Effects of creep
Name:
Dave Cartwright We machine an acetal part that 'creeps' after machining. Does the material reach a stable state post creep? If so is it safe to machine to oversize to allow for shrinkage?
- Login or register to post comments
- report this
- Suggest an Expert
Hi Dave.
I am not sure if you meant creep. Creep is basically a deformation derived from a long applied load. For example, if you put a significant weight on a piece of plastic and leave it hanging, after some time you might find that the length has increased.
To be more scientific http://en.wikipedia.org/wiki/Creep_(deformation).
What seems to be happening is that the part heats up during machining and upon cooling starts to shrink and deform. Another factor is the plastics don't like high temperatures and stresses and, consequently their mechanical properties decrease with increasing temperature.
As a first approach, check http://en.wikipedia.org/wiki/Polyacetal
Machining books, in general talk about this "cool" plastic, due to its use in several applications (e.g. gears and bearings).
You can also ask here http://www.eng-tips.com/threadminder.cfm?pid=712
Depending on the product, time and, of course money, you can contact an expert or your supplier.
Please, let me know on the outcome.
MPS