injection molding

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Wilbert Plastic Services

In the early days manufacturers came to us for a specific thermoformed or injection molded part or parts for a product they were making. Over the years we noticed that, more and more, they were coming to us for entire subassemblies and more complex parts that might incorporate both thermoformed and injection molded parts.

Based on that experience, and our knowledge of the pressures that manufacturers are under to increase efficiency and reduce cost, it became obvious to us that we needed to provide a wider array of services to help our customers increase their efficiencies, reduce their overall costs and maximize their ROI on each project, part or component. This vision has lead us to add assembly, decorating (in and post mold), reusable packaging, RFID and much more to our capabilities.

We believe that Lower Overall Customer Cost comes from an innovative, total solution made up of customer focused, operational excellence. By combining quality production and secondary services with design expertise, supply chain management, and world class logistics WPS has been able to help our customers find new ways to lower their costs and improve profitability.

Injection Molding is the process of forcing melted thermo plastic into a mold cavity. Once the plastic has cooled, the part can be ejected. The first injection molding machines were built in the 1930's.

There are six major steps in the injection molding process:

Clamping

An injection molding machine consists of three basic parts; the mold, the clamping unit, and

the injection unit or units. The clamping unit holds the halves of the mold under pressure during the injection and cooling.

Injection

During the injection phase, plastic material, usually in the form of pellets, are pulled from a hopper on top of the injection unit. The pellets feed into the cylinder where they are heated until they reach molten form. Within the heating cylinder there is a motorized screw that mixes the molten pellets and forces them to the end of the cylinder. Once enough material has accumulated in front of the screw, the injection process begins. The molten plastic is inserted into the mold through a sprue, while the pressure and speed are controlled by the screw or in some cases a ram.

Dwelling

The dwelling phase consists of a pause in the injection process. The molten plastic has been injected into the mold and the pressure is applied to make sure all mold cavities are filled.

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