Robotic welding station for aluminium car bodies: servo spot welding guns and the electrode care that decides weld quality

01

Electrode force that stays the same whichever way the robot holds the gun

Matuschek states that reproducible electrode force is an essential prerequisite for a good spot weld in both aluminium and steel, and must hold in every gun position even under interference. Its guns use one servo-electric actuator with integrated encoder and force sensor to build gun force and a second to compensate the gun's weight in the electrode direction; its SPATZ+ control evaluates motor current, encoder and force signals in real time and corrects the main motor within a few milliseconds, and uneven force from a changed gun position, misplaced parts or asymmetric cap milling is compensated down to a few newtons. The guns come in C and X designs. [4]

Give the supplier the body materials and sheet combinations (aluminium, steel, mixed), thicknesses and coatings, the number of welds per body and cycle time, gun reach and access for each weld group, the weld control type, and the dressing or polishing strategy the station must support.

02

Aluminium wears the electrode face: 400–900 welds, larger contact area, smaller nugget

Fukumoto and co-authors, in the Welding Journal, ran electrode endurance tests on 1.5 mm aluminium alloy 5182 with a medium-frequency DC welding machine and electrodes of 10 mm tip-face diameter and 50 mm radius: electrode life ranged from about 400 to 900 welds even with all process conditions held constant. Degradation enlarged the tip-face area and the electrode/sheet and sheet/sheet contact areas, lowering current density and leaving undersized nuggets; they judged the electrode/sheet contact area the best indicator to monitor because it needs the least extra work to measure. [1]

The University of Warwick reported in 2006 that research with Innoval Technology and Jaguar Land Rover engineers reached 50,000 high-quality welds on automotive aluminium sheet with one set of standard copper electrodes on an automated robotic system, by polishing the electrodes in the brief gap between each welded component, against a few thousand welds from regular form-cutter dressing; it also studied low-cost detection of electrode damage to decide when to maintain or change electrodes. [2] A GM patent shapes the weld face to a radius of about 20–40 mm, textures it to a peak-to-valley roughness of about 2–50 µm, re-textures it when needed and dresses it to remove contamination built up from the aluminium. [3]

Editorial calculation: if a 10 mm tip face wears to 12 mm, its area grows by a factor of 1.44, so at the same current the current density at the face falls by about 31%, which is the mechanism behind the undersized nuggets Fukumoto describes. [1]

03

Send the body, materials and maintenance plan together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Body: [model; weld count; cycle time]
Materials: [aluminium grades; steel; thicknesses; coatings]
Guns: [C or X; force range; servo compensation]
Control: [weld control type; monitoring]
Electrodes: [face shape; dressing or polishing; interval]
Quality: [nugget checks; electrode wear detection]

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