Miller Electric 255 User Manual
OM-157 066V
November 2000
Processes
R
MIG (GMAW) Welding
Flux Cored (FCAW) Welding
Description
Arc Welding Power Source And
Wire Feeder
Auto Arc 255
And M-25 Gun
For Warranty Claims And Technical Support, Contact:
Milweld Inc., National Distributor
P.O. Box 338, Hortonville, WI 54944-0338
Tel 920-779-0916 Fax 920-779-0924
WARNING
This product, when used
for welding or cutting,
produces fumes or
gases which contain
chemicals known to the
State of California to
cause birth defects and,
in some cases, cancer.
(California Health &
Safety Code Section
25249.5 et seq.)
The following terms are
used interchangeably
throughout this manual:
MIG = GMAW
TABLE OF CONTENTS
SECTION 1 – SAFETY PRECAUTIONS - READ BEFORE USING 1. . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-1. Symbol Usage 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-2. Arc Welding Hazards 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-3. Additional Symbols For Installation, Operation, And Maintenance 3. . . . . . . . . . . . . . . . . . . . .
1-4. Principal Safety Standards 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-5. EMF Information 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SECTION 2 – INSTALLATION 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-1. Specifications 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-2. Volt-Ampere Curve 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-3. Welding Power Source Duty Cycle And Overheating 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-4. Welding Gun Duty Cycle And Overheating 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-5. Installing Work Clamp 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-6. Installing Gas Supply 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-7. Installing Welding Gun 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-8. Installing Wire Spool And Adjusting Hub Tension 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-9. Setting Gun Polarity 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-10. Positioning Jumper Links 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-11. Electrical Service Guide 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-12. Selecting A Location And Connecting Input Power 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-13. Threading Welding Wire 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SECTION 3 – OPERATION 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3-1. Front Panel Controls 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3-2. Center Baffle Controls 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3-3. Weld Parameter Chart 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SECTION 4 – MAINTENANCE & TROUBLESHOOTING 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-1. Routine Maintenance 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-2. Circuit Breaker CB1 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-3. Fuses F1 And F2 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-4. Changing Drive Roll And Wire Inlet Guide 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-5. Replacing Gun Contact Tip 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-6. Cleaning Or Replacing Gun Liner 18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-7. Replacing Switch And/Or Head Tube 19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-8. Troubleshooting 20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SECTION 5 – ELECTRICAL DIAGRAM 21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SECTION 6 – PARTS LIST 23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
OPTIONS AND ACCESSORIES
WARRANTY
OM-154 501V
SECTION 1 – SAFETY PRECAUTIONS - READ BEFORE USING
1-1. Symbol Usage
Means Warning! Watch Out! There are possible hazards
with this procedure! The possible hazards are shown in
the adjoining symbols.
som _nd_4/98
Y Marks a special safety message.
. Means “Note”; not safety related.
1-2. Arc Welding Hazards
Y The symbols shown below are used throughout this manual to
call attention to and identify possible hazards. When you see
the symbol, watch out, and follow the related instructions to
avoid the hazard. The safety information given below is only
a summary of the more complete safety information found in
the Safety Standards listed in Section 1-4. Read and follow all
Safety Standards.
Y Only qualified persons should install, operate, maintain, and
repair this unit.
Y During operation, keep everybody, especially children, away.
ELECTRIC SHOCK can kill.
Touching live electrical parts can cause fatal shocks
or severe burns. The electrode and work circuit is
electrically live whenever the output is on. The input
live when power is on. In semiautomatic or automatic wire welding, the
wire, wire reel, drive roll housing, and all metal parts touching the
welding wire are electrically live. Incorrectly installed or improperly
grounded equipment is a hazard.
D Do not touch live electrical parts.
D Wear dry, hole-free insulating gloves and body protection.
D Insulate yourself from work and ground using dry insulating mats
or covers big enough to prevent any physical contact with the work
or ground.
D Do not use AC output in damp areas, if movement is confined, or if
there is a danger of falling.
D Use AC output ONLY if required for the welding process.
D If AC output is required, use remote output control if present on
unit.
D Disconnect input power or stop engine before installing or
servicing this equipment. Lockout/tagout input power according to
OSHA 29 CFR 1910.147 (see Safety Standards).
