The shelves must be injection molded and can be single parts or assemblies, however using multiple components when one part will due is almost always bad practice. Of course, there may be cases when multiple part assemblies perform so much better in use that such a design is warranted. A one piece shelf is not a strict requirement if a different design can be justified. Maximum part size is determined by mold plate size and machine shot volume size. Maximum part size based on mold plate size is 200 mm x 100 mm x 10 mm thick.
Maximum size based on volume of melt available is left to be determined as a course activity.
Maximum shelf thickness will depend on the structure design and the availability of milling cutters which can be used to produce the mold, ie., the possible depth of slots in the mold. A test fixture will have to be designed for evaluating the products produced by each group. Shelf size, support hole diameter and spacing and maximum part thickness should be set. Looking at available products is useful for design of both parts and manufacturing processes. The DuraShelve design comes in two models both with four shelves.