MARKET PLACE
Protomold, Telford, UK
Automated prototype production
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Image: Protomold
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Product redesign
Tensys Medical (www.tensysmedical.com) manufactures the T-Line Tensymeter, a noninvasive device that measures arterial blood pressure in real time on a beat-to-beat basis using a transdermal pressure sensor. As the product gained acceptance, the company gathered feedback from its users on ways to enhance the device. Users said they wanted it to be easier to operate. “Although the application process for using the T-Line is relatively simple, some of our users rotate between different hospitals and may use the device only once every few weeks, thus they may have to re-familiarise themselves with the process,” said Russ Hempstead, a Senior Engineer at the company. “To help reduce the learning curve, we removed a few steps from the application and redesigned certain components.”
Specifically, the plastic sensor frame was redesigned to allow medical staff to place the sensor over a patient’s radial artery. With the previous design, the sensor was attached to the frame with polyethylene tape that was manually applied during manufacturing. The new design integrates a serpentine “arm” that is fabricated as part of the original sensor frame and eliminates the manual labour and associated costs. It also re-centres the sensor after any shifts resulting from patient movement, thus helping users to more easily maintain proper placement of the device.
Although the redesigned sensor frame improved the product’s functionality, its unique geometry comprising large variations in wall thickness and sharp transitions posed a challenge for the company’s existing prototyping and production techniques. The engineers first used stereolithography to create a master part. This master was then used in rapid tooling efforts to create urethane castings of the components. Although the castings provided a conceptual design check, the limited material selection and short tool life posed testing and design verification constraints for the company’s engineers. The challenging geometry also jeopardised production plans.
The existing production tool vendor was not able to construct the tool properly. As a result, the new tool created a tremendous amount of flash (excess material caused when plastic leaks from a mould cavity and sticks out from the edge of the part). In a production situation, manually trimming each part is not acceptable because of the quality and expense.
While engineers and the production-tooling vendor were struggling to get production tooling underway, a Tensys design engineer came across information on rapid injection moulding. When investigating its capabilities, the company was particularly attracted to the possibility of fast turnaround time and low costs. “The fact that I can simply upload a computer aided design (CAD) file directly to a website, add a few detailed notes and just walk away, easily saves me 50 per cent of the time I typically would spend on the logistics of a quote,” Hempstead said. “In the past I have been forced to deal with incompatibility issues and trying to meet a supplier’s CAD file format or 2D drawing requirements. Not having to translate my CAD files or correlate software versions gives me time to spend elsewhere.”
Pleased with the rapid injection moulding prototype results, the engineers immediately stopped production tooling to move efforts toward further improving the design of the T-Line’s components, while keeping on target with the original timing specifications.
Advanced online quoting
Over the next couple of years, more online manufacturability analysis is likely to be available, which will further reduce the number of design iterations and prototypes required before and during testing. Designers can expect interactive, graphical mouldability evaluations with every quotation, including mould fill analysis and warp/shrink prediction. This will allow them to virtually prototype the design prior to having physical parts made for the first time, which will further reduce overall project risk.
Today’s 3D CAD programmes allow a design to be presented directly as data rather than drafted drawings. Analytical and graphic software tools enable systems to manipulate a CAD design in 3D to determine the actual steps needed to fabricate it. Hardware (processing power and storage capacity) is capable of managing enormous amounts of data in something approaching real time and at reasonable cost. The result is an online quoting system that utilises the capabilities of existing hardware and software tools to accept direct input of 3D CAD designs in a variety of formats. This type of system can analyse submitted designs and identify necessary or recommend changes based on best practice design and fabrication principles. It can graphically present those recommended changes to the user, online and in clear, rotatable, 3D renderings and feed approved and accepted designs to automated production facilities with a minimum of human intervention.
This kind of automation can substantially improve the cost, quality and speed of production. It reduces the need for human estimators and vendor costs and allows designers to comparison shop without unnecessary delay.
John Tumelty is Managing Director of Protomold, Telford, UK, tel. +44 800 7768 6665, e-mail: info@protomold.co.uk, www.protomold.co.uk
