Plastics and Injection Molding
Perfecting Plastic Forming Processes
Plastic objects are formed through processes such as compression, transfer, and injection molding. Our E-BI Plastics Specialty Group focuses on perfecting processes like these for each project our customers bring. Just as there are many different types of plastic, there are a variety of processes to mix and shape the material, since different materials must be worked in different ways. There are also various advantages to each method depending on the type of product that is to be produced. Our experts can help determine the best manufacturing route for your plastic part or product.
Processes
Injection Molding
Injection molding is a low-cost way of making thermoplastic parts in large quantities. Intricate parts can be made to close tolerance with no need for second operations. The single-stage reciprocating screw system is commonly used for the injection molding process it prepares material thoroughly for the mold and is general a faster system. Injection molding of thermosets average 25% faster than compression molding, but requires careful attention. Molds can also be costly and larger volumes are often required for economical operation.
Compression Molding
In compression molding, a specific amount of material in a mold cavity is squeezed by a punch or force. The plastic material is heated until softened, and it flows to fill the space between the force and the mold. The mold is kept closed until the formed piece has had time to harden.
Transfer Molding
Transfer molding is a process where material is heated, loaded into a chamber called a pot, and forced through a sprue into mold cavities. With this, closer tolerances and more uniform density can be held since the mold is enclosed, rather than open like in compression molding.
Blow Molding
Most common for hollow parts, in blow molding a die closes around a liquid plastic tube, is poured vertically, as air is forced into the hollow part of the tube. This forces the plastic to the outer part of the mold.
Film Insert Molding
This process is often used with injection molding. A thin film of plastic, either on a reel (IMD) or a die cut piece (IML), is inserted into an injection molding die and integrated with the part through the injection process.
Rotational Molding
Hollow molds are filled with a resin powder and the molds are heated and rotated, allowing the plastic to stick to the walls of the mold and itself. This is most commonly used for hollow, large, and durable parts.
Overmolding
Typically used for parts that need two different types of plastic (soft/rubber and hard) or two different colors (clear and opaque). The first shot (substrate) is usually covered —partially or fully— by the second shot (overmold).
Insert Molding
Used with metal inserts and injection molding, the insert is placed into the mold, then during the injection process the insert is encased by the plastic.
Vacuum Forming
A sheet of plastic is placed over the male die mold. Through heat, the plastic is vacuumed to take the shape of the mold. This is most commonly used for large, simple parts.
Thermoforming
Often used for shell parts, with thermoforming a sheet of plastic is heated and pressed between a male and female die. The plastic takes the shape of the space between the two parts.