Abstract: Taking the design of injection molds for 45 ° elbow pipe fitting with 8，4， and 2 cavities as the examples, described the number and arrangement of parts in one mold, the structural characteristics and action step of the mold were explored. The best design was found to be: for small size parts, using vertically arranged angle guide pillars; for large size parts, using horizontally arranged sleeve corepulling structure.

Key words: 45 °elbow pipe fitting, injection mould, injection molding machine, pull out core by slide, injection molding, action step