Material and Process Parameters that Affect Accuracy in Stereolithography
Experimental real time linear shrinkage rate measurements simulating stereolithography are used in an analysis of shrinkage during line drawing in stereolithography. While the amount of shrinkage depends on the polymerization kinetics, shrinkage kinetics and overall degree of cure, it also depends on the length of time to draw a line of plastic. A line drawn slowly will exhibit less apparent shrinkage than one drawn very quickly because much of the shrinkage is compensated for as the line is drawn. The data also indicates that a typical stereolithography resin in the green state may shrink to only 65% of its maximum, thus retaining considerable potential for shrinkage during post-cure. This infonnation can be used to predict the amount of shrinkage to be expected under certain exposure conditions and to fonnulate overall strategies to reduce shrinkage and subsequent warpage that causes shape distortion.