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What is Rapid Injection Molding?

Paul Scott
Paul Scott

Rapid injection molding refers to the process of making injection molds for the prototype, bridging, and short production run parts in less time and a reduced cost than full production molds. The injection molds typically made for prolonged production runs are very expensive and time consuming. In situations where production of injection molded parts requires fast-tracking and initial cost control, inexpensive and quick rapid injection molding techniques can produce molds better suited to low volume production runs.

Injection molding is a production method that delivers low unit costs during production but can be cost intensive and time consuming in its roll-out phase. Molds made for extended production may take several months to produce. This is not always feasible where small numbers of parts are required as prototypes for function and fit testing or marketing tests. In these cases, molds identical to the full production examples regarding design and dimension can be made, although they lack the longevity of the final molds.


Parts manufacturing subject to small final production volumes also benefits from the use of rapid injection molding techniques as the per-unit cost of the final product can be kept within viable limits. Bridging is another area of production that benefits from rapid injection molding; this allows manufacturers to start production while the final molds are being made, thereby "bridging" the gap between prototype and final product. Considering that rapid injection molds may be produced in approximately two to five weeks, these production needs can be met without incurring large peripheral expenses.

Rapid injection molding equipment is usually produced from aluminum using techniques such as rubber plaster molding, rapid prototyping, and CNC machining which allows for very quick production times. Although these molds generally lack the life span or qualities of a final production set, they can produce thousands of parts, are suitable for most materials and colors, and may even be textured. Modern machining techniques also means that rapid injection molding can produce ever increasing levels of complexity and size differences which further expands the list of possible benefits the process offers.

A further benefit of rapid injection molding in the pre-production phase of development is the low cost of geometry or design modification. Should unforeseen issues arise with fit and finish or the general design of the product, the retool losses incurred can generally be kept at a minimum. This sort of mold adjustment involving a final production mold set could have catastrophic financial implications. Rapid injection molding is therefore a highly desirable production method for prototype and short run injection molded plastic products.

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