RIM vs Thermoforming

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RIM offers

Higher Design Complexity

Greater Accuracy and Repeatability

than Thermoforming
Both of these processes are valuable for producing large-sized parts, but the design flexibility of RIM molding will make it a better and lower cost choice for complex parts.

Design Features

Since thermoforming is a sheet forming process, it cannot produce variable wall thickness without time-consuming, manual gluing of additional pieces to the thermoformed part. 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. Any outside features in a thermoformed part must be bonded on secondary, whereas RIM can incorporate all features into the mold for reduced assembly and lower cost.


Encapsulation cannot be done with the thermoforming process. The temperature needed for RIM molding is low enough to prevent damage to encapsulated materials. Antennas, batteries, metals, electronics, circuits and other features can be insulated to increase mass, strength, burst protection and branding of parts.

Finish & Surfacing

Produced thermoformed parts have acceptable cosmetics, but RIM parts take paint, silk screening and texturing well for improved cosmetic branding.


Both processes are appropriate for small to medium run volumes.

Lead Times

Both processes are appropriate for producing molds for quick turnaround.

Tooling Costs

While both RIM and thermoforming tools require a low up-front cost, tooling costs are typically less for thermoforming. However, for complex parts, the lower unit costs of RIM offset the higher tooling expense. RIM tooling is easier to change and will therefore be more cost-effective if market feedback, or engineering considerations, require that features be modified.

Other Design Benefits

Thermoformed parts are only as strong as their outside shell, and can often “oil can” or blemish from inherent process variation. RIM parts typically hold tighter tolerances than thermoformed parts. Stiffening ribs can be molded into RIM parts to produce high strength products in any size.

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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Industrial Designers

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