May 2008 Edition

medical machining

Quality for life

Utilizing Chiron Machines, Otto Bock increases its production of complex parts for prosthetic knee joints by 40 percent, all in one-stage prodedure

The Otto Bock Group has become a global leader in prosthetics thanks to innovative product ideas, quality standards and fast time-to-market. But success doesn’t happen by itself. Global competition never sleeps. As a result, every company must prove it is better than external service providers in regard to quality, on-time delivery, cost-per-part and complaint rates. Otto Bock did this by utililizing two Chiron FZ 15K S five-axis high-speed plus machines.

"We have to prove that we produce better, faster, less expensive and more reliable new series parts that are in the prototype phase," says Lothar Koch, head of production at Otto Bock HealthCare GmbH in Duderstadt, Germany. "We do these benchmarks both internally as well as with external service providers."

Approximately 50 percent of the mechanical components for different orthopedic products are purchased. Gregor Schönekehs, head of metal manufacturing at Otto Bock HealthCare, points out that up until now, "the unspectacular production parts are given to external contractors."

Stephan Conrady, NC programmer and equipment designer at Otto Bock HealthCare adds, "Anyone can do simple parts today. We concentrate on the production of complex components."

For network planning, organization, production, logistics and service worldwide, Otto Bock has put its trust in SAP/R3. The Development, Construction and Equipment Design Teams use Pro/E for 3D CAD and SolidCAM for 3D NC programming with all machines networked via DNC.

"In 2006, we invested approximately $8 million in the spatial, organizational and technical infrastructure of development and production in Duderstadt alone," says Koch.

An important part of this investment strategy was to purchase two Chiron FZ 15K S five-axis high speed plus machines for the complete machining of the load-bearing parts of the internationally successful prosthetic knee joint 3R60.

‘Anyone can do simple parts today. We concentrate on the production of complex components.’— Stephan Conrady

At this time, 10 different knee joint parts in six versions have been produced on five machines. With batch sizes of 100 to 250, that’s a significant challenge in work planning — multi-stage production takes time and because of frequent reclamping, the required tolerances are lost.

"We looked for a five-axis milling center with a turning option for a long time," says Schönekehs. "Chiron was the first manufacturer who accepted our machining challenge."

In order to fill Otto Bock’s requirements, Chiron engineers integrated a torque motor in the proven two-axis swivel rotary table. Remarkably, it accelerates the 450mm face plate up to 1,000rpm and allows turning machining which is as economical as it is precise with its 80 Nm of torque.

Each Chiron FZ 15K S provides five-axis milling, drilling and thread cutting, but also provides necessary turning machining operations that reduced the machining time by 50 percent and the order run-through by 40 percent. The required geometrical tolerances of 0.02mm are no longer a problem thanks to complete machining in one setup.

In order for Otto Bock’s investment to work long-term, high machine reliability is a must. To guarantee this, the two new milling/turning centers and Otto Bock’s other eight Chiron machines utilize the Siemens 840D control and have a "direct line" to Chiron’s Service Center via a tele-diagnosis system, ePS.

"The ePS signals all malfunctions automatically to Chiron Service, who call us immediately," says Schönekehs. "Most problems can be remedied by means of tele-diagnosis. If a technician is required, the cause of error is narrowed down to the degree that the repair is completed quickly. This feature saves us time and noticeably minimizes our service costs."

Chiron America

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