Injection Molding

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.

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.

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, 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 2-shot injection molding process creates the first plastic component, and the material molded round it, using a single mold and a 2-shot injection molding machine. 2-shot machines have two-barrels (one for each material) and they have the ability to rotate the mold. The machine injects the first shot material into cavities on one side of the mold, rotates the mold 180 degrees, and then injects the second shot material onto the first shot. The first and second shots occur at the same time. When the mold opens, it ejects the completed parts from the second shot cavities and it rotates the mold to position the first shot for the second shot. This is accomplished in a machine running in an automatic cycle. Because the 2-shot injection molding process is fast and highly repeatable, the shrinkage of the first shot is very consistent and two materials can be molded together with virtually no flash. 2-shot molding is the process of choice when molded-in graphics or other fine details are required. The elimination of the shrinkage variable allows 2-shot molding to produce details impossible to achieve with over-mold injection molding.

Silicon molding services produce molded components made from silicon. Liquid silicone is similar to normal silicone, but has different processing characteristics. It is purchased as a two-part raw material with a grease-like viscosity. Nowadays injection molding of liquid silicon rubber is becoming increasingly important. One reason for this is the increased performance requirements of the finished articles. In addition, more and more producers of rubber parts are seeing benefits in the high level of automation and productivity. Why the preferred use of silicon rubber in injection molding Silastic silicon rubber is a shear material and so its viscosity depends on shear rate. As the shear rate rises the product becomes lower in viscosity. It is this effect that is very favorable for the injection molding process. At the beginning of the injection process the injection speed profile should be programmed in such a way that the volume flow is high enough for the liquid silicon rubber not to begin to vulcanize before the cavity is filled, in order to avoid scorch of the material. Thus liquid silicon rubber is widely used for the process of injection molding.