Cylindrical and non-circular grinding

For 50 years, the Dutch machining centre manufacturer Unisign has been developing machine concepts adapted to special machining requirements. With over 80% of production in-house – the company relies on KELLENBERGER for its grinding technology.

Today, Unisign portal machines, travelling column machines and multitask machining centres go to logistics and energy companies, commercial vehicle manufacturers and general engineering companies all over the world, a large proportion are special machines. Parts machined on these machines includes truck axles, chassis side rails, lift mast profiles, excavator frames, crane beams and railroad bogie frames, which are often produced in a single clamping operation on Unisign machines. The machining length often exceeds 25m. The Unisign Technology Center houses an R&D department where new machine concepts are continuously developed.
“Here, we can demonstrate the performance of our machines,” says Operations Manager Paul Lennaerts, who is responsible for design, production and assembly. “We show customers how our machines can increase productivity. In our production, we manufacture the components for our machines mainly on Unisign machines, at least that goes for machining processes. For other operations, we use machines whose quality awareness is similar to ours, like KELLENBERGER”
For grinding operations on high-precision parts such as tie rods, mandrels and spacer rings, a KELLENBERGER KEL-VARIA (the predecessor model of the premium KELLENBERGER 1000 series) was purchased back in 2003. The performance is oriented to the precision production of prototypes as well as small and medium series. A solid machine table with a reinforced machine bed brings very high static and dynamic rigidity and stability, both decisive factors for quality, precision and great productivity.
In 2021, a KELLENBERGER 1000 was purchased, partly for capacity reasons and partly due to performance requirements. René van der Peet from the sales company BMT Machine Tools BV, which represents KELLENBERGER in the Netherlands guided the selection process for the new machine. “We weigh all parameters very carefully when buying a machine and leave nothing to chance. Our workpieces vary greatly in size and we mainly machine small batches and individual parts, which means the machine must be very flexible.”
The KELLENBERGER 1000 is equipped with hydrostatic guides in all main axes for maximum form accuracy in grinding tasks with interpolating axes. The CNC-controlled B-axis for the grinding head is hydrostatic and wear-free. It has a direct drive with a water-cooled high-torque motor and an angle encoder with a 0.1” resolution. The turret grinding head swivels about three times faster and positions with an accuracy of less than one angular second. This reduces non-productive time and increases productivity.
The company decided on a machine with a 1,600mm centre width and a centre height of 250mm. “We make full use of the working space when grinding long mandrels,” says Paul Lennaerts. Of the more than 30 different grinding head variants with external and internal grinding spindles that are available for the KELLENBERGER 1000, Unisign chose the UR 1-6-7 grinding head arrangement with an external grinding spindle and two high-frequency internal grinding spindles with speeds of 42,000rpm and 60,000rpm, respectively.
The purchase of the KELLENBERGER 1000 was well prepared with various grinding tests at the KELLENBERGER factory in St. Gallen. Among the acceptance parts were Capto C8 receptacles that Unisign manufactures in-house. The necessary grinding know-how for the Capto tool holders was supplied with the machine after the grinding tests. “That helped us a lot at the beginning,” says Paul Lennaerts.
“We are very satisfied with the new machine”, Paul Lennaerts sums up. “It has given us the required increase in performance. And we also appreciate the KELLENBERGER machine service, which has short distances due to its location. Overall, KELLENBERGER is not only a machine supplier, but also a consultant for manufacturing processes in the grinding sector.”