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MEDICAL MACHINING Dynamic motion empowering medical machining

Dec 13, 2019

The medical manufacturing industry is one of the most complex industries requiring absolute meticulousness. The following article explores how the CAD/CAM solution by Mastercam has enabled various companies to meet the difficult demands of the industry whilst simultaneously adding great value to medical machining. Vineet Seth, Managing Director - India, S Asia & Middle East, Mastercam

Medical manufacturing is one of the more demanding disciplines, and manufacturers in the medical industry require quality and precision at the highest level. From research to development, and prototyping companies to medical suppliers and contractors, manufacturers expect accuracy and repeatability on finished parts, with unrivalled material removal processes on even the most delicate or intricate medical parts.

CAD/CAM solutions, therefore, need to meet the rigorous demands of the industry in this field, including:

  • Ability to import, create or cut virtually any CAD model

  • Offer a wide range of CAM tools for solving complex machining issues

  • Adjust feeds, speeds, entry points and dwell for faster cutting with less tool wear

  • High-precision toolpaths for cutting extremely small parts

  • Streamlined 5-axis cutting, trimming and drilling with strategies to help eliminate burrs on critical medical parts

  • Simulation & verification, in-spec material removal and to detect interferences

  • Checking machining program against the CAD model for accuracy and quality assurance

Software or a CNC machine that is ideal for manufacturing medical components is the only one ingredient to achieve success. Collectively, software, machine, tooling and material suppliers need to work cohesively in order to help companies make quality components, efficiently as well as quickly.

The essential link in manufacturing

One such company that balances quality, costs and time effectively, is Greensboro, NC-based — Progressive Tool & Manufacturing, USA. The company has been making custom tooling & gauges for the medical industry, defence contractors & aerospace companies that conduct prototype testing, since 1984.

“All of our shop employees are skilled toolmakers,” Richard Dick Thompson, Founder, Progressive Tool said. “Even if they’re apprentices, they’re toolmaker apprentices. Everyone can do everything – from setting up the material and squaring up the parts to running the CNC machines to making the programs to doing their own set-ups and making their own fixtures.”

The company has 4-axis CNC milling machines, multi-axis CNC lathes, CNC sinker and wire EDM machines, run by Mastercam, allowing them to generate machine tool programs that can achieve extremely tight tolerances. Calling it ‘an essential link,’ Thompson noted that his company’s toolmakers don’t do any programming at the machine tool. “We do everything through the software.”

For most jobs, Progressive Tool starts with a solid model given to them by the customer or they design something inhouse. “We prefer to have solid models,” Thompson says & adds, “because, then, everything is there.” They take the files into Mastercam, create toolpaths and use the original design geometry from the model to run the toolpaths. “Basically, everything we do is custom,” he says & goes on, “I’m writing 10 to 20 different programs a day in Mastercam & running them one or two times.”

The company had been using Mastercam software for nearly 20 years. When it purchased new equipment – the CNC lathe with a sub spindle, C and Y-axis and live tooling – they upgraded to Mastercam’s latest version. The new equipment and software’s one feature that wowed everyone was the dynamic milling (or Dynamic Motion technology) which uses proprietary algorithms programmed into the software to automatically detect changes in the material as the tool cuts through. The tool remains constantly engaged with the material, minimising air cuts and allowing the machines to be pushed to their full capacity.

“It’s not for every part,” asserts Ryan Thompson, Thompson’s son and the company’s design engineer. “But with the right application, it works amazingly well.” Run times, too, have been reduced dramatically. “For example, one part we made in 304 stainless that used to take about an hour to rough and finish, now takes about 18 minutes – easily three or four times faster than the way we used to do things using multiple tools,” Ryan adds.

Progressive Tool’s ability to make parts with extremely tight tolerances have kept one customer in particular – a contract manufacturer of over-the-counter nutritional and pharmaceutical soft-gel products – coming back for over a decade to help design and make parts for their metering pumps and other production equipment. “The dosage that fills each gel cap has got to be precise,” mentions Ryan and continues, “Obviously, the system for metering the amount of formulation demands the same level of precision. The custom-designed machinery must always be operating accurately and reliably, pumping the medicine at very specific rates.” Today, the company maintains a reputation for having the highest quality shops in the area for custom parts.

