Plastic injection molding is a type of manufacturing that involves the process of pressing liquid plastic into a mold to form it into a shape. This allows for more intricate designs than would be possible with other methods of plastic production, such as CNC machining. It also cuts down on the number of steps required to make a part, further reducing production time and cost. In addition, it allows for the use of various additives that can help improve a product’s strength and performance.
The most popular types of plastic used in plastic injection molding are thermoplastics and thermosets. Both of these can be molded into a variety of shapes and are highly versatile. They are also less expensive than other types of materials to manufacture with, such as metals. This makes them a good choice for making large volumes of parts that need to be produced quickly and cheaply.
Injection molding can be used to produce a wide variety of products and parts, from simple containers to complex machines. In fact, it is one of the most commonly used manufacturing techniques in the world. It is often used to make components that need to be resistant to high temperatures or chemicals, such as automotive parts and household appliances. It can also be used to make products that require a high level of strength, such as furniture and medical equipment.
To begin the injection molding process, raw plastic pellets are fed through a hopper into a barrel that has a reciprocating screw inside. The screw is designed to heat the pellets and mix them to a molten state. The screw also reduces the size of the molecules, allowing the polymers to flow more easily. The screw can also serve as an injection plunger, injecting the molten plastic into a mold cavity. Older injection molding machines often used a combination of this type of mechanism and a nozzle to inject the plastic into a mold.
Once the plastic has been heated and melted, it is forced through a nozzle into the mold cavity by a piston or hydraulic cylinder in the injection system. It flows into the mold cavity through a sprue that is often shaped with perpendicular features called gates. These can be seen on the molded parts as small rough patches or dimple-like features known as gate vestiges.
A problem that can occur during injection molding is the formation of air pockets in the molded part. These can be caused by a poor injection system, which may not compress the molten plastic enough. It can also be the result of a too-high injection pressure, which will cause the plastic to disintegrate and separate from itself rather than being injected into a well-formed part.
Another common injection molding problem is uneven cooling of the molded part. This can happen if the gate is located in a thinner area of the mold, which causes the material to cool more quickly than the rest of the part. This can lead to warping and surface flaws in the resulting product.