INITIAL SITUATION AT THE PRODUCTION SITE IN ISERLOHN
One of the core products of Risse + Wilke Kaltband GmbH & Co. KG is the production of lead-free quenched and tempered cold-rolled strip, which is used, for example, for the production of high-quality saw blades. The steel strips used here must undergo a special quenching and tempering process to give them high strength and hardness for demanding applications. After passing through the quenching and tempering furnace, they are cut to length at the downstream cut-to-length shears and delivered to the customer as sheet metal blanks for further processing.
Due to the extreme hardness of the material to be cut, the process of cutting the quenched and tempered steel strip puts more strain on the cut-to-length shears than usual. In addition to wear, there is therefore also a risk of blade cracks in the production process, depending on the sheet length to be cut and the resulting cutting cycle "This must be rectified immediately," emphasizes Roland Pudelko, Production Manager for Heat Treatment processes at Risse + Wilke. At the production site in Iserlohn, immediate means a maximum time of 7 minutes until the looping pit positioned in front of the cut-to-length shear has run full, thus leading to a standstill of the strip running inside the furnace. "If the strip stops," says Roland Pudelko, "the entire length of the strip inside the furnace can no longer be used and has to be scrapped." At the Iserlohn production site, this corresponds to a strip length of up to 60 meters.
Unfortunately, blade cracks are not uncommon in the production process. The micro-chips produced during cutting can enter the cutting gap unnoticed and negatively affect the preset cutting gap adjustment. "As a result, we get cutting burrs both on the shear blade and on the strip material to be cut. This is not compatible with the high quality demands we place on the material pretreated by us," says Pudelko, defining the internal quality criteria.
A solution had to be found that would allow the shear blades to be changed within a very short time. At the same time, a precise cutting gap adjustment had to be ensured in order to meet the strip qualities required on the market for further processing of the pretreated steel strips. Requirements that Roland Pudelko attaches great importance to. "Risse + Wilke is a problem solver on the market for cold-rolled steel strips and promises its customers high-quality cut-to-size sheets. We process steel strips of 0.2 up to 6.20 mm thickness and 20 to 725 mm width. Our customers rely on us to deliver all material dimensions 'just-in-time' with a consistently high quality . Shear blade changes with a maximum duration of up to 6 hours were no longer acceptable for us," states Roland Pudelko, describing the task.
FROM AN IDEA TO THE (SPECIAL-PURPOSE) SOLUTION
With the basic idea in his mind to change the shear blades by means of a new assembly consisting of two slide-in units, Roland Pudelko got in contact with renowned metal shear manufacturers in 2018. However, various discussions revealed that an "off-the-shelf" solution could not meet the requirements defined by Pudelko which included both a shear blade change in less than 7 minutes and the precise cutting gap adjustment at t the same time
Since the available installation space was very limited and Roland Pudelko favored a simple solution that did not require any additional hydraulic, pneumatic or electrical auxiliary units and could also be easily integrated into the existing line peripherals, he also contacted hpl-Neugnadenfelder Maschinenfabrik GmbH. Being the manufacturer of the strip handling technology for the existing quenching and tempering line, hpl was very familiar with the quality requirements of the production site in Iserlohn and was therefore able to develop a solution together with Roland Pudelko that exactly met the customer's needs and could be easily integrated in the available installation space.
During the design phase, Risse + Wilke, in the person of Roland Pudelko and HPL, worked closely together, as Mr. Pudelko has detailed knowledge of both the material quality requirements as well as the experience of the operating and maintenance personnel and wanted to incorporate this knowledge into the development process. Thus, the basic principle of the new solution consisting of two slide-in units for a quick shear blade change was adopted by HPL and successively optimized. Initial considerations of moving the blade changing mechanism by means of a trolley were quickly rejected and replaced by a permanently attached swiveling table. This prevents the risk of tipping the solidly designed changing unit with a weight of 1.5 tons when being moved.
In order to ensure for the two slide-in units a high degree of reproducibility of the shear position/alignment to the strip, custom-fit centering pins were also integrated into the mounting device during the development phase.
