Plastic insert molding refers to the process of using a hot plastic material (polymer) and cold plastic material (polyimide) in combination to insert molding material into a mold, thus creating a strong, solid insert. The hot material (polymer) can be used to create the entire piece, while the cold material (polyimide) can be used to complete the form with cutouts, corners, domes, and other features. In either case, insert molding techniques are generally applied to plastic parts that require molding around certain shapes or sizes. This article describes the processes used to complete different types of insert molding jobs.
Most commonly seen uses of insert molding are in the aerospace and defense industry where solid pieces are needed for certain components, such as missile parts, airplane seats, and safety harnesses, or aircraft fuel tanks. Plastic components in these cases are typically created through a combination of hot air generation and cold air generation via injection into a mold from a high pressure canister. Overmolding is common in this process because the hot material allows for more surface area and more molding options. Cold molding typically occurs with thinner plastic materials where the material does not get as thick of an overloaded shape. With most polymer based products however, the entire product can be overloaded using only one type of process – depending on the desired result and the type of molds being used.
Another popular application of insert molding is in the production of plastic parts for hardware like car doors. With hinges, knobs, and handles, car door panels, and louvers are often made of plastic resin. These products have to be carefully built so that they can withstand the harsh environment during transportation. Parts made using these methods can experience wear and tear faster than parts manufactured from other materials, which limits their component reliability. The addition of insert molding can improve the component reliability of these parts because of the additional support provided by the casting.
There are also applications where overloading is used because of the fastener requirements of medical devices. The requirements for holding together a gasket in the nose of a medical device can vary depending on the device itself. In cases where the device needs to withstand pressure because of the presence of a diaphragm, the insert molding can be helpful because of its ability to expand into the exact form required. The material can be shaped without a large amount of distortion and without any gaps or holes. This improves the connection between the device and the diaphragm or other barrier. Other applications include areas where mechanical stability is critical for various parts, such as those that hold together the internal components of an air conditioner or other heating system.
Insert molding is also important in the manufacture of rubber materials. For example, a rubber insert molding might be used to create a layer of protective insulation around a motor in order to keep the motor and its components from becoming damaged by cold weather. The same thing can be said for other rubber components, such as those that are used to make up an air-conditioning system or a pump. A flexible rubber insert molding can be formed to fit the exact shape of these parts so that they will have no gaps or holes.
Another important application of insert molding processes is creating image sources for electronic parts. The process is particularly useful in building thin metal layers, such as those that go on top of computer motherboards. These thin layers can help keep electronic parts from becoming contaminated with dust or any other matter that might degrade the device’s performance. Moldings can be made to form an image of the motherboard so that it can be viewed when placed inside a computer case.