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Do You Know The Plastic Injection Molding Process?

Released on Nov. 09, 2021

Plastic Injection Molding

The plastic injection molding process requires six main steps, including plastic injection mold design, plastic injection mold construction, preparation of casting material, plastic mold injection, cooling, and finishing.


Plastic Injection Mold Design

The most critical element in the plastic injection molding process revolves around the formation of the dye or mold. Precision is a critical element in mold design. The mold design process includes the 3D rendering of the mold design as well as mold flow analysis. These aspects of the design process allow designers to predict how the molten material will flow and cool within the mold. The process also allows for the addition of cooling channels within the mold to facilitate uniform, conformal cooling. The use of these design tools helps save time and money in mold design while ensuring more predictable product quality and performance.


Preparation of Polymer Material

Polymer material preparation follows mold creation and placement into the plastic injection-molding machine. Preparation includes heating of the raw material into a molten state. Polymer material usually comes in the form of pellets, fed by a hopper into a large cauldron where they are heated. Various types of materials produce different end-product properties or better facilitate the production process and cooling. Formulation of the exact composition of the raw material is often the result of flow analysis used in the mold design phase.


Materials Used in Plastic Injection Mold Construction

Mold construction material choice is a critical element in plastic injection mold construction. The most common materials used include:

Tool Steel - Favored because it is easy to machine, or tool and holds up well for high volume production

Stainless Steel - Often used in situations where corrosion might cause contamination issues

Aluminum - Is easily formed and lightweight, but does not hold up as well when high volume production is necessary


Plastic Injection Mold Construction

Following mold, design creation is the process of mold construction. Mold construction includes the machining of the metal used to form the mold. Computer numeric control (CNC) allows for automated machining with a much higher degree of accuracy, which is extremely important when working with complicated shapes. This high degree of precision is especially critical where the edges of the two halves of the mold come together, limiting defects and decreasing the amount of time invested in finishing the component.


Plastic Mold Injection

Once heated into a molten state, the raw material is injected into the mold using sufficient pressure to ensure instant flow throughout the interior of the mold. The extreme temperature and pressure used in this stage of the process require adequate mold durability, which is why steel is the most common in-mold construction.


The molten material cools within the mold before the two halves of the mold opens and eject the formed item. Uniform cooling, achieved through the integration of conformal cooling in the design process, ensures characteristic integrity throughout.

Do You Know The Plastic Injection Molding Process?cid=5


The process of finishing usually includes inspection for defects using visual inspection equipment as well as the removal of any rough edges at the mold halves joints. Higher precision and lower tolerances in mold design, and machining, help limit the amount of finishing required.


Plastic Injection OEM

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