When designing a plastic injection mold, the mold designer must consider the type of resin and the resin properties that will be used in the molding process. Thermoplastic engineering resins are the most common type of plastic resin used for the injection molding process. An experienced mold design engineer will take into consideration the various properties of the resin such as elasticity, fatigue strength, shrink rate, resistance to corrosives or high temperatures, and finish such as matte or polished.
Elasticity and Fatigue Strength
The resin used to mold a particular product is chosen due to its properties. For a product that needs a rubber like property with some room to bend or give a little in its application, the print may call for a Thermoplastic Elastomer (TPE) with high elasticity properties. This type of resin is often used in over-molding applications where a vertical press will mold a rubber like finish around an insert, using a shuttle mold design.
The injection mold design engineer must be aware of the elasticity of the resin and any critical areas when designing the tool to meet part specifications.
Shrink Rate of Thermoplastic Resins
The shrink rate of the chosen resin is extremely important, as the cavities would have to account for shrinkage after ejection while still meeting part specification. The cooling rate is also an important property for ejection as the part must be completely solidified prior to ejection.
Resistance to Corrosives or High Temps
Some thermoplastic resins have a higher resistance to corrosives or high temperatures, and a mold designer should be aware of these properties when designing the injection mold, as the finish of the steel could affect part conformance to specifications.
Mold Flow Analysis
Mold Flow Analysis is a computer aided simulation that can be helpful to identify any critical areas in a part design by showing how a material will flow and fill based on its properties. Early identification of these areas can save valuable time in avoiding costly mistakes, and improving lead times.
Knowledge and Experience
Mold Flow Analysis is a valuable tool, but nothing can replace the knowledge of an experienced injection mold designer. Having experience with various thermoplastic resins and their specific properties is valuable knowledge when designing a plastic injection mold.
Michiana Global Mold has been designing and building injection molds for various industries since 1964. We utilize advanced technology combined with skilled journeyman mold makers to construct high quality tools for injection molding with various thermoplastic resins.
Michiana Global Mold is an ISO9001:2015 Registered mold making company with vast experience constructing custom, precision injection molds for various industries. Contact us today for a FREE design consultation with one of our experienced mold design engineers.