Design Of Residual Material Retaining And Ejecting Elements

The design of mold parts always depends on the operation of the workpiece, hence only general constructions of type can be shown. When the temperature drips the state of plastic material changes from flow to solid. The purpose of ejecting elements design is to remove the solidified plastic workpiece and residual material from the forming pin, sprue bush and the runner when the is opened, and to eject it in a simple way when the ejector is actuated.

Fig 6.7 shows those constructions which allow the removal and ejection from the mold of the plastics residuals solidified in the distribution runners. Usually, the residual material separates from stationary mold or sprue bush firstly, and than the residual material is ejected from runner system and cold-slug well. The cold-slug well do not only collects cold front polymer, but also pulls sprue out off the sprue bush as the mold opened. For this purpose, The cold slug wells are designed in different shape. Fig. 6.7a shows "Z puller construction, Fig. 6. 7b reverse taper puller, Fig. 6.7c ring puller,Fig.6.7 d sphericity puller.