Designing custom plastic components can leave the engineer with many feature options that can provide different functions and capabilities. This blog will discuss gussets and ribs for supporting bosses. Providing functionality and structural integrity for the plastic injection molded component.
Boss Design for Plastic Molded Parts
Functionality of a plastic component is virtually endless. One common situation is when a customer desires a place for a screw to hold two or more plastic parts together. This can be a common demand in housings and other components of the sort. An engineer will design in a boss to appropriate with the other piece to fit in conjunction. Depending on the placement of the boss, he will likely choose to add a support system to aide in the structural integrity.
Common sense might suggest that anchoring a boss using a primary wall would provide the boss with more support. However, with plastic injection molding one has to be careful about the thickness of the plastic. Adding a boss without the appropriate rib design or gusset can cause uneven cooling, sink, and warpage to occur. The best solutions include adding a rib design feature or gussets to the boss for support.
Ribs & Gussets
On the left of the example above, the bosses are reinforced via the ribs that attach to the primary wall. To the right, the boss is reinforced by the gussets. We spoke previously of the design tips for adding rib features to a design (link to rib design blog). Gussets are a more “lone standing” option that also provide added security.
Supporting the Boss using Gussets
Gussets, like ribbing, support the boss. Bosses are attached to the nominal wall for mechanical assembly features. Without the proper design and reinforcement they are more likely to crack. Some common tips are to avoid sharp edges. As you will see, many gussets are designed more like a triangle than a square, eliminating the weakness that would come from the corner of a square-like plastic protrusion. Additionally, having the appropriate wall thickness is imperative in improved structural integrity. This will vary depending on the material used. Thus, picking the right material will be based on the function of the part, the needed wall width, and the structural capacity of the material for that wall width. Expert engineers, such as at Nylacarb, have extensive experience in understanding plastic molding and material choice, as well as the best design options.