Spring 2010 Edition

Ask the Experts

QUESTION: Why is it important to use the correct unicable length for my robotic welding application?

ANSWER: Like any component in a robotic welding system, the unicables must work in harmony with the rest of the system in order to provide the best welding performance and efficiency. To help you achieve that goal with your own robotic welding system, our Tech Service experts explain the importance of having the correct unicable length and provide tips for making the proper unicable selection.

The Pitfalls

Unicables should be able to maneuver easily within the allotted work envelope, allowing ample room for the robotic MIG gun to reach the joints that the robot has been programmed to weld. However, for conventional robotic welding systems (not through-arm systems), it can be difficult to determine the proper length, as there are no set specifications for the unicables. Wire feeders for these type of systems may be mounted anywhere within in the weld cell and therefore, could require any number of different cable lengths. For this reason, each individual application will determine the unicable requirements. And unfortunately, if the length is not correct many problems can occur.

If the unicable is too short it will prevent the robot from completing that weld, as it obviously cannot extend the distance required to reach the joint.

Conversely, if the unicable is too long it can cause significant cable management issues. Long unicables tend to coil and/or form U-shaped bends that make it difficult for the welding wire to feed through to the robotic MIG gun. This feedability issue in turn can cause arc instability that leads to poor welding quality, and ultimately to expensive rework. Poor wire feeding may also shorten the life span of your robotic MIG gun and consumables, and increase your downtime. Specifically, poor feedability increases the chances of burnbacks that require more frequent contact tip changeover. In certain cases, the stress caused by bends in the unicable may also wear out the connections within it, creating electrical resistance that leads to premature failure of not only the unicable, but also the robotic MIG gun.

Making the Correct Selection

In order to select the correct length unicable, you should consider several factors. First, determine where you plan to mount your wire feeder. There should be ample unicable length to span the distance between the wire feeder and the joint that you’ve programmed the robot to weld.

Next, consider the amount of articulation or movement that the welding program requires. If the robot needs to complete very short welds that require only slight movements, a shorter unicable length will suffice.

You should also consider the air time of your program when choosing the correct unicable length. For example, some robotic welding applications may have an abundance of air time between welds. If the unicable is too long, it may continue moving after the robot stops and prepares for a new weld, and that movement can cause premature wear and failure.

If you are replacing an existing unicable, simply measure the one being replaced to determine your proper length. If you are purchasing a new unicable for a new or repurposed robotic welding system, you should contact the robot manufacturer for a proper recommendation. Your local Tregaskiss representative can also help.

Remember, every component of your robotic welding system is important. That includes the unicable. Havinga cable of the proper length can go far in saving you time, money and frustration—and it can help you get the best return on your investment.