I am designing a fixture used to measure several dimensions on a part that will be introduced to the fixture via an indexing conveyor.  I call the fixture the measurement helmet, because it has a cavity  that fits over the part when lowered from above.  The cavity has measurement probe tips that extend to contact the part once the fixture is in position over the part.

At this point, I need to decide on what materials, treatments, finishes, etc.. to specify for the components of the measurement helmet.

The movement of the helmet must be accurate and repeatable; ie the probes within the helmet must maintain the same location with respect to the part everytime it takes a measurement.

The helemt must be robust, as it will be used as part of an automated part measurement system that will measure 1000's of parts a day.  the helmet will be raising and lowering to measure each new part as it moves into position beneath the helmet.

Some of the helmet components will be regularly reconfigured to accomodate measuring different parts.

The helmet consists of 3 plates, each containing probes, that are sandwiched together. 

Any feedback or suggestions on fixture material specs would be greatly appreciated.

Thanks,

Howard