RIM vs Thermoplastic Injection

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RIM offers

Lower Tooling Costs

Lower Required Production Volumes

than Thermoplastic Injection
RIM can be a great alternative to achieve the mainstream look of molded parts without the high tooling costs or volumes needed for typical thermoplastic parts.

Design Features

Both processes allow for many features to be incorporated into a mold, but only RIM gives the designer the flexibility to produce parts with significant wall thickness variations – typically from 0.125″ to 1.125″ in the same part. RIM can also produce high strength large parts at a lower cost because mold pressures are significantly lower compared to thermoplastics.


While both processes provide a solution for encapsulation, the low temperature, low pressure RIM process is superior, and also safe for electronics and other material encapsulation.

Finish & Surfacing

Injection molded parts often have better fill characteristics associated with the higher molding pressures; however, RIM parts may require paint and silk screening for a distinctive finish.


RIM is valuable for producing low volumes at a low cost, reducing risk when launching new products, and allowing you to evaluate market success before producing higher quantities. For volumes under 500 per month, RIM often becomes the more cost-effective processing option.

Lead Times

Exothermic uses in-house machining centers to drastically reduce mold build time and create production molds within 4 weeks.

Tooling Costs

Because RIM molds can be machined from aluminum instead of steel, the upfront tooling costs are typically one half or less than that of a comparable thermoplastic mold. This is particularly beneficial when part volume is low or when a part size is large. Since RIM tools are made of aluminum, changes to tooling are also much more cost-effective than changes to thermoplastic steel tools.

Other Design Benefits

The reaction cycles of RIM are measured in minutes, not seconds, allowing for the addition of holes, side action and undercuts without premiums. The stiffness and strength of the polyurethane produced from RIM also eliminates sink marks that can occur in thermoplastic parts.

Though these are some of the main considerations to account for when deciding on a production process, there are many issues to balance when determining the most effective option. Let Exothermic help you uncover the opportunities for success and guide your design concept to meet those process needs.

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