To operate a multiple material stereolithography (MMSL) system, a material build schedule is required. The purpose of this paper is to describe a scheduling and process‐planning software system developed for MMSL and designed to minimize the number of material changeovers by using low‐viscosity resins that do not require sweeping.
This paper employs the concept of using low‐viscosity resins that do not require sweeping to minimize the number of material changeovers required in MMSL fabrication. A scheduling and process‐planning software system specific to MMSL is introduced that implements four simple rules. Two rules are used to select the material to be built in the current layer, and two rules are used to determine at which layer a material changeover is required. The schedule for the material to be built depends on the material properties stored in a user‐defined materials library. The developed algorithm produces sliced loop data for each material using the predetermined layer thickness from an input CAD model, and the four rules are applied at each layer. The algorithm then determines the build order for each material, the material‐specific number of layers to be built, and whether or not sweeping is required. Output data from the program are the scheduling and process‐planning report and the partitioned computer‐aided design models to be built before changing a material according to the process planning. Two examples of the algorithm applied to multiple material parts are provided.
The MMSL scheduling and process‐planning software system is developed using Microsoft Visual C++7.0. For verification, a simple demonstration is conducted on a two material part where the process plan could be easily determined through intuition. A more complex multiple material part is also tested that consisted of four subparts. Several cases of resin assignment are tested showing that the ultimate scheduling and process planning vary significantly depending on the material combinations and specifications. These examples demonstrate that the strategy, method, and software developed in this paper can be successfully applied to prepare for MMSL fabrication.
Although the software system is demonstrated on two multiple material parts, more extensive work will be performed in the future on fabricating multiple material parts using the MMSL machine. It is expected that additional rules will be developed as additional limitations of MMSL are identified. It is also anticipated that particular emphasis will be placed on building without sweeping as well as development of advanced non‐contact recoating processes.
As designs incorporating multiple materials increase in the future and additive manufacturing (AM) technologies advance in both building out of multiple materials and fabricating production parts, the scheduling and process‐planning concepts presented here can be applied to virtually any AM technology.
