Arc Welding 101: Achieving a good work lead connection
Q: What makes a good ground connection, and why is it important?
A: In a welding circuit, current needs to pass through as few connections as possible, and the circuit itself needs to be as short as is practical. On the positive (+) side for gas metal arc welding (GMAW), direct-current electrode positive (DCEP) passes through the (+) stud connection, the feeder connection, the gun connection, and the contact tip (to the wire) connection. With the exception of the wire, all of those connections are typically copper or brass. On the negative (-) side, current should pass through the (-) stud connection, the cable to the work lead (ground) clamp, possibly across a rotating surface, and then to the workpiece.
When any of these connections are anything less than clean copper, brass, or aluminum to clean copper, brass, or aluminum, the possibility of a poor connection and a current or voltage loss exists. These losses can be great enough to run outside the parameters of the weld procedure, causing spatter or a lack of fusion. That can get a welder into trouble.
Here are some good examples of poor connections:
- A work lead connected to a building column.
- A steel building column and a steel bolt—this connection will rust and create resistance.
- A work lead connected to a steel plate and run across the floor. Of course, the initial connection is the same as the building column. When that steel plate isn't of a sufficient size and that plate is joined by one or several welds, the conditions are ripe for a drop in current and/or voltage.
The two conditions mentioned above also create a safety hazard. Once a work lead contacts a building, it gives current alternate routes. One of the most popular is through a jib or bridge crane. Aside from creating havoc with the crane’s electrical system, current passes through the lifting devices such as the cables, hooks, and chains, heating them over and over, thus weakening them and making them susceptible to failure.
One last good example of a poor connection is an unlubricated rotary clamp, or a rotary clamp with a lubricant that is not made for electrical connections.
Bottom line, the best work lead connection is the one that runs from the stud on the machine to the workpiece close to the welding being done and at the shortest distance and with the least amount of connections in it. A key to quality welding starts with a good-quality circuit, and a key component of that circuit is the condition of the work lead.
Note: I’ve replaced the word ground with work lead. You should also make that change in your daily welding dialogue. Keep in mind, a welding ground doesn’t ground anything.
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