Off-the-shelf medical instruments
“We can mill up to nine components in the turret at the same time.”
The world’s most impressive “Swiss army knife” weighs more than four tonnes and can turn, mill, grind, bore, broach, saw, skive and even needle-etch with backlash-free precision to the micrometer: This was reason enough for surgical mechanic Peter Tschida from the district of Tuttlingen to order the Starrag Bumotec s191 mill/turn center – the “Swiss army knife” of machining.
Five years ago, Peter and Ivonne Tschida, owners and founders of Tschida Medical Solutions (TMS) in Fridingen (near Tuttlingen), made a very courageous decision. The family-owned company, located in what is often referred as the “Medical Valley” in the Swabian region of Germany, decided that it wanted to go beyond inventing, developing and designing medical instruments made of stainless steel using 3D CAD, it also wanted to manufacture them itself using the Bumotec s191 high-precision mill/turn center from Starrag. This took a great deal of courage, as Peter and his sons Florian and Maximilian were total laymen in the fields of CNC machining and CAM programming.
High precision with many extras
After around a year of training, with newly acquired knowledge, the Bumotec s191 and its many extras quickly opened a door into the world of CNC machining. The linear-driven mill/turn center can load and machine bar parts with a maximum diameter of 1.97 in. (50 mm), and the multi-grip device on the opposite station holds and supports complex parts very reliably, ensuring that very tight tolerances can be maintained even with six-sided machining. It also reduces unproductive set-up times: “We can mill up to nine components in the turret at the same time. This means we can avoid eight tool changes compared to individual production,” explains Tschida with a practical example.
Manufacturing costs in Fridingen are high, as instruments such as forceps, scissors and needle holders are produced from high-alloy stainless steel bar parts (X20Cr13, Diameter 0.98 in. (25 mm)), which Tschida Medical Solutions then combines into complex micro-spring, micro-bayonet and tube shaft instruments. Tschida’s team manufactures these components in series production 24 hours a day – even through the night during fully automated, unmanned shifts. Precise temperature management ensures safe and reliable repeating accuracy with precision to two micrometers on all five axes, while the stable and low-vibration machine bed offers near-net-shape finishing on the surfaces. But Tschida is especially proud of one thing: “The boldest fact about this machine is that all of the know-how remains in-house. We will continue to work through the puzzle under the radar until the innovation is fully developed.”
Success story: DeBakey forceps
So-called atraumatic DeBakey forceps, a double-articulated instrument with two jaw parts, were selected for manufacturing as a trial. This instrument is given special teething for picking up and holding very sensitive blood vessels safely. These tiny (less than 0.016 in. (0.4 mm) wide) cross teeth are milled using special tooling; they have a very small radius and interlocking, backlash-free longitudinal teeth on opposite jaws. In order to reduce the amount of work required, the s191 finishes the inner sides of the jaws so well that they do not need to be polished at the end of the process.
The case study was successful and Tschida will soon be able to supply its distributors with these DeBakey forceps, which stand out from the competition thanks to their high-quality toothing. “It’s not uncommon for the jaw parts to decay,” explains the surgical mechanic. “It only takes a few teeth to be missing or incorrectly positioned for the forceps to injure vessels.”
Despite the significantly higher manufacturing costs, the case study showed that the s191 produces these parts very efficiently (four parts in a turret). The DeBakey forceps are testament to what the s191 is capable of. Tschida: “The required form and quality of the individual parts remain consistently high in series production. The case study also shows us how to reduce the time required to refine the parts. In addition, the final assembly times are reduced, as the parts fit together and the desired function is achieved more quickly.”