D Properly install and ground this equipment according to its
Owner’s Manual and national, state, and local codes.
D Always verify the supply ground – check and be sure that input
power cord ground wire is properly connected to ground terminal in
disconnect box or that cord plug is connected to a properly
grounded receptacle outlet.
D When making input connections, attach proper grounding
conductor first – double-check connections.
D Frequently inspect input power cord for damage or bare wiring –
replace cord immediately if damaged – bare wiring can kill.
D Turn off all equipment when not in use.
D Do not use worn, damaged, undersized, or poorly spliced cables.
D Do not drape cables over your body.
power circuit and machine internal circuits are also
This group of symbols means Warning! Watch Out! possible
ELECTRIC SHOCK, MOVING PARTS, and HOT PARTS hazards.
Consult symbols and related instructions below for necessary actions
to avoid the hazards.
D If earth grounding of the workpiece is required, ground it directly
with a separate cable.
D Do not touch electrode if you are in contact with the work, ground,
or another electrode from a different machine.
D Use only well-maintained equipment. Repair or replace damaged
parts at once. Maintain unit according to manual.
D Wear a safety harness if working above floor level.
D Keep all panels and covers securely in place.
D Clamp work cable with good metal-to-metal contact to workpiece
or worktable as near the weld as practical.
D Insulate work clamp when not connected to workpiece to prevent
contact with any metal object.
D Do not connect more than one electrode or work cable to any
single weld output terminal.
SIGNIFICANT DC VOLTAGE exists after removal of
input power on inverters.
D Turn Off inverter, disconnect input power, and discharge input
capacitors according to instructions in Maintenance Section
before touching any parts.
FUMES AND GASES can be hazardous.
Welding produces fumes and gases. Breathing
these fumes and gases can be hazardous to your
health.
D Keep your head out of the fumes. Do not breathe the fumes.
D If inside, ventilate the area and/or use exhaust at the arc to remove
welding fumes and gases.
D If ventilation is poor, use an approved air-supplied respirator.
D Read the Material Safety Data Sheets (MSDSs) and the
manufacturer’s instructions for metals, consumables, coatings,
cleaners, and degreasers.
D Work in a confined space only if it is well ventilated, or while
wearing an air-supplied respirator. Always have a trained watchperson nearby. Welding fumes and gases can displace air and
lower th e oxygen level causing injury or death. Be sure the breathing air is safe.
D Do not weld in locations near degreasing, cleaning, or spraying
operations. The heat and rays of the arc can react with vapors to
form highly toxic and irritating gases.
D Do not weld on coated metals, such as galvanized, lead, or
cadmium plated steel, unless the coating is removed from the weld
area, the area is well ventilated, and if necessary, while wearing an
air-supplied respirator. The coatings and any metals containing
these elements can give off toxic fumes if welded.
OM-157 066 Page 1
ARC RAYS can burn eyes and skin.
BUILDUP OF GAS can injure or kill.
Arc rays from the welding process produce intense
visible and invisible (ultraviolet and infrared) rays
that can burn eyes and skin. Sparks fly off from the
weld.
D Wear a welding helmet fitted with a proper shade of filter to protect
your face and eyes when welding or watching (see ANSI Z49.1
and Z87.1 listed in Safety Standards).
D Wear approved safety glasses with side shields under your
helmet.
D Use protective screens or barriers to protect others from flash and
glare; warn others not to watch the arc.
D Wear protective clothing made from durable, flame-resistant
material (leather and wool) and foot protection.
WELDING can cause fire or explosion.
Welding on closed containers, such as tanks,
drums, or pipes, can cause them to blow up. Sparks
can fly off from the welding arc. The flying sparks, hot
burns. Accidental contact of electrode to metal objects can cause
sparks, explosion, overheating, or fire. Check and be sure the area is
safe before doing any welding.
D Protect yourself and others from flying sparks and hot metal.
D Do not weld where flying sparks can strike flammable material.
D Remove all flammables within 35 ft (10.7 m) of the welding arc. If
this is not possible, tightly cover them with approved covers.
D Be alert that welding sparks and hot materials from welding can
easily go through small cracks and openings to adjacent areas.
