Bosses and Studs

Factors—part shrinkage, dimensional tolerances, warpage, drafts and undercuts, location of holes, fillets and radii to promote resin flow and reduce stress concentration, wall thickness, weld and parting lines to improve appearance and avoid areas of high stress concentration, and the introduction of ribs, bosses and studs, and metal inserts to improve strength—are treated. Recommended safety factors as a function of load are given. 

A huh ban ht defined as a holfowed-out stud (or boss). All rules giYen for studs (height, draft angles, corner radii, size or diameter to be compatible with available ejectors and/or ejector sleeves) apply for hubs. 

Bosses are sometimes required to acconunodate screws, studs, pins, etc. and, if designed with a section thicker than an adjacent thin wall, will also cause unequal shrinkage. This can be minimised by making the variation in thickness as small and as gradual as conditions permit... 

Bosses are used to reinforce holes in the part and to provide mounting locations. Solid bosses are called studs. Bosses must be molded with rounded corners and adequate fillet radii. They usually are located in a corner or juncture of two or more surfaces to minimize the effects of sinking. The problem of shrink marks is lessened with GRTP because of their reduced shrinkage. It is generally recommended that the height of the boss be limited to twice its diameter. Vertical surfaces should have at least a 1 deg draft per side. Recommended designs are shown in Fig. 6-5. 

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