You’ve probably heard the allegory of the tortoise and the hare. The turtle was slow and steady, where as the hare would go fast and then stop for breaks. Many people live by the saying “slow and steady wins the race.”
The gas tungsten arc welding (GTAW) process is a slow and precise business. Quality of the weld, not time, is most often the major factor when GTAW is used. Skilled tungsten inert gas (TIG) welders earn some of the industry’s highest wages due to the precision and skill this manual technique demands.
However, as manufacturing continues to be challenged by a shortage of skilled welders, and companies look to increase productivity without compromising quality, they more frequently have turned to automated solutions.
“Robotic” and “TIG welding” provide the analogy to the hare and the tortoise, and today’s technology combines the best features of the two processes, and has also contributed to a number of significant breakthroughs. Here’s a look at those, as well as the pertinent factors your company should examine when considering robotic TIG welding.
Benefits of GTAW
The primary benefit of the TIG process is the high quality welds it is capable of making in almost all metals and alloys. While carbon steel, stainless steel, and aluminum applications are commonplace, examples of some of the more exotic materials include titanium, zirconium, columbium, tantalum, and austenitic nickel-chromium-based superalloys.
These materials are found in a wide range of industries, including power generation, nuclear, motorsports, and various military applications. In the aerospace and aircraft maintenance industries, these material types are commonly found in advanced turbine engines, blades, vanes, and thrust reverser applications.
The common thread among these industries is that they frequently utilize thin gauge, high performance materials that exhibit some combination of superior mechanical properties, electrical properties, and thermal properties, all of which require consistency, exact penetration, repeatable control of many factors, including travel speeds, gas coverage, temperature control, and precise heat control to avoid shrinkage and distortion.
The TIG process produces a narrow heat affected zone (HAZ), which in turn, reduces solidification stress, cracking, and distortion in the finished weld. The traditional “stacked-dime” cosmetic appearance of a TIG weld conveys a sense of visual quality to the process.
Procedure qualification and certification
The Federal Aviation Administration (FAA), the American Welding Society (AWS D17.1), and the American Society of Mechanical Engineers (ASME) provide widely accepted standards for TIG procedure qualification, and are written specific to many materials.
TIG welding to a specific code requires a welding procedure specification (WPS), a formal document describing welding procedures to assure repeatability by properly trained welders. A procedure qualification record (PQR) is a record of welding variables used to produce an acceptable test weldment and the results of tests conducted on the weldment to qualify a welding procedure specification.
Once procedures are established for a welding process and joint design, they must be strictly followed in subsequent production welding. This requirement encourages the combination of TIG welding and automation for repeatability, traceability, and the ability to establish limits and restrict the adjustment of any variable to stay within qualified procedures.
Benefits and applications of robotic GTAW
Robotic TIG is widely used in production or manufacturing segments, in addition to the repair and overhaul segments of aerospace. Robotic TIG provides a number of quality control advantages, including automated, repeatable, uniform, consistent welds, with increased productivity — especially when considering the speed of torch repositioning between welds. Using a robotic arm provides repeatable access to welds that might be difficult to reach or require torch rotation that would be impossible by the human counterpart.
The center at Davis Applied Technology College was completely revamped and outfitted with the latest Lincoln Electric welding equipment and technology.
ASME Turbo Expo 2011 will be held June 6-10 in Vancouver, British Columbia, Canada.