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: Corrosion resistance, resistant to magnetic fields, dirt, dust, water and dry ice
• Sector: Automotive industry
• Success for the customer: Short welding times and savings

REU-Schweißtechnik GmbH was founded in 1985 with a patented process for electrode cap recycling. Since 1995, the company has been offering training in the field of resistance welding and, since 2002, also in MSG welding. The third mainstay is the commissioning of welding guns and their parameter optimisation. The mechanical electrode cap changer has been in the programme for several years. This in-house development is suitable for all robot welding guns. In contrast to motorised versions, the investment is limited. The system works without its own drive and utilises the existing robot. This solution achieves the greatest possible success.

Welding cap changer from REU-Schweißtechnik GmbH

To compensate for tolerances in the tong movement, the company initially used elastic rubber buffers that were mounted on relatively locking bearings. "Following further development of the system, we now use linear technology that is not only guided in a defined manner, but can also withstand forces and always return to its original position," says technical director Michael Geisler. "It also has to be resistant to external influences such as dirt and dust." The linear plain bearings must be able to cope with magnetic fields that arise during welding, as well as with various cleaning agents such as dry ice.

As the welding systems are usually cleaned wet or with dry ice, corrosion resistance is one of the key factors for linear guides. The rail, the housing bearing and the sliding elements must be able to cope with these requirements.

This is where the incorporated lubrication of the "iglidur®" sliding elements pays off. The solid lubricants are embedded as microscopically small particles in the solid, usually fibre-reinforced material, millions of times over in tiny chambers. The plain bearings release tiny amounts of the solid lubricants from these chambers. This is enough to sufficiently lubricate the immediate surroundings.

In addition to the "drylin® W" guide system, tribo-optimised polymer plain bearings are also used in the grippers. They replace aluminium plain bearings, which were extremely cost-intensive to procure and always had to be machined afterwards as they were not available in the required dimensions. "The polymer plain bearings are unbeatable in terms of cost and can be used immediately," summarises Michael Geisler. "Open the bag, insert and the product is ready!"

iglidur®": low coefficient of friction, minimal wear
The solid lubricants help to reduce the coefficient of friction of the igus® bearing. They are not indispensable for the function of the bearing, but they do have a supporting effect. As they are embedded in the tiny chambers, they cannot be pushed away. They are always there as soon as the bearing or shaft starts moving. The lubricant is protected from external contamination for as long as possible and is therefore always able to achieve its full effect. The material used in this example is "iglidur® J200", a specialist for very low coefficients of friction and minimal wear on anodised aluminium shafts. Saving raw materials - and sometimes the environment - also plays an important role in this context. Just as the welding caps are changed with pinpoint accuracy, the guide system also requires no additional lubrication, which ultimately has a positive impact on the environmental balance. "You can rely on the system for a long time and permanently. After installation, no labour is required to maintain the guidance system," explains Michael Geisler.

Automotive industry: Flexible linear sliding system for automatic welding cap changer
The investment in this cap changer for robot welding guns pays off. The system, which is extremely reliable thanks to its purely mechanical design, is used exclusively in the automotive industry. It helps to sustainably reduce production costs. Robust linear guides with polymer sliding elements withstand the harsh operating and environmental conditions.
A total of around 1,800 welding cap changers are already in use worldwide. Quick and easy to programme, they can also handle different cap diameters in a way that is gentle on the welding gun. Coding on the magazine carrier makes it impossible to mix up different cap geometries. The welding cap changers are suitable for horizontal and vertical use as well as for stationary welding guns.

Savings are even possible in the millisecond range
The spiritual father of the mechanical cap changer at REU Schweißtechnik, Werner

Kaeseler and workshop and design manager Heinz-Peter Drießen were impressed by the robust polymer bearings' resistance to dust and sand a few years ago at Hannover Messe. "One year later, we already had the right application. The way we use the product today, there is no alternative to linear technology - for both economic and technical reasons. We customise them ourselves, as we cut the guide rails to the exact length in our workshop and then make the corresponding holes." Michael Geisler adds: "Our customers are delighted with the overall concept. It's simple and works without any problems. The automotive industry's requirements for the materials to be welded are becoming ever more stringent. The welding time needs to be as short as possible. Savings are even possible in the millisecond range. We have created a database in which a large number of component combinations are stored, so that we can now say with certainty which parameters should be used and when exactly an electrode needs to be changed." A similar database is also available at igus®; the design engineer can precisely predict the service life of the "drylin®"linear technology in his particular application.