Tiny surgical spring scissors, needle holders and forceps are the specialty of Microma Martin Alber GmbH & Co KG from Irndorf. In order to meet the requirements of such microsurgical instruments, quality is a must. The recipe for success at Microma is the combination of special machines, materials and precision tools. "Precision and quality are indispensable in medical technology and are uncompromisingly adhered to in our production. But of course we also always focus on efficiency and productivity. That's why we regularly put our processes to the test in order to tap into optimization potential. For example, we were looking for an efficient milling tool to reduce our machining times. We found what we were looking for at Nachreiner," says Jan Alber, Production Manager at Microma.
In-house coating expertise for differentiated tools
Precision tools for demanding machining tasks involving metal, non-ferrous metals, plastic and composite materials are the expertise of Nachreiner GmbH in Balingen. The company produces as much as possible in-house. Temperature-controlled production, technology for edge preparation and optimization of micro-geometry as well as grinding, measuring and automation technology are fixed factors in its tool production. For some years now, an in-house coating line from Cemecon AG, Aachen, based around the CC800 HiPIMS coating system, has also been a central component of production. Martin Seifriz, Managing Director at Nachreiner GmbH, reports: "Our aim is to develop the best cutting tools for our customers now and in the future so that they can achieve outstanding product quality. The CC800 HiPIMS is the key to differentiating ourselves better from the competition with high-quality coatings."
With the HiPIMS process, Cemecon says it has significantly improved the quality and performance of coatings compared to other processes. The process is flexible and suitable for coating many different tool variants. Whether small batches or large quantities: It can be adapted to different requirements, for example from micro-tools to tools for heavy-duty machining - and within a short time. Across this range, HiPIMS coatings are smooth, adhesive, hard and tough at the same time, have a fine crystalline, dense morphology, adapted residual stresses and high thermal stability. The uniform coating thickness distribution also contributes to the wear protection of the cutting tools.
Application with special challenges
The manufacture of microsurgical instruments places high demands on the cutting tools: they are made from stainless steel (1.4034 or 1.4022). These steels are characterized by their high resistance to corrosion and acids. They are also very tough and have low thermal conductivity. These are very good properties for use in medical technology, but a challenging combination for machining. This is because high temperatures are generated at the cutting edge during drilling, milling or turning, which can damage the tool. In addition, the machining process itself is very demanding: the milling tool must achieve a high material removal rate on a long and thin component while also achieving good surface qualities.
In a first step, Microma switched to the solid carbide HPC superstar milling cutter from Nachreiner's standard range, which was then adapted to the application in a second step. "The combination of a 3-edged and a 6-edged tool in our Superstar milling cutter enables both efficient roughing and smooth finishing with outstanding surface quality. This is because the unequal pitch prevents vibrations and oscillations, among other things, and is therefore responsible for the very smooth running and reduced friction," explains Seifriz.
TiAlSiN coating increases productivity and tool life
Even with the standard version, Microma was able to triple the feed rate and increase the cutting speed by more than 30 %. "We shortened our machining time and achieved first-class machining results with increased productivity," says Alber happily. But that was just the beginning; optimizing the tool further improved the results. The experts worked closely together to adapt the milling cutter to Microma's application and almost doubled the tool life. In addition to adapting the microgeometry, the TiAlSiN coating in particular provided the additional boost.
The standard milling cutter from Nachreiner has an AITiN coating. When machining stainless steel, however, the TiAlSiN coating offers significant advantages: thanks to its high temperature stability of up to 1,100 °C, it protects the tool from heat during the machining process and the heat is dissipated through the chip. "The extreme smoothness caused by the HiPIMS process further reduces the heat. TiAlSiN also has a low affinity to stainless steels. This reliably prevents built-up edges and ensures process reliability," says Marc Semder, Sales Manager at Cemecon.
The collaboration between Microma and Nachreiner shows how crucial the exchange between user and tool manufacturer is. By using Cemecon's HiPIMS technology and optimizing the tool geometry, Microma was able to shorten the machining time while at the same time significantly increasing tool life.