The Stahlwille die forge manufactures tools at the Starrag Heckert H55 machining center
Stahlberg, Erzwiese and “Finstertal" mine: In the district of Schmalkalden-Meiningen, Germany, many place names point to the high volume of ore in the area. Due to mineral resources of iron, silver and copper, many tool workshops, ironworks and forges have been built on the edge of the Thuringian Forest since the Middle Ages. Among them were artisan pioneers, such as tool manufacturer SWM-Gesenkbau, who was part of the industrialization in the early twentieth century and is still going strong today.
A castle ruin, a hammer and pliers: The coat of arms of Steinbach-Hallenberg clearly points to the town’s specialities. According to the town’s website, “the long tradition of the local smithery is still being perpetuated with great enthusiasm, exemplified by the impressive metal working museum and the only corkscrew workshop in the world”.
Just as impressive is the 60-year-old SWM tool factory, which has been a part of the Wuppertal-based STAHLWILLE Group – one of Germany’s leading tool manufacturers – since 1996. Since then, the die forge in South Thuringia has supplied the entire group with forged parts for the production of high-quality screwdrivers and gripping tools as well as for the manufacture of intelligent torque technology. Die forging is one of SWM’s particular strengths, as the tools have always been made in-house in Steinbach- Hallenberg. Combined with decades of experience, the integrated CAD-CAM chain ensures efficiency and quality. This is especially evident when the tools are fed into one of the partially automated production lines.
At the center of the newest, cutting-edge SWM production line is the new Starrag Heckert H55 machining center. Those involved in the manufacturing industry are probably surprised to hear that a die forge uses a high-precision compact machining center. But the reason is obvious if you know both the engineer who devised this production line and his ideas.
Enrico Danz: The Gyro Gearloose of the die forging sector
The human factor, which is particularly important in tool making, plays a key role in this area: Enrico Danz explains how the success of a company stands and falls with its employees. Production Manager Danz started as a car mechanic and completed a mechanical engineering degree at night school while working at SWM. The mechanical engineer now specializes in tool technology, yet this genius has not gone to his head. Danz is certainly not a boss who spins his theories and makes decisions from behind his desk. He knows every workpiece inside out; there is no movement that Danz has not already done many times himself. “To identify potential for improvement, I have to visit the site myself. There’s no other way”, says Danz.
“The Heckert is a workhorse. It has allowed us to open up countless new possibilities, with more being discovered all the time.”
One day, the pragmatist realized that the production of large pliers showed potential for optimization. For him, the typical approach of increasing the degree of automation with robots and complex, standardized clamping devices was not enough. In his opinion, metal cutting was the weak point – clamping and milling the pliers’ heads took too long. Moreover, the spindles had a limited capacity. Danz explains further: “In addition, the product variety was severely limited and retooling was very time-consuming. So it was clear that we had to rethink the production line. Our goal was to significantly shorten the production process and keep the set-up time as short as possible”.
The greatest challenge was the building structure at the mechanical production site. According to Danz, the production hall is “a GDR building from the 1960s, where the width of the stud frames and the load capacity of the floors set the pace”. The only solution was to bring in production technology from Chemnitz. After all, the Heckert compact series is characterized by one feature in particular: it offers maximum productivity with minimal space requirements.
The “assistant” from Schmalkalden
Anyone who is familiar with the world of Disney comics knows that even a technical genius like Gyro Gearloose doesn’t work alone. And while Gearloose gets his help from a lightbulb with legs, Danz looks to Jan Hilpert of Schmalkalden. The Managing Director of automation specialist ROBOTICS was, as usual, one of the first to hear about Danz’s latest plan. “When he presented me with his idea for the new production line, I immediately understood the challenge”, he recalls. “How can we achieve an automated shift with a planned product range of 26 different workpieces and an average processing time of 30 seconds?” Danz adds: “While Jan was thinking about automation, I was designing the fixture on which at least four different workpieces can be clamped”.
Why does SWM not involve fixture design specialists in the project? Danz was quick to dismiss this: “All the fixture manufacturers I found had little experience with forged parts and their tolerances”. “In our case in particular, there were fluctuating manufacturing tolerances due to the shrinkage rates during die forging. Basically, this was not their area of expertise. That’s why it was probably the wisest decision to use our own expertise and planning capacity”.
High-precision machinery in the forge – Using a sledgehammer to crack a nut?
The topic of manufacturing tolerances is fascinating. What use is a high-precision machining center like the Heckert H55 to a company whose usual tolerances are a few tenths of a millimeter? “In typical applications, accuracy may be the decisive factor, but for us it came down to the stability, space requirements and amazing flexibility of the Heckert center”, says Danz. “At the moment, we are still working on getting the planned products onto the machine, one by one, but new ones are constantly being added. We are now also receiving parts from sister companies that have to be machined on the reverse side and finally joined together. We have also been impressed by the precision and repeating accuracy of our new machine”.
The die forge requires very rugged and versatile fixtures, which can weigh half a tonne on their own. “With a maximum loading weight of 1,764 lb. (800 kg), the Heckert can easily cope with this”, says Danz happily. “The Heckert holds up so well with an incredibly stiff and optimally damped spindle that I can now really maximize the performance capacity of my HSS profile cutters. At present, we have increased cutting speeds by around 40% in conjunction with the fixture developed in-house compared to previous production runs. In addition, start-up strategies can be programmed and can identify further potential for optimization. With the H55, completely new tool concepts can be created for machining that were not possible before”
Rapid changeover facilitates automation
The machining center not only scores in terms of stability, but in terms of flexibility too. “For me, the loading mass is also ideal in terms of flexibility, because it gives me more design options for the fixture”, says Danz, adding another example of flexibility gains: “I used to have some parts mechanically machined manually in half a shift. Today, thanks to the Heckert, I can changeover so quickly that I can actually automate the process and deploy the employee elsewhere. The changeover takes just over half an hour, by which time the next part is already running. In pallet sequencing mode, it is easy to quickly have two, three or four parts”
When asked what he particularly likes about the Heckert, “everything” is his first response. But he eventually adds: “The Heckert is a workhorse. It has allowed us to open up countless new possibilities, with more being discovered all the time. This makes me smile every single time. With this knowledge, I can now start to rethink completely different areas of our portfolio, which makes the future even more exciting. Incidentally, this is based on investing in a second Heckert H55 which is identical in design”.
No fear of speed!
Take a closer look at THE highly dynamic solution that masters even ambitious cutting on workpieces up to 1.5 tonnes despite lightning-fast positioning! In the video, Starrag's CSO Alexander Attenberger and experts from the plant in Chemnitz introduce the new Heckert H65.