A boss is a cylindrical protrusion placed on a part’s wall. A boss can have various functions, such as the following:
The embodiment and dimensions of a boss depend on its function. It should fit neighboring or fixation parts and, if applicable, be able to bear loading. However, manufacturability and aesthetics should also be considered: thick sections need to be avoided as these can lead to an increased injection molding cycle time, non-uniform shrinkage, sink marks and molded-in stresses. If the boss is to be used to accommodate self-tapping screws or inserts, the wall section must be controlled to avoid excessive hoop stress in the boss.
General recommendations regarding boss dimensions include the following (see Figure 1):
The strength of a boss doesn’t only have to come from its wall thicknessk, it can also be increased by adding gussets (see Gussets) or by connecting it to a sidewall by adding a rib. In that case:
Figure 1 - Proper boss design.
Figure 2 - Correct positioning of bosses
Figure 3 - Boss Spacing