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Using Cast Urethanes and 3D printing for Advanced Medical Manufacturing

By Emran Mursalin Stratasys Direct Manufacturing

Two advanced methods get married

When injection molding is cost-prohibitive, medical equipment manufacturers are turning to a marriage of two advanced methods—urethane casting and 3D printing. These two can successfully fill in the gaps for prototyping, bridge production and low-volume production.

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The polyjet 3D printing process used to create a cast urethane mold.

Urethane casting is a low-volume molding manufacturing process that features quick-curing silicone molds instead of hard tooling. The process starts with a master pattern that is covered in high-grade silicone and removed after curing, resulting in a perfect cavity. The cavity in the mold is then injected with polyurethane materials, goes through controlled steps involving vacuum, heat and pressure, to form casts of the original pattern. Most urethane cast molds are good for 20-50 shots.

Through my years of experience with this technology, I’ve seen it used as a perfect way for product development teams to work through iterations. With its shorter mold life and rapid turn-around times, cast urethane is a perfect solution for products that go through yearly redesigns due to aesthetics or test marketing cycles. Urethane casting is an ideal fit for projects like urethane housings and enclosures for medical carts or equipment. These need to meet high-quality standards but don’t need the high volumes typically needed for injection molding.

Stratasys Direct Manufacturing offers the traditional production method with proprietary evolutions, including the use of 3D printing to produce master patterns. 3D printing gives you the freedom to design complex master patterns with holes, organic shapes and channels. It also opens the door to part consolidation in which multiple components can be combined into one-part designs to cut down on the number of molds.

Creating Complex Designs

3D printing makes possible the design freedom for complex casts. Unlike injection molding, urethane casting allows for varying wall thickness and does not require draft. Production with a 3D printed master pattern allows designers to incorporate organic shapes, embossed text and consolidated part designs into a cast.

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A final part made from cast urethane process.

Due to the soft silicone molding process, Stratasys Direct can produce very large parts quickly. Production of medical cart housings and large panels are possible for bigger products. We also provide full finishing and post-processing of casts, including production painting and texture, EMI/RFI shielding and co-molding inserts.

Eliminating Hard Tooling Costs

Due to the quick production of silicone molds, cast urethanes have low overhead tooling costs. At Stratasys Direct, parts can be delivered in as little as seven days. Frequently, engineers will use cast urethanes when they need to develop lower quantities of parts quickly and are unsure about long-term quantities for the market and therefore cannot make significant capital investments in production tooling.

Cast urethanes allow production of parts quarter by quarter, with the added benefit of easy design changes. Speed to market continues to be key for the medical industry, and the improved production time possible with urethane casting allows for early revenue.

Use in Medicine

One great example of using 3D printing and urethane casting together is seen at InTouch Health, a telehealth solutions provider. InTouch Health, along with iRobot, is the creator of RP-VITA, a telemedicine robot that operates remotely on hospital floors. The telemedicine robot’s casings are mainly manufactured with urethane casting and prototyped with 3D printing technology.

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A worker extracting a part from the hardened silicone mold.

“We have five other product lines involving telemedicine robotics,” said Danny Sanchez, an engineer at InTouch Health, “and we have been using cast urethanes from Stratasys Direct Manufacturing for many, many years. We start with SLA 3D printing for prototype parts and move to cast urethanes for lower volume production.”

Once volumes are sufficient, InTouch invests in tooling and injection molding. “For RP-VITA, we’re using a really good UV and chemically resistant material that doesn’t require post-processing,” Sanchez said. “For some of our other divisions, we’ve been using cast urethane production parts for five to seven years.”

Consideration for your next project

With a diverse production material catalogue including plastics exhibiting properties like UL94V-0 flame rating and MR transparency and the benefits of 3D printing in conjunction with urethane casting, I’d recommend trying this unique manufacturing solution. Urethane casting produces applications early in the product development life cycle, such as cosmetic units and assembly line development units, while longer lead time production tooling is produced. Product components can meet industry standards and requirements while engineers and designers wait for tooling to be manufactured.

Emran Mursalin is vice president of conventional manufacturing at Stratasys Direct Manufacturing.

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