Traditionally, manufacturers have relied on manual welding to assemble high-mix, low-volume products. But, more companies are turning to a new breed of flexible robots, software and controls.
No matter how it’s defined, small batch sizes are becoming more common in many industries today, as customers demand multiple product variations. Manufacturers and job shops need flexibility to easily accommodate part fluctuations, low quantities and frequent changeovers.
However, contrary to popular belief, it’s not always cost-effective to automate small-batch welding. Robots have not been widely used in the past, because they were not economical.
“The size of the part and the volume of welding done are some of the factors for determining whether or not to automate,” says Josh Williamson, robotic segment manager for North America at Fronius International GmbH. Small manufacturers and job shops have been reluctant to invest in robots for a variety of reasons, such as ”lack of knowledge, fear of investing in capital that will not function correctly, and the fact that some companies are just complacent and naturally default to their existing capabilities,” notes Williamson.
“There is work involved with bringing robotic welding into a company, but the benefits far exceed the initial transition,” claims Williamson. “Many companies just don’t grasp the concept that a little time spent up front will save them greatly for years to come.”
“Traditionally, a majority of batch welding is done manually, because the setup time is proportionally higher than the weld time,” adds Chris Anderson, welding technology leader at Motoman Robotics. “Parts in smaller batches may not warrant the expense of robotic holding or tacking fixtures.”
“To apply a robot, the historical rule of thumb is that the parts need to be repeatable within ±0.02 inch to ensure acceptable weld quality,” says Geoff Lipnevicius, operations manager in the automation division of Lincoln Electric Co., which partners with FANUC Robotics America Inc.
“Repeatable workholding is, therefore, required,” Lipnevicius points out. “However, with high-mix, low-volume, the equipment, fixturing and programming time cannot always be spread over the cost of the job, so manual or semiautomatic welding becomes the default.”
Traditionally, robots are great at repetitive welding tasks, such as assembling a continuous line of minvan bodies, but they are not as flexible as humans when it comes to moving quickly from job to job. That’s starting to change, however. A new breed of compact, flexible robots that feature large work envelopes, quick programming and user-friendly controls make it easier than ever to justify small-batch robotic welding.
For many years, the biggest obstacle to automated small-batch welding has been ease of programming, claims Efi Lebel, CEO of SmartTCP Inc., a company that has developed software that allows robots to be more flexible.
“Robots are built to be flexible, but programming is difficult and time-consuming,” Lebel points out. “With our product, it can take minutes to hours, rather than hours to days, to program tasks, depending on the application.” The software automates complex and tedious robot programming tasks.
“Automating the welding process is good practice, because it saves labor cost, solves quality issues and shortens time to market,” notes Lebel. “However, small-batch fabrication automation is not economically feasible unless you have the right technology.
“To deal with high mix, you need a machine with a large, flexible working envelope and many axes to handle a variety of part shapes and sizes,” says Lebel. “You need adaptive welding that treats each member of the small batch as a one-off, as usually parts are fitted manually and not exactly similar to each other.
“Traditional on-line and off-line programming is time-consuming and doesn’t work for a small number of parts; it is cheaper and faster to weld the few parts manually,” explains Lebel. “You need quick programming to justify robotic welding.”