Micro-hardness measurement of photopolymer in stereolithography.

Abstract

The curing of liquid photopolymer is determined by the exposure (optical energy) deposited. In laser stereolithography, laser exposure is considered as non-homogenous within the radiation area. In order to investigate the difference of the cure degree within the cross section of a single cured strand, a micro-structure was evaluated by hardness measurement. The hardness distribution was found to be not homogenous, the hardness reaches its peak at the center of laser beam on the photopolymer surface and is almost zero at the boundary of the liquid and solidified polymers. Further experiment shows that the hardness is linear to the laser exposure within a certain range. These results clarify that the theoretical derivation of laser exposure distribution is reliable.