NEW PHOTOPOLYMER MATERIAL FROM DSM SOMOS® PROVIDES COST AND PERFORMANCE BENEFITS VERSUS TRADITIONAL POLYURETHANE MODEL MAKING
30 September 2002 - DSM Somos

The results suggest that parts manufactured using additive manufacturing processes such as SL are often the most economical solution for a project’s goals. The economics of prototyping have significantly changed over the past couple years with the introduction of new material advancements which have expanded the application and range of additive manufacturing technologies.

General Pattern’s SL material of choice was Somos® Raven™ 7620, a clear, amber liquid photopolymer. The dark color created through photo-imaging creates a tinted or smoked appearance to SL parts. In addition to its unique appearance, Somos® 7620 also offers high humidity resistance as well as tough, general purpose properties.

General Pattern had yet another motivation for wanting to test Somos® Raven™. According to General Pattern’s North American General Manager, Denny Reiland: “We operate stereolithography equipment that is truly on the cutting and bleeding edge of technical capabilities. We saw Raven™ as being a leap ahead in materials technology and very compatible with our processes. Beyond that, however, we were very pleased with the price point and viewed this as a great opportunity to compare a new photopolymer material against RTV/Polyurethane modeling.”

Traditionally, the procedure for prototyping from a urethane casting requires the following steps to obtain a master pattern:

1.) Approximately 1.5 hours to gate and vent the part and build a pattern box.
2.) An additional 24 hours for the silicone mold to cure.
3.) Within an 8 hour workday it is possible to produce 3-5 castings with regular urethanes or 10-16 parts with quick setting urethanes
4.) The general rule of thumb is that an additional RTV tool should be built if quantities exceed 50 pieces.

With regard to General Pattern’s specific register assembly application there were thirteen individual components: a housing, damper arm, vane link, thumbwheel, damper door, thumbwheel busing, barrel bushing, barrel, and five vanes.

In total, the cost of modeling and molding enough pieces for ten complete register assemblies using the RTV/Polyurethane method was $10,300 and required a turnaround time of ten days.

By way of processing comparison, Somos® Raven™ 7620 photopolymer is used in the solid imaging process to build three-dimensional parts and is intended to be used with a variety of layer thicknesses. After part formation via UV light exposure in a stereolithography machine --- in this instance an SLA 5000 from 3D Systems – the excess resin was removed by rinsing with a solvent (propylene carbonate or tripropylene glycol monomethylethers are acceptable), followed by a rinse in isopropyl alcohol (IPA or isopropanol). The part was then post-cured by UV fluorescent light.

In total, the cost of modeling and molding enough pieces for ten complete register assemblies using Somos® Raven™ 7620 was $5,295 – nearly half the cost of RTV/Polyurethane. Of equal importance, the required parts were produced in only three days – more than three times quicker than RTV/Polyurethane modeling and molding.

“It is clear to us, says General Pattern’s Denny Reiland,” that designers, engineers and OEM’s all should be alert to the emergence of new materials that offer the potential of improving cost and turnaround versus traditional methods of modeling and prototyping. We have no doubt but that such advancements in materials will continue to positively impact economic cycles of product development.”

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