Wednesday, April 8, 2015

Discover How The Process Of Plastic Injection Molding Works

By Genevive B. Mata


The process of manufacturing plastic components varies according to the type of part being made. Most parts of this sort are made by a technique known as plastic injection molding. Quality production depends on understanding this process and how it can be adjusted to create components which possess the desired features for their application.

Items made using this technique include bottles, containers, toys, automotive parts, to name a few. The main advantages of manufacturing components in this manner are that it minimizes waste, offers high precision, a wide range of materials can be used for it, it keeps labor costs down, and above all, allows many items to be made at once.

Plastic polymers suitable for molding, mostly fall into one of the following groups; thermosets, elastomers, and thermoplastics. The chemical composition of each polymer blend has different properties which give the manufacturer a large selection. Polymer types are matched to the strength required and intended use of the product.

The equipment involved in this process includes a press, or injection molding machine, and molds. A press consists of a hopper, plunger, and heating unit. These machines are rated by tonnage, which refers to the tons of clamping force exerted to keep the molds closed when in use. Molds can be made from a variety of metals, and consist of hollow shells in the shape of components being made.

First, solid plastic is dropped into the machine's hopper, pushed further in by the plunger, then heated and melted, forced into a nozzle, injected through the gate into the mold, allowed to set using a constant temperature and pressure, then cooled and ejected. Many manufacturing defects are the result of undue stresses on the plastic parts being molded. With some careful planning, molded components can be designed in a way that minimizes structural stress, resulting in fewer defects.

Molds have openings known as gates, which vary in design, location, and size according to the components being produced. These gates are the site where the molten plastic is injected into the mold cavity. Manufacturers must also consider the wall thickness of the molded parts, and strive to make them as thin as possible since this helping speed up the cooling cycle and uses materials efficiently.

If something other than a smooth surface is desired for a molded object, a process known as texturing is implemented. Patterns are added to the surface of the part to give it a particular appearance. Besides serving an aesthetic purpose, this technique can also be useful in a practical sense for disguising minor flaws and to minimize the effects of friction over time.




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