A SOUND INVESTMENT: DRILLING PROCESSES ON THE TEST BENCHThis article show a customer success story for gear machining with the customer IMS Gear SE & Co. KGaA, headquartered in Germany.
IMS Gear SE & Co. KGaA is one of the leading manufacturers in the field of gear technology. Headquartered in Donaueschingen, Germany, the company has developed from a pure parts supplier into an engineering and solutions provider in the automotive industry. It manufactures gears, assemblies and components primarily for the automotive sector at three German sites and in plants in China, Mexico and the United States and has some 3,400 employees worldwide. Gears and drives from IMS Gear are in operation in almost every car on the road, providing steering assistance, electric seat adjustment, lumbar support, electronic parking brakes, automatic tailgate opening and more.
Reinhold Gnädinger is the manufacturing manager at IMS Gear. “The core competence of our business unit is quite clearly the production of precise, long-lasting transmission components from 2,000 to 3,000 metal and plastic elements,” he says. By overmolding the metallic hubs and shafts with purpose-developed plastic materials, use of the specific material properties can be optimized so that high torques can be transferred reliably and quietly.
Noise is an issue. The hub of the steering gear When you must produce half a million drill holes cost-effectively, optimization is key. That was the challenge for production specialists at Germany-based IMS Gear. Their goal was to significantly improve process reliability and reduce noise levels in the production of high-grade steel, with a material removal rate of 80 percent. PHOTO: AUDI EDGE / 2.2019 21 CUSTOMER: IMS GEAR worm wheel, which is made up of three components, is manufactured in parallel on four offthe-shelf six-spindle machines, using a micro-alloyed AFP stainless steel with a strength of about 900 N/mm2 . The inside diameter of 23.5 millimetres is drilled in the first machining stage, which, at a cutting speed of 130 m/min and a high material-removal rate over a very short operation period, involves a very unpleasant, continuous high-frequency noise.
The high noise level had long been criticized by representatives responsible for safety, explains Burhan Kaya, manufacturing engineer at IMS Gear. “The incredibly high volume of chips when drilling leads to extremely high stress on the drill body,” he says, adding that the abrasion caused by the high strength and the pressure of chips created erosion in the chip chambers of the Perfomax indexable insert drills used at the time. Subsequently the drill bodies became increasingly unstable. They vibrated and frequently had to be replaced prematurely. “It was no longer possible for us to reliably plan the process,” Kaya says. “The cost of replacement bodies was too high.”
Thus there was no question of being able to return to the crown drills used previously. Essentially, the performance data of the Seco Tools Perfomax drills with a tool life distance of around 48 metres and a service life of more than 1,500 parts per cutter was also more than convincing.
Reinhold Gnädinger explains that the continuous optimization of existing processes is an essential requirement that arises in the automotive industry. As part of the product development the Industrial Engineering area at IMS Gear ensures that when new products are launched the production plants and processes are transferred completely to the production areas. In the current large-scale production operation, process engineers such as Kaya must then take care of the necessary improvements. “We had to solve the familiar problems of noise emission and drill body service life, so we re-evaluated the entire drilling process,” Kaya explains. “Tool technology is steadily evolving, and we wanted to see what was achievable.” Kaya initiated, managed and documented the improvement process and asked five tool manufacturers for their solutions.
IMS Gear’s criticisms of the Perfomax drill bodies it was using were passed back to Seco’s product
The hub of the worm wheel is a safety-relevant component of automotive steering gears.
development at group headquarters in Sweden. Despite the convenience of laboratory tests, Seco only takes new products to market after elaborate practical tests. At the start of the new benchmarkingat IMS Gear, the Seco team was working on redeveloping the successful Perfomax series. At the time, an additional production line was just being built in Sweden for the advanced design of the new, highly stable Perfomax drill. On three machining centers, arranged one after the other, the drill bodies, now made of heat-treated material, were provided with a wave-like surface structure on the chip spaces and on the outer diameter. The chip contact area in the chip chamber was subsequently laser-hardened to 65 HRC. The design of the insert seat, which now ensures a larger contact surface with the insert, was also revised.
In addition to a stable drill body, the high quality of the cutting material is decisive for safe chip control and a long tool life. The DP3000 insert for central and peripheral cutting required for the task at IMS Gear has a patented Duratomic coating. This is characterized by an ordered crystal structure and thus a smooth surface, with the result being a particularly high thermal stability and edge stability. Four competitors appeared, one after another, at IMS Gear in Donaueschingen. Over a period of four weeks each, the four Index MS 42C lathes were equipped with the holders and inserts of each supplier; with the tool life obtained, the wear to the drill bodies and the noise were clearly documented.
“With a planned output of more than 120,000 parts per week, the worm wheel hub naturally offers an optimum database for an absolutely fair evaluation of the individual drilling tools,” Kaya explains. The test results spoke clearly. In the case of the applicant with an exceptionally low machining noise, the tool life, at 500 to 600 parts per cutter, was far below the required 1,500 parts. The other tool suppliers came close to the service life requirements but failed on the noise level or the service life of the drill bodies. At IMS Gear the very open and cooperative partnership with Seco Tools was much appreciated, as were the results of the new Perfomax generation. After initial test results with four prototypes, the position of the laser-hardened contact point in the chip chamber of the new Perfomax was moved back. According to Kaya, the expenditure on this project has been well worth it for both IMS Gear and Seco Tools. With the new material and design of the basic Perfomax body, the wave-shaped surface of the chip chamber and the laser-hardened chip contact surface, the criticisms of the preceding version have disappeared, as has the noise in the production hall. The newly acquired stability of the Perfomax reduces vibration and significantly increases quietness. Since the new optimized Perfomax generation has been in use at IMS Gear, it has also been possible to more than halve the use of insert carriers. “The expected service life of 100,000 holes drilled per carrier will be exceeded,” says Kaya.
Gnädinger, the manufacturing manager, adds: “The safety of the machining process is fully restored. We have the right tool cost factor and can reliably plan our capacity.” Production experts from IMS Gear rate the cooperation with Seco Tools extremely highly. Comments Gnädinger: “Just as for IMS Gear operating as a partner in the automotive industry, a tool manufacturer like Seco Tools must constantly optimize and develop its products. The current benchmarks show how beneficial cooperation on equal terms can be for both sides.” During this improvement process the grooving process on the hub of the worm wheel, which attracted the attention of IMS Gear and Seco Tools, was also jointly optimized. It was possible to double the tool life, compared with competitors’ tools, and improve the process reliability of the tightly toleranced grooving operation by using the X4 grooving system combined with the new TGH insert grade from Seco Tools.