Medical centrifuge maker innovates with e-manufacturing

When Hettich Zentrifugen GmbH of Tuttlingen, Germany built its first centrifuge for medical applications nearly 100 years ago, it was a historic innovation. Today, the company produces a wide range of industry-leading centrifuges for medical analysis of blood and other fluids. Moving into manufacturing via laser sintering shows clearly that it is still innovating.

The Rotolavit is an automatic cell washing system for serological testing that Hettich began marketing in January 2004. Prior to blood transfusion, medical specialists use a centrifuge to help verify that the donor and recipient are compatible. It needs to free the blood electrolytes of any plasma residue. The Rotolavit is designed to perform the mechanical part of this multistep process automatically, rapidly, and with the utmost precision.

From a performance standpoint, the central rotor that fills 12 or 24 tubes equally and spins at up to 3500 rpm could be considered the most critical performance component. Hettich has substantial experience with them.

The washing rotor for the Rotolavit centrifuge is an all-new design, a concept made possible by Hettich’s entry into the realm of e-manufacturing using laser sintering, specifically an Eosint P 380 system from EOS. The previous version of the rotor was assembled from 32 components. The version going to market in the Rotolavit has only three parts, two of them made via laser sintering.

Naturally, this saved cost in production, assembly, handling, and overall parts logistics. But it also saved on tools. With e-manufacturing, the part is sintered directly from nylon powder guided by the CAD file.

When Laser Sintering Makes Sense

There are a number of reasons to go this route, but the most compelling for Hettich is its production batches. Typically, these specialized products call for less than a thousand pieces per year. Searching for short-run solutions and hearing about the laser sintering process, Hettich visited EOS on a fact-finding mission. It liked what it saw and quickly did an economic analysis that showed considerable cost savings using the laser instead of tools.

Next, it needed to test the material (EOS PA 2200) thoroughly to see if it could handle the heavy stresses, maintain ultracritical dimensional stability, and meet the medical environment demands. While the material was passing all the tests, Hettich was exploiting the design freedom sintering provides compared with tooling. Undercuts, no matter how radical, are not even an issue, let alone a problem. Desired functionality could be achieved without compromises to suit the physical limits of tooling. With sintering, a designer can even create closed voids inside the part structure if they make sense.

The two rotor parts sintered on the Eosint P 380 also do not require the deburring needed by previous designs. The advantages for Hettich are clear: It can produce critical components to very high standards in low quantities on demand. Further, it can change the design as easily as reworking the CAD file to meet a particular customer need—without erasing any of the cost savings. Not surprisingly, it is looking at acquiring another laser sintering system to support other product lines.

Click here, to read about EOS's new Eosint M270 machine.