D Watch for fire, and keep a fire extinguisher nearby.
D Be aware that welding on a ceiling, floor, bulkhead, or partition can
cause fire on the hidden side.
D Do not weld on closed containers such as tanks, drums, or pipes,
unless they are properly prepared according to AWS F4.1 (see
Safety Standards).
D Connect work cable to the work as close to the welding area as
practical to prevent welding current from traveling long, possibly
unknown paths and causing electric shock and fire hazards.
D Do not use welder to thaw frozen pipes.
D Remove stick electrode from holder or cut off welding wire at
contact tip when not in use.
D Wear oil-free protective garments such as leather gloves, heavy
shirt, cuffless trousers, high shoes, and a cap.
D Remove any combustibles, such as a butane lighter or matches,
from your person before doing any welding.
workpiece, and hot equipment can cause fires and
FLYING METAL can injure eyes.
D Welding, chipping, wire brushing, and grinding
cause sparks and flying metal. As welds cool,
they can throw off slag.
D Wear approved safety glasses with side
shields even under your welding helmet.
D Shut off shielding gas supply when not in use.
D Always ventilate confined spaces or use
approved air-supplied respirator.
HOT PARTS can cause severe burns.
D Do not touch hot parts bare handed.
D Allow cooling period before working on gun or
torch.
MAGNETIC FIELDS can affect pacemakers.
D Pacemaker wearers keep away.
D Wearers should consult their doctor before
going near arc welding, gouging, or spot
welding operations.
NOISE can damage hearing.
Noise from some processes or equipment can
damage hearing.
D Wear approved ear protection if noise level is
high.
CYLINDERS can explode if damaged.
Shielding gas cylinders contain gas under high
pressure. If damaged, a cylinder can explode. Since
gas cylinders are normally part of the welding
process, be sure to treat them carefully.
D Protect compressed gas cylinders from excessive heat, mechanical
shocks, sla g, open fl ames, sparks, and arcs.
D Install cylinders in an upright position by securing to a stationary
support or cylinder rack to prevent falling or tipping.
D Keep cylinders away from any welding or other electrical circuits.
D Never drape a welding torch over a gas cylinder.
D Never allow a welding electrode to touch any cylinder.
D Never weld on a pressurized cylinder – explosion will result.
D Use only correct shielding gas cylinders, regulators, hoses, and
fittings designed for the specific application; maintain them and
associated parts in good condition.
D Turn face away from valve outlet when opening cylinder valve.
D Keep protective cap in place over valve except when cylinder is in
use or connected for use.
D Read and follow instructions on compressed gas cylinders,
associated equipment, and CGA publication P-1 listed in Safety
Standards.
OM-157 066 Page 2
1-3. Additional Symbols For Installation, Operation, And Maintenance
FIRE OR EXPLOSION hazard.
D Do not install or place unit on, over, or near
combustible surfaces.
D Do not install unit near flammables.
D Do not overload building wiring – be sure power supply system is
properly sized, rated, and protected to handle this unit.
FALLING UNIT can cause injury.
D Use lifting eye to lift unit only, NOT running
gear, gas cylinders, or any other accessories.
D Use equipment of adequate capacity to lift and
support unit.
D If using lift forks to move unit, be sure forks are
long enough to extend beyond opposite side of
unit.
OVERUSE can cause OVERHEATING
D Allow cooling period; follow rated duty cycle.
D Reduce current or reduce duty cycle before
starting to weld again.
D Do not block or filter airflow to unit.
STATIC (ESD) can damage PC boards.
MOVING PARTS can cause injury.
D Keep away from moving parts such as fans.
D Keep all doors, panels, covers, and guards
closed and securely in place.
H.F. RADIATION can cause interference.
D High-frequency (H.F.) can interfere with radio
navigation, safety services, computers, and
communications equipment.
D Have only qualified persons familiar with
electronic equipment perform this installation.
D The user is r esponsible for having a qualified e lectrician promptly
correct any interference problem resulting from the installation.
D If notified by the FCC about interference, stop using the
equipment at once.
D Have the installation regularly checked and maintained.
D Keep high-frequency source doors and panels tightly shut, keep
spark gaps at correct setting, and use grounding and shielding to
minimize the possibility of interference.
