Flatness relative to part thickness?
Flatness relative to part thickness?
(OP)
I have a composite structure or panel that is somewhat large in size. Design engineering is trying to control the bow or warp of these parts with a flatness callout. How can I use a CMM to measure the flatness or warp of the part with respect to a surface plate? If I take points on top of the part then my numbers are dependent of the part thickness tolerance at each point location. How do I take measurements to control flatness and take into account the part thickness tolerance?
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Joejack7
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Joejack7





RE: Flatness relative to part thickness?
Flatness does not reference anything but itself.
There are a couple of ways to perform flatness on a CMM and I will give you the better way.
Take 3 points on the surface that are 120 degrees apart and close to the edge. Create a plane. Hopefully your software will do this. Now take at least 24 points one the surface usually in a circular motion from the outside of the surface towards the centre of the surface relative to the plane that you just created.
The software should give you the actual flatness which is the FIM or TIR of all your readings.
Hope this helps.
Dave D.
www.qmsi.ca
RE: Flatness relative to part thickness?
Jim Sykes, P.Eng, GDTP-S
Profile Services
CAD-Documentation-GD&T-Product Development
www.profileservices.ca