Valk Welding: Realised projects

Grasso Products Den Bosch 2004

Combined welding/ cutting robot for Grasso Products performing on all fronts

The steel construction sector too has its eyes on the automation of welding and cutting processes. Not only for reasons of efficiency, but also to increase the accuracy of the welding process, to reduce the finishing process and to prevent that employers are exposed to welding and cutting vapours. For flat materials, a 2D cutting system will provide enough possibilities for rapid and accurate cutting of holes. But once H-profiles, tubular materials or other three dimensional forms are involved, more and more use is made of autogenous cutting torches. However, Valk Welding has proven that using a robot for cutting processes can be very efficient, certainly when welding and cutting processes are being carried out by one and the same installation.

Most cases in which Valk Welding employs a robot for cutting processes involve the machining of construction profiles and tubular material, sometimes up to 400 to 500 mm ø. For suche processes, Valk Welding installed a plasma cutting robot at among others Boeters Kassenbouw and Dalsem Tuinbouwprojecten for cutting holes in and for cutting cylinder profiles; a process up to then carried out with separate punching, drilling and sawing machines. The first combined welding and plasma cutting robot was already by Valk Welding in 2002 at Wolter & Dros. In this case, the robot handles a plasma cutting torch to cut holes in tubular material, a welding torch to weld tube parts with counter form square to the tube and a gripper to position the workpieces. With the robot handling several ‘tools’, the welding duty of the robot can be utilized to the maximum, whereby the robot changes automatically between welding torch, plasma cutting torch and gripper. A major advantage for this installation is the tight cutting line made by the robot. As a result, form and counterform fit precisely, while in the past with manual cutting, the product had to be finished with a manual grinder.

With the introduction of a combined welding and plasma cutting robot at Grasso Products in Den Bosch, automn 2004, Valk Welding has again taken a giant leap. Grasso builds compressors for industrial applications based on welded bodies. Here, Valk Welding realised a complete production cell whereby one robot on one track 'serves' four clamping places where notches in bodies and cylinder heads are cut and complete combinations are externally and internally welded. From a technical point of view, this means that besides the 6 robot axes an additional 7 external axes can be controlled. To do so, the robot changes between a couple of welding torches and a plasma cutting torch. The installation not only provides increased efficiency and laboursaving, but also increased quality.

GEA / Grasso Products B.V. in Den Bosch manufactures compressors for cooling and freezing for among others the food industry, soft drink producers and breweries, meatworks and abattoirs and fishing boats. A unique feature is that the compressors consist of welded and not moulded bodies. A welded body better resists temperature differences, with possibility to apply cylinders in stead of screw wheels, and can be carried out in larger capacities. Hence, the Grasso compressors are known for their high quality, safety and reliability, and that is why they call them the Rolls Royce in on the market.

Production leader Eric van Krieken: ”Cutting holes in bodies and welding-on cylinder heads is a very labour intensive process which is not only very expensive and time-consuming, but also requires qualified professional welders. In order to stay competitive, robotised welding and cutting has become a necessity. With this installation we will be able to completely cut and weld the compressor housings with the robot.”

Besides the advanced efficiency resulting from automation, the employment of robots has also largely increased the accessibility for welding processes. Internal welding of bodies in particular was a difficult job up to now. For these processes, the welding robot has no limitations; overturned robot welding of cutting forms no problem whatsoever.

The Grasso cell consists of four workstations, for cutting notches in bodies, and for welding cylinder heads, supports and top plates onto the bodies. Technical Advisor Bas van Haagen of Valk Welding, who is guiding the project: “In order to serve all stations, the robot can move along a track of 20 m. Each station in its turn is equipped with manipulators, to rotate components and bodies synchronically with the process. This means that a total of 13 axes can be controlled simultaneously.”

The welding robot changes between welding torch and plasma cutting torch to cut notches in the bodies. To do this, an oxygen plasma cutting system of Hypertherm is being used. This plasma cutting generator, able to cut under an angle of 42º, delivers a cutting speed of 1.5 m/min, thus increasing the cutting speed with a factor 5 compared with an autogenous system and moreover, the accuracy is higher.