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Many of the problems that occur during the design and implementation of robotic-welding cells can be eliminated through proper planning and education, and by pa) ilg close attention to part tolerances, tooling design, and training.
The robotic arc-welding systems available today are more accurate and repeatable than they have ever been. With positioning accuracy of plus or minus 0.004 inch, customers know that the robot arm will move to the same place every time. However, this high degree of precision creates one of the most frequent problems with robotic-welding systems: when the parts to be welded do not have the same high degree of accuracy or poor tolerances, the success of the work cell is jeopardized. It is critical, then, to fabricate parts with tolerances that reflect the accuracy of the robot. Here are some examples of how poor part tolerance and fitup can hinder success.
Gaps in the weld joint Depending on the type of joint, gaps can affect weld penetration. Reducing penetration can reduce weldment strength and increase rework time and cost, as well as result in scrapped parts. Excessive gaps can also cause arc failures, created when the arc does not ignite or the wire bums back into the contact tip. Arc failures increase robot downtime which decreases efficiency and throughput. Some larger gaps can cause burnthrough, which can be remedied by using a cooler first pass. However, this requires the use of extra filler material to fill the gap and the use of slower travel speeds. Slowing down travel speed and adding multiple passes to a weld joint increases heat input to the weldment and increases the chance for warped, and thus scrapped, parts. Slower travel speeds also reduce efficiency and throughput.
Joint location Gaps and poor fit can cause inaccurate, unrepeatable weld-joint location. This creates lots of scrapped parts, increases rework time and...