An industrial robot can achieve more than three million aluminum arc starts per week using a push-only wire feed system. But while technology has improved the reliability of such systems, some proven tips should be followed.
An industrial robot can achieve more than three million aluminum arc starts per week using a push-only wire feed system. But while technology has improved the reliability of such systems, some proven tips should be followed.
The wire feed path can be separated going into and out of the wire feeder on the robot arm. From the wire feeder, the following considerations help reliably push the aluminum electrode through the torch:
-Keep the torch length as short and direct as possible.
-Use a water-cooled torch for improved feeding.
-Reduce the number of breaks in the feed system.
-Use a jump liner in the end of the torch.
-Limit the torch barrel angle for the application.
While these guidelines are certainly applicable to the setup of a robotic torch for an aluminum weld system, everyday practices can still impact the productivity of a robotic workcell. To maintain a torch on the shop floor, manufacturers should apply the following:
-Don’t cut your plastic liners with wire cutters or welpers. Use a knife to cut the plastic liners to length.
-Don’t reuse a liner after a bird’s nest in the feeder.
-Don’t mix consumables for aluminum and steel.
-Check your feed path resistance.
-Check your feed roll tension.
-Change your torch liners more frequently than with steel wire.
Wire cutters deform the end of plastic liners when cut and should be avoided.
Trimming the liner with a knife leaves a clean edge. The hole in the power pin was enlarged to allow the plastic liner to get close to drive rollers.
Also critical is the delivery of the electrode from the package to the robot. Most bulk packaging of aluminum electrodes comes in drums. It is reverse wound when spooled into the drum so it does not flip when pulled out of the package. Using a dispensing package with a rotating arm lets the electrode enter the feed path through ceramic inlets and avoids tangling or dragging on cardboard edges.
Depending on the feed distance, it might be advantageous to add an assist feeder to pull the wire out of the package and lightly push it toward the robot. Aftermarket assist feeders that operate by pneumatic or electronic control are independent of the power source feed system and feed on-demand when they sense the wire being pulled.
Just like the torch liner, the rear conduit should be made of plastic polymer to reduce friction and not abrade the wire. A variety of commercial products are available that will provide smooth surfaces for the wire to transition from the wire package into the conduit. Angled transitions with rollers can allow the wire direction to bend into the workcell without adding significant drag or wear on the wire.
A more flexible section of conduit is needed to lead into the feeder on the rear of the robot. Conduit with roller segments allows the electrode to travel around bends with less resistance, but these cost more. Wire conduit is a consumable and should be changed before it breaks down, and it might cause wear points on the wire. Plastic polymer reduces friction but can also develop nicks or sharp edges that scrape the soft aluminum electrode.
Welding Equipment Considerations
The power source is a key element in the aluminum welding system. Manufacturers should have process schedules for the aluminum alloy and wire diameter desired. These schedules should have arc starting parameters designed for reliable positive arc starting. A good aluminum arc start sounds crisp and does not pop or extinguish.
Arc ends are more critical than starts. The wire should terminate with a sharp point or small radius on the end. A ball on the end of the wire will make it more difficult to start the next time due to its larger oxidized surface area.
A power source manufacturer that promotes its power source for aluminum push applications will have plastic wire guides for its feeder along with drive rolls with U-shaped grooves for the 3/64- or 1⁄16-in.-diameter electrodes. Electrodes smaller than 3⁄64 in. should be avoided with push-only systems.
Collaborative Push-Only Perspective
The popularity of collaborative robots (cobots) for welding is bringing back traditional torch mounting with an external torch cable. While not always ideal, using this setup on cobots for aluminum welding can be successful. The torch length should still be kept as short as possible with the feeder mounted above or behind the robot. The torch cable should be supported in an arch over the robot and not allowed to make sharp bends or wrap around the arm or wrist.
Present Push-Only Success
TnL Welding, a fabricating operation in Sidney, Ohio, successfully welds more than 35,000 high-quality aluminum parts (68 in. long with 60 welds per part) via a push-only wire feed system. Robust tools, including several Yaskawa ArcWorld® welding workcells of different generations, facilitate this production. Capable of welding various metals, each ArcWorld is equipped with one or two high-performance arc welding robots that expertly accommodate push-only wire feed systems. The newer welding technology provides improved results when welding aluminum. Other companies can achieve high-quality aluminum welds via traditional push-only feeders when certain criteria are followed.
High-quality robotic welds with many starts and stops can be achieved via push-only wire feed systems if certain criteria are met. (Image courtesy of TnL Welding.)
This article was written by Chris Anderson (associate chief engineer at Yaskawa America Inc., Motoman Robotics Division, Miamisburg, Ohio) for the American Welding Society.
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