The essential guide
The robot will consistently move to its programmed positions to a very high accuracy
(± 0.04 mm) and it is therefore important that the components are accurately positioned.
These are usually loaded in a welding fixture, but large assemblies may be pre-
The tolerance on a gaps should not exceed a total tolerance of 0.5 mm to 1.0 mm depending on material thickness. Larger gaps can be bridged by using the weaving facilities of the robot, but it is important that the gap condition is consistent The welding parameters are tuned to provide optimum results for a particular condition and if that condition changes, it will have an effect on the quality of the weld. If gap conditions vary then this can be measured using a vision system, which will make adaptive fill corrections to the welding process. It is almost always preferable to ensure that the components are consistent rather than relying on sensing technology. The cost of these sensors is relatively high and requires quite a high level of expertise from the robot programmer.
It is important to have the correct joint design and if this could be changed to suit robotic welding, it will be much easier to achieve success. The ideal joint is a fillet joint, but an overlap joint is also easy to weld. For thin gauge materials joint design and gap conditions become even more critical and it essential that the components are cut and bent with CNC equipment.
By modifying the joint design of an outside corner, it will be much easier for the robot to weld. Even if the integrity of an outside corner has to be maintained it would be helpful if the joint could be designed so there is a lap condition.
Butt joints on thin gauge materials represent a serious challenge for robot welding. By changing the design to an overlap joint the success rate can be dramatically improved.
If there are too many variants that are only produced in low volumes, there will be an additional investment requirement for fixtures. Companies should consider the minimum batch volumes and if these are too low, it will affect the uptime on the robot system due to set up times. It is possible to integrate robots in a flexible manufacturing system (FMS) where single products can be welded without set up times. These systems require high capital investments. The alternative can by a system that comprises more than two work station, in which case any fixture change over does not affect the robot's productivity.
Critical outside corner joint
Change outside corner joint to fillet joint
Change butt joint to overlap joint