Miller AUTO ARC 255 Owner's manual

Brand: Miller

Model: AUTO ARC 255

Category: Welding System

Type: Owner's manual

This manual is also suitable for

KE629034

Miller AUTO ARC 255 is a DC/CV welding power source and wire feeder designed for GMAW and FCAW welding. It can weld with hard wires from .023 to .045 inches in diameter and flux-cored wires from .030 to .045 inches in diameter. The AUTO ARC 255 has a maximum output of 200 amps at 28 volts DC and a 60% duty cycle. It also features overheating and motor overload protection, a built-in gun and shielding gas valve, and a variety of welding modes and settings to suit different welding applications.

auto_arc 7/93 − ST-157 072 PRINTED IN USA

OWNER’S

MANUAL

June 1994 Form: OM-157 066-A

Effective With Serial No. KE629034



Read and follow these instructions and all

safety blocks carefully.

Have only trained and qualified persons

install, operate, or service this unit.

Call your distributor if you do not understand

the directions.

Give this manual to the operator.

For help, call your distributor

or: MILLER Electric Mfg. Co., P.O. Box 1079,

Appleton, WI 54912 414-734-9821

DC/CV Welding Power Source/Wire Feeder

For GMAW And FCAW Welding

Uses .023 − .045 Hard Wire And .030 − .045 Flux Cored Wire

200 Amperes, 28 Volts DC At 60% Duty Cycle

Uses Single-Phase Input Power

Overheating And Motor Overload Protection

Includes Gun And Shielding Gas Valve

Auto Arc Model 255

ARC WELDING SAFETY PRECAUTIONS

WARNING

PROTECT YOURSELF AND OTHERS FROM POSSIBLE SERIOUS INJURY OR DEATH. KEEP CHILDREN

AWAY. PACEMAKER WEARERS KEEP AWAY UNTIL CONSULTING YOUR DOCTOR.

In welding, as in most jobs, exposure to certain hazards occurs. Welding is safe when precautions are taken. The

safety information given below is only a summary of the more complete safety information that will be found in the

Safety Standards listed on the next page. Read and follow all Safety Standards.

HAVE ALL INSTALLATION, OPERATION, MAINTENANCE, AND REPAIR WORK PERFORMED ONLY BY

QUALIFIED PEOPLE.

ARC WELDING can be hazardous.

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

power circuit and machine internal circuits are also

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.

1. Do not touch live electrical parts.

2. Wear dry, hole-free insulating gloves and body protection.

3. Insulate yourself from work and ground using dry insulating mats

or covers.

4. Disconnect input power or stop engine before installing or

servicing this equipment.

5. Properly install and ground this equipment according to its

Owner’s Manual and national, state, and local codes.

6. Turn off all equipment when not in use.

7. Do not use worn, damaged, undersized, or poorly spliced cables

8. Do not wrap cables around your body.

9. Ground the workpiece to a good electrical (earth) ground.

10. Do not touch electrode while in contact with the work (ground)

circuit.

11. Use only well-maintained equipment. Repair or replace

damaged parts at once.

12. Wear a safety harness to prevent falling if working above floor

level.

13. Keep all panels and covers securely in place.

ARC RAYS can burn eyes and skin;

NOISE can damage hearing.

Arc rays from the welding process produce intense

heat and strong ultraviolet rays that can burn eyes and

skin. Noise from some processes can damage

hearing.

1. Wear a welding helmet fitted with a proper shade of filter (see

ANSI Z49.1 listed in Safety Standards) to protect your face and

eyes when welding or watching.

2. Wear approved safety glasses. Side shields recommended.

3. Use protective screens or barriers to protect others from flash

and glare; warn others not to watch the arc.

4. Wear protective clothing made from durable, flame-resistan

material (wool and leather) and foot protection.

5. Use approved ear plugs or ear muffs if noise level is high.

FUMES AND GASES can be hazardous

to your health.

Welding produces fumes and gases. Breathing these

fumes and gases can be hazardous to your health.

1. Keep your head out of the fumes. Do not breathe the fumes.

2. If inside, ventilate the area and/or use exhaust at the arc to

remove welding fumes and gases.

3. If ventilation is poor, use an approved air-supplied respirator.

4. Read the Material Safety Data Sheets (MSDSs) and the

manufacturer’s instruction for metals, consumables, coatings,

and cleaners.

5. Work in a confined space only if it is well ventilated, or while

wearing an air-supplied respirator. Shielding gases used for

welding can displace air causing injury or death. Be sure the

breathing air is safe.

6. 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.

7. 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.

WELDING can cause fire or explosion.

Sparks and spatter fly off from the welding arc. The

flying sparks and hot metal, weld spatter, hot

workpiece, and hot equipment can cause fires and

burns. Accidental contact of electrode or welding wire

to metal objects can cause sparks, overheating, or

fire.

1. Protect yourself and others from flying sparks and hot metal.

2. Do not weld where flying sparks can strike flammable material.

3. Remove all flammables within 35 ft (10.7 m) of the welding arc. If

this is not possible, tightly cover them with approved covers.

