Welding

robot
applications

Welding can be split into two areas; seam welding (including MIG, TIG, arc and laser) and spot welding. Both applications have been robotised for many years and the interface between the robot and welding units are highly evolved. Welding robots can be very highly specialised. For example "poke welding" robots are spot welding robots that use the arm itself to generate the mechanical force needed.

CO2 laser welding robots are fitted with a complex system of mirrors to take the laser to the end of the arm. Having said this MIG, YAG, TIG, ARC and normal spot welding use standardised machines that are widely available.

Seam welding will require a robot with excellent path following and precision. MIG and TIG systems are very frequently fitted to small robots of around 5 to 10kg payload and with a reach of less that 1.8m although it is possible to use bigger robots such as the 2.4m reach ABB IRB 6400. Robots often have weave functions to give a fantastic quality of weld - probably better than that of a skilled human welder. They can also control many of the welding parameters such as power, wire feed, gas flow etc. By using "service stations" that combine torch cleaners and "bullseye" or a centring device it is possible to maintain production 24-7 without the need for intervention.

As arc welding is hazardous with fumes as well as the blinding light from the arc itself, a robot is a sensible choice from a heath and safety standpoint. Arc welding cells obviously have screens around the work area and manipulators are often used to present parts to the robot to prevent anyone getting too close and to keep production rates high.

Pictured are four ABB IRB 1400 robots equiped with ESAB MIG welding gear. The wire feed units are the black boxes mounted on the top of the arms. In this case the robots are welding a car chassis. The robots will be connected so that they are aware of each others location to prevent collisions. The orange Y shaped stands between the robots are the bullseyes used to calibrate the robots.

Spot welding robots will generally carry a complete spot weld gun and power pack on the end of the arm. As these frequently weigh in excess of 100kg it is not surprising that this a task to which robots have been applied since the early days. In fact Kuka were spot welding specialists for many years before they started making robots. Using spot welders by hand is a very difficult job indeed and trying to manoeuvre such a heavy-weight piece of kit accurately is near impossible. A spot welding robot will on the other hand position a spot gun with remarkable dexterity and speed. J-guns, G-guns and some truly monstrous scissor guns are often equipped to robots. The robot will also require a substantial loom to carry services to the welder (air, water and power as well as sensor information) so the robot is designed to bear a substantial supplementary load to do this. The weld timer is closely linked to the robot and this allows a robot to respot a point if the welding process has not occured as it should. Tip dressing stations are usually fitted in a spot welding cell so that quality of weld can be consistent.

The ABB IRB 6600 pictured is a very heavy weight spot welder and it is carrying a scissor gun which could easly reach most of the way across a car body. Other robots frequently used for spot welding include the ABB IRB 6000 and 6400 models, Fanuc 420, 430 and R2000 models and Kuka KR125, and KR150's. Most major robot manufacturers have at least one robot designed for spot welding.