Automated welding can provide large gains in productivity and profitability – in the right applications.
Welding is arguably the most complex manufacturing process and is frequently the least understood. A surprising number of companies spend millions of dollars to automate assembly while ignoring the welding process. Manual welding is still the best process for many assemblies. However, many assemblers are implementing automated welding systems to increase quality, productivity and profitability.
Welding automation can be broken down into two basic categories: semiautomatic and fully automatic. In semiautomatic welding, an operator manually loads the parts into the welding fixture. A weld controller then keeps the welding process, motion of the torch, and stillness of the parts to preset parameters. After the weld is completed, the operator removes the completed assembly and the process begins again.
In fully automatic welding, a custom machine, or series of machines, loads the workpiece, indexes the part or torch into position, accomplishes the weld, monitors the quality of the joint and unloads the finished product. Additional “part in place” and final product quality checks may also be designed into the machine if necessary. Depending on the operation, a machine operator may be necessary.
Not every welding operation is a good candidate for automated welding. Applications will benefit most from automation if the quality or function of the weld is critical; if repetitive welds must be made on identical parts; or if the parts have accumulated significant value prior to welding. Excellent candidates for automation include batteries, capacitor cans, solenoids, sensors, transducers, metal bellows, relay enclosures, light bulb elements, fuel filters, thermos flasks, medical components, nuclear devices, pipe fittings, transformer cores, valve elements and airbag components. Companies that assemble limited quantities of products requiring accurate or critical welds may benefit from a semiautomatic system, but would probably not need fully automated systems.
Benefits of Automated Welding
Automated welding systems offer four main advantages: improved weld quality, increased output, decreased scrap and decreased variable labor costs.
Weld quality consists of two factors: weld integrity and repeatability. Automated welding systems ensure weld integrity through electronic weld process controllers. Combining mechanized torch and part motions with electronic recall of welding parameters results in a higher quality weld than can be accomplished manually. This offers instantaneous quality control. Furthermore, because a weld is made only once, defects are readily visible and detectable. Humans tend to “smooth over” a mistake with the torch, hiding lack of penetration or a possibly flawed weld. In some cases, leak testing and vision systems can be integrated into fully automated systems to provide additional quality control.
Repeatability is a function of the quality of the weld process controller and of the engineering of the machine motions. Mechanized welding provides repeatable input parameters for more repeatable output. Assuming the controller is functioning properly, the question becomes: Can the mechanisms of the machine position the parts or the torch within the specified tolerances for welding? The answer to this question will attest to the quality of system purchased.
Semiautomatic and fully automatic systems increase output by eliminating the human factor from the welding process. Production weld speeds are set at a percentage of maximum by the machine, not by an operator. With minimal setup time and higher weld speeds, a mechanized welding system can easily outpace a skilled manual welder.
Automating the torch or part motions, and part placement, reduces the possibility of human error. A weld takes place only when all requirements are satisfied. With manual welding, reject welds often increase when welders become fatigued. Depending on the value of the parts when they arrive at the welding station, the cost savings in scrap alone may justify the purchase of an automated welding system. Automation should also be considered when assemblers need to minimize the risk of shipping a bad part to a customer.
Typically, a semiautomatic system has at least twice the output of a skilled welder. A fully automatic system can be built with twin welding positioners on an automated shuttle. Such a system can load and unload parts at one station while welding occurs at the other. In this way, a fully automatic system can run at four Arial the pace of semiautomatic system, or eight Arial the pace of a skilled welder.