Creating Prototypes In Injection Molding Material Just as with overall product design, mold design is another opportunity to prevent defects during the injection molding process. We have previously written blogs on the Top 10 Injection Molding Defects and Avoiding Mistakes in Injection Molding, but here are some examples of how poor mold design can be a costly mistake: 

Not designing the proper draft: This refers to the angle at which the finished product is ejected from the mold. An insufficient draft can lead to ejection problems, costing significant time and money. Improperly placed or sized gates: Gates are the openings in a mold through which thermoset or thermoplastic material is injected. Each will leave a vestige (scar), which can create aesthetic or functional problems if not properly placed. 

When a product has been properly designed, approved, and die cast, it’s time to start the actual manufacturing! Here are the basics of the injection molding process. 



Thermoset or thermoplastic material in granular form is fed through a hopper into a heating barrel. (Learn more about the differences between plastics in our PLASTICS course.) The plastic is heated to a predetermined temperature and driven by a large screw through the gate(s) and into the mold. Once the mold is filled, the screw will remain in place to apply appropriate pressure for the duration of a predetermined cooling time. Upon reaching this point, the screw is withdrawn, the mold opened, and the part ejected. Gates will either shear off automatically or be manually removed. This cycle will repeat over and over, and can be used to create hundreds of thousands of parts in a relatively short amount of time.

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