Injection moulding (injection molding in the USA) is a manufacturing process for producing parts by injecting material into a mould. Injection moulding can be performed with a host of materials, including metals, glasses, elastomers, confections, and most commonly thermoplastic and thermosetting polymers. Material for the part is fed into a heated barrel, mixed, and forced into a mould cavity, where it cools and hardens to the configuration of the cavity. After a product is designed, usually by an industrial designer or an engineer, moulds are made by a mouldmaker (or toolmaker) from metal, usually either steel or aluminum, and precision-machined to form the features of the desired part. Injection moulding is widely used for manufacturing a variety of parts, from the smallest components to entire body panels of cars. Advances in 3D printing technology, using photopolymers which do not melt during the injection moulding of some lower temperature thermoplastics, can be used for some simple injection moulds.

Injection molding is used to create many things such as wire spools, packaging, bottle caps, automotive parts and components, Gameboys, pocket combs, some musical instruments (and parts of them), one-piece chairs and small tables, storage containers, mechanical parts (including gears), and most other plastic products available today. Injection molding is the most common modern method of manufacturing parts; it is ideal for producing high volumes of the same object.

If you need your industrial products to be molded, you can contact Baysource Global to help you assess your new project. We’ll identify the best potential solutions for manufacturing success. Our Industrial Products Include:

  • Mechanical components cover the spectrum of all plastics grades, ferrous and non-ferrous metals and cast metal parts.
  • Injection Molded Assemblies; all grades of commodity and engineering grade plastics. Single and multi cavity tools. Single shot, double shot and over molding options.
  • Stamped Assemblies, Progressive, Deep Draw, Transfer and Single Operation pressings available in all grades of ferrous and non-ferrous metals. Spot welding and all painting types available.
  • Cast Components & Assemblies; Pressure casting in Magnesium, Aluminum & Zinc, Investment
  • Casting in steel and stainless steel. CNC machining, sand blasting, polishing, painting and lacquering options available.
  • Projects requiring a high degree of value added engineering and quality control services

The Overmolding Process

Overmolding is a very difficult process, requiring adherence to the very tightest of tolerances. The general concept is quite similar to insert molding, but has more opportunity for mistake and a much smaller margin of error. Some overmolding processes create parts specifications as tight as 0.001”. In that case, the manufacturer needs to utilize the finest high-tech injection molding equipment. Because the materials used shrink as they cool following the molding process, special consideration must be made in the creation of molds.

Five Overmold Considerations For Injection Mold Design

  1. Substrate coring for uniform wall thickness of 2nd shot. It is necessary to maintain a uniform wall thickness in the areas of the substrate that will be filled or covered by the second shot.
  2. Shutoff areas between substrate and 2nd shot. It is often necessary to provide cosmetic “style” lines between the substrate and the over molded part.
  3. Evaluation of material bonding vs. mechanical bonding of dissimilar materials. Adhesion between the substrate and the over molded part is usually necessary to proper fit and function of the final product. Preheating the substrate might be necessary to bring its surface temperature closer to the melt temperature of the over mold, so as to reach optimum bond strength between the two materials.
  4. Obtaining flow between isolated or separate areas of 2nd shot. Often times the over molded part will have isolated or multiple areas needing to be filled.
  5. Ability to support substrate during 2nd shot. The molding process generates hundreds of thousands of pounds of pressure against the cavity walls of the mold.