Greater engagements in manufacturing

Similarly, NOVO Engineering in Vista, California, provides the engineering behind a variety of medical devices, life science automation, digital imaging equipment and commercial products from clients such as Medtronic, Synthetic Genomics, Hewlett-Packard and TaylorMade. Its start-to-finish contract design service offerings include concept development, engineering, prototyping, fabrication, testing and transition to manufacturing.

NOVO has 26,000 square feet of space in San Diego and 12,000 square feet in Minnesota devoted to design offices, testing labs and a well-equipped prototype shop offering CNC turning and milling, FDM and PolyJet 3D printing technologies and various other processes, including surface grinding and welding. Machinist, Leo Castellon explains that each machinist in the shop notes the required tolerances and geometries, designs any workpiece fixtures, sets up the CNC machines, machines the part, inspects it and then releases it for assembly and testing. Each industry sector that NOVO is engaged in generates different challenges. Drug delivery systems, such as wearable injectors, routinely use tiny components; scientific instruments require high precision or unusual materials, and optical devices rely on tight assembly tolerances. Parts are designed in CAD and then seamlessly transferred to Mastercam. Design changes are simple to make and don’t trigger extensive reprogramming. “We do a lot of iterations of our parts, so if we make a change in CAD, we can quickly pick it up in Mastercam and regenerate the model to create the new geometry. Mastercam will pick up the right code,” says Castellon. An example of this streamlined approach was a prototype part for a beam splitter. The material was a soft plastic that would be exposed to direct light, and a smooth surface was required to avoid image distortion. Through systematic trial and error, the engineers and machinists came up with a prototype that had a surface smooth enough to meet the optical requirement, yet strong enough to withstand the impact of a drop onto concrete.

The team went through six iterations of that design, and while it sounds time-consuming, Dr Rajan Ramaswamy, President and Chief Technology Officer, NOVO, was quick to point out how Mastercam supports rapid iteration. “Regardless of the improvements made in computer simulation tools, prototype and test iterations remain an essential part of the development process for the types of products that NOVO develops,” he said. This is especially important when developing medical products that require extensive FDA testing, often necessitating the fabrication of dozens of prototypes to support all the required verification and validation tests.

Many of the parts NOVO works on require tight tolerances, usually within 0.002”, on small features. For example, drilling 0.008” diameter holes through stainless steel or plastics. “With medical devices, one is working with parts where the hole diameter is frequently well below 0.040”. Orders for some of the parts have us going through 0.120” of material with an 0.008” diameter hole,” said Ramaswamy.

Mastercam Dynamic toolpaths efficiently remove a large volume of material in a timely fashion. This is the result of proprietary algorithms programmed into the software that intelligently detect changes in the geometry, allowing the tool to have greater engagement with the material, resulting in higher material removal rates.

The machinists also find Mastercam’s twelve plus surfacing toolpaths particularly useful because on complex parts, any one toolpath often can’t perform all the functions needed. For parts below 0.020” thickness, the team does not use Dynamic toolpaths. “This is because the controller can’t keep up with the processing speeds and that’s a limitation with our CNC machine – it can’t process enough blocks per second to do it efficiently,” explains Castellon and goes on, “The machine has to catch up. So, when I use the Dynamic toolpath at the smallest, I am using maybe a 0.0625” diameter end mill. Anything less and there are problems with not being able to process the code fast enough to keep up.” Instead, Castellon uses 3D legacy toolpaths for the smaller parts. When machining plastic, the Dynamic toolpaths often take the machining time down from 10 minutes to 30 seconds.

The machinists use the tool library to create their own tools. For one project, they needed a 4-inch diameter end mill and created it easily in the tool library, imported the tool to ensure that all clearances were right and found that it worked well in that application. Although the company rarely does repeat jobs, if an application is akin to something they have done before, they locate a similar tool in the library, regenerate the geometry and Mastercam will pick it up.

Castellon has found the Mastercam Forum to be invaluable when seeking advice on how to work with unconventional specifications. Even when the most unusual of parts come through, he can find advice from the Mastercam user community.

Adding value to manufacturing

It is without a doubt, that advanced CAD/CAM systems continue to add great value to medical machining, and collaboration between machine tool, software and tooling suppliers provide the added knowledge base for medical manufacturers to go the distance.

Image Gallery

  • The files in Mastercam create toolpaths and use the original design geometry from the model to run the toolpaths

  • Proprietary algorithms programmed into the software allows the tool to have greater engagement with the material

  • Vineet Seth

    Managing Director - India, S Asia & Middle East

    Mastercam

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