Video: Servo-Controlled Robotic Spot Welding Guns More Compact than Fluid Powered
James Anderton posted on August 10, 2018 |
Save space, increase accuracy and control, and reduce wear and tear on your line.

James Anderton: On an automotive assembly line, or in consumer goods, or in anyplace where you’re spot-welding high-volume sheet metal assemblies, line space is at a premium. Ideally, of course, you want to get as much automation as possible and create as many spot welds in each individual cell as possible, but that can be a challenge.

I’m with Will Harlos, Integrator Sales Manager at Yaskawa Motoman Canada. Will, we're standing in front of what looks to me like a pretty big robot.  You're telling me that this, in fact, is a compact unit?

Will Harlos: What we’ve tried ato do at Yaskawa Motoman is to make a completely-integrated spot-welding robot. In other words, when the customer (typically the integrator that's going to build it into a complete welding line) receives it, they have a complete piece of motion with the welding gun already integrated to it. In this instance here, I'll talk a bit about the spot gun because it is unique as compared to conventional spot-welding guns.

Traditionally, spot welding guns are “air over oil” or “oil over oil” hydraulically actuated units. What's becoming more and more popular over the last decade or so is what we call the servo spot gun. In this case, we have a motor driving the action of the gun. This motor is actually tied back into the robot control package, so, in essence, it's like a seventh axis of the robot. What this allows us to do is to come in very precisely to the part we're going to weld, and in a very controlled fashion, control the pinch force that we're going to apply to the part. This makes for a better weld, and a better location for the weld on the finished part. This is a very compact gun, it is very lightweight compared to other spot-welding guns on average. This lighter weight contributes to the smaller size of this robot.

This robot is called our MS-100, or the ‘Master Spot’ with 100 kg payload. Typically, our spot-welding robots fall into the 180 - 225 kg payload range. The purpose behind having the smaller spot-welding robot is to allow more robots to fit into a given unit length of production line. For a given fixture, a given station, whether you’re welding a washing machine or an automotive body-in-white, the cost of fixturing comes down because we can get more done for a given fixture. Better line density, smaller production line, and greater space efficiency are the ideas behind this.

What's also unique to this robot, which makes it a spot-welding robot as well, is that the entire dress-out, all the services that come to this gun—electrical power, cooling water, everything you need to put out to it—is all run through this conduit here into what we call our little “can” back here. It’s all wrapped around the forearm and all nicely managed as well. As the robot moves without having this dress-out, typically you're going to damage those water and power lines and create all kinds of maintenance issues, as well as interference issues with the robots that are beside it. This harness will last 40,000 cycles before we'll ever have to replace anything in there.

JA: Will, with this move towards servos away from traditional pneumatics and hydraulics, it seems to me it's making the end-effector smaller and lighter. Does that make your job easier as a robot manufacturer?

WH: It allows us to build a slimmer arm that can move faster, for one thing. In terms of process, by having this gun nice and short and compact, now I can shove it into much tighter spaces. It opens up the manufacturing capacity, the capabilities of what you can build on the floor, by having the end effector smaller.

JA: Compact, smaller footprint robotic welding saves time and money, says Will Harlos of Yaskawa Motoman.


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