Overestimating welding arc-on time is a common mistake. Manufacturing operations may be surprised to discover that the average arc-on time in a semi-automatic welding operation is only 10 to 12 percent. When companies aren’t thinking about how to improve arc-on time, they’re missing out on key ways to improve throughput and, of course, the bottom line.
Welding arc-on time directly affects how many parts go out the door each day. The arc-on time metric does not include the time spent on part fit-up, prepping the material for welding, or post-weld cleaning or grinding, but these are steps that can add significant time to the overall process.
It’s important, therefore, to consider the activities performed before and after the weld – and not just during the welding itself – to find ways to improve arc-on time. Taking some common-sense tips on how to increase throughput in manufacturing applications that use gas metal arc welding (GMAW) can help.
Pay attention to part fit-up. Long before a welder strikes an arc, proper part fit-up is a determining factor in the weld’s outcome. The welder may be responsible for part fit-up, but it could be anyone else in the operation; problems with part fit-up have been traced all the way back to the engineering or design stage of the process. Regardless, make sure that part fit-up is correct before beginning to weld.
Spending the time to ensure consistent, even part fit-up will eliminate gaps between the parts and pay off in time savings later. When there are large or uneven gaps between the parts being welded, it slows down the welder and increases the amount of spatter, which requires more time for post-weld grinding.
The right process
Use the right welding process. As simple as it sounds, for some manufacturers, the idea of changing their welding process can be daunting. Sure, it may require additional training and re-approval of any changes to the Welding Procedure Specification (WPS), but switching the process can yield significant productivity results in the right applications.
Welding process options include standard GMAW, modified short-circuit GMAW or numerous pulsed GMAW processes. If an operation has big part gaps that can’t be fixed in fit-up, for example, a modified short-circuit GMAW process is a good solution because it offers superior gap-filling capabilities.
Pulsed processes provide numerous benefits for productivity, including less spatter, lower heat input and faster travel speeds. A pulsed process can provide 10 percent faster travel speeds using the same heat input compared to straight GMAW. In addition, some advanced pulsed processes, such as Accu-Pulse technology from Miller Electric offer a 28 percetn wider operating window. This makes the process easier to use, so welders of all experience levels can create high-quality welds even when technique or parameters vary.
Making a change to the filler metal or shielding gas can also help improve productivity in the operation. Be aware that gas and filler metal changes may also require reapproval of the WPS. Many manufacturers use a solid wire for GMAW applications, but flux-cored and metal-cored wires can offer benefits in certain applications. The right filler metal solution depends on the process being used, the material being welded and the shielding gas. For example, metal-cored wire can deliver significant productivity benefits thanks to very fast travel speeds, but it can be difficult to use in pulsed welding.
Different shielding gases may also be better suited to certain applications and processes. A 100 percent CO2 gas is common in manufacturing because it’s affordable and offers easy weldability for operators with less experience. However, it results in much more spatter than a mixed gas, requiring more time for post-weld grinding. A mixed gas like 90 percent argon/10 percent CO2 can provide faster travel speeds and lay down a better weld, so there is less time spent on post-weld cleanup.
Ensuring the parameters are correctly dialed in during welding is also critical when producing good welds that don’t require time-consuming rework. Travel speed that is too fast or slow, heat input that is too hot or cold, and improper wire stickout are parameters to watch.
A too-slow travel speed results in more heat input in the weld zone that can cause warpage. Maintaining adequate travel speed helps to control heat. But moving too fast (and too cold) can pour too much filler metal into the weld too quickly, resulting in spatter or a lack of penetration that requires rework. Another cause of increased spatter is having too much wire stickout.
When the goal is improving arc-on time, the worst thing a welder can do is put down a bad weld that requires rework. The time necessary to cut out the bad weld and replace it with a new weld can triple the time wasted, or even more.
Time spent troubleshooting problems such as wire feeding issues takes away from arc-on time, so it’s important to keep the GMAW gun properly maintained for optimal performance. If the gun liner or contact tip is too worn or the drive roll tension is improperly adjusted, these problems will contribute to wire feeding issues that can result in increased spatter and poor weld quality. Weld quality issues are also commonly caused by worn weld cables or poor cable connections.
Before each shift – and after any changes are made in the welding process – double-check all consumable connections in the wire feeding system to ensure everything is installed and tightened correctly. Also look for signs of wear or damage. This helps reduce the time spent troubleshooting, so the welder can spend more time under the hood.
Rely on tech
As the industry struggles with a skilled welder shortage and many companies seek ways to improve productivity, technology can help. When a welding power source delivers greater ease of use and improved arc control, it’s easier for welders of all skill levels to produce high-quality welds and reduce mistakes – and, therefore, improve arc-on time.
Synergic control: More welding power sources are designed to automatically make changes to correspond to the operator’s adjustments. When the operator makes a change to wire feed speed, the machine will adjust the voltage to match, ensuring the optimal parameters are used.
Simplified setup: Some new welding systems offer an “easy button” for machine setup, so welders can get under the hood faster. This can be especially helpful for less experienced welders. With this technology, the operator only needs to input the material thickness, and the power source will automatically set the other parameters appropriately. This saves time and helps reduce the chance for spatter and distortion that increase post-weld cleaning and may require rework.
Locks and limits: Welding power sources that include this feature allow certain parameters to be locked within a set range. For example, if the lock is set at 28 to 32 volts, the operator can’t go outside of that window. When a manufacturer is training new welders, this technology is helpful for keeping them within the parameter ranges for a specific job. Some systems can also send alerts to let managers or supervisors know when a welder is working outside of specified parameters.
Weld data monitoring: Digital weld monitoring is available on more power sources than ever, allowing manufacturers of all sizes to track important performance metrics. Available solutions range from basic systems that verify weld parameters and report on productivity to more advanced monitoring software that detects welding mistakes, tracks parts and delivers real-time feedback to welders. Tracking and understanding this data is a key part of improving arc-on time and productivity. This detailed data can also help manufacturers train new welders and get them up to speed faster.
Improving welding arc-on time in a manufacturing operation requires looking at many factors from start to finish in the process. Tracking and understanding arc-on time – and where time is being spent elsewhere in the operation – is the first step toward improvement.
Proper welder training also plays a role in improving arc-on time and throughput, especially anytime there are changes to the welding process, filler metal or shielding gas.