Plastic Molding Machines

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 plastic 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.

Over-mold injection molding and two-shot injection molding are two distinctly different molding methods even though both are used to combine multiple polymers 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, molding 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.

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.

Composites with polypropylene (PP) and jute fiber were prepared by injection molding technique. One of the important investigations of the research was the effect of fiber attrition, which occurred during the injection molding, on the mechanical performance of jute/PP composites. Contribution of a fiber to strengthening the composite performance is considerably high, when the fiber is sufficiently longer than the critical length. On the other hand, the higher the adhesion between fiber and matrix polymer, the shorter is the critical fiber length. The ideal situation occurs when the fibers in the composite are longer than the critical fiber length and when the adhesion between the fibers and the matrix polymer is high. Generally, hydrophilic jute fibers do not adhere well to PP, which is hydrophobic.