides adequate support strength.

    From the Print Settings menu, select the Grid Style dropdown menu.

    Grid Styles:

    Standard: Use in the vast majority of cases.

    Heavy: Use for large models needing much support. When printing models with Agilus30 or Tango, Heavy grid style is selected automatically.

    Lite: Use for models printed with SUP706 Support material and for delicate models needing little support, for easy support removal. In cases such as these, Lite is selected automatically.






  6. Step 6: Choose Support Type

    With the release of the new advanced slicer on the J735 and J750, you can apply a suitable support structure in GCP. 

    The new support settings provide better support for holes, cavities, overhangs, and thin, tall parts. They also ensure better part quality for delicate geometries and allow different support options for matte and glossy.


    There are three support options:


    Default—available for glossy only

    This option adjusts the Support material around holes and cavities, as shown in the

    example below.

    Smart—Available for Glossy and Matte

    This option fills gaps and spaces in models and adds Support material around and

    under them. For example, when printing a model with the Smart option, the area under

    the opening of the hole is covered in Support material, as shown below.

    Wide—available for matte and glossy

    This option adds a broader support structure for tall, thin parts, as shown in the

    example below.

    You set the support options in the File > Preferences > PolyJet dialog box. 



    The support policy you select will apply to all future trays until changed again in the preferences.







  7. Step 7: Choose a Printing Mode

    Before the model is sent to the printer, you need to select the desired printing mode. The printing mode affects the layer thickness, surface smoothness, and speed. You can build models using three possible printing modes.

    A summary of each mode and its capabilities and advantages per printer.

    Press Print at the bottom right of the screen when you are ready to send the model to the printer.


    In the Print Options screen, select the print mode you want to use and click Continue.

    Printing Modes:


    High Speed (HS)


    In this mode:

    ·        Models are produced in 30-micron layers, suitable for producing larger models.

    ·        Much less time is required to print most trays, compared to the High Quality setting. 

    ·        This setting is only available when model material can be used in four print heads, in single-material printing.


     High Quality (HQ)


    In this mode:

    ·        Models are printed in 16-micron layers, resulting in smooth surfaces, suitable for producing fine-detailed and delicate items.

    ·        Almost twice as much time is required to print most trays, compared to the High Speed setting.

    ·        This setting is only available when model material can be used in four print heads, in single-material printing



    Digital Material (3 material) or High Mix (6 material)—


    This mode is used when producing trays designed from two or more materials. On the Connex3 printer, this mode is named Digital Material mode and allows you to print mixtures of 3 materials. On the J7 series printers, this mode is named High Mix and allows you to print mixtures of 6 materials. Models are produced in 30-micron layers, but the printing is near-high quality.



    Additional features of this mode include:

    ·        Producing a tray containing two or more models, each designed to be made from a different (single) model material. 

    ·        Producing models from only one of the model materials loaded in the printer by printing with only two of the print heads.

    ·        Printing time is similar to printing time in High Quality mode.

    ·        Although printing time is longer than with High Speed mode, Digital Material mode can make material replacement unnecessary—saving both time and the cost of wasted model material.

    ·        Digital Material mode is selected automatically when more than one model material is assigned to objects on the tray.

    Tail light with Vivid materials, printed in Digital Material mode. 



    That concludes our tutorial on optimizing settings in GrabCAD Print for PolyJet models. In the future, we will develop more detailed, advanced tutorials for using these and other features.

    And stay tuned for our tutorial on optimizing material selection for PolyJet models.


    Leave any questions or comments below!



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