Design for Anti-Warp of ABS Parts
by GuardToad, published
Describes how to fight warping for parts printed in ABS.
Problem: Parts printed in ABS on personal 3d printers warp.
Details: 3d printed ABS parts warp due to temperature differential. For example, an 8 inch long beam printed on a 230 deg F hot bed plate in an 80 deg F build chamber will suffer shrinkage of the top part (away from the hot bed) of about 1/16 inch. In other words, the bottom of the part will be 8 inches in length and the top will be 7 15/16 inches in length. In effect, there is a pinching of the top which causes the entire part to bend - this causes the warping.
Solution: Changes in design can minimize the warp. Try to break up long profiles, especially at the top - away from the build plate.
Examples - plate is an 8 inch long optical bench that needed to be fairly flat. Notches were cut to distribute stresses and the part printed flat. Jig is a part used to hold delrin pieces in a vise to be milled. The part needs to be straight or the mill will not cut the delrin parts correctly. The first design of the jig used a monolithic block of plastic and warped badly. The part was redesigned to reduce long runs of plastic and printed straight and true.
Ref: Linear thermal expansion coefficients are from:
Units are in/in/deg F. To calculate the change in length in inches, multiply the thermal coefficient by the length of the part in inches, then multiply by the change in temperature in deg F.