The stamping facility in Weinheim reduces engineered waste in metal part production with the help of a program developed in-house.
The theme is somewhat reminiscent of cutting out gingerbread or butter cookies from rolled-out dough. If you use the dough surface carefully, you can get lots of shaped pieces of dough and place them on the baking tray. If, on the other hand, you place your shapes unsystematically, you will cut out far fewer pieces on the same surface. At the same time, a lot of leftover dough remains unused.
Such residues are not a problem with dough, as they can be processed again after a short kneading process. The situation is different with steel strips, technically known as coils, from which metal parts for radial shaft seals are punched. Steel that remains on the edge and between the blanks is waste. At Freudenberg Sealing Technologies (FST), this is collected as engineered waste for recycling. But reprocessing it is time-consuming and costs energy.
The Stamping Facility in Weinheim has therefore been working for a long time to minimize this engineered waste for the sake of efficiency and sustainability – which specifically means making optimum use of the strip widths or surfaces of the steel coils. One successfully practiced solution for this is the so-called zigzag feed. It enables metal rings of different diameters to be punched in different patterns from the same wide strip: sometimes arranged one behind the other, sometimes next to each other, sometimes at an angle, sometimes offset – always with the aim of punching as many metal parts as possible from a coil with as little excess steel waste as possible.
The plant in Weinheim produces almost 5,000 different items on 13 presses, many of them in small batch sizes. It also uses coils in up to 15 band widths, each in differing material thicknesses. These figures alone give an idea of how complicated and time-consuming production planning geared towards operational excellence is. Any waste of material costs money, every coil change costs time. The top priority is therefore to punch as many parts as possible from a coil while generating as little punching waste as possible. It is particularly efficient if different items or dimensions can be produced from the same coil one after the other – after the obligatory tool change.
The Stamping Unit in Weinheim has developed a planning tool that does justice to this enormous complexity: the bandwidth calculator. “This is a program into which we enter all our article data, including the respective annual quantities. Each article is now assigned to a specific belt. The parameters of all our systems are also stored, i.e. what each of our presses can achieve,” says Bernd Wolf, Head of Tools & Process.
Until now, the plant has based the widths of its coils on its top 100 articles. The new program now takes into account the entire range of almost 5,000 articles. For each of these articles, the calculator defines the best band width and band utilization, i.e. the most efficient pattern in which the blanks are cut. The program even calculates alternatives if a material is not available.
“Lessons learned”
Based on this data, the stamping plant in Weinheim was able to optimize its warehousing in the first step and determine which coil widths it has available in its limited storage space. “The main advantage, however, is material utilization,” says Claudia Romanski, Plant Manager. “With the help of the coil width calculator, we can significantly reduce our engineered waste and save 240 tons of steel per year.” This CO2 saving literally weighs even more heavily when you consider that around 1.9 tons of CO2are generated for a single ton of steel produced. Moreover, the 240 tons of steel saved do not have to be purchased and processed in the first place: This is a sustainability gain that also pays off in terms of costs.
Two special features: Firstly, the program can be easily transferred and used in other FST plants – which is already happening in terms of “best practice” and “lessons learned”. Secondly, the bandwidth calculator is now even available as an app. This means that production managers can also check values on their cell phone from time to time.
