by Eric McKellar
Whenever applying automation to weld a product, a company’s goal is to improve consistent quality, increase production and decrease overall cost. At the end of the day, whether manual or robotic, the overall machine is ultimately still a “welder”. Although a robotic welding machine appears to be more complex, general rules of sound welding are the same as manual welding.
While being heavily involved with initial setup/configuration and site installation of various robotic welding processes over the last 10 years, I’ve seen many instances that involve troubleshooting a situation to ensure proper weld process output to help achieve a quality product. These situations often involve similar instances of mechanical neglect or improper setup, welding technique and/or training/process experience.
One of the most common issues when dealing with automated Gas Metal Arc Welding (GMAW) is with wire feeding. Technical personnel must ensure correct wire feed drive-roll size and style to match the wire type (eg. solid steel, aluminum, cored). Worn drive-rolls can cause slippage and inconsistent wire feed speeds (WFS). This then will cause arc-out faults such as wire burn-back or arcing inside a contact tip fusing the weld wire. It is also important to utilize the ideal equipment selection for the process (wire drive systems, liner material and system control ability).
Some Quick tips to check the correct wire feeding:
1)With all applicable wire drives engaged, jog welding wire manually from the teach pendant or wire-feeder push button, hold a block of wood or use the palm of your hand at the torch end and the wire should curl with no slippage under this induced pressure.
2) Disengage all wire drives, at the welding torch you should be able to pull the wire from the spool or drum through all conduit, torch whip and connection points with light force and just two fingers.
Don’t forget, it’s still a welder.
As with any discipline, proper technique plays a huge role in sustained success, whether this is driven by training and experience and/or policies and procedures. The robot may be a sophisticated tool holder, but is simply an extended arm of humanity. By this I mean the robot is only as smart as the programmer. Proper welding technique involves: torch angles (travel and work), electrical stick-out (ESO), travel speeds and weave motion (if applicable). Anyone who has manually welded will use the same exact techniques. Unless these aspects are correctly managed, setting the weld process parameters (WFS, Voltage or Arc Length) to achieve the optimum weld will be a moving target to say the least.
Don’t forget, it’s still a welder.
Training and Experience
To build on the previous points, training and hands-on experience are the keys to decisions for correct troubleshooting and technique. Knowing “how to weld” helps eliminate the types of issues noted above, and allows the next piece of the “welder” to be analyzed. This could be the process parameters, product tooling, robot manipulator and controller, or welding power source.
In the end, to improve quality, increase productivity and decrease costs, a robotic welding system needs to be properly maintained to avoid costly downtime. Knowing the general rules will help achieve that goal.
Oh, and one more thing…don’t forget, it’s still a welder. SMT
Eric McKellar is a robotic welding applications specialist, ABB Inc., Brampton, ON