Preparation For Start-Up; Earth Connection - Soyer BMH-22i Operating Instructions Manual

BMH-22i
5.2

Preparation for start-up

Connect the stud welding gun and earth cables to the stud welder prior to start-up.
5.2.1

Earth connection

• Attach earth cable to earth cable connectors and lock by turning to the right until stop.
• Attach earth clamps to workpiece.

Ensure optimum contact with workpiece. Owing to the high welding current, an
unbalanced current distribution may cause a magnet blow effect on the arc, i.e. the
arc for welding the stud is asymmetrical. This is shown by an irregular course of the
weld upset on the side of the stud. The welding results are unsatisfactory and not
reproducible.
For this reason, you should attach the earth clamps to the workpiece in such a manner that the
welding gun is positioned as close as possible to the centre of the connecting route of both earth
clamps. This guarantees a current distribution around the stud that is balanced to the largest possible
extent and satisfactory welding results.
Difficult areas are welds on the edge of the workpiece or considerable differences in material
thickness, i.e. the material thickness varies by a few millimetres or additional material is welded or
riveted to the metal. This also includes stud welding on profile sections.
To ensure good welding results, carry out several test welds under different conditions. For example,
simply change the position of the earth clamps or turn the welding gun.
You may determine the symmetry and quality of the arc during the preweld current test and then
optimise them by combining earth connection and gun position accordingly.

Please ensure that the contact areas of the earth clamps are always kept clean and
do not oxidize, otherwise high transition resistances could occur that may result in a
considerable reduction of the rated welding current.

In addition, make sure that the earth clamps are clamped securely to the workpiece
and the earth cables as well as the gun cable are securely connected to the stud
welder. This prevents high transition resistances and arc losses on the clamps or
plug-in connections which in turn would result in poor welds.
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