Calculating Plastic Mold Shrinkage

The Plastic injection molding machine has two parts: the injection unit which melts the plastic and injects the plastic into the mold, and the clamping unit which holds the mold. The injection molding unit clamps the mold in a closed position during injection, opens the mold after cooling, and ejects the finished part. Injection molding's efficiency varies by the number of parts you plan to produce. For a small quantity, such as 10 parts, it may be less expensive to simply machine the desired part utilizing a milling machine. On the other hand, if you desire several thousand parts, injection molding is ideal. When you submit your order calculating for an injection molding part, the websites will assign staff plastic to help evaluate the most appropriate mold material which will vary by part tolerance and number of units anticipated.

Over-mold injection molding and two-shot injection molding are two distinctly different molding methods even though both are used to combine multiple polymers mold into a single part. Because of this similarity, the two are often confused or misapplied by the design engineer. The more finite capabilities of these two molding methods differ as much as their required tooling, machines and often, the resulting part cost. Choosing the right method can be a critical factor in achieving targeted features, cost and time-to-market. Both methods can be used to create the soft-touch products popular in today's marketplace. However, both methods can be applied to other applications where multiple polymers must be combined into a single part. Over-mold injection molding is used for parts that do not require fine detail and can absorb the higher cost of machine time and labor. 2-shot injection molding is reserved for parts requiring fine detail and low part cost.

The wonderful thing about plastic injection molding is the low cost of the parts being produced when you need a large volume of parts. The downside is the cost of injection molding tooling. The toolings, or the molds, range in price anywhere from $2000 for a simple one, to over a hundred thousand dollars for a big and complex injection mold. The way the injection molders figured out how much to charge per part was to weigh the part complete with runner to determine how much plastic resin is used for each part. The size of the part determines what size injection molding machine must be used, and how big the mold is etc.

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.

The ability to reverse engineer existing molds and molded parts allows us to build new and improved custom tooling for the customers. Digital data files and computerized machining are used almost exclusively for tooling of plastic injection molded custom molds. Computerized plastic injection molding machines in China are used almost exclusively for production. For plastic injection molding in China aluminum short-run rapid prototype molds are faster and are an economical solution for customers needing shrinkage to prove out new part and product designs prior to production tooling. The company specializes in plastic injection molding in China to produce a wide variety of products from high-tech parts with very tight tolerances to children's toys and entrepreneur's inventions. Some examples of these products are pictured to the right.