Plastic injection molding is a cost-effective process for mass-producing consumer products. Plastic pellets are melted and injected into a mold, which cools and hardens the plastic. The process is quick and can be automated. Different types of plastics and molds are used depending on the product and budget.
Plastic injection molding is a popular and cost-effective industrial process for manufacturing a wide range of plastic consumer products. These include knobs, washers, valves, pulleys, gears, power tools, bottle caps, toys, car panels, computer monitors, keyboards, furniture, and so on. These articles are mass-produced using forming machines of various sizes and different specific needs.
The injection molding process was invented by John Wesley Hyatt. In 1868, he produced billiard balls by injecting celluloid into a mold. Later he built a piston-type injection molding machine to facilitate production. Another inventor, James Hendry, improved upon Hyatt’s invention and built a screw injection molding machine in 1946.
Both piston and screw injection molding machines are used in the modern plastics industry. The difference between the two is in how the plastic is transferred to the mold. Screw injection types are more cost effective and are more widely used.
In the plastic molding process, plastic resins are used in pellet or granular form. The choice of the type of plastic depends on the type of product made, its needs and the overall budget. Of the hundreds of plastics available, only a few are safe for consumer use. Some of those used in the plastic injection molding process include polystyrene, polycarbonate, polypropylene, polyethylene, polyamide, polyvinyl chloride, Teflon®, Delrin® and acrylic.
Plastics are not degradable and therefore not environmentally friendly. The plastic injection molding process, however, plays a positive role in reducing waste. The plastics used in the process can be reused as many times as necessary.
Plastic pellets or pellets are poured into the feed hopper of an injection molding machine. The feed hopper is a large container that opens into a heating cylinder. In the heating cylinder, the pellets are subjected to intense heat until the plastic melts.
A plunger or screw then pushes the molten plastic forward through a nozzle into a split mold mold. The mold is the reverse side of the part to be made and can have one or more cavities to make several parts at the same time. Molds can be made of strong and expensive steel or cheaper and less durable aluminum or beryllium alloy.
As with selecting the right type of plastic, the choice of mold metal depends on product, cost, and durability factors. Manufacturers often use a less expensive metal mold for prototype stampings and get stronger, more precisely machined molds as production demand increases.
The molten plastic cools in the mold, hardens and takes the shape of the mold. The mold opens and the part is ejected. It is then ready for packing or is it ready for any other secondary operation. The entire plastic injection molding process is completed in minutes and can be done automatically.
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