Manufacturing by the micrometer

In medical manufacturing, smaller is often better. Surgery, for example, relies on precision, with intricate tools used to perform delicate procedures. Implants need to fit patients comfortably without excess bulk. As medical developments advance, manufacturing must keep pace with the industry, fabricating the increasingly tiny, precise components medical professionals need. It’s a job for specialized manufacturing – micromachining.

Micromachining is an evolving technology whose purpose is in its name – to machine components at the micrometer level. It originated in the mid-20th century and is still increasing its capabilities to manufacture smaller and smaller parts. Processes such as turning, milling, drilling, and grinding are being miniaturized, and they require specialized tooling capable of removing tiny amounts of material with the utmost accuracy and delicacy.

Expanding creative freedom while reducing tool size

Kennametal, a developer of metal cutting tools, materials, and other manufacturing products, has been providing micromachining tooling systems for years. Founded more than 85 years ago, Kennametal has a long history with industries such as aerospace and transportation, and recently entered the medical manufacturing space. The increasing demand for micromachining applications in medical manufacturing has created a need for small, high-precision tools – a need Kennametal’s expertise in precision tooling has seamlessly addressed, making its entry into the medical industry a natural progression.

“If you think about a bone screw, it could start out as a cylindrical part,” explains Scott Etling, vice president, global product management at Kennametal. “The process is first shaping it with a turning or grooving tool, next threading it, and finally cutting it off to bring it to size. To do this precisely requires the right tools, machine, and knowledge in the micromachining area which can be vastly different from, say, machining an engine block which uses a completely different machining environment. Kennametal is focused on being a leader in micromachining.”

Many engineers who design precision medical components don’t think about the logistics of machining them, which is where Kennametal comes in. The company works directly with its customers to develop designs for medical components as well as the tools required to manufacture them.

“When cutting tool companies collaborate with manufacturers that require micromachining, it enables creativity and precision required for the next generation of medtech components,” Etling says.

This creative freedom enables the design of parts such as patient-specific implants or devices, an area of healthcare that’s growing rapidly as patients and professionals move toward increased personalization for better comfort and effectiveness. A tooling manufacturer that can support micromachining technology allows for a more effective iterative process – if an engineer creates a part, tests it, and decides it needs changes, a company such as Kennametal can tweak the tools accordingly. This adds up to finely tuned medical devices for optimal, individualized patient care.

The recipe for the right tool

Micromachining requires extremely tight tolerances, and Kennametal works to come up with technologies to design inserts, drills, end mills, and other tooling systems that can hold those tolerances. The precision of micromachining requires high spindle speeds, and many medical components are made from exotic, difficult-to-machine materials such as titanium, cobalt chrome, and stainless steel. For those materials to withstand the necessarily high heat generated by the machining process, they need to be coated, and Kennametal’s products include coatings as well as the carbide substrates themselves. Typically, for this type of application, Kennametal would use a physical vapor deposition (PVD) coating, which is thin but hard and results in high corrosion- and wear-resistance. The company recently released several new grades including carbides KCU10B and KCU25B as well as titanium grade KCS10B, all featuring new PVD coatings for better abrasion resistance and longer tool life.

Micromachining involves a delicate balance – an operator needs to apply enough pressure and heat for chip formation, but not so much pressure that the miniature tool or workpiece breaks. When machining to tight tolerances, the goal is to avoid failures such as notching and breakage, and designing a tool to machine miniscule depth of cut (DOC) while avoiding excessive wear and maintaining a long, productive life depends on several factors including material, workpiece, and a customer’s specific needs. Developing the optimal grade for a specific application is like following a complex recipe – a challenge Kennametal embraces as it works with its customers.

Thinking small for the future

Recently, Kennametal launched KenDrill Micro, a solid carbide drill series specifically for machining small parts. Currently the drill is offered in diameters as small as 1mm, but the company will be releasing a 0.5mm diameter as well – about the size of mechanical pencil lead and suited for micromachining components such as coolant valves. Around the same time, Kennametal introduced TopSwiss (MBS), which stands for micro boring solid and includes nearly 200 toolholders and inserts with options for standard, premium, or high-performance precision.

“These are highly precise, micro boring bars, with features that are specifically needed in micro component manufacturing,” Etling says. “In micromachining, you have to reach into parts and create a bore or a hole inside the parts. It could be to reduce weight or create the thread that you might see on a spinal implant pedical screw for example. We already have, on the medical side, a pretty solid portfolio. In the past, our portfolio had a few gaps on the micromachining side where customers required smaller inserts and drills. We’ve launched innovative new lines of drills and inserts to fully support micromachining applications.”

Kennametal plans to continue developing and releasing new tooling systems for micromachining, a technology Etling believes will continue to grow in every market segment. In the medical industry, this translates to less cost and more overall ease for patients, as micromachining not only creates greater precision in medical devices but also better comfort. No one wants to physically feel a medical or dental implant in their body, so the smaller and more precise the implant can be, the better for the patient – a challenge for machine tool manufacturers to see just how “micro” they can go.

A goal for medical professionals is to be as minimally invasive as possible when it comes to both procedures and implants, for reduced risk and quicker healing. New developments in minimally invasive technology will continue to emerge as other technologies, such as robotics and advanced imaging, progress. To support these developments, the medtech industry will need increased collaboration between manufacturers and medical professionals, as well as collaboration between medical device manufacturers and tooling companies, and micromachining should be on everyone’s mind.

Kennametal
https://www.kennametal.com

About the author: Clare Scott is associate editor for GIE Media’s Manufacturing Group. She can be reached at CScott@giemedia.net or 216.393.0314.