A Fanuc robot on a linear track interconnects the machines with a washing station, a coordinate measuring machine and several storage systems for tools and workpiece pallets.
Helmut Böhler, manager of the toolroom, explains: “Our department works on the same principles as the main factory, but flexibility needs to be even higher. Batch size is low and frequently one-off. To maximise utilisation of our machines, we look to automation and also to reducing the number of component set-ups. We try to integrate cycles that were previously performed sequentially on one or more machines into a single operation, such as the high speed milling and jig grinding of prismatically shaped components. The approach is not only more efficient and less costly, but also increases accuracy, due to fewer reclampings.”
The company has relied on high speed milling centres from Roeders since 2003. In the early days, they were used for producing highly accurate EDM electrodes in copper or graphite. With the more recent machining centres, the focus shifted to hard milling and jig grinding on a single platform.
As they are automated, the Roeders machines can be used with minimal operator involvement, especially since grinding tools can be exchanged in a similar way to the milling cutters and drills.
Workpiece datuming is carried out automatically within the machine by a measuring probe. The part does not have to be fixtured accurately, saving time, as its position and orientation are updated in the control, which automatically recalculates the NC program shift. Periodic in-process measurement of key parameters allows tool offsets to be sent to the machine control to ensure machined parts stay within tolerance. Drawing tolerances for injection mould tools are especially tight, typically ±5 micron for dimensions and ±3 micron on bore diameters.
The machines feature linear motors in all axes, linear scales for absolute positional feedback to within 50 nm, weight compensation in the Z-axis and fast movement in all axes without stick-slip on reversal, all ensuring accurate interpolation.
In the Blum toolroom, the mix of jobs involves not only complex geometries that need to be programmed offline but also simpler parts that can easily be programmed directly at the machine. The suitability of the Roeders RMS6 CNC system to accommodate both approaches was an important criterion.
Moreover, as it was developed in-house, the control software is able to be easily and promptly upgraded. Blum has already benefitted by taking advantage of recently improved cycles for helical and rapid traverse jig grinding; all Roeders machines at Hoechst are updated to the latest software release.
Ralf Hildebrand, manager of the Blum grinding department, adds: “Product quality is only one factor for achieving success. The other is cost efficiency. The only way we can achieve that is to extend the quality ethos to the machines we use as well as to our practices on the shopfloor, in the metrology department and all the way along to the packing section.”
This article was first published in the September 2016 issue of Machinery magazine.
