Injection Molding Process

Cast kirksite cavities from SLA models can provide excellent rapid tools for prototype and bridge to production injection molding parts. Parts can be molded in two to three weeks in any thermoplastic production resin, this technology has been around for many years, but with the growth of stereolithography and the need for rapid turnaround of plastic parts in the correct production material, the kirksite approach has re-emerged. More complex parts can be made using handloads. Injection molding tapers are important and are best incorporated in the master file. One of the advantages of kirksite aluminum/zinc alloy moulds is the ease of making geometry modifications by either welding or adding inserts. Another main benefit is the ability to mold most materials.

Injection molding is a relatively new way to manufacture parts. It is a fast process and is used to produce large numbers of identical items from high precision engineering components to disposable consumer goods. Injection molding is often used in mass-production and prototyping. It produces such small products as bottle tops, sink plugs, children's toys, containers, model kits, disposable razors and parts of cameras. The process can even mould such large items as dingy hulls and kit car body shell parts. The advantages of injection molding are: high tolerances are repeatable, wide range of materials can be used, low labor costs, minimal scrap losses, little need to finish parts after molding. The disadvantages of injection molding are: expensive equipment investment, running costs may be high, parts must be designed with specific molding consideration.

Injection molding is a common method of producing intricate plastic components in high volume. Injection molds are made from hardened tool steel, although aluminum may be used for some low volume applications of injection molding. Injection molds can vary from simple open-shut injection molds, single cavity injection molds to complex multi-cavity injection molds with moving cores, stepped shut-offs, unscrewing devices. Due to the tonnage used in this high pressure process, proper materials, supports, parting line locks etc. must used to ensure the life of the mold. Cavities may be polished or textured to achieve a desired finish on the injection molded part.

Reaction Injection Molding (RIM) produces parts with intricate detail that are dimensionally stable, chemically resistant, physically tough, and wear resistant. This process is an excellent choice for larger plastic parts produced in short run or low volume production quantities. Considerable design freedom is possible, including thick and thin wall sections that are not good for injection molding, due to the uniform shrink characteristics. Foamed polyurethanes are natural thermal and acoustic insulators. Excellent flowability allows for the encapsulation of a variety of inserts.

Reaction injection molding is used in many industries for many types of parts. While bumpers for vehicles are produced in this process, most applications are for large, complex parts produced in quantities less than 5,000 units. Examples include panels for electrical equipment, enclosures for medical devices, and housings for computer and telecommunications equipment. If you think that your next project may benefit from Reaction Injection Molding, contact the correlative companies to learn the advantages and differences when compared to other plastic molding processes.