Accuracy of Stereolithography Parts: Mechanism and Modes of Distortion for a "Letter-H" Diagnostic Part

Rapid Prototyping and Manufacturing (RP&M) users need to compare the accuracy of various commercially available RP&M materials and processes. A good diagnostic test for both material and the fabrication process involves a 4-inch long "letter-H" diagnostic part. This diagnostic part, known as "H-4", was developed to measure the inherent dimensional characteristics ofvarious RP&M build materials. It is also less dependent on the calibration status of particular RP&M machines, and is excellent for the purpose of generating simple but meaningful accuracy information, which can be used to further understand the mechanism and the modes of distortion in RP&M materials. H-4 parts were prepared and built in Stereolithography Apparatus (SLA) using Ciba-Geigy epoxy based resins SL 5170 and SL 5180, and results were compared to acrylate based SL 5149. Experimental data involving the magnitude, mechanism, and the modes of distortion for these three resins are analyzed in this paper.