January 12, 2010
Want to get more from your robotic GMAW system? Find out how selecting the appropriate wire, consumables, liner, filler metal package, and welding gun can help decrease downtime, increase productivity, and improve quality.
Robotic gas metal arc welding (GMAW) can provide companies with significant gains in productivity and excellent return on investment — when done right. Unfortunately, companies often make the mistake of focusing too much on big-picture items, like the power source and robotic arm, and neglecting the small but equally important details like the welding wire, gun, and consumables.
While the power source and robot arm certainly are important components to consider, even the most carefully chosen and configured robotic system can fail to reach its potential without the right components to support it.
Following are five tips for maximizing your robotic welding productivity and reducing robot downtime by choosing the proper wire, gun, and consumables.
Because robotic welding involves very precise tolerances and even minute variations in wire feeding can result in unacceptable welds, it is important to choose a wire designed to feed smoothly through the drive rolls and liner. Wires engineered specifically for robotic applications often provide better feeding characteristics than those designed for all-purpose use.
Another consideration unique to robotic applications is the wire's arc-starting performance. A wire that produces unreliable and inconsistent arc starts can negate the productivity benefits of a robotic system by creating substantial downtime or downstream rework.
For many robotic GMAW applications, a metal-cored wire provides excellent weld quality, metal deposition, mechanical properties, bead appearance, and travel speed. Because it contains deoxidizers and other arc stabilizers in its core, metal-cored wire also produces very little to no spatter, which reduces postweld cleanup and how often the welding gun must be cleaned. This is particularly evident when welding over mill scale.
Another benefit unique to metal-cored wire is that it reduces subsurface porosity caused by extended wire stick-out and changes in gun angles, which often goes undetected during visual weld inspection. Also, the wide, round penetration profile of metal-cored wire allows a greater margin of error in wire placement, particularly in fillet welds where fusion at the root is critical.
Metal-cored wire isn't the right solution for every robotic application, however, so be sure to check with a robotic welding expert or wire manufacturer before selecting the wire.
Responsible for delivering electrical current to the welding wire and shielding gas to the weld pool, GMAW gun consumables play a crucial role in ensuring weld quality. The challenge lies in delivering consistent current under extreme heat for hours and days without interruption.
Because robotic welding often involves numerous and frequent tack welds, it is important to choose consumables that reduce arc-start failures and contact tip burnbacks.
Another feature to look for in consumables is a common platform that allows them to be used for either robotic or semiautomatic applications. Because most shops that use robots also have semiautomatic applications, using an interchangeable consumables system can reduce inventory footprint and downtime associated with retrieving the correct consumables when replacement is needed.
Also look for a consumables system that uses contact tips that can be rotated to expose a new contact area when the bore becomes worn away by the welding wire. Such contact tips can cut consumables costs significantly.
Front-load liners allow you to replace the liner from the front of the gun instead of the back end, where the welding cable connects to the wire feeder. These liners take less time to change than standard liners, which allows you to change a liner on a proactive basis during short periods of downtime, rather than waiting for the next available time allotted for preventive maintenance (PM).
A front-load liner typically requires you to install a retainer at the back end of the gun during initial installation. Following this initial installation, you simply remove the front-end consumables, pull out the old liner, slide the new liner on over the wire, and replace the consumables.
The benefits of robotic GMAW rely on volume and uptime, so it should be no surprise that reducing robot downtime for routine wire changeovers can be one of the most effective ways of maximizing return on investment and productivity.
The ideal filler metal package for a robotic application should be large enough to reduce wire changeovers as much as possible, yet not so large that the same wire sits on the shop floor for more than a few days. Filler metal usually is shipped in airtight containers, and once opened, it runs the risk of absorbing moisture, dust, oil, or other contaminants that can affect welding performance.
Also consider where the filler metal will be located within the welding cell. In some cases, weld cell configurations make large filler metal drums impractical, but when possible, stocking at least one extra filler metal package near the robot can help reduce downtime.
Finally, selecting recyclable filler metal packaging can reduce cost and the time employees spend properly separating and disposing of recyclable and nonrecyclable packaging materials.
Durability is a desirable quality in both semiautomatic and robotic GMAW guns, but in the case of robotic applications it is absolutely paramount. Inevitably, the welding gun occasionally crashes into other equipment (such as clamps and fixtures) or the weldment itself. While it's difficult to avoid collisions completely, selecting a robust robotic GMAW gun greatly reduces the downtime, lost production, and product replacement costs associated with these unforeseen collisions.
Typically, the gooseneck of a robotic GMAW gun bears the brunt of the impact, so choosing a product with sufficient armor should help maintain the tool center point (TCP) and minimize costly productivity interruptions. Selecting a robotic gun with a large work envelope also helps improve joint accessibility, reduces programming complexity, and lowers the possibility of unexpected collisions.
Turning production over to a robotic welding system is never a task to be undertaken lightly. Done hastily and without carefully selecting the right equipment, including the wire, GMAW gun, and consumables, the endeavor could result in excessive downtime and greater expenses. Properly considered and done right, however, robotic welding can yield impressive gains in productivity, reduced downtime and rework, and increased bottom-line profitability.
Rob Ryan and David Bellamy are product managers at Tregaskiss, 2570 N. Talbot Road, Windsor, ON, Canada N0R 1L0, 519-737-3000, www.tregaskiss.com. Doug Krebs is sales and marketing manager at Hobart Brothers, 101 Trade Square, Troy, OH 45373, 937-332-4000, www.hobartbrothers.com.