How to 3D Print Jigs & Fixtures, Part 1: Choosing Your Target
This tutorial series will take users who are new to 3D printing and show them how to:
- Choose which Jigs or Fixtures from your factory floor might be best improved with 3D printing (Part 1)
- Optimize your J&F designs for 3D printing by using stress-analysis tools, CAD tools and new 3D print prep tools (Part 2)
- Choose which FDM materials to print in for best performance (Part 3)
- Post-process your Jig or Fixture for greater utility with inserts, painting, numbering, etc. (Part 4)
Step 1: Definitions
Jigs & Fixtures represent the single largest area where your production floor can benefit from 3D printing. But first, some definitions:
A jig is a device used to guide tools during manufacture of a part, such as this guide to make sure the holes in cabinet shelves always line up:
A fixture is a device to hold down the workpiece so it doesn’t move during an operation, such as this monstrosity used to inspect bent tubes for NASA spacecraft:
As you walk around your shop floor, you will notice most jigs and fixtures are heavy, blocky devices built mainly out of bolted together metal. Why is this?
1. Jigs & Fixtures need to be stiff to not deform during operation. And then engineers overdesign them.
2. In low quantities, it's faster and cheaper to just cut and bolt stock metal together than injection-mold lightweight plastics in the exact shape you need.
3. Most companies want to spend time and money designing the product they're actually going to sell rather than the jigs and fixtures needed to get them there. (And most engineers would rather do the tenth (or twentieth!) iteration of a cool part than the second iteration of a simple welding fixture.)
As a result, most Jigs & Fixtures are bolted-together assemblies of heavy, rectangular blocks of metal designed as quickly as possible, without much thought to optimizing for human use or comfort:
Studies have shown that each hour spent improving your factory’s jigs and fixtures has an ROI of 3-5x vs. an hour spent optimizing your product one more time.
So let’s get started.
Step 2: How to choose which Jig or Fixture to redesign first
Every company will have their own scoring system when starting this type of project, but here are criteria which have proven most useful for previous companies we've worked with:
1. Look for Jigs & Fixtures that are too heavy for a single operator to easily move.
Most jigs have to be taken on and off a work piece tens or hundreds of times a day. Fixtures sometimes need to be dragged between stations on the manufacturing floor.
Converting blocky metal fixtures into ergonomic 3D printed plastic designs often reduces weight by 50-90%, usually leading to faster cycle times, not to mention reductions in repetitive stress and back injuries for your workers:
2. Look for chances to turn highly-skilled labor into a simple plug-and-play operation.
Is there a certain operation only a few workers in your shop can repeatably do? A set of parts that always has to be lined up ‘just so’? Or a kit of nuts and bolts that has to be painfully assembled out of bins each time, double-checking part numbers to make sure you’ve gotten the right sizes?
The reason most companies haven’t made a custom jigs & fixtures for ALL their important operations is the belief that it’s ‘too hard’ to make a fixture that holds your part at just the right angle for a certain operation – “Better to have Jane do it each time."
Or that it’s ‘too expensive’ to make a tray with exact-sized cutouts of the parts needed for a certain operation.
But with 3D printing, neither of those assumptions are true any longer. It's simple to make complex fixtures for your high-skill, repetitive operations. Even dunnage trays are a big help. I mean, which would you rather have:
3. Look for fixtures made up of many bolted-together part numbers that could be 3D printed as one unified item to reduce part count.
Most Jigs and Fixtures are made with stock parts that were on hand. Need to attach that clamp to this base? Bolt it on. Need to hold a block at a certain part of a plate? Bolt it on. Look at this welding fixture again:
How many blocks, bolts, washers and nuts does it take to make that? How many entries in your inventory management system do people have to enter to track it?
If a fixture needs to adjust to a wildly different shape every single time, maybe that’s okay. But most fixtures need to hold the same part over and over and over again. Why not 3D print a shape that cradles your part exactly, without a hundred bolts to adjust each time?
Even simple shapes like this gun-stock drilling fixture can be improved with 3D printing:
Again, that's just blocky metal shapes bolted together. Why not 3D print a cradle that held that gun stock perfectly every time, without any precise adjustment needed?
Some of our customers have netted a 90% reduction in part count on their fixtures, removing hundreds of useless sub-assemblies and part numbers from their production floor.
4. Look for uniquely shaped parts being held by generic fixtures because it’s ‘too much effort’ to make a ‘complex’ shape to hold them.
Engineers tend to design in flat planes, blocky rectangles or perfect circles because those are the easiest shapes to describe to the machinists making the tools. CNC machining allowed more complex shapes to start to be made, but 3D printing finally breaks the limits.
For example, what if, to hold your work piece, you needed a net shape that looked like this:
This sort of shape would be pointless to try and machine, but a 3D printer doesn’t care. You can make your jig or fixture as complex as you want. In 3D printing, there is no penalty for part shape complexity.
(In fact, complex parts like above would 3D print faster than a fully solid block of the same height – the complex shape has less material to lay down!)
So, to review:
1. Look for jigs & fixtures too heavy for operators to easily move.
2. Look for chances to turn skilled labor into plug-and-play operations.
3. Look for assemblies or sub-assemblies of many bolted-together parts which could be printed as one piece.
4. And look for complex parts held by generic fixtures when a tailored shape would be better.
In part 2 of this series, we will go over HOW to redesign the jigs or fixtures you have chosen, to take best advantage of 3D printing: