Plastic injection moulding is by far the most popular method to manufacture plastic parts in the world today. This process is used for everything from inexpensive commercial products, like disposable eating utensils, toys to severe environment, highly stressed technical components, like critical parts for automotive and aerospace industries. You’ll find extensive use of injection molded plastic parts in electronics world for things like enclosures for cell phones, computers, televisions and the like, as well as in the medical world where things like syringe bodies, breathing apparatus and a wide range of other life-saving devices are employed. No other process has come to dominate modern manufacturing as injection plastic molding, and its use increases every year. Recently, critical steering components for General Motors cars and trucks were changed from stamped and machined steel parts to an Injection mold China assembly resulting in a lighter part, at lower cost, quieter, and more reliable.
Injection molding is the process of heating thermoplastic resin to a liquid then shooting it under high pressure into a mold cavity that is the negative image of the desired part, allowing it to freeze, then opening the mold to allow the completed part to be ejected. In most cases features can be built into the mold cavity to give the part everything it will need when finished, so that no other operations are needed once the part comes out of the mold. Textures, or high polishes, markings, screw holes, lens shapes, and any other features needed in the finished part can be built into the mold so the finished part automatically has these features incorporated.
The beauty of plastic molding is that many parts, even millions, can be made in exactly the same way and will come out the same no matter what. Each piece will have the identical features, dimensions, and physical properties. It is the ideal way to make high volumes because of this consistency. Properly maintained, injection mold tools can last decades making millions of parts per year. Properly set-up and controlled, the 20 millionth part will be identical to the first part in every measurable way. No other manufacturing process has the potential to operate at this consistency.
Multiple cavities of each part can be built to the injection molding tool, so that each time the mold opens, you make 8 or 16 or some other multiple of parts for each cycle of the injection moulding machine to really increase the production rate and greatly decrease the cost of making a part. In some cases several different parts, for instance a right and left hand version of an enclosure can be made in a single tool as well to reduce the number of machine cycles required to make multiple parts of an assembly, increasing production and lowering the cost. Injection moulding also offers flexibility not possible with any of the other manufacturing processes.
Injection molding also offers one of the lowest scrap rates of any other manufacturing processes as well. Since no second operations are generally required, no material is cut off and thrown away. It is possible to use a special technique to completely eliminate even the small pathways the plastic flows through to cut the material scrap rate to virtually zero, or often, any Custom plastic molds removed in the process can be reused by pelletizing it and mixing it back into the fresh plastic resin in closely controlled proportions. These capabilities mean a higher percentage of the raw material becomes part of the finished part than in any other process. Injection plastic molding is highly efficient.