Plastic injection molding manufactures parts by injecting molten plastic into a mold. The molten plastic is poured into a barrel and then injected into the mold. The process repeats until the desired number of parts has been produced. When the plastic in the mold solidifies, the part is removed. There are two basic categories of plastic:  thermoplastic and thermosetting. Thermoplastic can be remolded and reheated, while thermosetting materials cannot be remolded and reheated. 

In California, plastic injection molding companies produce small individual components and large complex shapes. The high-volume manufacturing process is fast and cost-effective. 

6 Prime Steps for Success in Plastic Injection Molding

Clamping the Mold

The first essential step in injection molding is clamping. Injection molds are generally made in two clamshell-style pieces and are pressed together by a machine press. This process applies pressure to the mold to ensure even plastic distribution. The mold is tightly closed to avoid air pocket formations.  


The molten plastic is injected into the mold under high pressure to ensure the plastic is forced into all the cavities and there are no air pockets. If the pressure is too low, the plastic will not fill the mold correctly. 

Plastic manufacturers in California use the latest technology to ensure quality products. The correct pressure is used according to the plastic and mold requirements.


After the plastic is injected, it cools and solidifies in the mold. The cooling time will depend on the type of plastic and mold. The longer the part is left in the mold, the higher the quality. However, if the part is left in the mold too long, it will become brittle, and breakage could occur. 

Custom injection molding companies have the knowledge and experience to cool the plastic to produce high-quality parts.

Reloading the Barrel

Once the part is cooled and removed from the mold, the next step is reloading the barrel. This process is repeated until the desired number of parts has been produced.

The barrel must be filled with fresh plastic after each cycle. If the barrel is not refilled, the quality of the parts will decline. It is critical the barrel is appropriately heated to melt the plastic.  

Ejecting the Part

The final step in the process is ejecting the part. After the part has been cooled and solidified, it is removed from the mold by ejector pins. The part is pushed into a bin or onto a conveyor belt. The ejector pins must be aligned to eject the part from the mold correctly. If the part is not removed correctly, it could damage the mold.

Any waste that is created during the injection molding process is recycled. It helps to preserve resources and reduce costs. California’s plastic molding companies are committed to sustainability and use the latest technology to reduce waste.

Quality Control & Finishing

The quality control check assures the parts meet the specifications. If the component does not meet the specifications, it is rejected.  

Finishing is essential to ensure that the part looks professional and includes painting, plating, and stamping.  

The injection molding process manufactures high-quality parts and requires expertise and experience. In California, plastic manufacturers use the latest technology to reduce waste and produce high-quality parts. A quality plastic injection molding company can help determine how plastic injection molding can benefit your company.

Universal plastic mold (UPM) offers consulting, management, assembly, distribution, and shipping services in California. Search injection molding near me and find the perfect partner for your business.