German cookware manufacturer WMF Group introduced a standardisation strategy that helped it streamline production processes at its tool- and mould-making division, thereby creating the scope for services for external customers, assisted by a C 22 UP machining centre from Hermle.
WMF was founded in 1853 as Metallwarenfabrik Straub & Schweizer, and has been part of the French SEB Group since 2016. More than 2,200 employees at the Geislingen headquarters and the nearby Hayingen plant alone are engaged in the development and production of high-quality cookware and cooking knives. Many of these products are still manufactured through the primary and secondary forming of sheet metal blanks, with most of the required tools produced in-house at its tool shop in Geislingen.
“For about 30 different knife models alone, we use between 100 and 150 die tools, each consisting of an upper and a lower tool made of hardened hot-forming steel,” explains Hans Brühl, Part Production and Tooling Technician at WMF.
To guarantee consistent product quality, the mould makers have to rework the tools after roughly 3,000 strokes. This involves precisely milling and removing approximately 0.5mm of material, a process that is possible up to 15 times with the dies.
“In the past, we performed all these milling and finishing operations on an HSC milling machine,” says Bruhl. “However, this machine could only accommodate two dies at a time, which then had to be processed successively and in several time-consuming setups. As knife production in Hayingen increased, more dies were obviously needed and this led to capacity shortages.”
An evaluation process, which included tests to assess contour accuracy, precision and surface quality and to determine whether machining time for refinishing had been significantly reduced, saw the C 22 UP five-axis machining centre from Hermle come out on top. A machining process developed together with Hermle led to extraordinary results: not only was the desired reproducibility of contour accuracy and surface quality achieved, the machining time was also reduced considerably.
With the C 22 UP machining centre, which features an 11-fold PW 150 pallet changer, it is now also possible to rework dies automatically – during the night and at weekends. This means additional capacity is now available for processing internal and external orders.
The fact that WMF’s tool and mould making division was able to achieve new levels of productivity is due, on the one hand, to standardisation of the dies. On the other hand, a self-developed pallet and workpiece clamping system with four-fold bolting directly to the pallet and the automation provided by the PW 150 pallet changer have allowed machining to become significantly more efficient.
“We were able to reduce the machining time by 50% and more when refinishing the dies,” says Axel Spadinger, Head of Tool Engineering & Making at WMF. “Since this work is generally carried out at night and over the weekend, we can therefore use the C 22 UP machining centre very flexibly during the day for all other machining operations. Combined with our knowhow in tool and mould-making, we are thus in a position to meet external customer needs on time.”