„Programmed for high performance“

Dreefs: 1,100 silver contacts per minute

Since the end of 2018, Dreefs Schaltgeräte und -systeme GmbH has been using a BIMERIC to manufacture stamped and bended parts with silver contacts. Working together with his team, Managing Director Harald Müller programmed the NC units via the VC1 controller to enable the system to perform a possibly record-breaking 1,100 welds per minute – and save more than €100,000 worth of silver each year at the same time.

Dreefs Schaltgeräte und -systeme GmbH was founded in 1903 and has been part of the Italian Everel Group since 1998. The Group is one of the world’s leading suppliers of electromechanical components for domestic electrical appliances, the automotive industry and the healthcare sector. The portfolio includes oven switches and ceramic cooktop regulators, as well as contacts for car door locks and blower switches. For all these components, for which final assembly is performed in Italy and Romania, Dreefs manufactures the necessary stamped and bended parts – approximately 440 million of them each year! For many years, the stamped and bended parts with welded silver contacts, in particular, were manufactured on five older punches and welding systems, of which four, however, were replaced in late 2018 by a Bihler BIMERIC BM 1500 servo production and assembly system.

In-house development work

To manufacture the silver contacts, the new BIMERIC BM 1500 performs approximately 550 rotations and produces approximately 1,100 welds per minute – a potentially record-breaking speed that actually considerably exceeds the machine’s normal capacity. However, this immense performance was made possible by the intensive extension and optimization work that Dreefs performed in-house at the system. “We acquired only the machine body of the BIMERIC, the NC units and the feed mechanism. Everything was only loosely pre-assembled and we also developed the strip guide and positioning system for the electrode holders ourselves,” recounts Dreefs’ Manging Director, Harald Müller. “We then attended the Bihler training course on the VC 1 controller before programming this to meet our precise requirements.”

Simultaneous movement

The clear, easily traceable program structure of the VC 1 controller provided practically unlimited possibilities for this task. As a result, it was possible to program all the necessary travel profiles and, in particular, all the NC units in such a way that, compared to the usual horizontal time sequence of separate, successive operating steps, the individual process steps follow one another much more rapidly, and in some cases run in parallel. Thus, the welding electrode starts to close while the strip is still moving, thereby taking full advantage of this onset phase. These tuning measures, accomplished to an accuracy of milliseconds, not only brought about thedesired increase in speed but also another advantage: “The optimized travel profiles also help reduce wear at the units,” explains Müller with conviction. This is because the feed mechanism no longer has to work at full speed in order to be as fast as possible but is instead able to run more slowly thanks to the improved timing. “Even at the highest speeds, the BIMERIC runs extremely quietly and stably.”

Set up and save

However, the enormous productivity achieved by programming the VC 1 controller was not the only reason for procuring the BIMERIC. “Another vital consideration was the fact that we can continue to use our 300 or so existing tools on the new system.” At present, 60 tool sets are already in use at the BIMERIC. “We also benefit from the short setup times, which we have reduced from as much as twelve hours to just four hours today,” continues Müller. Another vital factor was that the BIMERIC reduces the amount of silver required for the contacts each year by at least 20 percent, saving approximately €100,000, because it produces larger weld connections and thus permits smaller-sized silver contacts with no loss of functionality.

Fully-networked control

At Dreefs, all the VC 1 controller data is used for process monitoring and the complete status of each manufacturing job is visible in real time in the EMS system. This capability dovetails perfectly with the Industry 4.0 principle which is consistently and coherently implemented at Dreefs and with which the new BIMERIC with its enhanced capacity utilization, efficiency and quality is fully compatible.