An Injection Mold Design

A competent mold designer must have thorough knowledge of the principles of the mold making as the design of the various parts of the mold depends on the technique adopted for its manufacture. From the manufacturing viewpoint we classify the mold into two parts (i) the cavity and core and (ii) the remainder of the mold is bolster.

The injection mold is an assembly of parts containing within it an ‘impression’ into which plastic materials is injected and cooled. It is the impression which gives the molding its form. The material may be directly injected into the impression through the sprue bush or the molds containing several impressions it may pass from the sprue bush hole through a runner and gate system before entering the impression. The ejector system in a mold is to provide some means by which molded part can be positively ejected from the core has (i) the ejector grid, (ii) the ejector plate assembly and (iii) the ejection techniques.

It is necessary to provide a flow-way in the injection mold to connect the nozzle (of the injection machine) to each impression. This flow- way is termed the feed system. Normally the feed system comprises a sprue, runner and gate.

In injection molding, hot material enters the mold, where it cools rapidly to a temperature at which it solidifies sufficiently to retain the shape of the impression. The temperature of the mold is therefore important as it governs a portion of the overall molding cycle.