Welding Automation: Arc Motion vs Work Motion

Welding Automation: Arc Motion vs. Work Motion

The welding world consists of a broad spectrum of technologies suitable for a wide range of use cases, budgets, and levels of complexity. Between the two extremes of entirely manual and entirely automated processes is welding mechanization. Mechanization can be accomplished using devices that move the workpiece, move the arc, or both simultaneously. Regardless of the mechanical device used, the goals are the same: to make a welding operator’s work easier and more productive.

An Introduction to Welding Positions

To better understand the target applications of these devices, a quick refresher on welding positions can be helpful. Both the American Welding Society (AWS) and the International Standards Organization (ISO) use terms and designators to communicate the position of the axis of welding relative to the vertical and horizontal planes for both plate and pipe. The four fundamental welding positions for plate are:

 

• Flat (aka 1G/1F depending on if the weld joint is a Groove or Fillet weld, respectively)
• Horizontal (aka 2G/2F)
• Vertical (aka 3G/3F)
• Overhead (aka 4G/4F)

 

The four fundamental welding positions for pipe are:

• 1GR (rolled horizontally oriented pipe)
• 2G (vertically oriented pipe/horizontal welding axis)
• 5G (horizontally oriented pipe, vertical welding axis)
• 6G (~45° inclined pipe)

Welding in the flat and horizontal positions provides the greatest opportunity for the use of high-productivity welding parameters since the influence of gravity on the weld pool is not (or at least less) detrimental. Conversely, welding in the vertical and overhead positions often requires comparatively low amperages and wire feeds to fight gravitational influence, even if an all-position welding electrode or wire is used.

 

In-position welds are also favorable from an ergonomic perspective; out-of-position welding can be physically taxing, and the ability to mechanize an application provides an opportunity to locate the operator away from the welding arc in a more favorable location.

 

Welding Positioners

In a perfect world, every weld could be performed in the flat or horizontal welding positions and, in the case of a pipe, rotated during welding. “Work motion” devices allow the workpiece to be repositioned during or between welds and are also known as “positioners.”

 

Weld Rotator

•  Weld rotators have a rotating platen that the workpiece can be mounted to using a chuck or fixturing. Often, the platen is designed to tilt approximately 90 degrees so that a workpiece oriented vertically is reoriented horizontally. These positioners are available in sizes ranging from benchtop to multi-ton heavy-duty units. Note that these positioners typically leave the workpiece cantilevered, which may constrain the maximum weight that can be placed on the unit before reaching rated capacity. These positioners are popular for applying flanges to process piping. In some applications, the welding cell can be designed to use a welding rotator to permit welding on one assembly while another is being welded.

Headstock & Tailstock

• Like weld rotators, headstock and tailstock positioners have one powered rotatable platen that allows the workpiece to be rotated about the horizontal axis. However, the workpiece bridges from the powered headstock to the idle tailstock so that the workpiece is supported and not cantilevered. These positioners are excellent for large, unwieldy weldments such as large boom assemblies or even entire railcars. With proper fixturing, the workpieces need not be cylindrical.

Turning Rolls

• Turning rolls also provide the rotational movement of a workpiece. Unlike weld rotators and headstock/tailstock positioners, the workpiece is not fixtured to turning rolls, it is simply cradled by them. These positioners are popular for performing circumferential welds on very large cylinders or pipes found in the oil, gas, and power generation industries

 

Arc-Motion Devices

While work-motion devices such as welding rotators help make welding easier by placing the weld in the ideal position, arc-motion devices serve to make welding easier by mechanizing the actions of the welding operator. Some common arc-motion devices are:

Welding Manipulators

• These devices consist of a vertical mast mounted to a horizontal boom. Typically, the vertical movement of the boom up and down the mast is powered using an electric motor. If the horizontal movement of the boom is powered as well, the device can be used to perform longitudinal welds. However, some manipulators do not have mechanized boom travel and exist primarily to hold the torch at a fixed point in space above a welding positioner. Small manipulators may be mounted to a base having castors or lift points that permit ease in moving the device to the workpiece.

Track Torches:

• These devices are typically portable and consist of a track and carriage. The welding torch is mounted to the carriage, and the track is typically affixed to the workpiece using magnets, permitting both in- or out-of-position welding. Specially designed track torches can be affixed to pipes for circumferential welding.

Seam Welders/Seamers

• Seamers are specialized side-beam that has integrated workpiece clamps. The workpiece clamps are cantilevered over the equipment’s base, which allows loading and unloading from a single side. Seamers are especially popular for performing longitudinal welds on smaller-diameter tanks and pipes.

Welding Oscillators

• Oscillators are an important accessory for many of the arc-motion devices described above. These devices can be affixed to a carriage or boom and permit the mounting of a welding torch. The oscillator is then able to finely manipulate the position of the torch—back and forth—similarly to how a welder would perform wide weave weld passes.

Conclusion

The adage “work smarter, not harder” can certainly be applied to the use of welding positioners and arc-motion devices. And because there is such a wide range of equipment types and capacities, finding a device that fits within your budget is not a complex task.

 Furthermore, these devices can be rented, allowing you to invest in the best technology for the job when you need it. Sometimes, the best solution may be to integrate both a work-motion and arc-motion device into a single weld cell. Red-D-Arc Welder Rentals has automation specialists who are able to help you identify the best devices for your application.