Compensating 6-pount clamping lowers manufacturing costs

The requirement for high manufacturing precision involving close tolerances means that traditional three-jaw chucks quickly reach their limits. Either a considerable measurement outlay is undertaken to attain the required qualities or one invests in a cost-effective and thus time-saving alternative as is the case with Neunkirchener Achsenfabrik AG (NAF AG).

In the Upper Franconian town of Neunkirchen am Brand, the Neunkirchener Achsenfabrik (NAF AG) with its workforce, currently at a 450 figure, manufactures axles, transmission gears and tandem axles over a
production area of square metres. The company has been family-run since 1960 and is now in the hands of the 3rd generation. The exacting demands placed on quality and a continuing endeavour to improve has enabled NAF AG to become the international leader in tandem axles. Today across the world, one finds NAF AG axles and transmission gears driving machines in building construction, forestry and agriculture.

Klaus Bungeroth, Head of Manufacturing Development at NAF AG also knows that success also brings along its obligations: “The primary factors for smooth running, service life and reliability, for instance, of our transmission gears and axles involve a high degree of accuracy and precision.” Looked at in this light, the requirements of customers and those of Design on e.g. cylinder form (cylindricity) and CONCENTRICITY of parts have constantly risen. Whilst H8 quality components used to be acceptable, the call today is more one of H7 or H6 qualities.

“When we still manufactured the parts in the traditional three-jaw chuck, an immense measurement outlay was needed as it was exceptionally difficult to reach the tolerances required. The inspections meant that we lost a huge amount of time”, recalls Klaus Bungeroth.

In the spring of 2010, the NAF AG Development Manager became aware of the INOZet^® clamping system with which in just a few minutes a 3-jaw chuck was convertible into a compensating 6-jaw chuck. The benefit came from the compensating effect which offset out-of-roundness in the blank and resulted in the clamp optimally resting against all six points on the component. Moreover, even distribution of gripping power across six clamping points instead of three produces a minimum of deformation during actual clamping (polygon formation). Thus, the combination of these two INOZet^® technical properties provides the optimum pre-conditions for manufacturing components with maximum requirements put on their CONCENTRICITY. Even CONCENTRICITY in H7 quality and above therefore no longer pose any challenges. It soon became very clear during the first informative talks in March 2010 that NAF AG not only expected high-quality manufacturing results from the INOZet^® clamping system but also placed exacting requirements on its handling and flexibility in actual applications. Looked at in this light, converting the existing 3-jaw chuck to the compensating INOZet^® 6-point clamping takes no longer than ten minutes. Moreover, just one set of gripping jaws covers the full clamping range of the chuck for inner and outer clamping.

“It was immediately clear to me that fitting this clamping system would considerably improve the CONCENTRICITY”, comments Klaus Bungeroth. The machine operator integrated the new clamping system into his own manufacturing strategy within a very short time and very quickly a particular advantage appeared. Out-of-roundness – which thanks to the system is not incorporated at all in the component – does not need to be eliminated again in the second clamping operation. “As we can decisively lengthen or extend the inspection interval, we now have less work and thus lower costs”, reports Klaus Bungeroth. During a test phase with the first INOZet^® clamping system, NAF AG decided in the spring of 2011 to equip additional machines with this adapter. In the meantime, a total of five INOZet^® pendulum bridges for 250 mm, 315 mm, 400 mm, 500 mm and 630 mm chuck diameters are now in operation. The NAF AG decision in favour of the INOZet^® pendulum bridges is understandable all the more so since alternatives, such as a 6-jaw chuck, would have required a far higher investment. “This reason also ruled out traditional pendulum jaws since a corresponding number of pendulum elements and support jaws would have been comparably much more expensive – let alone the raised setting-up outlay needed.

The considerable flexibility of the INOZet^® clamping system enables us to convert a 3-jaw chuck to INOZet^® 6-point clamping within a few minutes”, says Udo Schroft, a NAF AG employee. “CONCENTRICITY is far less of a topic today; it used to be quite a different story”; that is the positive conclusion of Klaus Bungeroth.