All elements of the concept hpl developed were checked by Roland Pudelko for their usability on-site and were jointly agreed. After a three-month design and development phase, a product was created whose function can be described in just a few words:
#solid #compact #precise #quick to operate #problem solved
During line operation, one of the two slide-in units is in use, while the second is on the swiveling table, which is situated parallel to the strip forward movement. When changing the shear blade, the table is swiveled at 90° to the strip forward movement. This allows the first slide-in unit to be removed from the shear housing and the second slide-in unit, precisely preset with new shear blades, to be pushed into it. This process only takes a few seconds, and after less than a minute the line returns to normal production operation.
The actual shear blade change at one of the two slide-in units takes place on the table, which is swiveled back into its parking position. Günter Veldmann, project manager at hpl, sees great benefits for his customer: "The interacting slide-in units were also a real novelty for us. With the new changing unit consisting of two slide-in units, the operators have plenty of time to change the shear blades and adjust them precisely. Furthermore, we create safety, because nobody needs to work directly in the shear housing under time pressure.”
The cutting gap can be infinitely adjusted between 0 and 1 mm with a precision of 1/100 mm using two eccentrics. Thanks to the small overall width, the new cut-to-length shears can be easily integrated into existing strip processing lines.
POSITIVE REVIEW
In almost 12 months from the receipt of order to commissioning at the production site in Iserlohn, Risse + Wilke and hpl worked closely together to develop a special-purpose assembly that is characterized by the required simplicity and solid design, but at the same time ensures the desired precision in the cutting gap adjustment and a shear blade change in under a minute.
After six months of operation, it has already been confirmed that the intensive development work has paid off in full. The new quick-change shears have not only increased the productivity of the quenching and tempering line, but have also significantly improved employee satisfaction. In the past, unplanned knife changes often meant that maintenance personnel had to be called at the weekend. Today, maintenance personnel can prepare the slide-in unit in parking position unhurriedly during their scheduled shift, thus preventing any possible production downtimes in a forward-looking manner. Changing shear blades shortly before the end of the working day is now a thing of the past at the Iserlohn production site.
The introduction of the new quick-change shears also brings additional benefits for the end customers of Risse + Wilke Kaltband GmbH & Co. KG. While the company was already operating at a very high level of quality in the heat treatment area, the described process and handling optimizations based on a close cooperation on the product itself, are now leading to a continuous increase in productivity throughout the complete production site. With the development of this innovative product, Risse + Wilke Kaltband GmbH & Co. KG has once again proven that its customers are seen as valued partners, for whose satisfaction it continuously invests in the optimization of product quality.
All advantages considered, the new quick-change shears have harmonized many processes in the strip processing area and made them more flexible, because the precise cutting gap adjustment and the extra time available enable Risse + Wilke to operate a more flexible product matrix and no longer has to divide up orders according to the strip thickness to be cut. The reduced handling effort also means that a reduced quantity of experienced and trained maintenance personnel must be available to operate the quick-change shears.
ADDED VALUE THAT COUNTS
The costs for the quick-change shears will amortize within two years and the shears are worth it," explains Roland Pudelko. "Originally, we had been aiming for a duration of less than five minutes for changing the shear blades. hpl has far undercut this specified value: After just one minute, the strip continues moving forward. For us, this means that we produce a larger quantity of high-quality strips for our customers."
Mr. Heß and Mr. Pollok, both operators at the quenching and tempering line, add enthusiastically: "Blade changes in continuous running strip lines are always associated with time pressure. Thanks to the new quick-change shears, this pressure is a thing of the past and makes work more relaxed. Another positive aspect is the ease of operating the new shear. Due to the smooth-running rollers of the swiveling table, you hardly notice that you are moving 1.5 tons of weight. The new shears are also characterized by significantly lower noise operation compared to that of the other shears operated in the production site at Iserlohn."
These are reasons that speak for themselves and, just six months after commissioning, suggest that the use of the quick-change shears should be expanded further. The installation of a further quick-change shear on the parallel running quenching and tempering line is currently being planned so that this line can also be used more productively and efficiently in the future
