Prototype Plastic Mold

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.

High volume injection molding capabilities and precision tool makers in their China Factory allow us to provide quick-turn service on medium to high volume orders, where they build dedicated long-run production molds. The company specializes in high volume plastics injection molding custom plastics jobs. High-end second-op machining is also available. Their PVC and plastic injection molding factories in China manufacture very high quality products that are extremely cost effective. Their warehousing and distribution facility in Austin, Texas also allows them to service custom injection molding projects in Dallas, Houston, San Antonio and other cities across the country very easily.

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 prototype 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.

Injection molding caused a high fiber attrition resulting in an average fiber length of 390 and 350 µ m for formulations with and without coupling agent, respectively. The effect of jute fibers on the tensile and bending strengths was poor when there was no coupling agent. The addition of MAPP as coupling agent improved the composite performance by enhancing the adhesion between jute fibers and PP. The improved adhesion did partially offset plastic the fiber attrition and the associated strength loss that resulted from injection molding. Fiber orientation occurred mainly in the melt-flow direction.