When it comes to Plastic Injection Moulds, choosing the right materials matters

Injection molding is a process that involves heating plastic resin pellets and forcing the melted plastic into a mold cavity. The tooling for this type of production is expensive and the process requires months to complete.

The chosen thermoplastics start as raw pellets which are fed into the hopper of the machine through heated zones on the reciprocating screw. The melting point of the material is reduced by the heat and compression of the screw.

Material Selection

When it comes to Plastic Injection Moulds, choosing the right materials matters. This is because the material must be able to withstand the high pressures applied to it during the injection process. It must also have good resistance to chemical, abrasion and water resistance.

Acrylic (methyl methacrylate) is an example of a plastic resin that combines good mechanical strength with a clear, see-through appearance. It is often used for decorative showcases and protective casings for solar panels. However, it isn’t resistant to oil and grease, which can affect its clarity.

Nylon is an excellent choice for products that require high impact, abrasion and UV resistance. It is available in several grades and trade names, including Nylon 11 which has high dimensional stability, Nylon 12 which has low water absorption, Nylon 46 for high operating temperatures and Nylon 66 that resists acids used in chemical processing. This plastic can also be molded with glass fibers for improved stiffness and strength.

Designing the Part

Once the correct thermoplastic has been selected it is time to start designing the injection molded part. Injection molding allows manufacturers to produce parts with complex geometry that would be difficult or impossible to make with other methods. This is due to the fact that the plastic can be injected into a split-die mold which forms the final shape.

Injection molded parts have to be designed with consideration for DFM (Design for Manufacturing) principles. This will improve quality and reduce cycle times. These include avoiding thick sections of the component which require coring or ribbing, keeping radii and thickness transitions as consistent as possible and considering the fact that different polymers behave differently and will flow through or cool at different rates.

It is also important to consider the fact that changes to steel tooling are costly and time consuming. This is especially true when high numbers of parts are being produced. For this reason, it is important to design the part correctly before starting production of the steel mold.

Selecting the Mold

Injection molding is a process that involves combining the right thermoplastics and molds to produce a plastic part. There are hundreds of different types of thermoplastics that impart a wide range of end-use properties.

It is important to select the proper material for injection molding as it can save you a lot of money by avoiding costly mistakes and reducing production time. The right material selection is also critical in order to meet product specifications and quality standards.

When selecting the proper plastic, it is important to consider its hardness and flexibility. This is a vital factor because different applications require specific levels of hardness and flexibility.

The plastic must be able to withstand the injection molding cycle, which includes applying clamping pressure to hold the mold halves together during the injection and dwelling step. If the proper clamping pressure is not applied, it could result in leaking molten plastic or crushed mold vents. This can cause costly damage to the machine and the tooling.

Injection Process

Injection molding requires multiple types of auxiliary equipment before, during and after the process to keep the resin free of moisture and contamination and at the proper temperature for mold injection. This includes equipment to store, move and dry the plastic resins and provide consistent airflow throughout the molding area.

Raw plastic resin pellets are fed into the hopper of the injection machine where they are heated and melted by heating jackets on the reciprocating screw. Then the molten material is injected into the mold through channels called sprue and runner that connect to the injection nozzle. As the injected material cools, it solidifies into the shape of the molded part.

Once the molded part has been cooled and ejected from the clamping unit, the sprue, runner and injection nozzle are cut away. The trimmed scrap plastic is recycled and reground to be used in the injection molding process again.