It is essential to understand injection molding step by step when choosing it for the custom manufacturing of your product. Production with injection molding provides plastic and elastomeric components in almost every industry, from consumer products, automotive, medical devices, household products, computer products, and robotics to aerospace. 

Choosing the right company for your production determines the quality of your end product, for better or for worse. ARRK North America, Inc.’s knowledgeable team will guide you through the process for the best injection molding solution.

Production made by an injection molding machine


Injection molding involves the high-pressure injection of a polymer into a mold, or tool, where it is shaped. The individual stages of this process are fast, and the injection molding process lasts from 2 seconds to 2 minutes. The steps in the cycle are the mold set and clamping, injection, cooling, ejection, and preparation for the packaging stages.


Before the mold is injected with material, both halves of the tool have to be closed. Next, the halves are placed in an injection molding press where one half can slide. Then, the halves are clamped together tightly in preparation for the injection of thermoplastic material.  The clamping unit presses the halves together throughout the material injection process. Larger machines are required as the size of parts increases and necessitate more clamping power. Therefore, taking longer to close and clamp the mold.


Thermoplastic pellets are fed through a hopper into the injection molding machine. These pellets move towards the mold by the injection unit. The heat surrounding the barrel and the pressure serve to melt the pellets. The injection “shot” is finished when the mold is filled. Injection time is estimated by factors such as injection pressure, power, and shot volume. The injection rate and pressure that can be reached are determined and controlled by the hydraulic system in the machine. Since it is hard to precisely calculate the injection time because the plastic flow is constantly changing and dynamic, you want an experienced team to produce precision parts. 


The cooling process involves the plastic inside the mold beginning to cool after making contact with the interior mold. As the plastic cools when it hardens, it will take the desired shape. At the same time, thermoplastic material shrinks slightly during cooling, so tools are designed with consideration of the shrink factor. Only when the cooling period has elapsed can the mold be opened. It is from the wall thickness of the part and the thermodynamic properties of the plastic that the cooling time can be estimated.


The mold is designed with an ejection system to remove parts. When the tool opens after cooling, the finished component is pushed out. Force is used because material shrinks and sticks to the mold. This ejection process signals the machine to start the cycle again. 


Once the piece is ejected from the mold, it may require post-processing. For injection molding, each tool must contain a gate that allows the hot plastic to enter the cavity. Depending on the type of gate used, there may be a remnant of material that requires trimming. 

Parts are then ready to be packaged. The packaging service can be simple boxing and shipping. Or, if several parts are being manufactured together, they can be grouped in sets or even assembled.

Having ARRK North America, Inc. as a trusted and experienced partner for your project will increase your assurance to meet deadlines and company production goals.

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