The temperature dependence is very interesting!
I don't think that the difference is metal versus plastic, because plastic in general has much higher coefficients of thermal expansion than metals.
ABS plastic has a coefficient of 72 - 108. The units work out to microns per meter per degree C.
So, a 1 meter rod of ABS ought to expand by 72 to 108 microns if heated one degree C.
Acrylic is 68 - 75 in these units. Epoxy and fiberglass is 36. Nylon is 50-90. Polycarbonate is 65-70.
Meanwhile, aluminum is 21 - 24 in the same units. FAR less than the plastics.
Steel is 10.8 to 12.5. Stainless steel is 9.9- 17.3 depending on the alloy.
I find this very counterintuitive, but it is the case. Note that the plastic used in most 3D printers is ABS and it is very bad - even worse than the 72-108 listed above.
Normally speaking stability under temperature is something that lens designers worry about because glass in very different than either the plastics or the metals they are mounted in. Glass is 4 to 9 in those units, so far less than the others.
Edited by nathanm, 05 July 2020 - 05:26 PM.