Best-in-class clamping tools are sourced from Albert Klopfer GmbH of Renningen near Stuttgart, Germany. The family-owned business is now in its third generation of making collets and clamping cylinders, arbour presses, lathe chucks or centring bits. In-house production manufactures everything from cut blanks to high-precision clamping devices. Since Klopfer is specialising in tailored solutions, production has to deal with a broad diversity of parts. Not long ago, the Mudau factory purchased a UGrind-series hard fine machining unit supplied by DVS Universal Grinding GmbH. In an interview with Dr. Manuel Tröndle, operation manager Norman Speckert enthuses about the new machine.
Mr. Speckert, what made you aware of the DVS UGrind machine?
Speckert: “For a long time we were searching for a CNC machine that helps us optimising our processes. When we visited the booth of the DVS TECHNOLOGY GROUP at the GrindTec exhibition in Augsburg, we noticed the UGrind of DVS Universal Grinding. We were particularly impressed by the possibility of combining hard turning with grinding processes which we were sure would allow us to save on machining time. Combining hard turning and grinding in a machine for small to medium-size lots was a possibility we had not been aware of before. Our main aim has always been to save time and to be able to handle several operations by a single setup.
We were delighted by the modern design of the machine. It is very compact and also houses the coolant unit which saves space by not having to put up an extra external unit somewhere. Key arguments in favour of the machine were its granite bed and a total weight of 7 tons both of which suggest the high rigidity and stability of the machine. In our opinion these were very convincing points. At the moment, we are still learning when to lathe, when to grind or when and how to combine the two. In many cases, we just need to hard turn.“
What influence does the machine have on processing times?
Speckert: “We are saving 30% of time in machining processes involving up to 7 steps. Just lathing without any grinding saves us up to 70% of time. That unfortunately doesn‘t work for every product, of course. But as already mentioned, we are trying out various combinations.“
Which level of precision do you achieve with the UGrind?
Speckert: “Some of our customer orders require maximum tolerances of 5 µm, while flat end faces often need to be within 3 µm of precision. That‘s as easy as pie for us. What is fascinating me most is that just lathing is enough to achieve the 5 µm, even on hardened workpieces of a hardness of HRC 55.“
Which kind of components do you use the UGrind for?
Speckert: “We mainly grind gear rings for serrated Hirth couplings which are predominantly used for indexing discs of rotary indexing tables in machine tools.“
How often do you retool the machine?
Speckert: “Our current lot sizes amount to about 100 pieces. We try to minimise our retooling efforts. The UGrind makes rigging a lot faster which is very obvious in small-batch orders and the much shorter handling times compared to before.“
How long does it take to programme an entirely new workpiece?
Speckert: “After some familiarisation time, programming the machine is quite simple. The graphical interface assists setting up a grinding process particularly well.
A standard workpiece normally comprises two flat faces, four diameters and a chamfer. The chamfer can be machined like a fillet. Most of our programming concerns simple geometrical shapes such as male or female cylinders and tapers. That‘s done very quickly. Owing to the UCee user interface and its free programming options, even rare geometries just take a short while to set up in the machining process.“
Which lathing tools do you use?
Speckert: “We use CBN turning tools for machining after heat treatment and conventional turning tools for machining before heat treatment. We normally start with machining before heat treatment, then we harden with nitrogen and turn or grind for finishing touches. We used to take a long time to pre-grind the soft components. the UGrind now allows us to do pre-turn, which is a lot faster. Pre-turning also produces very high precision levels of 5 to 10 µm which suits us very well because we use plasma nitriding to harden our components as this process creates very little warpage. All we need to do afterwards is to regrind the part a little.”
Germany 
