Neither Scrap nor 100 Percent Inspections Thanks to a New Geometry

A lean project at the stamping plant in Weinheim, Germany, has simultaneously improved quality, productivity and on-time delivery. Freudenberg Sealing Technologies (FST) has honored it with the Lean Systems Award Europe.

Nearly 1.2 million metal parts, individually checked by hand. It takes little imagination to understand that the process takes a massive amount of repetitive, manual labor. There is an urgent need to take action in our manufacturing process, if deformations are regularly found during the 100 percent inspection, and the defective parts are sorted out as scrap. In this case, the response took the form of a lean project lasting several days.

“The problem was multilayered. Numerous causes were considered possible. So a systematic approach was required,” said Dr. Jörg Avemann, Manager, Lead Center Stamping. The lean project’s core team included Claudia Romanski, Lean/GROWTTH, Guido Will, Quality Management, Gregor Kempf, Engineering, and fitter Peter Fieger, all from the Weinheim Stamping Facility. Over the course of the project, the team used methods from the “lean toolbox,” among other options, but was able to draw on multifaceted support from the facility’s employees and the tool shop as well. The interdisciplinary team worked out very well, contributed added value and was a key success factor for our project,” Romanski said.

SHORTER THROUGHPUT TIMES

But first things first: “At the very start, during brainstorming, we came up with some possible reasons for the deformation,” she said. “The geometry of the channel became the focus during a systematic analysis in which the metallic parts are shot with compressed air after stamping and forming. At the end of the channel, impact flaps slow the approaching metal rings and guide them on their way to the transport box. It turned out that the impacts on the channel led to damage, no matter what the stamped parts’ trajectory was. In addition, an open edge in the parts’ impact zone was not protected. It was possible for the rings to strike them and suffer damage.

The ejection channel also needed a new design. Here the team is making valuable progress with the help of the 3P method (see box). The trajectory of the parts in the channel has been changed, the edge rounded, and the impact protection reinforced with three curtains. “With the new process, we do not need to inspect all the parts. This will greatly shorten throughput times. In monetary terms, we are saving more than 40,000 euros,” Romanski said.

There is another positive side-effect that falls into the “lessons learned” and “transferability” categories. Stamping plants in other FST facilities are taking advantage of the insights gained in Weinheim. Among other uses, these findings flowed into a new concept for an automated stamping cell, ACDC (see Sealing World 03_2021 as well as page 30 of this issue).