D Put on grounded wrist strap BEFORE handling
boards or parts.
D Use proper static-proof bags and boxes to
store, move, or ship PC boards.
MOVING PARTS can cause injury.
D Keep away from moving parts.
D Keep away from pinch points such as drive
rolls.
WELDING WIRE can cause injury.
D Do not press gun trigger until instructed to do
so.
D Do not point gun toward any part of the body,
other people, or any metal when threading
welding wire.
1-4. Principal Safety Standards
Safety in Welding and Cutting, ANSI Standard Z49.1, from American
Welding Society, 550 N.W. LeJeune Rd, Miami FL 33126
Safety and Health Standards, O SH A 29 CFR 1910, from Superintendent
of Documents, U.S. Government Printing Office, Washington, D.C. 20402.
Recommended Safe Practices for the Preparation for Welding and
Cutting of Containers That Have Held Hazardous Substances,
American Welding Society Standard AWS F4.1, from American
Welding Society, 550 N.W. LeJeune Rd, Miami, FL 33126
National Electrical Code, NFPA Standard 70, from National Fire Protection
Association, Batterymarch Park, Quincy, MA 02269.
ARC WELDING can cause interference.
D Electromagnetic energy can interfere with
sensitive electronic equipment such as
computers and computer-driven equipment
such as robots.
D Be sure all equipment in the welding area is
electromagnetically compatible.
D To reduce possible interference, keep weld cables as short as
possible, close together, and down low, such as on the floor.
D Locate welding operation 100 meters from any sensitive
electronic equipment.
D Be sure this welding machine is installed and grounded
according t o this manual.
D If interference still occurs, the user must take extra measures
such as moving the welding machine, using shielded cables,
using line filters, or shielding the work area.
Safe Handling of Compressed Gases in Cylinders, CGA Pamphlet P-1,
from Compressed Gas Association, 1235 Jefferson Davis Highway,
Suite 501, Arlington, VA 22202.
Code for Safety in Welding and Cutting, CSA Standard W117.2, from
Canadian Standards Association, Standards Sales, 178 Rexdale
Boulevard, Rexdale, Ontario, Canada M9W 1R3.
Safe Practices For Occupation And Educational Eye And Face
Protection, ANSI Standard Z87.1, from American National Standards
Institute, 1430 Broadway, New York, NY 10018.
Cutting And Welding Processes, NFPA Standard 51B, from National
Fire Protection Association, Batterymarch Park, Quincy, MA 02269.
OM-157 066 Page 3
1-5. EMF Information
Considerations About Welding And The Effects Of Low Frequency
Electric And Ma g netic Fields
Welding current, as it flows through welding cables, will cause electromagnetic fields. There has been and still is some concern about such
fields. However, after examining more than 500 studies spanning 17
years of research, a special blue ribbon committee of the National
Research Council concluded that: “The body of evidence, in the
committee’s judgment, has not demonstrated that exposure to power-
frequency electric and magnetic fields is a human-health hazard.”
However, studies are still going forth and evidence continues to be
examined. Until the final conclusions of the research are reached, you
may wish to minimize your exposure to electromagnetic fields when
welding or cutting.
To reduce magnetic fields in the workplace, use the following
procedures:
1. Keep cables close together by twisting or taping them.
2. Arrange cables to one side and away from the operator.
3. Do not coil or drape cables around your body.
4. Keep welding power source and cables as far away from operator
as practical.
5. Connect work clamp to workpiece as close to the weld as possible.
About Pacemakers:
Pacemaker wearers consult your doctor first. If cleared by your doctor,
then following the above procedures is recommended.
