Injection Molding Machines

Injection molding machines are used to manufacture parts for many different types of businesses. Injection molding is commonly used to make electronic, automotive, aerospace, medical, engineering, and telecommunications parts. For large orders of standard parts, clients can use the services of injection molding companies. For small custom orders, companies are available that can create injection molded parts by hand.

Options for Injection Molding Materials

Injection molded parts can be made from metal, rubber, or plastic. Metal is the most desirable type of material for this process because it is extremely high in strength, has thermal conductivity, corrosion resistance, great magnetic permeability, and retains its strength when subjected to high temperatures. However, it can be very expensive to work with. Therefore, metal is typically only used for specialized parts or custom orders.

Plastic is the most common choice of material for injection molding because it is durable, adaptable, and comparatively low in cost. Clear plastics such as polystyrene, polycarbonate, ABS, PVC, polyester, polyurethane, acrylic, and nylon are commonly used to create plastic parts. Rubber is slightly more expensive and offers many of the same benefits as plastic. The most desirable types of rubber for injection molding are silicone rubber and neoprene rubber. These materials are very easy to work with and offer benefits that cannot be found with organic rubbers.

Injection Molding Processes

Plastic or rubber injection molding is also known as liquid injection molding. With liquid injection molding, rubber or plastic pellets are initially melted into a liquid. The liquid is then inserted into a specified mold. The part can be removed from the mold after it has cooled and hardened.

Metal injection molding is different from liquid injection molding because the metal is not melted into a liquid initially. Rather, fine metal powder is combined with a small amount of binder and then inserted into a mold. While the powder rests inside, the mold is exposed to extremely high temperatures. The heat causes the metal to shrink and to harden. As the heat increases, pores in the metal surface will decrease in size and the part will become strong.

Design Methods for Injection Molding

Mold design is crucial in the process of injection molding. The wrong design can produce weak and uneven surfaces on parts. Mold designs should allow for easy removal of parts, otherwise parts may suffer from harmful stresses and may not last as long. Using angles in the design will help with removing parts from their molds. Using rounded corners that will not get stuck in molds is also a helpful method.

Wall thickness is another concern for injection molding. Companies who are looking to save money should make sure that walls are as thin as possible for parts. By using thin walls, parts will be lighter and will cool more rapidly. Therefore, cycle time, weight, and material costs will be minimized. Walls should also be uniform in thickness. Thick sections will take longer to cool than thin sections. Therefore, warping, twisting, or cracking could occur with uneven walls.

Custom Injection Molding

Custom injection molding is desirable for clients who need a small amount of parts with exact measurements. Shapes that are commonly customized include molded inserts, seals, diaphragms, bushings, extrusions, and o-rings. Depending on the company used in the process, custom orders can be produced by hand or with injection molding machines. With custom orders, clients will need to customize their own mold designs and decide on which materials to use for their custom parts.