Design criteria for harmonics

[BobM3]

I haven't had to design much mechanical fixturing for awhile. I used to just use the criteria that I wanted my mechanical fixture resonances to be above the fundamental excitation frequency the fixturing would see. Now I need to design a fixture for holding a part in a milling machine. Milling tools produce impact loads which produce harmonics. I'm curious, what criteria do you guys use for design when there might be significant energy content in the harmonics?

 

[CharlieEnz]

On the occasions when I have designed fixturing for milling the rule has been to design it with as much rigidity as possible. For substantial parts with "thick" walls or features this is enough. The only time there may be an issue is during roughing cuts. Usually finish cuts (.010 or less) do not excite the vibration.
If you are machining thin sections then vibration is highly likely and there are several cures. These are: support the section either by clamping the opposite side in the fixture, by filling cavities with cerraloy, or a plug. I have seen rubber sheet clamped to the outside of the part by hose clamps used as a damping mechanism on thin walled lathe work.