Injection molding is an extremely versatile method of producing products. It is one of the preferred methods of making parts because it has multiple advantages over other part molding methods. This manufacturing method is often the preferred option for molding individual thin-walled plastic parts.
Almost any plastic part or component can be made efficiently and accurately with injection molding, from parts for kitchen utensils, electronics, automobiles, medical devices, and other items too numerous to count.
Simple pieces are easily done. But complex parts can also be manufactured quickly using this method, because the high pressures of injection molding force the material to enter every nook and cranny of the tool (mold). This cannot be done efficiently with other casting methods. Because injection molding is in fact a high-pressure casting, that is, the addition of die-casting materials, it is possible to cast a wider range of details in the part design compared to other casting methods. .
Another great advantage over other types of casting methods is their low operating cost during production. Also, typically very little post-production work is required because parts often look very finished when ejected.
The injection molding manufacturing process itself is quite simple. Small plastic granules are put into a hopper. The granules are then crushed and heated in a thick plastic slag. The hot melt slag is fed to a piston that injects the liquid at very high pressure into a metal matrix. The matrix is the negative form of the finished part. As this space fills, the plastic cools and the finished part is ejected and the process is repeated thousands of times a day.
Of course, with all the manufacturing benefits, there are also limitations to injection molding. The main disadvantage of injection molding is the cost of the machinery. The cost could range from $ 7,500 to $ 75,000 and the size of the machine could fit in a 400-square-foot garage. Newer machines cost $ 75.00 to $ 400,000. Part size limitations must also be considered. For example, injection molding equipment can only perform work that conforms to set parameters if the product must be a complete part. Similarly, different designs and materials may limit the wall thickness of the product.
Large cut pieces cannot be molded using this method either. The initial cost to create tools (molds) is very expensive. So even though the cost of production is low, to amortize the cost of the tools, the production of parts must be high. Therefore, injection molding for small productions is often cost prohibitive and the option of more cost-effective methods is eliminated.
However, for prototype work and for short product runs, a cost-effective injection molding process can be used, whereby a two- or multi-part block mold is created from silicone rubber and then injected. a polyurethane casting resin under pressure into the mold with a large plastic hypodermic needle. The resulting casting can have extremely thin walls and the method can be used as a proof of concept before ordering expensive tools.