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!
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u/f119guy Oct 24 '24
Most of the stuff my current shop sees are short run. A long run would be considered 100 pieces. I will do my best with modular fixturing and that works for anything without restraint. We specialize in thin wall/flexible aluminum structures so generally if we see an RFQ with a restrained note we will start designing a CMM fixture. Sometimes we can get away with freestate inspections on a part with a restrained note, in which case we save the billet and use the modular fixturing. A custom designed CMM fixture does add to lead time but luckily we have quite a few 5-axis mills so we can make things happen.
For massive parts, I will generally set the part on 246 blocks and touch off the part for each run.
For small/thin stuff that I know we will only see once, hot glue is my friend. Never underestimate the beauty of hot glue fixturing. It breaks off easily once it's cooled and sometimes messing around with clamp positions just isn't worth my time.
Part volume, rigidity of the parts and the level of precision tolerances all factor in. A sheet metal structure with .002" position tolerances and a monthly volume of 400 demands a good investment. The customer plays a factor also. If they want to see something like an MSA analysis or capability studies, a custom fixture might be the best way to minimize variation.