You’re Olympic bobsled champions, but how do you transfer the proven speed of handmade blades into a new standardized material mandated by the sport’s governing body? An appeal in a German metalworking magazine by Team Kiriasis, a two-person women’s bobsled team, brought a partnership proposal from Renishaw (Hoffman Estates, IL), Siemens (Berlin, Germany), Sescoi (Neu-Isenburg, Germany) and Iscar (Ettlingen, Germany). Renishaw used its latest measurement technologies, including the Revo ultra-high-speed measuring head for coordinate measuring machines (CMMs), to deliver precise data capture of the legacy blade geometry that had carried Team Kiriasis to a world championship in 2005 and Olympic gold at Turin in 2006.
Success at blade replication won Team Kiriasis both the 2006-2007 International Federation of Bobsleigh and Tobogganing (FIBT) World Cup and World Championships. In fact, running the new blades, the team won the world championship by more than 2 seconds, the biggest margin ever in championship history where races are usually decided by hundredths of a second.
After taking the gold medal at the FIBT championships in St. Moritz with brakeman Romy Losch, driver and team captain Sandra Kiriasis told TV broadcasters, “The blades are the secret of my success.” To show her appreciation, in September 2007 she brought her bobsled to Renishaw’s booth at the EMO machine tool show for display.
Team Kiriasis’ success highlights the impact that engineering technologies can have at the highest levels of competitive speed sports. Notes Rainer Lotz, managing director of Renishaw GmbH, the company’s German subsidiary, “We know about the small margins between success and failure at the highest levels of international sports. Renishaw is already making significant technical contribution in the world of international motorsport, such as F1 and NASCAR racing, both in engine manufacture and on-car monitoring systems.”
The blade project arose following new rules introduced by the International Federation of Bobsleigh and Tobogganing in October 2006. The new rules aimed to remove on-going disputes over the use of various materials and treatments in blade manufacture. All bobsled teams must now use the same specification steel with creativity allowed only in blade form.
Kiriasis prized the competitive edge achieved by her existing blades, but as these had been created using manual techniques, there were no drawings or electronic CAD data to allow them to be re-manufactured using the new standard specification steel. The first step by the Renishaw- Siemens-Sescoi-Iscar partnership was to send the existing blades to Renishaw’s United Kingdom research facility.
There Renishaw’s Revo five-axis measuring head for CMMs was used to scan the blades, quickly capturing many thousands of data points to enable form geometry to be defined in exact mathematical detail.
Unlike conventional touch scanning methods, which rely on speeding up the motion of the CMM’s three axes in order to scan quickly, the Revo head combines horizontal and vertical rotary axes to perform high-speed “infinite” positioning of the touch probe. A 3-D measuring device in its own right, the head does the direction-changing measuring work to minimize CMM motion errors. The head’s low-mass, low-inertia design allows scanning at speeds of up to 500 millimeters per second and capture of 4,000 data points per second.
Once the blade geometry data was captured, both drawing interchanged format (DXF) and initial graphics exchange specification (IGES) files were created and sent electronically to Sescoi, a software specialist for tool and mold making. It created a computer-aided design/computer-aided manufacturing (CAD/CAM) program for a Siemens Sinumerik 840D computer numerical control (CNC) and ShopMill HMI fitted to a DMG CNC milling machine located at tooling manufacturer Iscar Germany.
The vast number of data points to work with enabled high geometric and contouring accuracy as well as very smooth surfaces. The finishing program for the runner surfaces ran 5 megabytes and contained about 100,000 lines, producing surfaces almost as polished as a mirror.
Following machining, the finished blades were checked for form while still fixtured on the machine tool, using the Renishaw OMP400 touch probe. The touch probe uses a patented strain gage sensing mechanism and electronics that allow low, highly consistent contact forces, enabling sub-micron 3-D probe measurement and verification of the contoured surfaces.
Sandra Kiriasis was on hand to personally evaluate the machining. She received runners machined to exactly the same geometry as her championship-winning blades. Mounted to her sled, the new blades performed as well or even better than the old ones, continuing her edge over world-class competition.
- Renishaw Inc.