Freedom from maintenance and corrosion instead of dirt and dry ice cleaning

Profile

• What was needed: drylin® W guide system and tribo-optimised polymer plain bearings
• Requirements: resistance to corrosion, magnetic fields, dirt, dust, water and dry ice
• Industry: automotive industry
• Success for the customer: short welding times and lower costs

REU-Schweißtechnik GmbH was founded in 1985 following the patent of a process for recycling electrode caps. It has offered training in resistance welding since 1995 and in MIG welding since 2002. The company's third service is commissioning welding tongs and optimising welding tong parameters. The mechanical electrode cap changer has been in our product range for several years. This in-house development can be used with all robotic welding tongs. The investment is less than that for motorised variants. The system works without its own drive – it uses the existing robots. This solution achieves the greatest possible success.

REU-Schweißtechnik GmbH welding cap changers

To compensate for tolerances in tong movement, the company first used elastic rubber buffers that were mounted relatively rigidly. "After refining the system, today we use linear technology that not only is guided in a defined manner, but can withstand forces and always returns to the starting position", says Technical Manager Michael Geisler. "It must be resistant to external influences such as dust and dirt. " The linear plain bearings must be able to handle both the magnetic fields that arise during welding and various cleaning agents such as dry ice.
 
Because welding systems are generally cleaned wet or with dry ice, one important characteristic for the linear guides is resistance to corrosion. The rail, pillow block and sliding elements must meet these requirements.

This is where the lubrication incorporated into iglidur® sliding elements pays off. The solid lubricants are microscopic particles embedded in millions of tiny chambers in the material, which is usually fibre-reinforced. From these chambers, the plain bearings release tiny amounts of solid lubricants during movement. This is adequate to sufficiently lubricate the immediate surrounding area.
 
In addition to the drylin® W guide system, tribo-optimised polymer plain bearings are used in the grippers. They replace aluminium plain bearings, which were very expensive to procure and then required machining because they were not available in the required dimensions. "The polymer plain bearing cost is unbeatable, and the bearings can be used right away", Geisler says. "You open the bag, insert the bearing, and that's all there is to it."
 
iglidur®: low coefficient of friction, minimal wear
The lubricants help to reduce the igus® bearings' coefficient of friction. They are not indispensable for the bearing's function, but have a supporting effect. Since they are embedded in the tiny chambers, they cannot be forced out. They are always there as soon as the bearing or the shaft is set in motion. The lubrication is protected from outside contamination for as long as possible, which means it can always be counted on for its full effect. The material used in this example is iglidur® J200, which has been specially developed for a very low coefficient of friction and minimal wear on hard anodised aluminium shafts. In this context too, raw materials savings, which is part of environmental concerns, plays an important role. Just as the welding cap change is performed very precisely, the guide system requires no additional lubrication, with positive effects on the net environmental impact. "The system can be relied upon for long and continuous operation. No maintenance work on the guide is necessary after installation", says Geisler.

Automotive industry: flexible linear sliding system for the automatic welding cap changer
The investment in this cap changer for robotic welding tongs is worth it. The purely mechanical set-up produces a reliable system that is used only in the automotive industry. It helps reduce production costs sustainably. Robust linear guides with polymer sliding elements withstand tough operating and environmental conditions.
In all, about 1,800 welding cap changers are being used worldwide. They can also be quickly and easily programmed to handle various cap diameters, making it easy on the welding tong shaft. The coding on the magazine carrier rules out confusion when different cap geometries are being used. The welding cap changer can be used both horizontally and vertically and for stationary welding tongs.
 
Even in the millisecond range, time savings are possible here.
The intellectual father of the mechanical cap changer at REU Schweißtechnik, Werner

Kaeseler, and the head of workshop and design, Heinz-Peter Drießen, were impressed by the robust polymer bearings' resistance to dust and sand at the Hannover Messe several years ago. "Just one year later, we had a suitable application. The way we use the product today, there is no alternative to linear technology – commercially or technically. We assemble it ourselves, since we cut the guide rails to the exact length in our workshop and then drill the necessary holes. Michael Geisler adds, "Our customers are enthusiastic about the overall concept. It is simple and works without any problems. Automotive industry demands on materials to be welded are becoming more and more stringent. Welding time should be as short as possible. Even in the millisecond range, time savings are possible here. We have created a database containing very many component combinations. As a result, we can now say with certainty what parameters should be used for work and exactly when an electrode must be changed." igus® also provides such a database and can determine the exact service life of drylin® linear technology for a given application in advance.