Entry-Level Crossbow Design

The project sponsor, a crossbow manufacturer, asked the team to design a new entry-level crossbow made 80 percent from pre-existing parts. The sponsor also specified use of its injection-molding plant to use up spare capacity and to create a carbon-fiber-reinforced thermoplastic component. Design focused on plastic part design and mold capability restrictions to ensure that designed parts could be made at the sponsor’s production facility. Injection molding limitations required the team to research methods that would allow multiple pieces to be connected while maintaining the structural integrity of the bow. One of the difficulties with injection molding, especially with a carbon fiber material, is that a relatively uniform thickness is required throughout the design. This required the insertion of coring and ribbing features to the design to reduce the range between maximum and minimum thicknesses. The resulting crossbow is lighter in weight with a better center of gravity – that is, closer to the trigger – than the previous model.