Plastic Molding Factories In China

Thermoplastic injection molding is the most widely used of all plastic processing methods. The injection molding machine reduces pelletized raw material and colorants into a hot liquid. This "melt" is forced into a cooled mold under tremendous pressure. After the material solidifies, the mold is unclamped and a finished part is ejected. Injection molding offers the lowest piece prices available, but tooling prices are generally the highest. Thermoset injection molding is similar to thermoplastic injection molding except that uncured thermoset resins are mixed, injected, and held in the mold until cured. As with thermoplastic molding, the price per piece can be low, but the tooling prices are generally very high.

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.

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 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.