Investigation of the effect of various build methods on the performance of rapid prototyping (stereolithography)

Stereolithography, which was the first commercially available Rapid Prototyping (RP) technique, currently represents a major portion of the worldwide RP market share. Parts manufactured with the stereolithography apparatus (SLA) are presently used for design verification, medical modeling and rapid tooling applications. Dimensional accuracy of the prototype is very important for design and form/fit applications. Tooling applications, such as patterns for investment casting, also require good surface finish. Stereolithography provides three different build styles and many part and recoat parameters which can be optimized for these various applications. This paper presents the results of an investigation into the effects of build styles (ACES, WEAVE and Quick CAST) and build parameters (Z level wait, pre-dip delay, dip velocity and acceleration, sweep period and workpiece geometry angle) on the performance measures of dimensional accuracy, surface roughness and build time. All of the prototypes were built on an SLA-250 which used the SL-5170 photopolymer resin. Statistical analysis of the results of the fractional factorial design showed that ACES produced the highest degree of dimensional accuracy while QuickCast was the least accurate build style. On a horizontal surface, ACES produced the best surface roughness and WEAVE produced the least desirable surface roughness. However, on an inclined surface, QuickCast produced the best surface roughness and ACES produced the least desirable surface roughness. The QuickCast workpieces were produced in the shortest time and ACES workpieces took the longest time. In addition to the statistical analysis, surface profiles of the prototypes were studied with Data Dependent Systems (DDS), a stochastic modeling and analysis methodology. DDS analysis of the surface profiles found that layer thickness was the major component of the profile on inclined planes and hatch and fill spacing were the major components on horizontal planes.