4. Be alert that welding sparks and hot materials from welding can

easily go through small cracks and openings to adjacent areas.

5. Watch for fire, and keep a fire extinguisher nearby.

6. Be aware that welding on a ceiling, floor, bulkhead, or partition

can cause fire on the hidden side.

7. Do not weld on closed containers such as tanks or drums.

8. 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.

9. Do not use welder to thaw frozen pipes.

10. Remove stick electrode from holder or cut off welding wire a

contact tip when not in use.

11. Wear oil-free protective garments such as leather gloves, heavy

shirt, cuffless trousers, high shoes, and a cap.

FLYING SPARKS AND HOT METAL can

cause injury.

Chipping and grinding cause flying metal. As welds

cool, they can throw off slag.

1. Wear approved face shield or safety goggles. Side shields

recommended.

2. Wear proper body protection to protect skin.

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.

1. Protect compressed gas cylinders from excessive heat,

mechanical shocks, and arcs.

2. Install and secure cylinders in an upright position by chaining

them to a stationary support or equipment cylinder rack to

prevent falling or tipping.

3. Keep cylinders away from any welding or other electrical circuits

4. Never allow a welding electrode to touch any cylinder.

5. Use only correct shielding gas cylinders, regulators, hoses, and

fittings designed for the specific application; maintain them and

associated parts in good condition.

6. Turn face away from valve outlet when opening cylinder valve.

7. Keep protective cap in place over valve except when cylinder is

in use or connected for use.

8. Read and follow instructions on compressed gas cylinders

associated equipment, and CGA publication P-1 listed in Safety

Standards.

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, OSHA 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.

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.

EMF INFORMATION

The following is a quotation from the General Conclusions Section of

the U.S. Congress, Office of Technology Assessment, Biological

Effects of Power Frequency Electric & Magnetic Fields −

Background Paper, OTA-BP-E-53 (Washington, DC: U.S.

Government Printing Office, May 1989): “. . . there is now a very large

volume of scientific findings based on experiments at the cellular

level and from studies with animals and people which clearly

establish that low frequency magnetic fields can interact with, and

produce changes in, biological systems. While most of this work is

of very high quality, the results are complex. Current scientific

understanding does not yet allow us to interpret the evidence in a

single coherent framework. Even more frustrating, it does not yet

allow us to draw definite conclusions about questions of possible risk

or to offer clear science-based advice on strategies to minimize or

avoid potential risks.”

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 the body.

4. Keep welding power source and cables as far away as practical.

5. Connect work clamp to workpiece as close to the weld as

possible.

About Pacemakers:

The above procedures are among those also normally

recommended for pacemaker wearers. Consult your doctor for

complete information.

Considerations About Welding And The Effects Of Low Frequency Electric And

Magnetic Fields

NOTE

mod10.1 4/93

TABLE OF CONTENTS

SECTION 1 − SAFETY INFORMATION 1. . . . . . . . . . . . . . . .

ECTION 2 − SPECIFICATIONS 1. . . . . . . . . . . . . . . . . . . . .

2-1. Volt-Ampere Curves 2. . . . . . . . . . . . . . . . . . . . . . . . . . .

2-2. Duty Cycle 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ECTION 3 − INSTALLATION 3. . . . . . . . . . . . . . . . . . . . . . .

3-1. Installing Work Clamp 3. . . . . . . . . . . . . . . . . . . . . . . . . .

3-2. Installing Gas Supply 4. . . . . . . . . . . . . . . . . . . . . . . . . . .

3-3. Gun Polarity And Range Selector 5. . . . . . . . . . . . . . . .

3-4. Installing Drive Rolls And Welding Gun 5. . . . . . . . . . .

3-5. Connecting Input Power 6. . . . . . . . . . . . . . . . . . . . . . . .

3-6. Installing Wire Spool And Adjusting Hub Tension 8. . .

3-7. Threading And Feeding Welding Wire 8. . . . . . . . . . . .

SECTION 4 − OPERATION 10. . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 5 − MAINTENANCE & TROUBLESHOOTING 1

5-1. Routine Maintenance 1

. . . . . . . . . . . . . . . . . . . . . . . . .

5-2. Overload Protection 1

. . . . . . . . . . . . . . . . . . . . . . . . . . .

5-3. Wire Drive Assembly Maintenance 1

. . . . . . . . . . . . . .

5-4. Gun Maintenance 1

. . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-5. Troubleshooting 1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 6 − ELECTRICAL DIAGRAMS 1

. . . . . . . . . . . . .

SECTION 7 − PARTS LIST 1

. . . . . . . . . . . . . . . . . . . . . . . . .

Figure 7-1. Main Assembly 1

. . . . . . . . . . . . . . . . . . . . . . . . .

Figure 7-2. MWG-21C Gun 1

. . . . . . . . . . . . . . . . . . . . . . . .

