BMK-8 U /
BMK-12 W
24
5.1.5
Fuses (items 1 and 3, chapter 5.1)
The BMK-8U / BMK-12 W stud welders are protected by the following fuses:
- Fuse F1
0.315 A slow-blow
- Fuse F2
2 A slow-blow (with 400V up to 500V) or 3.15 AT with 230V
CAUTION
Should it become necessary to replace fuses, only use fuses with the specified electrical
values. Oversized fuses could either cause defects on the electrical system or a fire.
WARNING
Disconnect the mains plug from the mains supply when replacing fuses.
5.1.6
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 magnetic 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
collar 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.