From the Contact Tip to the Robot: Answers to Frequently Asked Questions About Welding Automation
Robotic welding systems, when implemented properly and for the right application, can add great value to a welding operation. In addition to offering faster speeds and greater productivity, robotic welding systems can improve weld cosmetics, reduce rework and repairs, lower materials costs by limiting overwelding and also reduce labor costs. The consistency of these systems and the typically rapid return on investment (ROI) make them especially appealing for companies looking to gain a competitive edge.
Still, setting up a robot and selecting its components — the consumables and the gun, for example — can be a complicated business, especially for first-time users. In fact, the simple question of whether to automate may itself be confusing to a company that hasn’t used a robotic welding system before.
For insight into welding automation, consider these answers to some of the most frequently asked questions.
What are the best applications for a robotic welding system?
High-volume, low-variety applications are well-suited to robotic welding; however, lower-volume, higher-variety applications may also work if implemented with the proper tooling. Companies will need to consider the additional cost for tooling to determine if the robotic welding system can still provide a solid return on the initial investment.
In either case, it is critical that the application have simple, consistent parts so that the robot can repeatedly execute the weld in the same location. Having a blueprint or electronic CAD drawing is helpful. Robotic integrators can review the blueprint or create a software simulation that can assess the suitability of the part for welding automation. These assessments can not only help to visualize the quality of the part to be welded, but they can also identify ways to fine-tune tooling to optimize the process. Workflow is also important. Companies should be certain to have a high enough flow of parts to the robotic welding cell for the application so that it can operate consistently. Delays in upstream parts fabrication can cause bottlenecks that result in costly downtime.
Is it better to use fixed automation or a robot?
Each type of automation has its own best applications. Fixed automation is an efficient and cost-effective way to weld simple repetitive straight welds or round welds, where the part is rotated. It is good for high volume applications of a single part. Fixturing for fixed automation can be expensive, however, so companies will need to factor that cost into the initial investment and determine whether this type of automation is still cost-effective for the long-term. They also need to determine if future jobs will require retooling, as that will add further to costs.
For companies wishing to have the flexibility to weld on multiple applications, a robotic welding system is a better choice. Because a robot can be programmed for multiple jobs, it can often handle the task of many fixed-automation systems.
Who is the best candidate to operate a robotic welding system?
Robotic welding systems require a trained operator. Skilled welding operators or those with previous robotic welding management experience are good candidates. The person overseeing the robotic welding system should be able to program it, troubleshoot errors and perform preventive maintenance. Robotic OEM manufacturers can often provide the appropriate training for employees who are new to welding automation. It is recommended to look for ongoing training support. Some robotic integrators or welding solutions providers offer online tutorials, troubleshooting information and/or additional on-site training as part of their aftercare support.
Can an air-cooled robotic MIG gun be used instead of a water-cooled gun?
In many cases, yes. It is absolutely necessary, however, to ensure that the air-cooled robotic MIG gun is rated at a high enough amperage and duty cycle for the application. For example, an air-cooled robotic GMAW gun rated at 500 amps with 60 percent duty cycle using mixed gases will be capable of welding continuously for 6 minutes (out of an available 10 minutes) at about 350 amps. When welding with pulsed waveforms it is very important to review the peak currents and ensure they do not exceed 350 amps at any time during the welding process.
Air-cooled MIG guns offer the advantage of being less expensive — both to purchase and maintain — but if a company anticipates longer periods of welding or higher amperage needs, it may be necessary to shift toward a water-cooled gun. There are also “hybrid” robotic MIG guns available in the marketplace. These guns feature a durable neck similar to an air-cooled MIG gun, but offer the higher cooling capacity of a water-cooled model by way of exterior water lines. These guns can be easier to maintain than a standard water-cooled MIG gun and typically offer 300 to 550 amperage welding capacity at 60 percent duty cycle (using mixed gases), making them adequate to weld on a variety of applications.
What are the best consumables to use?
The style of consumables — contact tips, diffusers (or retaining heads) and nozzles — depends entirely on the application. Ideally, the consumables should be durable enough to last the duration of a robotic welding shift to help minimize downtime for changeover. High-amperage applications (over 300 amps) with high levels of arc-on time can often benefit from heavy-duty consumables. Chrome zirconium products are a good choice. For lower amperage applications or applications with short arc times, standard-duty consumables (often copper) are appropriate.
Companies also need to consider the access required to reach the weld joint. In some cases, it may be necessary to use a bottleneck, straight or tapered nozzle, all of which are narrower, to maneuver around tooling or into complex areas.
It is equally important to consider the mode of welding being used. For example, pulsed welding programs can be especially harsh on consumables due to the higher levels of heat that the process generates. These applications can benefit, often, from heavier-duty consumables.
What is the benefit of touch sensing?
Touch sensing, sometimes called joint touch sensing, is a software system that employs the welding wire or nozzle to help locate the joint in a robotic welding application. This software allows the robot to store position data and send electrical impulses back to the controller once it has located the joint. For applications that have slight variations in parts, touch sensing helps maintain weld consistency. It is also more cost-effective than investing in new tooling and fixturing to hold a part in a precise location; if the part moves slightly, the robot can still locate the joint and weld accurately, as long as the joint has well-defined edges. Touch sensing does add a few seconds to the cycle time, but it is a good choice especially for companies welding large, thicker parts that would be costly to rework should the joint be welded poorly.
To gain optimal results, it is a good idea to combine touch sensing with a robotic MIG gun that has a wire brake feature. The wire brake holds the welding wire in a set position while the robot articulates and searches for the weld joint, ensuring more accurate touch sensing readings. ?
Is it necessary to add peripherals to a robotic welding system?
It is always advisable to add peripherals, particularly a nozzle cleaning station (also called a reamer or spatter cleaner), to a robotic welding system. This peripheral cleans spatter from the inside of the welding consumables on the front end of the MIG welding gun, including nozzles, contact tips and retaining heads. It helps extend consumable life, and with that, reduces downtime for changeover during production and also the cost for replacing consumables. Nozzle cleaning stations also help reduce the risk of losing shielding gas coverage (due to spatter build-up) that could potentially lead to expensive re-work.
Adding a sprayer provides additional benefits, too. This peripheral can be mounted on the nozzle cleaning station and works by applying an anti-spatter compound to the front-end consumables after they have been cleaned. This compound coats the inside and outside of the nozzle, and also the contact tip, creating a protective barrier between the consumables and spatter.
What type of payback can be expected from a robotic welding system?
The payback on a robotic welding system can be relatively quick in many cases. To determine it, companies need to assess their parts volume, as well as the amount of time it takes to weld those parts manually, and compare that information to the potential cycle times of a robotic welding system. Determining this volume is critical, given that labor comprises 75 percent of the cost of a manually welded component. Even if a company produces the same amount of parts, labor could be reallocated elsewhere to increase productivity and enhance the payback on the robotic welding system.
Companies should also calculate the savings for overwelding often associated with semi-automatic welding applications. A weld bead that is 1/8-in. larger than necessary can often double filler metal costs. Because robots are more precise in their placement, companies should calculate the potential savings for filler metals when calculating payback. Because robotic welding systems use bulk filler metal drums that require fewer changeovers (and sometimes have the perk of bulk purchasing discounts), that savings can also be considered.
As always, when companies encounter problems with a robotic welding system or have questions about a program or component, it’s best to contact a trusted robotic integrator, welding distributor or welding equipment manufacturer for support. Robotic welding systems aren’t cheap and companies should never take chances with their investment by guessing about the right course of action. The right information is the best way to gain productivity, quality and cost improvements from a robotic welding system.