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Smoothing the seams

Anyone who has to process weld seams with an angle grinder has a choice of three types of grinding disc. The grinding disc, fibre disc and abrasive mop disc differ in more than just their physical characteristics. We asked two users which criteria matter to them when choosing their tool.

Smoothing the seams

Anyone who has to process weld seams with an angle grinder has a choice of three types of grinding disc. The grinding disc, fibre disc and abrasive mop disc differ in more than just their physical characteristics. We asked two users which criteria matter to them when choosing their tool.

 

Slewing cranes are one of Vetter Krantechnik GmbH in Siegen's specialist fields. Flexible and agile, they are used in many places - at stations and airports, in shipyards and foundries, and in production halls and on construction sites. Around 4,000 of the cranes are produced each year. The company has two welding robots, but the majority of the work continues to be carried out by hand. The 40-strong team of welders connects tubular pillars with pedestal flanges and struts made from construction-grade steel, welding pressure supports onto the boom.

 

“After this, we need to process the weld seam transitions. To help us do this, we are increasingly using the abrasive mop discs from Klingspor instead of the classic grinding discs. The flexible slats mean that we achieve a clean, dynamic transition between the components. With the grinding disc, there is always the danger that you will cut into the depth of the weld seam, and this would impair its function”, explains employee Axel Schmidtgen.

Bildmotiv Innovation

“With the abrasive mop disc, we create a dynamic transition between the components.”
- Axel Schmidtgen, Vetter Krantechnik

 

Bildmotiv Innovation

“The grinding disc is perfect for coarse seams.”
- Tobias Baum, Heyden Metallverarbeitung

However for Tobias Baum, welder at Heyden Metallverarbeitung, grinding discs are the tool of choice. Since 2006, the company from Frohnhausen has specialised in the extension of forklift truck forks. The somewhat short forks of conventional forklift trucks are extended to make loading and unloading easier. Four steel parts are welded together to do this. “The weld seams are pretty coarse, which is why we only use the 230 mm grinding discs from Klingspor to process them. We've already tried grinding discs from other manufacturers, but none of them comes close to the quality from Klingspor. For us, it's the ideal disc,” says Tobias Baum.


Finding the ideal abrasive
Dirk Wahler, Product Manager at Klingspor, knows just how difficult it can be to find the ideal abrasive: “The decision depends on a number of factors: the service life, the removal, the procurement costs, ergonomics and ultimately also habits.”
 

The grinding discs are arguably the most commonly found tool in weld seam processing, simply because they have been around the longest. The grinding pattern is relatively coarse, the surface rough and working with the grinding disc is not for novices. The pressure must be right, and that's despite the strong vibrations that can be very challenging to muscles and joints. With too little pressure, the disc will skip. Too much pressure will generate heat and the material will discolour. Nevertheless, the grinding disc does have advantages over abrasive mop discs (AMDs) and fibre discs. It can remove layers of scale and is ideal for grinding fillet welds. Inexpensive and aggressive: the key features of fibre discs. When a hard backing pad is used, the grinding grain can penetrate deeper into the surface. “In relation to surface grinding, the AMD does not achieve very much removal. For freely accessible weld seams, fibre discs are very much recommended”, says Dirk Wahler
With a hard backing pad, a fibre disc will remove coarse weld seams effortlessly, and with a soft backing pad it generates an even grinding pattern. Their disadvantage is their short service life and therefore higher equipment costs. Convenient grinding - the hobby horse of the AMD. The grinding tool with slats achieves high levels of removal with a long service life and can process weld seams on workpieces with rounded surfaces especially well. The welders at Vetter Krantechnik, who use the grinding discs for coarse grinding and the abrasive mop discs for fine grinding, have a clear preference - as Axel Schmidtgen admits. “The AMD is much nicer to work with. Less vibration and less noise. It's more expensive, though, although you also need to compare the wage costs. Anyone who ruins the surface with a coarse grinding disc and needs to perform another pass before painting has not made any profit. You need to bear all this in mind.”

 

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