"It could hardly be more abrasive" - wear-resistant linear guides ensure 50 percent longer service life in grinding tool machinery
 

Profile

• What was needed: Robust linear round guides
• Requirements: Thermal and mechanical loads on the tools
• Industry: Mechanical engineering
• Success for the customer: significant increase in service life

Schleifscheibenfabrik Rottluff GmbH in Chemnitz produces around 150,000 grinding tools per day with the most diverse diameters and shapes. The business of the approximately 100-year-old company has been going well for years. For the approximately 150 employees, everything revolves around the grinding wheel five days a week in three shifts. End customers and large consumers are supplied.
 

Problem

The cut-off, grinding and abrasive flap wheels are characterised by high durability and short cutting times. Their design is tailor-made in terms of abrasive grain, bonding, structure, shape and composition. Added to this are state-of-the-art manufacturing technologies that create a comprehensive range of products. As a member of the Association of Abrasive Manufacturers and the oSa, the organisation for the safety of abrasive tools, the specialist makes an active contribution to user safety. After all, the processing speeds of hand-guided discs, for example, are 80 or up to 100 m/s, which can lead to enormous thermal and mechanical loads on the tools. Grinding wheels essentially consist of a reinforcing material, a moulding compound, the bonding (usually fibre glass fabric) and a label with a bore ring. The moulding compound contains a wide variety of abrasive fillers to enhance the cutting properties. These grinding agents are extremely abrasive and ensure a high degree of wear and tear on our machines and equipment. For example, when hard silicon carbide is pressed into wafers for use in the stone industry, an extremely large amount of dust is produced, which further increases wear. And since work is carried out in three shifts, maintenance and repairs can only be carried out on a regular basis at fixed times. In terms of the ambient conditions, it could hardly be more abrasive. The bearings have to permanently withstand the various materials used in grinding wheel production.
 
The automatic pressing machines work under the harshest conditions; they guarantee consistent thickness and pressing of the products. The cutting and grinding wheels are then moved to the curing ovens. In order to guarantee consistently good quality here, they are first placed between steel plates, which must be removed again after the curing process. This, in turn, is done by tailor-made automatic separators, which are used for the necessary destacking.
 

Solution

The grinding wheels are made to customer specifications, and they easily withstand the most diverse requirements. Pressing and separating machines play an essential role in the extremely rough production process. To significantly increase their service life, metallic bushings have been replaced with robust linear round guides with quickly measurable success. Self-lubricating and maintenance-free, they prove their suitability for everyday use right from the start.  Ordered and installed as operating equipment, the linear guides ensure the necessary machine availability. Up to ten linear bearings are each used in the heart of the grinding tool machinery, the hydraulic pressing and separating systems.
 
The drylin R linear bearings are based on highly wear-resistant polymers developed especially for linear technology. Their dimensions are compatible with standard linear ball bearings. They use round shafts as counter partners and accept a wide variety of shaft materials. At Rottluff, steel shafts that excellently withstand the harsh environmental conditions prove their worth. The special geometry of the guides guarantees high safety under all operating conditions. As the bearing surface consists of individual gangways with interruptions, contamination is no problem. Even if moist dirt strikes the shaft, it is wiped off by the individual glide pads and forced back into the open areas. The running sections of the bearing then slide on the track that has been cleared of the dirt. The linear guides are 100 percent lubrication-free. Easily exchangeable standard liners made of the iglidur J material ensure good coefficients of sliding friction.
 
Although the operating conditions, i.e. the moulding compounds, change on the machines, it can nevertheless be stated that their service life is considerably longer than that of the previously used metallic bushings. And the durability of the steel shafts has at least quadrupled, so that not only technical advantages speak for the linear guides, but the investment in these operating resources also pays off economically. In addition, the wear limit is looming on the horizon today. It does not occur abruptly, but an appropriate replacement can be initiated at the next maintenance interval as scheduled. The linear guides prove their efficiency not only in the pressing and separating machines, but also in a shrink wrap machine.