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A final scenario can occur when the electrode is placed on top of a
large wire being welded to a base material at a high weld energy setting. In this
case the plasma can push the wire metal down to the base metal surface but there
may be no penetration into the base material.
HANDS ON: Try adding fill wire using the top placement method. Build up a small
mound of material.
As a rule of thumb it is always best to use the side electrode placement.
is is especially true of larger fill wire diameters. If it is essential for a
top placement weld, the process will be improved by using very fine laser
wire to ensure full wire melting. Choosing the correct wire gauge for your
application is very important. For example, on micro-scale applications,
it is important to select the smallest fill wire available. If a wire is selected
that is similar in size to the base metal, there is a good chance that the
energy setting required to melt the wire will also melt the base metal.
Alternatively, if the wire is small relative to the base metal, the wire can be
melted adding material to the base metal without any damage or warping
to the base metal. For larger features, select a wire size that will allow you
to perform your task efficiently. For example, filling a large pore should not be done with ultra-fine wire, but instead with
wire of approximately the same diameter as the pore. In this case the repair can be accomplished in literally one weld. In
comparison, with the ultra-fine wire, the repair would take many welds.
Pulse Arc Welding: Pushing Metal
ere are two competing forces at work during the pulse arc welding process. e first is the surface tension of the molten
metal. Surface tension is a force between the metal atoms that is pulling the molten pool of metal flat during the metal’s
liquid phase. e Second is the electrons from the plasma pushing the molten metal in the direction the electrode tip
points. e plasma tries to push the molten metal, while the surface tension tries to keep it in place.
THIS MEANS:
1. Some metals with lower surface tension (e.g. silver) are easier to “push” around than metals with high surface tension
(e.g. Stainless).
2. Surface tension itself can be used to move metals around. By placing the electrode between a high and low spot, the
melting process will try and “flatten” the two –stealing material from the high and moving it toward the low.
Pushing Metal is accomplished by placing the electrode at a 90 deg angle from the workpiece surface with the electrode
tip on the edge or slightly interior to the edge of the metal mound. e welding process will then take material from the
mound and spread it into the surrounding material. One should repeat this process until the proper spread of material is
achieved.
By placing the electrode between a high and low spot, the melting
process will try and “flatten” the two – taking material from the high
area and moving it toward the low area.
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