Klenk & Stiefele

Complex Machining of Complex Workpieces

The INTEGREX i series machines have been specially designed for the complete machining of complex workpieces. This concept, called "Done-in-One" by Mazak, integrates all machining processes from the supply of the raw part through processes such as turning, milling, drilling, and much more without any repositioning process. This significantly reduces the lead time of a workpiece in manufacturing, increases machining accuracy, and considerably relieves the operator. The machines are available with different travel ranges and turning lengths. The main and counter spindle each operate at 5,000 RPM, and the powerful milling spindle, which can swivel in the B-axis, operates at 12,000 RPM to ensure the necessary dynamics. The C-axis with a direct drive motor enables 5-axis simultaneous machining.

"The quality of the processed workpieces was outstanding, and this has spread among the customers. As a result, we could hardly keep up with the inquiries."

Andreas Stiefele's strategy paid off: The number of employees quickly grew to four, then to nine. Corina Stiefele was always by his side. "We both trusted that the risk we were taking with the purchase of the machine would be worth it," she recalls. "After all, the machine cost the equivalent of a single-family house." Andreas Stiefele adds: "It quickly became clear that we had hit the nail on the head, so to speak, with the INTEGREX regarding customer requirements. The quality of the processed workpieces was outstanding, and that spread among the customers. As a result, we could hardly keep up with inquiries."

A planned new building for a necessary company expansion failed in 2016 due to the lack of construction land. Instead, the Stiefeles took over a company that was for sale and had a spacious office building with production space. Thus, the purchased Klenk CNC technology and Stiefele metal processing became Klenk & Stiefele CNC Technology GmbH. It is a small but important note that the former owners Klenk are still active in the company today, and almost all customers remained loyal to the company. Currently, 48 employees work in about 2,600 square meters of production, storage, and office space; 27 are in production on a total of 17 machine tools. "We only have skilled workers at the machines; this is crucial for quality because we are somewhat 'splitting the µ," says Andreas Stiefele. "The demands of our customers are constantly growing. This is partly due to the ever-increasing price pressure."

High-Teh Solution Outside The Norm

Meanwhile, many parts at Klenk & Stiefele are machined with 5-axis milling. Materials such as steel, stainless steel, aluminum, bronze, brass, copper, and plastics like PEEK are processed for industries such as aerospace, medical technology, food and semiconductor industry, and the automotive industry - especially in the field of premium interiors. Customers are primarily supplied in Germany, with a growing trend also in neighboring countries.

The machinery must meet these high demands at all times. A Mazak machining center VTC 300C-II with pendulum machining was specially purchased for a customer from the medical technology sector. Like aerospace and the semiconductor industry, medical technology is one of the most demanding sectors when it comes to the quality of the workpieces. With the VTC, the machining time for the demanding parts was reduced by 60%. "A contract manufacturer must purchase new machines exactly as needed," says Emanuel Stiefele, who is already in his family’s second generation of leadership. It is not surprising that he became the state champion in training as a cutting machine operator in 2012, given his background. The team is also actively supported by sales manager Björn Nürnberger, who joined the company in 2020. "Our turning shop is currently being newly equipped," says Nürnberger. "And the production flow has been completely overhauled."

The latest machine acquisition is a high-tech solution that is out of the ordinary, as Emanuel Stiefele explains. The machine configuration of a VARIAXIS i-700 with tailor-made automation was developed and implemented together with Mazak and a proven Mazak automation partner. The VARIAXIS machines are ideally suited for a wide range of automation solutions. In this case, a double pallet changer was integrated, which can be coupled with a 24-fold pallet changer to drastically minimize setup times and allow for a variety of processing options.

The VARIAXIS machines are ideal for the complete machining of complex workpieces due to the combination of high spindle power and enormous torsional rigidity. They allow for the highly efficient machining of workpieces in a single setup. The cast construction designed for maximum torsional rigidity guarantees outstanding machining results without any loss in performance or accuracy. This is thanks to the robust 35 kW spindle with 18,000 min-1 as a major advantage, the linear guideways on all linear axes, and the spindle-mounted table with a roller gearbox for the A and C axes.

Andreas Stiefele is not only enthusiastic about the machines when it comes to Mazak, but also about the Mazatrol control system. "Accuracy is the measure of all things for us," says Stiefele. "The SmoothX control system we use provides this accuracy with absolute process reliability. We program 98% of the machining on the Smooth control system, also externally with a digital twin under Mazatrol. Here, primarily 3+2-axis machining is programmed. External CAM programming is only necessary for simultaneous machining." In these cases, Emanuel Stiefele performs the pre-programming on the PC.

In the meantime, next to the SmoothX, Mazak has made available the SmoothAI, a control variant that is even easier to program with the help of artificial intelligence, even for complex machining. Andreas Stiefele is observing the new control with interest. A test version is already in his possession, and internal preparations for a possible application are underway.

"Compatibility must of course be considered, but that is not a problem with Mazak controls."

"Mazak collaborates well with the customer in all respects, including service," confirms Andreas Stiefele. "The Mazak support is quickly reachable and takes care of issues exemplary. Spare parts are available overnight if needed. The Mazak service hotline is free and accessible 24 hours a day, and a 24-hour service for spare parts is available. As mentioned, we don't often take advantage of this, as our Mazak machines generally run very reliably and without interruption!"

The enthusiasm for Mazak machines is still unbroken with Andreas Stiefele after all these years. In 2019, the Stiefeles visited the Mazak headquarters in Japan together with their sons Emanuel and Christopher. And just now, a further step towards a successful future has been taken at the AMB with the purchase of a QUICK TURN 350MY with a bar loader. In the future, workpieces with a diameter of 100mm can also be produced directly from the bar at Stiefeles.