OM-157 066 Page 4
2-1. Specifications
SECTION 2 – INSTALLATION
Rated Welding Amperage Range Maximum Open-
Output DC Circuit Voltage DC
200 A @ 28 Volts DC,
60% Duty Cycle
40 – 250 42
250 A @ 28 Volts DC,
40% Duty Cycle
Amperes Input at Rated Load
Output, 50 or 60 Hz, Single-Phase
200 V 230 V 460 V 575 V KVA KW
46
1.1*
40
1.3*
20
0.5*
16
0.4*
Wire Type And Diameter
Solid Steel /
Stainless Steel
.023 – .045 in
(0.6 – 1.2 mm)
*While idling
Operating Temperature Range – –20C to +40C Storage Temperature Range – -30C to + 50C
Flux Cored/
Aluminum
.030 – .035 in
(0.8 – 0.9 mm) And
3/64 in (1.2 mm) Alu
Wire Feed Speed Range Overall Dimensions Weight
Length: 37 in (940 mm)
90 – 1030 IPM (2.9 – 26.2 m/min)
Width: 19 in (483 mm)
Height: 32 in (889 mm)
2-2. Volt-Ampere Curve
The volt-ampere curves show the
minimum and maximum voltage
and amperage output capabilities of
the welding power source. Curves
of other settings fall between the
curves shown.
9.5
0.31*
8.3
0.18*
225 lb
(102 kg)
ssb1.1 10/91 – SB-049 424-C
OM-157 066 Page 5
2-3. Welding Power Source Duty Cycle And Overheating
60% Duty Cycle At 200 Amperes
Duty Cycle is percentage of 10
minutes that unit can weld at rated
load without overheating.
If unit overheats, thermostat(s)
opens, output stops, and cooling
fan runs. Wait fifteen minutes for
unit to cool. Reduce amperage or
voltage, or duty cycle before
welding.
Y Exceeding duty cycle can
damage unit and void
warranty.
6 Minutes Welding 4 Minutes Resting
Overheating
0
15
Reduce Duty Cycle
Minutes
A or V
OR
2-4. Welding Gun Duty Cycle And Overheating
CAUTION
WELDING LONGER THAN RATED DUTY CYCLE can damage gun and void warranty.
• Do not weld at rated load longer than shown below.
• Using gasless flux cored wire reduces gun duty cycle.
Definition .023 To .045 in (0.6 T o 1.1 mm)
0
10
Minutes
Duty Cycle is percentage of 10
minutes that gun can weld at
rated load without overheating.
Hard Or Flux Cored Wires
100% Duty Cycle At 200 Amperes
100% Duty Cycle At 150 Amperes
Using CO
Using Mixed Gases
2
.023 To .045 in (0.6 To 1.1 mm) Hard Or Flux Cored Wires
60% Duty Cycle At 300 Amperes
Using CO
60% Duty Cycle At 200 Amperes
Using Mixed Gases
duty1 4/95 – SB-150 215
warn7.1 8/93
2
OM-157 066 Page 6
Continuous Welding
6 Minutes Welding 4 Minutes Resting
SB1.1 8/93
2-5. Installing Work Clamp
1 Work Cable
2 Boot
Slide boot onto work cable. Route
cable out front panel opening from
4
5
1
2
inside.
3 Negative ( –) Output Terminal
Connect cable to terminal and
cover connection with boot.
4 Hardware
5 Work Clamp
Route cable through clamp handle
and secure as shown.
Close door.
3
2-6. Installing Gas Supply
7
1
Tools Needed:
1/2, 3/4 in
1 Cylinder Rack
2 Chain
Obtain gas cylinder and chain
cylinder to rack.
3 Gas Hose Fitting
4CO2 Washer
5 Regulator
Install washer and regulator onto
cylinder.
6 Gas Hose Connection
Obtain gas hose with fittings and
install between regulator and
welding power source.
7 Flow Adjust
Typical flow rate is 20 cfh (cubic feet
56
4
per hour).
ST-800 918-C
2
3
Tools Needed:
5/8, 1-1/8 in
ST-154 623-A / Ref. ST-109 492
OM-157 066 Page 7
2-7. Installing Welding Gun
1
24
3
2-8. Installing Wire Spool And Adjusting Hub Tension
1 Drive Assembly
2 Gun Securing Knob
3 Gun End
Loosen securing knob. Insert gun
end through opening until it bottoms
against drive assembly. Tighten
nut.
4 Gun Trigger Plug
Insert plug into receptacle, and
tighten threaded collar.
Close door.
Ref. ST-800 921-C
Use compression spring with
8 in (200 mm) spools.
Tools Needed:
OM-157 066 Page 8
15/16 in
When a slight force is needed to turn spool, tension is set.
ST-072573-B
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