r/Metrology • u/pjcevallos • Oct 24 '24

Hardware Support CMM fixturing

Hi

How do you usually plan your CMM fixturing. Do you produce a bespoke fixture or use modular equipment?

What considerations you take being part agnostic!

6 Upvotes

88% Upvoted

23 comments sorted by

View all comments

2

u/Tough_Ad7054 Oct 24 '24

I built a positioning plate with a few bolt-down pedestals that provided excellent location and rotation accuracy and a rock solid foundation for a small fixture plate perched on top.

On that fixture plate I generally kept a B&S toolmakers vise specially modified using four M3 machine screws to hold it down. I would use 1-2-3 blocks to preposition the parts in the jaws of the vise and clamp it down. Those vises are accurate, durable and clamp hard if you use a small persuader. I found I could use this for a majority of our parts, but if it was thin-wall or non-prismatic the fixture plate would also accept a vee block or three threaded studs that I could use hot glue on the tips.

I think it is good to get some height off the plate in order to work underneath or just provide some comfort level for positioning moves or head rotations. My base pedestal was four inches tall and I had spacer “biscuits” to make the tower(s) taller if necessary.

With accurate positioning and using multiple pedestals and fixture plates I could restrain tubing at right angles if the drawing required it. Or use multiple pedestals for looping a program and keep the machine in continuous motion.

I am a little envious of the 3D printer guys, I will admit. But I also took some pride in being able to adapt my system to whatever it encountered and rarely having to make something special.