We all know that welding aluminium castings requiČres more than a standard recipe - the structure is not the same as that of standard aluminium and this meČans you need to establish the correct combination of gas, welding wire, parameter settings, and you

We all know that welding aluminium castings requi­res more than a standard recipe - the structure is not the same as that of standard aluminium and this me­ans you need to establish the correct combination of gas, welding wire, parameter settings, and you need a great deal with knowledge and experience to meet the imposed quality requirements. The MGG Group acquired a wealth of experience with the manual welding of heat exchangers in the past and over time they developed their own recipes. The increase in the numbers, the greater complexity, and the increased competitive pressure from China made automation the inevitable next step. Together with Valk Welding and gas supplier Air Products, MGG has successfully managed to robotise the welding process.

With sites in Tegelen in Limburg, Bergen and Antwerp in Belgium, the MGG Group B.V. is one of the largest aluminium casters in Euro­pe. The entire process of engineering, tooling, casting, finishing, machining and assembly takes place within the group. The site in Tege­len largely focuses on sand casting automo­tive parts and aluminium heat exchangers for the boiler industry. To give you an example of the production - each day this site processes approximately 30 tonnes of aluminium.

Weld up slots later

MGG supplies to all the major names in the boiler industry. It is clear that the products are subject to stringent requirements, and the finished castings must be hundred percent tight. All castings are tested carefully, visually and with x-ray, before they are machined further. The aluminium automotive parts and heat exchangers are cast in a mould that consists of a top and a bottom half. The inside of the mould is obtained by inserting a sand core, which needs to be removed after the material has hardened. In order to make this de-coring possible, some castings have slots; these slots must be welded up later on, and within MGG that work is carried out by two welding robots.

Robot supplier with welding knowledge

Ruud Jagt, welding technician of MGG, re­members welding the castings by hand in the past and his experience was essential during this welding-robot project. “We had set our­selves the target of doubling production by using the welding robots. Any robot supplier can meet that requirement, but successfully robotising the welding process requires a supplier with in-house knowledge of robots and welding technology. Valk Welding was able to supply the complete package and was prepared to work together with us to develop the welding process on the robot.”

Simple cell and complex welding process

Valk Welding supplied its first cell in 2000 - a standard cell with a Panasonic VR006 welding robot and turning table was sufficient to meet the required capacity. The manipulator and the clamping jig were made by MGG itself from a perspective of simplicity and safety. The operator puts one heat exchanger in the clamping jig and fixes the strips with a tack weld before the welding robot fully welds the strips. Ruud Jagt, “As the heat ex­changers need to be one hundred percent gu­aranteed tight, this is carried out with a pe­netration of 5-6mm and an advance speed of 50 to 100 cm/min. In close co-operation with Valk Welding and gas supplier Air Products, we switched to Argon/Helium in combina­tion with AISI12 welding wire. This achieves better penetration at higher advance speeds and with lower amperages.

95% less manual work

Besides achieving a production increase, obtaining consistent quality was an equally important objective on using welding robots. Ruud Jagt, “By using the welding robot and achieving a higher and more consistent qua­lity, we were allowed to use the slots more often. In turn that meant we were processing more castings in our department. In 2004, we commissioned a second welding-robot cell with a VR006L welding robot and a program­mable three-axis rotating manipulator. This improved the access to the products and significantly shortened the cycle time. Both cells are now used five days per week in a three-shift system. All in all we have reduced manual work by 95%, which did not only meet our objective, but the work for the ma­nual welders has become less monotonous and less heavy.”

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