The wheels count amongst the most important design elements of a car, and many owners use light alloy rims to give their car a more individual, sporting look. Very often they choose products from BBS, which achieved cult status after it started producing a golden, three-piece cross-spoke model in the 1980s. The cast rims are subjected to a turning process, and as part of this BBS uses high-precision touch probes from Blum-Novotest in its main plant in Schiltach, Germany.
The most important step in producing the cast rims at BBS involves machining the centre. “First, this means turning the centring hole in the middle of the rim to an accuracy of a hundredth of a millimetre. Then the groove on which the hub cap will be placed is turned. This also requires extreme precision so as to make sure that the cap fits properly,” explains Oliver Kalmbach from the Procurement department. “The positional tolerance at the centre of the rim blank is larger than the tolerance that is available to us for the cap groove, so we have to re-measure each rim before it is machined. That is why we have always used touch probes in the lathes.” The wireless touch probes are attached to the turret together with the turning tools, and they are swivelled to the machining position for the measurement operation. Then the machine can carry out the required measurements with the touch probe and adjust the zero point in the NC program in such a way that the centring hole and the cap groove can be machined exactly.
At BBS, the cutting parameters can be very demanding: 3 mm cutting depth and 1000 to 2500 RPM are quite common. And during these operations, the touch probes are subjected to the direct flow of the cooling lubricant and a full barrage of chips. Also, the turning operation causes strong vibrations, for instance when the lathe tool has not yet found its way completely into the material or when it encounters small cavities in the aluminium. These vibrations are transmitted to the probe via the turret on which both the tool and the probe are fixed, which can cause erroneous measurements.
Faced with the unusually difficult challenges at BBS, where the vibrations are stronger than with other turning applications, the lower mass of the BLUM TC62 probe works to its best advantage. The T variant was selected, because it has a higher measuring force compared with the standard version for milling machines, and this prevents erroneous deflections that could be caused by the extreme turret movements. Also, the higher measuring force means that the viscous oil used in lathes as cooling lubricant can be reliably displaced during the measurement. Finally, the touch probe fulfils the requirements of protection class IP68, so there are no problems in connection with ingress of moisture or chips. In addition, a newly developed vibration damper was used between the tool holder and the touch probe for the first time. This protects the measurement electronics against damage due to the worst vibration peaks.
One of the main advantages of BLUM’s TC62 T probe is the special measurement tool technology: The trigger signal is not generated by means of a mechanical contact, but optoelectronically via shading of a miniature light barrier inside the touch probe. This means that it is completely wear-free, guarantees the greatest possible reliability even under extreme operating conditions and, in contrast to a mechanical solution, it is not influenced by the strong vibrations in the lathe. On top of that, the radio transmission of the TC62 T touch probe is extremely fast and reliable: It sends the data that have been registered to the receiver using BRC radio technology. The advantage of this technology consists in each individual bit of a radio signal being run across the entire width of the frequency band, thus making transmission particularly resistant to interference.
BBS has now switched completely to BLUM touch probes, and new machines are equipped exclusively with them. The newly developed vibration damper has been functioning smoothly in combination with the robust touch probes for more than 1½ years now. “The BLUM touch probes have provided us with an extremely reliable technology. Also, the Blum-Novotest probes shorten the measuring time by 70%, because the measuring points can be approached at speeds of 2000 mm/min, whereas the probes we used previously only managed 300 mm/min at the most,” says very a satisfied Oliver Kalmbach. “The good cooperation with Blum-Novotest has been very beneficial: A reliable partner as well as reliability and speed in the machining process.”
BBS was founded in 1970 by Heinrich Baumgartner and Klaus Brand in Schiltach. At first, only plastic chassis parts were produced, but then a three-piece racing wheel was launched in 1972. From that moment onwards, the company maintained a high profile in motorsports. In addition to the year-round product programme for the aftermarket, another core segment of the company is the supply of original equipment to leading car manufacturers – thanks to BBS’s high quality standards and many years of experience. All products are manufactured in Germany. The customers include Audi, Porsche and AMG, as well as Mazda and Hyundai. The Schiltach and Herbolzheim sites provide work for over 500 employees.