When a specific design requires combining multiple materials into one finished part, the cost-effective process known as insert molding may be the solution you need.
With Insert molding, a plastic part is formed or molded directly over or around metal or plastic components, resulting in a single piece assembly. A typical example is a plastic handle molded over a metal screwdriver shaft. This value-added molding operation eliminates the need for a costly additional assembly process.
The process was originally developed to place threaded inserts in molded parts, and to form the plug around the prongs on the ends of electrical cords. It was found that molding directly over the metal parts saves time and money by eliminating an assembly step. Today, there are few design limitations or restrictions on material combinations.
A variety of inserts can be molded into a product during processing, they include tubes, frames, stamped components, machine fasteners and castings. The insert is completely encapsulated by the molded material and will maintain the integrity of a hollow product.
Most inserts are made from metals, usually brass, which is a harder and more durable material than most plastics. In threaded inserts, the higher tensile strength of metal is the main reason for the specification of an insert.
Where a higher strength than the base plastic material is required a metal screw in type insert is used. Often the application of this type of insert permits a metal screw / bolt to be repeatedly unscrewed.
Where a component assembly calls for plastic mouldings of differing properties of plastics, or where it would be uneconomic to complicate the moulding tool, a separate injection moulding is used as an insert.
By the insertion within the moulding process of metal inserts of specialist metals (Brass and Gunmetal etc) a post moulding assembly is dispensed with. Additional benefits are a strong key to the base plastic.
This is a term used where larger pieces of press tooled metal plates are used as an insert within an injection-moulding tool. By a series of both runner forms and hot tip feed devices, plastic materials are fed to multiples of plastic over-mouldings or "inserts" which are mechanically bound to the press tooled metal plate.
Applications include VCR and Camera chassis plates, which require the rigidity and dimension stability of a metal plate, but also demand the flexible and excellent frictional properties of plastic materials.