How to fixture your parts to get the most out of your scans
Fixturing Goals
Fixturing is an essential step in the scanning process. There are some high-level goals any of your fixturing efforts should aspire to.
- Isolate the object you are scanning from things you do not want to see (such as the turntable).
- Prevent unwanted motion of the part. Any motion other than the controlled rotation of the part by the stage is unwanted.
- Minimize artifacts to maximize the results you desire.
Video Tutorials
The best way to learn about fixturing is to watch these short videos from Lumafield CT experts.
How to take advantage of Lumafield's fixturing materials.
Orienting and Fixturing Parts for CT
Fixturing Materials
The ideal fixturing materials are lower density than the parts you are scanning by a lot - this allows for easy separation of the part from the background using the range mapper in Voyager. Green floral foam is a cheap and effective solution for one-off parts - it is easy to cut to size and crush your part into place. Some customers design custom fixturing if scanning a similar item repeatedly. This is often done with carbon fiber or a lower-density plastic if applicable. If you want repeatability in your process, you will almost certainly need to develop a carefully designed custom fixture.
Fixturing Angle
It is generally best to angle the part when fixturing. This can minimize artifacts and help your part better fit into the field of view.
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Note the artifacts seen around the surfaces of the scan where the part was fixtured with no angle.
Fixturing Accessories Guide
Breadboard Turntables
Effortlessly secure your parts with our Breadboard Turntables, featuring industry-standard 1⁄4”-20 threaded holes for CMM and CT fixturing. Choose from three diameters (60mm, 100mm, and 175mm) for versatile fixturing options. Use our included accessories to achieve secure and adaptable fixturing. Each Breadboard includes tie-down points for velcro straps, engraved lines for alignment assistance, and compatibility with industry standards.
At the bottom of the article you will find CAD to download the hole patterns for the breadboard themselves. This will allow you to design custom fixtures that will bolt directly to the plate.
Angled Foam Fixture
The Angled Foam Fixture comes in three sizes (60mm, 100mm, and 175mm) with poka-yoked pins for easy assembly. Restrain parts securely with velcro straps and elastic bands. The metal base ensures stability when used with floral foam. Align the pins with precision during assembly to optimize fixturing performance.
Things to Remember:
- Do not force parts into the Angled Foam Fixture like you would with floral foam
- Velcro straps are fantastic for holding parts on both the Angled Foam Fixture and Breadboards
Option 1: Lollipops
Enhance fixture versatility with our Lollipop option – foam balls on carbon fiber rods in two sizes (100mm and 170mm tall). Create fixtures supporting various geometries by installing multiple Lollipops on a Turntable in an equilateral triangle formation. Use Standoffs (1” and 3” tall) for height adjustment, ensuring secure part placement. Tighten by holding the carbon fiber shaft during installation.
Option 2: Foam Retention Spikes
Foam Retention Spikes are available if using floral foam is preferred. Install 3 or more spikes into an appropriately-sized Turntable. Use an adjustable wrench or pliers for tightening, if needed. Press floral foam onto the spikes for a secure fit, keeping the part centered.
CAD for Foam Retention Spikes (STEP & STL)
Twist-to-Release Collet System
Newer scanners include a Twist-to-Release Collet System, a tripod mount by Leofoto that secures your part with minimal effort. Rotate the outer ring clockwise to lock and counterclockwise to unlock. Check to make sure that the Collet is in the unlocked position with a metal pin visible at the center of each of the three notches before inserting a fixture. Additional plates for the QS-60 system are available online, and we have included a dimensioned drawing of the mounting hole pattern for added convenience, if you want to design your own custom fixtures.
Amazon link for QS-60 Collet Plate
Things to Remember:
- When installing a fixture in the machine, do not over tighten the Collet ring. It does not take much torque, and the ring will only rotate a small amount.
- Check that the fixture is fully seated in the Collet by attempting to rotate the fixture.
FAQ
How do I fixture spheres and cubes?
Use three Lollipops on an appropriately-sized Breadboard, forming an equilateral triangle.
How do I fixture irregular objects?
Experiment! The Angled Foam Fixture can hold a variety of shapes, and the Breadboard is highly configurable.
Design files to support your custom fixtures.
CAD for Foam Retention Spikes (STEP & STL)
Off the Shelf Links
Lumafield's second-generation fixturing includes breadboards, allowing users to customize their methods. These work off 1/4-20 screw threads, meaning a variety of off-the-shelf components can plug straight in.
Cone Support for Inspection & Measuring Kits
Amazon link for QS-60 Collet Plate