Injection Molding -Examples One part is made of polyethylene(聚乙烯).ts length is 80mm.What is the part cavity length? shrinkage of polyethylene 0.025 Dc=Dp+DpS+DpS2=80+80x0.025+80x(0.025) =82.05mm a Shrinkage Injection pressure Compaction time Molding temperature Part thickness Shanghai Jiao Tong University 11
Shanghai Jiao Tong University 11 Injection Molding – Examples n One part is made of polyethylene（聚乙烯）. Its length is 80mm. What is the part cavity length? n shrinkage of polyethylene = 0.025 Dc= Dp+DpS+DpS 2 =80+80x0.025+80x(0.025) 2 =82.05mm n Shrinkage n Injection pressure n Compaction time n Molding temperature n Part thickness
Compression Molding Compression molding is the most widely used process for thermosetting polymers.In this process,a pre-measured amount of material,preheat to some temperature is placed in an open mold cavity.A plug or cover closes the most,and then heat and pressure are applied to cause the polymer to soften,flow to fill out the mold and cure.Curing of thermosetting polymer involves a time dependent chemical reaction. Hydraulic cyclinder Part Heated cavity is Flash charged with a measured quantity of powder or a preform Knockout pin Shanghai Jiao Tong University 12
Shanghai Jiao Tong University 12 Compression Molding Compression molding is the most widely used process for thermosetting polymers. In this process, a pre-measured amount of material, preheat to some temperature is placed in an open mold cavity. A plug or cover closes the most, and then heat and pressure are applied to cause the polymer to soften, flow to fill out the mold and cure. Curing of thermosetting polymer involves a time dependent chemical reaction