Miller Electric KC237900 - Manual (Page 25)

OM-530 Page 21
Table 6-1. Maintenance Schedule
Frequency* Maintenance
Every month. Units in heavy service environ-
ments:
Check labels, weld cables, clean
internal parts.
Every 3 months. Check weld cables (see Section
6-1A).
Every 6 months. Check all labels (see IMPORT-
ANT block, Section 6-1). Clean
internal parts (see Section 6-1B).
*Frequency of service is based on units operated
40 hours per week. Increase frequency of maint-
enance if usage exceeds 40 hours per week.
A. Weld Cables
Every three months inspect cables for breaks in insula-
tion. Repair or replace cables if insulation breaks are
present. Clean and tighten connections at each inspec-
tion.
B. Internal Cleaning
Every six months blow out or vacuum dust and dirt from
the inside of the unit. Remove the outer enclosure, and
use a clean, dry airstream or vacuum suction for the
cleaning operation. If dusty or dirty conditions are pre-
sent, clean the unit monthly.
6-2. TUNGSTEN ELECTRODE (Table 6-2,
Figure 6-1 And Figure 6-2)
Use Table 6-2 to select the correct size and type tung-
sten electrode. Prepare the tungsten electrode using
the following guidelines. A properly prepared tungsten
electrode is essential in obtaining a satisfactory weld.
1-1/2 Times
Electrode
Diameter
AC And DC
Electrode Positive
2-1/2 Times
Electrode
Diameter
DC Electrode
Negative
S-0161
Figure 6-1. Properly Prepared Tungsten
Electrodes
A. For AC or DC Electrode Positive Welding
(Figure 6-1)
Ball the end of tungsten electrodes used for ac or dc
electrode positive welding before beginning the welding
operation. Weld amperage causes the tungsten elec-
trode to form the balled end. The diameter of the end
should not exceed the diameter of the tungsten elec-
trode by more than 1-1/2 times. For example, the end of
a 1/8 in. (3.2 mm) diameter tungsten electrode should
not exceed a 3/16 in. (4.8 m) diameter end.
B. For DC Electrode Negative Welding (Figure 6-1
And Figure 6-2)
CAUTION: HOT FLYING METAL PARTICLES
can injure personnel, start fires, and dam-
age equipment; TUNGSTEN CONTAMINA-
TION can lower weld quality.
•
Shape tungsten electrode only on grinder
with proper guards in a safe location wearing
proper face, hand, and body protection.
•
Do not use same wheel for any other job, or
the tungsten will become contaminated.
Shape tungsten electrodes on a fine grit, hard abrasive
wheel used only for tungsten shaping. Grind tungsten
electrodes so that grinding marks run lengthwise with
the electrode. These procedures reduce the possibility
of the tungsten electrode transferring foreign matter into
the weld and help reduce arc wander.
Grind the end of the tungsten electrode to a taper for a
distance of 2 to 2-1/2 electrode diameters in length. For
example, the ground surface for a 1/8 in. (3.2 mm) di-
ameter tungsten electrode should be 1/4 to 5/16 in. (6.4
to 8.0 mm) long.
For additional information, see your distributor for a
handbook on the Gas Tungsten Arc Welding (GTAW)
process.
Stable Arc
Straight Ground
Flat
(The Dia. Of This
Flat Governs
Amperage Capacity)
TUNGSTEN PREPARATION: IDEAL
Arc Wander
Point
Radial Ground
TUNGSTEN PREPARATION: WRONG
S-0162
Figure 6-2. Tungsten Preparation