If a straight filler wire is pushed into a straight wire conduit with correct diameter, as shown in the picture, very little force is needed to push the filler wire.
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| Filler wire | Wire conduit |
If a straight filler wire is pushed into a curved wire conduit as shown in the picture, the filler wire is pressed against the wall of the wire conduit.
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| Filler wire | Wire conduit |
When pushing the filler wire through the wire conduit, the friction between the filler wire and the wire conduit is causing need for bigger wire feeding energy. The friction is greater when the angle of the curves is greater in the wire conduit. In practice, even in good operating conditions, the welding gun is always little bit curved.
In general, the situation in the welding gun is such that the end of the wire conduit has a curve (neck). When diameter of the wire conduit is too big in relation to the filler wire, the filler wire is having more curves in the wire conduit and friction is repeated.
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| Filler wire | Wire conduit |
The repetition of the friction depends on the length and angle of the curves in the wire conduit, and the material of which it is made.
The material of the wire conduit and the surface of the filler wire greatly affect the movement resistance! Furthermore, dirt and dust in the wire conduit can increase the movement resistance so much, that the filler wire cannot be fed through the welding gun. The pressure of the feed rolls usually causes metal dust to come off the filler wire. |