Medical Designers Save Time, Parts With Software

HIGH STRESS: The sensor in Tensys’ new blood-pressure
monitor floats within a rigid frame attached to a serpentine arm designed
to flex. Engineers used SolidWorks and COSMOSWORKS to design the arm and
see how it would perform under real-world flexing, saving prototypes.

“Faster, cheaper, better” is a phrase that may have its genesis in the
aerospace industry, but it has launched breakthrough designs in other industries
as well. Case in point: the medical industry, where device manufacturers have
used CAD and FEA to give flight to new design ideas while slashing
product-development time.

Two recent examples, one in the U.S. and one in the U.K., show the improvements and time/cost savings engineers have realized from their use of engineering software.

In Camberly, U.K., the design team at reseller Williams Medical Supplies set up a new technical development department to design medical products and settled on Solid Edge (UGS) as its core design tool. “Our aim is to take a routine surgical instrument and bring something new to the design that will provide significant benefit,” says Robert Steele, technical development director. Among their projects: the Opmaster Series 4 surgery operating table. The enhanced design allows a patient to be examined, operated on, and recover on the same table.

Using Solid Edge, the team modeled parts and ran collision and interference analyses and motion simulation. “We were able to sit with sales and marketing during the initial design stage and get feedback,” says Steele. “Engineers don’t always get it right, but with the software we could rehearse the design and minimize the risk of getting it wrong.”

The result was a major time savings, largely the result of not doing many prototypes. “In fact, we were almost able to dispense with the prototyping phase and go straight to manufacturing,” Steele asserts.

Working with different software and on a vastly different product line, engineers at San Diego-based Tensys Medical, Inc. had similar results.

Using SolidWorks for CAD and COSMOSWorks for FEA (both from Dassault Systemes, Inc.) the engineering team developed the T-Line[R] Tensymeter, a non-invasive arterial blood-pressure management system for use in surgery. Their goal was to replace the traditional cuff-based monitors that provide only intermittent measurements every few minutes. That kind of irregular monitoring can delay recognition of rapid changes in blood pressure.

The design concept uses an actuator to move a sensor over the patient’s wrist to find the best position for producing a continuous waveform. “The sensor has to float within a rigid frame attached to a serpentine arm that’s designed to flex. The team used COSMOSWORKS to identify areas of high stress for the olefin-based serpentine arm and used the analysis results to make design modifications.

Among those modifications, says Senior Engineer Russ Hempstead: “We removed the stress risers, added radii, and added thickening sections.” He and the engineering team didn’t expect to see the stress risers, but when they did they put static flexing on part of the serpentine arm so they could move it the way it would move in the real world. The software enabled the team to shorten the design cycle by 60 percent. They cut manufacturing time by four percent, material costs by three percent, and labor costs by three-four percent. In all, engineers did seven or eight analysis studies in just a couple of days.

Hempstead says the team cut the number of parts by putting as much functionality in a part as possible. It’s a strategy he recommends to others. “It may complicate tooling, but it still eases manufacturing,” he says. “We got rid of four components.”

Industrial workplaces are governed by OSHA rules, but this isn’t to say that rules are always followed. While injuries happen on production floors for a variety of reasons, of the top 10 OSHA rules that are most often ignored in industrial settings, two directly involve machine design: lockout/tagout procedures (LO/TO) and machine guarding.

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