Continuing our exploration of the right molding process for part design (“Determining the Right Molding Process for Part Design”), this blog entry considers RIM Molding vs. Thermoform Molding
Both of these processes are valuable for producing large-sized parts, but the design flexibility of RIM molding will make it a better choice for complex parts. Since thermoforming is a sheet forming process, it cannot produce variable wall thickness or internal details
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 of up to .125” to 1.125” in the same part. Any inside features in a thermoformed part must be bonded on secondary, whereas RIM can incorporate all features into the mold for reduced assembly and lower unit cost.
The temperature needed for RIM molding is low enough to prevent damage to encapsulated materials. Antennas, metals, electronics, circuits and other features can be insulated to increase mass, strength, burst protection and branding of parts. Encapsulation cannot be done with the thermoforming process. Produced thermoformed parts have the quality finish of the sheet material, but RIM parts take paint, silk screening and texture well for improved cosmetics.
Both processes are appropriate for small run volumes and for producing molds for quick turnaround. RIM and thermoforming tools also both require a low up-front cost, but RIM tools are easier to change and will therefore be more cost-effective if market feedback shows that part features should be modified.
Other Design Considerations: Thermoformed parts are only as strong as their outside shell, and can often “tin 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.
Read more about it in our white paper, “Determining the Right Molding Process for Part Design. How RIM Molding Advantages Compare with Traditional Production Technologies”.
Download the paper at (www.exothermic.com).