A Common Thread Between Textiles & Grinding? You Bet
Barmag AG, a manufacturer of spinning machines and pumps was founded in 1922. Over the years the company developed numerous innovations in natural and man made textile machines for spinning, winding, twisting and extruding. Today, Barmag is part of the multi-billion dollar Oerlikon Sauer Textile Group, the world leader in solutions in textile machinery and a constant contributor to ever-more efficient textile production. Here’s how grinding plays a role in the continued success of machines for the textile industry:
REMSCHEID, GERMANY - Not far from Düsseldorf to the east and Köln to the south sits Remscheid, a city in northwestern Germany along the Wupper River, south of Wuppertal, in the heart of the Bergisches, a hilly, wooded district in the lower Rhine River valley. Mentioned in the late 11th century as an estate given to the Hospitallers by the count of Berg, it was chartered in 1808 and absorbed neighboring towns like Lennep.
It’s also the home of Barmag, a world leading high-tech manufacturer focusing on the machinery and engineering systems and solutions for the textile industry. According to Andreas Böttcher, (senior manager, Fulfillment, Spinning Machinery), Barmag has 800 employees at Remscheid, 300 at Chemnitz, just south and west of Hanover, and more than 1,700 others around the world, including a manufacturing facility in China.
“Today, Barmag is the world market leader in the area of spinning systems for numerous manmade fibers - polyester, nylon and polypropylene - and texturing machines,” says Böttcher. “In addition to spinning and texturing systems, our core competencies include the manufacture of components such as winders, pumps and godets, rotational, symmetrical mechanical components in the spinning process and which are needed for the production of high-quality man made fibers. In the Oerlikon Barmag tech center, which is the largest of its type in the world, we focus tremendous energy on innovative processes and technologies for what we foresee as the product needs of the future.”
Roughly 120 employees work two or three shifts a day on the Barmag production line, where they produce the core components for the winders and godets. The facility is 6000 sq meters and is state-of-the-art. There are some 60 CNC machines, some with full automation, including loading and unloading systems. “Our expertise,” says Böttcher, “is manufacturing rotational, symmetrical units of the highest precision to take up the man made fibers at the rate of more than 6000 m/min.”
Barmag works with a wide variety of materials, including steel (heat-treated, nitrided, high-tensile and specialty), aluminum, cast iron and brass. From these, they produce hardened shafts, winder housings and rotors, godet bearing components and godets.
Böttcher says Barmag currently has six Kellenberger Kel-Varia grinders, two CNC 225/1500s, one CNC 175/1000 with B-axis and two conventional machines, a 225/1500 and a 125/600 for ID/OD work in Remscheid A single CNC 225/1000 is located in the Chinese plant. The 1000s are equipped with dual wheelheads. Currently, there are plans to purchase another Kel-Varia.
“Before 1999,” Böttcher says, “we exclusively used a German grinding product. However, it’s been quality - quality in the machines, in their performance, in the repeatability of the precision parts and components - that made us change grinding machine brands. The Kellenbergers are just a superior product.” Böttcher notes that Barmag has increased productivity with the Kellenberger machines by approximately 20% -25%. At the same time, they’ve reduced throughput time by 30% or more. Böttcher notes further that all his operators have undergone three years of grinding training from Barmag - in addition to special training by Kellenberger.
A typical grinding example: winder shafts made of a special nonhardened fine grained steel, 20MnV6.. These are 1500 mm in length and are done between centers on the Kel-Varia 225/1500s. Diameter tolerance: 0.01 mm. Cylindrical form: 0.005 mm. The batch size for these shafts is 72 pieces. Grinding time per part is 65 min.
A Swedish mill makes this steel just for Barmag. Changeover time for one batch of winding shafts to another is 45 min. A second Kel-Varia 225/1500 produces the same shaft from the same special material to the same exacting tolerances.
Another Kel-Varia grinds hardened shafts for the godets. Shaft length is 850 mm. In a single setup, Böttcher says, they grind the shaft, two cones, six shaft bases and one plane surface. Overall diameter tolerance is 0.008 mm. The cone: 0.005 mm. Cylindrical form: 0.004 mm. Common zone tolerance: 0.005 mm. Batch size for the godet shafts is 96 pieces, and the grinding time per part is roughly 42 min. Material is nitrided 42CrMo4V.
“For this process,” Böttcher says, “we work with the Kel-Set automatic grinding wheel measuring system for diameter and length. This machine, a Kel-Varia CNC 175/1000, has two grinding wheels and an additional B-axis for grinding the cones. Other high-precision shaft parts, also for the winding system, have very tight diametric and concentricity tolerances. Again, we use the Kel-Set system. The material is non hardened 42CrMo4V. The grinding time per part is 28 min. and the batch sizes are 120 pieces.”
Böttcher notes that on Kel-Varia CNC 225/1000 they produce components for their own special godet bearings. These bearing components are hardened steel 100Cr6. Diameter tolerance is 0.004 mm and the cylindrical form tolerance is 0.005 mm. Grinding time is 18 min per part and a batch size is 60 pieces..
“I think this kind of very high precision is only possible with the hydrostatic guideways and the exact measuring systems on the Kellenberger machines,” Böttcher says. “You see, we needed a machine that reliably and repeatably gave us very, very high precision and required the absolute minimal set-up times. Our opinion is that we have made the best choice for all our needs and processes with Kellenberger.”
Böttcher relates some observations regarding the Kellenbergers, which go beyond the realm of tolerances and precision. “Our scrap rate,” Böttcher says, “has fallen to less than 0.5%, which is a great improvement over the previous grinding method. The surface finishes are so perfect that we can significantly reduce the post grinding hand-polishing effort, which was very time consuming and operator intensive.”
He also observes that the estimated use of the CNC machines is 4400 hrs/yr and 2800 hrs/yr for the conventional machines. Overall uptime is more than 96%. “With the start-up of the first Kellenberger machines we knew we had increased our capacities permanently,” Böttcher says, “which has played a large role in the satisfaction of our customers. Altogether we have improved dramatically the efficiency of our manufacturing capacity in Germany and China via investments in Kellenberger. Would we do it all again? You bet.”