As the tried-and-tested machines were no longer available on the market, Schuler Pressen had to find other ways of tackling the production bottlenecks that were looming. The solution came in the form of milling the driveshafts on a modern turning/milling machining centre using a specially manufactured profile cutter, together with carrying out measurements in the machine itself. “Previously, we had no way of directly measuring the form deviations of the tooth flanks,” explains Thomas Vujica from the production planning and NC programming department. “That wasn’t required with the gear cutting machines, in fact, because they are constructed in such a way that there is always an involute. The question of measurement only became an issue when the gear production migrated to the turning/milling centre.” A workaround was found that involved transporting the heavy driveshafts to another company where each individual shaft was measured on a special measuring machine. However, depending on order backlogs and waiting times, that took two to three weeks. And that cancelled out the advantage in time that the milling technique brought with it.
The solution found by Schuler Pressen was the Blum-Novotest TC64-DIGILOG touch probe. The advantage of the DIGILOG touch probe is that it can carry out both digital measurements as well as analogue scans. This means that it is possible to guide the probe over a surface and register measurement data continuously.
The complete measurement of a cogwheel consists of 144 individual measurements on a slanted track along the whole tooth flank – 36 teeth with two flanks each, and in both halves of the double helical gear. The complete measurement procedure only takes 13 minutes at a scan speed of 1.8 m/min. During this time, the DIGILOG touch probe records 570,000 individual measurement values. However, only the linear axes are used during the scan so as to exclude any errors of the rotation axes used for production.
Software developed by Thomas Vujica allows for rapid inspection of the driveshaft. Using the network, the software adopts the measurement data recorded by the DIGILOG touch probe and generates a report including diagrams by way of illustration. The report provides a simple means of establishing whether there are deviations from the ideal form, and if so how big they are. This makes it possible to assess the manufacturing quality. The machine operator can keep track of the measurements on the PC as they are generated and differentiate between outliers caused by impurities and genuine quality issues. Also, the automated measurement technique avoids errors that cannot be prevented in the course of manual measurement.