Implementation and evaluation of thin-shell rapid prototype

Abstract Rapid prototyping processes, like stereolithography, have gained wide industrial acceptance in recent years. The main advantage of rapid prototyping over conventional manufacturing processes is faster speed. Unlike material removal from a stock (as in machining), most rapid prototyping processes have to build the solid volume layer by layer. The tracing of the cross-sectional solid area in each layer is the most time consuming process. Yu and Li [K.M. Yu, C.L. Li, Speeding up rapid prototyping by offset, Proc. Instr. Mech. Engr. 209 (B1) (1995) 1–8] and Yu et al. [K.M. Yu, T.W. Lam, K.M. Cheung, C.L. Li, Thin-shell based rapid prototyping, Third International Conference on Manufacturing Technology in Hong Kong, Chiang Industrial Charity Foundation, 13–16 Dec. 1995, p. 230–233] have proposed to use solid offsets to cut down the solid volume to be built. A thin-shell solid is obtained by subtracting the original solid from its offset counterpart. Faster speed can thus be achieved by tracing the thin-shell solid that contains less solid material. The background theory and implementation algorithms for obtaining the reduced-volume solid are explained in the paper. The approach is applicable to solids defined by constructive solid geometry and extensible to other solid modelling schemes. The paper also reports the experimental results that test the validity of the theory. Solid objects built in AutoCAD have their volume offset. This reduction in volume results in faster processing time and less material cost in building the prototypes. Other beneficial properties resulted from the thin-shelled solid are also highlighted. Several cases are tested in a stereolithography apparatus (SLA) and the results are supportive. Finally, possible refinements on how to construct the thin-shell rapid prototype are raised.