Welding and pressure joining with one robotPrint this page
More than 25 years now, the Belgian supplier Rolco is making transport carts for eggs, packed in trays of 30 eggs each. These so-called 'egg containers' have a simple construction with corner profiles, filled with thin-walled galvanised plate material with raised edge. Until shortly, this product was spot welded in a mould and then manually finished outside the mould. In the meantime, Rolco too has problems finding qualified welders to produce this product. That is why Rolco, together with Valk Welding, sought a solution to have the work done by robot.
Roel de Cat of Rolco: "We have chosen to replace spot welding with pressure joining. Therefore, the robot had to be able to position both pressure joining tongs and a welding torch. To do this, Valk Welding employed a Schunk exchange system so that both works can be done with one robot. The product is now being 'toxed' at almost 100 spots, after which the robot changes the pressure joining tongs for the welding torch and the complete construction is being finished."
The construction requires enough rigidity to absorb the transport movements, and therefore prior spot connection is required. The quality of the pressure joining between two galvanised steelplates is constant. Before, more spot welding connections had to be made in order to have a reliable fastening. The pressure joining has several advantages. The tongs are lighter than spot welding tongs, and hence a lighter robot will suffice with less power consumption.
Completely welded in one action
In the new situation, the complete egg container is now finished in a mould in one action. The mould, developed by Rolco itself, has been provided thereto with both manual and magnetic clamps. When the product has been 'toxed', only the magnetic clamps are switched off, after which the outside seam of the product is completely finished by the robot. The magnetic clamps work with compressed air. The TOX pressure joining tongs are almost completely hydraulic, whereby the oil pressure is transferred via a hose pack to the pressure joining tongs.
Improved working conditions
With this new TOX/welding robot cell, Rolco disposes of two clamping places with two moulds, so as not to interrupt production for loading and unloading. Ever since the installation of the cell in October 2000, Rolco can do the production with just one man. Roel de Cat: "Beside the efficiency advantages, the robot offers production continuity. Indeed, a manual welder can weld as fast, but he cannot continue welding all day long, certainly not with summer temperatures. Operating the spot welding tongs was quite stressing, certainly to apply spot welding in places that were difficult to reach. In addition, we avoid our collaborators having to work over the released vapours."
(With many thanks to Roel and Raf the Cat of Rolco NV)
(Source: Valk Melding no. 1, autumn 2001 / various professional magazines)