I was curious if anyone had good references, set of equations and/or perhaps some empirical data they could point me to for calculating part/mold spring-in/cupping. Working on a few tight tolerance components right now and it would be most helpful. I know I can alter the properties using asymetric laminate or homogenizing to lower the B matrix, but I’m kind of in a time crunch and looking for a bit of a kickstart to accurate results, or at least a method to quantify.
Thanks,
Mike
Hey Mike,
I’m not familiar with these terms “calculating part/mold spring-in/cupping.” Could you provide an explanation or a link to an explanation of what they are? Google is giving me mixed results and I don’t know what to look for.
Basically when a mold or part is made, due to the varying degrees of shrinkage in the 123 directions, a part can and will change shape. Usually it will cup or warp to the inside of a U-shaped section. On thick sections and some geometries this can be fairly substantial, even when using a balanced symmetric laminate with minimal B matrix values. I have found tools/equations to calculate residual stresses in a cured laminate, and that is the way I’m heading in finding a solution. But basically I’m looking for a second opinion, confirmation, alternative method before I devote significant time to it path.
use carbon foam tooling. same shrink rate as the part.
Thank you for the suggestion. However, while that would in fact make the mold stable (I assume, as I haven’t used the foam before), the part would still be subject to the same conditions. It isn’t a mismatch of the CTE that causes the issues. Out of curiousity, do you happen to have rough pricing on the carbon foam? It might be applicable to smaller components for us, however, I think it is probably cost prohibitive on many of our larger parts.
Thanks,
Mike
If you use carbon as reinforcement, yes. But 99% or even more is glass/polyester…