Draper Expert 70052, Instructions Manual

Page: 7 / 18

– 7 –
Fan cooled.
I
2
Welding
current
(AMPS)
Indoor use
only. Do not
expose to rain.
U
2
Welding
current
(VOLTS)
Class F
Insulation
rating.
Unit’s
maximum
absorbed
current
(AMPS).
†
Symbols can be combined,
for example:
f
1
f
2
1~
Single Phase D.C MMA
Welder.
Unit’s effective
absorbed
current (AMPS).
European
reference safety
standard.
* Waste Electrical & Electronic Equipment
7. SETTING THE WELDER
Make certain the location does not pose any hazards as
detailed in the safety instructions, before attempting to
start the machine.
Note: Refer to the rating label for energy input details.
Note: For TIG operations, ensure the gas bottle is
securely mounted and in a vertical position according to
the manufacturer’s instructions.
Warning! Remove the plug from the socket before
carrying out adjustment, servicing or maintenance.
7.1 TUNGSTEN ELECTRODES –
SELECTION & PREPARATION –
FIGS.1 – 4
The correct selection of tungsten size and type will vary
for each application dependent upon amperage,
material thickness, equipment and shield gas, however
as a general rule for DC output negative electrode
machines a 1.6mm thorium oxide tungsten electrode will
suffice.
Tungsten Ø Amp Range
≤
1.2mm
≤
70A
1.6mm 70 - 140A
2.4mm 140 - 250A
3.2mm
≥
240A
The selection of the ceramic shroud is based on the
tungsten electrode and should be 4 to 6 times the
tungstens diameter. For example a 1.6mm tungsten
could be used with a No.4 (6.4mm) ceramic shroud, a
No.5 (8.0mm) or at the maximum a No.6 (9.8mm).
There are a variety of different tungsten electrodes
available with the most common categories, shown in
the table below and on page 8.
Before welding can commence the electrode must be
prepared, i.e. the tip ground to a suitable point.
For DC welding the tip should be ground into a point to
help produce a stable arc. If using a grinding wheel, a
dedicated abrasive wheel must be used to prevent
contamination of the tungsten. The tip must be ground
straight, i.e. perpendicular to the grinder’s drive spindle.
1 FIG.
Colour code Band Content Composition Comments
Green 99% Pure Tungsten
Predominantly AC providing a stable arc. Typically
used for Aluminium welding.
Brown 0.3-0.5% Zirconium Oxide
Predominantly AC with a high contamination
resistance.
White 0.7-0.9% Zirconium Oxide