ADVANCING AUTOMATION COLUMN
BY JOSH LEATH
While robotic welding has existed for decades, the use of collaborative robots (cobots) for industrial welding is relatively new. Offering pinchless designs with smooth surfaces, cobots work safely with or in close proximity to humans. Built-in safety-rated power and force limiting (PFL) sensors allow the machine to monitor external forces applied to its body and stop as needed to not exceed preset thresholds. This reduces and eliminates the requirement for external safety sensors and protects workers from potentially harmful contact situations.
They’re also much more efficient than their human counterparts. Arc-on time for manual welding is 20% compared to 85% for a robot, making one robot equivalent to 3.5 welders. In addition to lowering cost per part, a robot frees welders to perform value-added tasks such as custom welding.
These benefits make cobots a go-to option when space is scarce and production throughput needs a boost. But while cobots save space and are easy to program, keep the following in mind when considering if and how to integrate the technology into your welding operation.
Applications Go Beyond the Welding Itself
A huge advantage of cobots is the versatility they can provide. In addition to MIG/MAG welding for high-mix, low-volume production runs, they can be used to load/unload a resistance pedestal welder, load/unload a standard welding workcell, part and weld seam inspection, and place welded parts into containers.
Tasks taking place in harsh environments may require a cobot with an easy-to-clean surface. Not all models offer this feature, so look at the big picture and do your homework before placing an order.
Lighter-weight cobots like our HC10XP, which weighs around 115 pounds (52 kg), are easily wheeled up to large, heavy workpieces or placed beside weld tables to supplement manual welding. So as you shop, think about how you’re going to move the cobot around the shop floor. A small wheeled base (i.e., roughly 3 feet by 3 feet, or 1 meter by 1 meter) or a small fork truck will usually suffice, but prefabricated carts are available as well.
While a cobot doesn’t usually require safeguarding, some hardware will probably be needed to adapt the unit to the application it’s slated to perform. In most situations, a solid mount riser or cart can position the cobot at a working height similar to a human, minimizing production line changes.
Reach and Payload
Cobots come in a variety of sizes and payload capacities. Some applications, such as machine tending, require minimal movement through space; while other applications, like palletizing, require an arm long enough to lift boxes onto stacks 7 feet high.
Another major benefit of welding cobots is their ability to consistently create long continuous seams. A human can weld a 2-foot seam in one continuous motion, whereas a cobot can weld a 4-foot seam. Because the cobot works with fewer starts and stops, it produces higher-quality welds on long parts.
Wider adoption of welding cobots and larger part sizes will likely require longer arms in the near future. If you require a longer arm or heavier payload capacity, consider using an industrial robot equipped with one of the four collaborative modes: Safety Monitored Stop, PFL, Hand Guiding, or Speed and Separation Monitoring. Pending a risk assessment of the entire application, using one of these modes can qualify a robot as being collaborative, giving you the flexibility to fulfill the uptick in consumer demand for unique parts.
Torch and Tooling Requirements
For an application to be truly collaborative, the entire robotic system must be assessed, including the end-of-arm tooling (EOAT). Important things to keep in mind with EOAT or torches include:
- Torch should be long enough to reach inside the workpiece, if needed
- Water-cooled torches are needed for high-heat and high-deposition applications
- Positioners aren’t yet collaborative, so fixturing must provide access to all weld joints.
Extending Functionality with Control Options
A common control interface, such as our Universal Weldcom Interface (UWI), further extends cobot flexibility by enabling welders to use specialty processes built into the power supply regardless of brand. This pendant application allows them to easily control any weld process or parameter, including voltage, amperage and wire feed speed; and better control functions such as strike and crater parameters and multiple process waveforms via a “Dual Pulse” feature.
Another helpful feature is I/O toggle which enables use of a semiautomatic welding power supply. This may not give the most robust process control, but it does allow use of a power supply that may already be in the shop, and it provides control of the arc trigger like a human welder would.
Cobots that offer a trifecta of programming options — traditional programming via a teach pendant, Hand Guiding, and I/O jogging — are ideal. Made possible by PFL, Hand Guiding uses a series of button commands to lock out specific axes for simpler programming and better torch angle. I/O jogging from a momentary command device wired to the controller is a quick, intuitive way to change things like torch angle or tooling coordinates.
Certain cobot applications, especially part picking and placing, may benefit from a unified environment that uses programmable logic controllers (PLCs). Unified control systems like the MLX300 provide a user-friendly approach to automation by allowing control via PLC function blocks. This enables faster integration and better utilization of floorspace by consolidating hardware and eliminating redundant electrical interfaces. Up to four robots and positioners can be connected.
Seven Peripherals That Increase Efficiency
Various cobot options welding operations find useful include:
- Stack light. An Ethernet/IP-interfaced stack light mounted on a robot cart or near the robot helps to visually confirm robot status or gives an “about to weld” warning to employees near the work area. A “talking” version that gives audible commands is also available.
- Touch sense. Through-wire touch sensing that works on all conductive materials facilitates joint detection if/when they’ve shifted slightly due to tooling changes or inconsistency in parts.
- Momentary command device. Wired to the controller, the device enables I/O jogging via joystick-like control for quick and intuitive updating of things like the torch angle and tooling coordinates.
- Area scanner. An additional collaboration mode that increases speed and mitigates risk, one to two units mounted below the cobot allow it to move at full speed until the protected area is broken.
- Cable management device. Protects the torch cable. An on-arm device or a cable balancer for overhead cable management is suggested. The latter helps expand the robot work area.
- Welding cart/table. Prefabricated tables and carts accommodate a wide variety of production needs.
- Fume capture device. In addition to welding tables with fixed hoods, there are portable options that capture fumes at the torch level and have filtration packs that “ride along” with the cobot.
For an application to qualify as collaborative, the entire robotic system must be assessed. This includes the robot, robot work area, workpiece, and EOAT. If any fails to meet the specified safety standards during a risk assessment, the application can’t be deemed collaborative.
Offer proper employee training and, depending on the risks associated with a given application, appropriate personal protective equipment (PPE). For example, a welder still needs proper clothing and eye protection for protection from hot parts, weld spatter and arc flash.
And remember: Cobots don’t offer external axes compatibility. Thus, applications requiring positioners for coordinated motion or a robot track must be mitigated by fencing, light curtains or other safety measures.
The Path Forward
If you’re looking to gain flexibility and optimize operations, you’re wise to consider adding cobots to your welding workspaces. A clear understanding of the application will help you determine the ideal robot type, and a thorough risk assessment with adherence to ISO standards will guide the proper selection of peripheral tools. Only then will the right “recipe” of cobots and technologies add capacity, increase quality and catapult momentum.
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