Trends in Robotic Welding Guns

Metal fabrication environments are dynamic, ever changing with the economy, customer demands, available labor and skill sets, and competitive forces, among other factors. To maintain a favorable position in the industry, it is critical for fabricators to continually look for ways to increase efficiencies while also improving quality and decreasing costs. For many, that means a shift toward welding automation, which has experienced its own changes in the last ten years.

During this time, robotic welding manufacturers have transitioned away from the manufacture of conventional robotic welding systems to the development of through-arm styles, in which the power cable of the robotic MIG gun runs through the arm of the robot as opposed to over top of it. These are now the prevalent robot styles in the industry and this change has had a direct impact on the design of the robotic MIG guns for the marketplace. But it is not the only trend associated with robotic MIG guns. Like any component of the welding operation, this equipment has continued to evolve to the demands of the industry and to provide solutions to improve the business of welding.

THROUGH-ARM BENEFITS
Improving and simplifying cable management has been the driving force behind the shift toward through-arm robots and, therefore, the development of through-arm robotic MIG guns to accompany them. With conventional style robots and guns, the cable is prone to “whipping” during air movements, which causes undue stress on this portion of the gun, and can lead to premature wear and failure caused by the cable rubbing against the robot or tooling. It also creates additional cost and time for companies to implement cable management systems.

The through-arm style robot and through-arm robotic MIG gun make it easier for companies to minimize downtime associated with cable management and reduce costs for cable replacement. It also eliminates the risk of selecting the wrong cable length, a common mistake that occurs with conventional robotic MIG guns. The through-arm robot model dictates the length of the robotic MIG gun cable, so there is no concern about it being too long (which requires extra cable management or could cause wire feeding issues) or being too short (which can cause the cable to stretch and fail prematurely) — both issues associated with conventional robotic MIG guns.

There are other benefits to the shift to through-arm robots and through-arm robotic MIG guns, namely that they can accommodate for increases in welding speed that are also becoming customary in the industry. Robots are getting much faster, but with the through-arm robot there is no longer the concern of the robotic MIG gun cable getting caught on tooling during quick movements. Too, it is easier to complete offline robot programming or welding simulation and have it work with these robots because there is less concern about having to accommodate for clearance for the power cable in an application. If a robotic MIG gun fitted for a through-arm robot works in simulation, it will most likely work in the real-world application.

CABLE DURABILITY, SIMPLIFIED REPLACEMENT
As fabricators strive for greater arc-on time and higher productivity, robotic MIG gun manufacturers are helping by providing increasingly more durable power cables on this equipment and implementing features that simplify cable changeover. Some manufacturers offer a rotating power connection on the front of the cable that allows the robot to spin on its final axis as much as necessary without binding the cable. This feature helps minimize stress due to routine torsion and to extend the life of this part of the gun, as well as to increase the robot’s operating range by allowing it to rotate a full 720 deg (360 deg in both directions) and weld faster. Built-in quick-change features on many robotic MIG guns also expedite cable replacement, adding to the operation’s productivity, while the use of stronger cable materials help better resist wear and UV damage from the arc for longer component life.

SOLID MOUNTS
Another trend associated with robotic MIG guns is the use of solid mounts (also called solid arm mounts) as opposed to the clutch mounts that were used previously to protect the gun in the event of a collision — an occurrence commonly caused by an incorrectly position work piece or tooling that has been left out of position, among other factors. This trend is due to more sophisticated collision detection software being built into today’s robots. This software is increasingly capable of monitoring current rates and/or torque so it can quickly stop the robot when an impact occurs. Solid mounts are made from durable, high-strength aluminum alloys, and are an alternative to the clutches used with older robot models.

There are two key benefits to using a solid mount for robotic MIG guns compared to a clutch: 1) they offer greater repeatability for higher weld quality and 2) they are less expensive. Clutches (also called shock sensors) are designed to recognize the physical impact of the robotic MIG gun on a solid surface during a collision and send an electrical signal back to the robot controller, causing the system to stop. While effective, clutches are designed to move, which can affect tool center point (TCP) after a collision. Also, since it is an electrical device, it costs more than a solid mount and is more prone to failure because of its internal components — expenses that many companies can now happily omit.

MORE SPACE, BETTER JOINT ACCESS
As fabricators seek ways to become more competitive and produce higher volumes of parts, they need to maximize floor space to make room for more robots to do the job. As a result, robots and welding cells are becoming smaller and in many instances, tooling has become more complex. These changes pose greater space constraints when it comes to the robotic MIG gun. Many robotic MIG gun manufacturers have responded to this trend by creating guns that provide a more open work envelope around the mounting arm (the depth from the wrist of the robot to the tip of the robotic MIG gun) so maneuvering around tooling and gaining joint access becomes less cumbersome. There are also more options for neck lengths and angles available for robotic MIG guns, which helps companies gain access to complicated joints.

MORE COOLING OPTIONS
Because many robotic welding applications tend toward higher amperages and longer arc-on times, it is critical for companies to have a robotic MIG gun that provides adequate amperage without overheating. The complexity and increased cost of water-cooled robotic MIG gun systems (compared to air-cooled models), however, make some companies wary of the investment for their high amperage applications. Too, if there is an issue with the coolant flow, there is the risk of the robotic MIG gun overheating and failing — an event that can be costly not just for replacement of the gun, but also potentially for rework of the part should quality problems occur.

A development in recent years that addresses this concern is a hybrid robotic MIG gun. This type of gun has a durable neck like an air-cooled model and water lines that run external to the neck down to the nozzle. Should the coolant flow fail, the gun can rely on the underlying air-cooled unicable to provide enough current-carrying capacity for the job for a period of time, saving downtime and costs to address a complete robotic MIG gun failure. These guns also offer the higher amperage associated with a standard water-cooled gun, making them a good option for companies who need greater cooling capacity for an application.

ADDING EXTRAS
Because time is at a premium when it comes to robotic welding, companies are always looking for ways to extend their robotic welding cycle time — down to the second. To help maintain greater arc-on time while still protecting the robotic MIG gun and consumables from spatter build-up that could affect weld quality, adding air blast to robotic MIG guns is becoming a popular choice with some companies. This optional feature can be added to the robotic MIG gun and functions by blowing compressed air through the gun at a high pressure (approximately 100 psi) to clear debris loose in the front end while the robot is moving out of the way so the table/fixture can index. This addition can help companies reduce the number of times that the robotic MIG gun needs to be reamed out by a reamer or nozzle cleaning station, resulting in more arc-on time and greater productivity.

MORE TO COME
While robotic MIG guns may seem like a small part of the whole automated system, their design and functionality can have a significant impact on the cost, productivity and quality of an application. The trends discussed here are just some of the ways that robotic MIG gun manufacturers have adjusted the designs and capacity of the products to help companies gain the best results in recent years. As with any piece of welding equipment, robotic MIG guns will need to continue evolving just like any equipment in order to meet companies’ changing needs and to meet the demands of the fabrication and manufacturing industry.