company news about Welding Wire Cast and Helix

What are cast and helix?

There are two physical elements of weld wire to be aware of in a robotic welding application. The first is the cast, which is the natural curvature of the wire. The second is the helix, which is the natural winding geometry of the wire's radial shape.

CAST is the diameter of the circle formed by a length of wirethrown loosely on the floor. Cast is normally checked before itenters the wire feed system.

HELIX is the "pitch" of a single strand ofweld wire measured asthe distance one end of a strand of wire laying on a flat surfacerises off that surface. Helix is normally checked before it entersthe wire feed system.

Why Does the Weld Process Need Cast?

You need cast because of your contact tip. Your contact tip makes contact with the wire to help bridge current. If the wire doesn’t make contact on that tip, we run into microarcing and poor weld quality.

Based on how weld wire is packaged - via either a spool or a barrel - all that cast does is take a curved wire and send it through a straight body, i.e. the wire liner and torch body. When you do that, the wire incurs friction and, by design, rubs against the inner diameter of the contact tip. That's what's going to be your conductor.

You get all your power from your welder to your wire from the relation between the wire cast and the contact tip.

Checking Your Wire Cast

The first thing to do when checking your cast is to check the mate up between your consumables and your wire. This is exceptionally important because this will be a root cause for microarcing and burnback.

If you are noticing any potential cast issues, you'll want to deliver two to three feet of wire through your feed system using the feeder. Two things you do not want to do if pull it by the hand or take it straight out of the barrel. What it looks like in barrel will not matter.

You will care what it looks like after it's gone through the conduit. You care about what your feed rolls are doing. You care about the liner and going through the torch, the width and out the tip. The wire cast will ultimately be affected by the sequence that these items are put together.

These elements are either going to make it better or make it worse. You want to simulate exactly what you're going to do in production. In order to do this, I would recommend the following:

1.Feed out two to three feet of this wire

2.Take a brand new contact tip that has never been used and slide that on the wire

You should be able to hold the end of the wire and then slide the tip down the wire and feel a constant, positive contact through it. Ideally, that weld wire should be able to hold a contact tip on the wire without skipping down to the bottom. The contact tip should never fall straight to the floor. Instead, it should have enough friction in it with that cast to hold itself within that wire.

If you run into difficulty with running the wire up and down the contact tip, then you have a bad fit up between your consumable and your wire cast. When that happens it’s either because the inner diameter of your contact tip is too small or the wire is too large. Either of these symptoms will lead to premature wearing of your tips.

Wire Types and Cast

With cored wires, you're going to feed cast that's held onto in the cored wires a whole lot more than you will on a solid wire. That happens because you have a smaller cross section of actual solid metal in there. This means it will hold that shape a little bit better.

Solid wires tend to straighten out a little bit better from these barrel packs that I alluded to in the last section.

A cored wire will have more cast until you pull it. If you think of a solid tube versus a pixie stick, a pixie stick is a tube with a bunch of sand in it. And when you get into flux core wires, because there's less material, metal material on the outside, it will actually have more cast in the barrel. However, when you pull it through the system, that cast relaxes much, much faster than the solid core because the solid core has more spring to it because it's solid.

With thicker wire, it's almost the same principle. It's going to have more of a spring steel action. It's harder to hold around the core because it's thicker. However, it's also going to hold up better pulling through. Whereas, with .035” wire, it's going to wrap around the core easier, but it's going to be more fragile pulling through, obviously.

Aluminums are likewise completely different. Aluminum cast is almost negligible. It has a great cast around the core and then as soon as you pull it out, it's straight as an arrow. You don't have microarcing issues with aluminum, either. It's usually a steel, stainless steel, galvanized type wire where you will encounter more of that kind of problem. 

Troubleshooting Wire Cast Issues

A very good way to troubleshoot casting issues is to change the wire source. Usually cast issues are from barrel packs of wire. Whether it’s 500 pounds or 1,000 pounds, the barrel packs of weld wire tend to be a greater source of wire caste issues than smaller spools. Because when you wind wire around a core in a spool, it has a much tighter, heavier cast than if you drop it into a bucket, which is how barrel packs are made.

The best remedy to microarcing due to wire cast is to take off that barrel pack just for a little bit, and put on a 30 pound spool. That microarcing will go away. You'll see it almost instantaneously. What this means for you is you’ll have to closely follow your wire feed delivery to ascertain whether you need to add or subtract cast in the wire to avoid microarcing from the wire barrel.