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BLUM touch probes on Strama-MPS

By Niraj M Wanikar, Chief Editor, CNCTimes.com, 2019-03-12 11:45:00

20 million high-speed measurements each year with touch probe TC76

Straubing-based Strama-MPS’ machining centres offer maximum efficiency and productivity thanks in part to their rotary indexing design, but also thanks to Blum-Novotest touch probes. Two TC76 touch probes simultaneously measure two cams in about two seconds with a measuring speed of 3 m/min.

Strama-MPS’ special-purpose machine for machining cams for motor vehicles is distinguished by its fast cycle time and high productivity. Camshafts are increasingly being assembled as opposed to being made from a single part. This minimises manufacturing costs, reduces weight, offers maximum flexibility in terms of geometric form and allows different materials to be combined. Before the joining process, the inside contours of the forged, edge-hardened cams made of bearing steel must be machined with high precision, for which the cams are inserted facing the first rotary table of the special-purpose machine. At the same time, two other cams are finished at a second station before the processed inside diameter is measured by 2-point-measurement at the third station using two TC76 workpiece probes from Blum-Novotest. At the second rotary table, the parts are cleared, washed and dried.

The wired touch probes are attached to an axis-mounted cross mount where they measure the diameter of the cams at a speed of 3 m/min. This is especially remarkable given that the measuring speed recommended by Blum-Novotest for the TC76 touch probe is normally 2 m/min and other touch probes can often only be used at speeds of 400-500 mm/min. Markus Noack, development engineer for software technology at Strama-MPS, sees even more potential. “We conducted some tests and did not identify any loss of precision even when the measuring speed was increased to 3 m/min. During long-term operation, the touch probe also demonstrates no flaws despite the high measuring speeds.” The optoelectronic signal generation of the extremely compact touch probe with a diameter of just 25 mm means that it suffers from no wear at all and remains stable for long periods. 

Strama-MPS’ machines are capable of producing ten million cams a year. This means up to 20 million measurements a year for the touch probe. But to date, there have been no problems with the systems – not even the probe styli have needed replacement, and this in a system that has been in service for five years. The measurements are performed in a TWIN structure, which means that two cams are measured simultaneously alongside one another in about two seconds. During the process, the measurements are transferred to the controller and visualised on the control screen in the form of a “measuring line”. This allows the machine operator to immediately recognise any trends in the measurements, enabling them to adjust the program before the tolerance range of 1/100 of a millimetre is exceeded. Tool costs are also reduced as a result of the workpiece measurement – because measurement is performed in the machine, the finishing tools can be used until the end of their service life. The result is a 100% stable process with 100% compliant workpieces.

Because a machine operator is often responsible for three or more machines, setup time plays an important role alongside cycle time. The use of the TC76 touch probe has enabled Strama-MPS to reduce the type-specific setup costs while also offering the customer an easier and more reliable setup process. Setup involves placing the outer form of the cam with the touch probe on four points and displaying the values on the machine controller. This data is used by the operator to position the clamping device so that the finishing diameter is located at the centre of the cam. The outer points are probed using the ruby ball at the bottom of the stylus. A special stylus is part of BLUM’s standard range, enabling both lightning-fast part measurement and part set-up in this particular application. Strama-MPS’ in-house production incidentally also makes use of Blum-Novotest measurement technologies, with a laser measuring system and a touch probe present in almost all of the 25 machining centres.

Blum-Novotest’s measurement technology has absolutely proven its worth at Strama-MPS. The TC76 touch probe is a standard feature of the special-purpose machining system and is expected to remain so. The engineering company was wholly impressed by the complete product & service package. “When developing a process with minimal cycle times, we need experts in all areas. Working together with BLUM, we’ve managed to perfect the measuring sequence so that our customers can now enjoy a comprehensively high-quality package,” concluded Markus Noack positively. “The quality of the touch probe is also superb without a doubt. When we were searching for a new measurement solution, we were quick to choose the BLUM TC76.”

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