A navigation device shows the way while the heated seats ensure comfort: electronics in cars are no longer pure luxury. For fuel consumption to nonetheless decrease, the power generators must become more efficient. This is ensured by claw poles from the Robert Bosch GmbH factory in Stuttgart. The company now relies on the DuraMax coordinate measuring machine from Carl Zeiss to guarantee optimal quality assurance in production.
In simple terms, a claw pole is a fist-sized piece of metal with six or eight hooked teeth pointing upwards and a hole in the middle. It is a key component of alternators, i.e. generators, which supply practically every motorized vehicle with power. Unfortunately, there is hardly a straight surface, barely a symmetrical tooth, rarely a perpendicular edge. A challenge for quality inspection: up to 10 different gauges were used in the past. Random measurements were time consuming and susceptible to errors. The greatest problem became obvious with the latest claw pole generation developed at Bosch, which will deliver up to 30 percent more power: the parts are shaped so that many features cannot even be inspected with manual measuring equipment.
Today, two DuraMax measuring machines from Carl Zeiss Industrial Metrology (IMT) ensure that maximum quality is achieved. "Without these coordinate measuring machines, we would not even have been able to measure the new claw pole," emphasizes Uwe Kasten from metrology methodology development at Bosch. "When this measuring machine was introduced at the 2008 Control Show, we knew that it was exactly what we had been looking for." A robust machine for shopfloor use, sufficiently accurate for the required tolerances and economical. After comparing various providers and numerous test measurements, Bosch invested in two DuraMax machines in November 2008: one for claw pole production and one for tool-making for the initial inspection of the punching and forming tools.
Production has still not completely switched to serial inspection with the coordinate measuring machine. However, the potential of shop floor coordinate measuring technology is already obvious: the measuring results are available in just six minutes – instead of half a day. With a minimal modification of the carrier, employees can reliably inspect each of the 37 different types of claw pole – even the latest. Furthermore, operator influence has been virtually eliminated and the employees are not even needed for the measuring process, i.e. they have time for other jobs. Uwe Kasten is more than satisfied. He would gladly expand the partnership with Carl Zeiss in the future, e.g. with a user day for CALYPSO software that would cover all Robert Bosch GmbH sites.
The Robert Bosch GmbH factory in Stuttgart produces 16.5 million claw poles annually. They are delivered to all Bosch generator factories around the world where they are integrated into the alternators. The manufacture of claw poles has been the responsibility of the Stuttgart factory for more than four decades. The other areas of alternator production gradually wandered abroad – England, Spain, Brazil, South Africa and India. Only the claw poles are still manufactured in Stuttgart because the sophisticated punching technology with the associated tool-making could not be transferred to other sites.