Figure 7-3. Baffle w/Cmpts 1

. . . . . . . . . . . . . . . . . . . . . . . . .

OM-157 066 Page 1

SECTION 1 − SAFETY INFORMATION

mod1.1 2/9

Read all safety messages throughout this manual.

Obey all safety messages to avoid injury.

Learn the meaning of WARNING and CAUTION.

1 Safety Alert Symbol

2 Signal Word

WARNING means possible death

or serious injury can happen.

CAUTION means possible minor

injury or equipment damage can

happen.

3 Statement Of Hazard And Re-

sult

4 Safety Instructions To Avoid

Hazard

5 Hazard Symbol (If Available)

6 Safety Banner

Read safety blocks for each sym-

bol shown.

7 NOTE

Special instructions for best oper-

ation − not related to safety.

NOTE

ELECTRIC SHOCK can kill.

• Do not touch live electrical parts.

• Disconnect input power before

installing or servicing.

WARNING

READ SAFETY BLOCKS at start of

Section 3-1 before proceeding.

WARNING

1 2

CAUTION

MOVING PARTS can injure.

• Keep away from moving parts.

• Keep all panels and covers closed

when operating.

Turn Off switch when using high frequency.

Figure 1-1. Safety Information

SECTION 2 − SPECIFICATIONS

Table 1-1. Welding Power Source

Specifications Description

Type Of Output Direct Current/Constant Voltage (DC/CV)

Rated Weld Output 200 Amperes, 28 Volts DC, 60% Duty Cycle (See Section 2-2)

Type Of Input Power Single-Phase; 60 Hz; At 200 Or 230 Volts AC

Input Amperes At Rated Output 46 A At 200 V, 40 A At 230 V

Maximum Input Amperes While Idling 1.2 A At 200 V, 1 A At 230 V

KVA/KW Used At Rated Output 9.5 kVA/8.3 kW

Maximum KVA/KW Used While Idling 0.24 kVA/0.17 kW

Max. Open-Circuit Voltage 42 Volts DC

Control Circuit Voltage At Gun 24 Volts DC

Welding Processes Gas Metal Arc (GMAW) And Flux Cored Arc Welding (FCAW)

Calculated Speed Range At No Load 128 To 1051 ipm (3.2 To 266.9 mpm)

Wire Diameter Range .030 To .045 in (0.8 To 1.1 mm) Flux Cored Wire; .023 To .045 in (0.6 To 1.1 mm) Hard Wire

Overall Dimensions Length: 37 in (940 mm); Width: 19 in (483 mm); Height: 30-1/4 in (768 mm)

Weight Net: 225 lb (102 kg); Ship: 271 lb (123 kg)

Welding Gun

Rated Output (Air Cooled) 200 Amperes At 100% Duty Cycle Using CO

Shielding Gas (See Section 2-2)

Cable Length 12-1/2 ft (3.8 m)

OM-157 066 Page 2

2-1. Volt-Ampere Curves

ssb1.1 10/91 − SB-049 424-D

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.

Figure 2-1. Volt-Ampere Curves

2-2. Duty Cycle

CAUTION

WELDING LONGER THAN RATED DUTY CYCLE can damage unit or gun and void warranty.

• Do not weld at rated load longer than shown below.

wfwarn8.2 8/93

sb1.3 8/93 − SB-150 215

60% Duty Cycle At 200 Amperes

6 Minutes Welding 4 Minutes Resting

100% Duty Cycle At 200 Amperes Using CO

30% Duty Cycle At 200 Amperes Using Mixed Gas

3 Minutes Welding 7 Minutes Resting

Duty Cycle is percentage of 10

minutes that unit or gun can

weld at rated load without over-

heating.

Minutes

Definition

Chart

UNIT

GUN

Continuous

Figure 2-2. Duty Cycle

OM-157 066 Page 3

SECTION 3 − INSTALLATION

3-1. Installing Work Clamp

1 Work Cable

2 Boot

Slide boot onto work cable. Route

cable out front panel opening from

inside.

3 Negative (−) Output Terminal

Connect cable to terminal and cov-

er connection with boot.

4 Hardware

5 Work Clamp

Route cable through clamp handle

and secure to top of clamp with

hardware.

Close door.

Ref. ST-154 630-A

Tools Needed:

1/2, 3/4 in

Figure 3-1. Installing Work Clamp

OM-157 066 Page 4

3-2. Installing Gas Supply

WARNING

CYLINDERS can explode if damaged.

• Keep cylinders away from welding and other

electrical circuits.

• Never touch cylinder with welding electrode.

• Always secure cylinder to running gear, wall, or

other stationary support.

BUILDUP OF SHIELDING GAS can harm

health or kill.

• Shut off shielding gas supply when not in use.

warn4.1 9/91

1 Cylinder Bracket

2 S-Hook

Crimp between small hole in brack-

et and chain.

3 Chain

4 Snap

Crimp onto open end of chain.

Obtain gas cylinder and chain to

running gear.

5 Cap

6 Cylinder Valve

Remove cap, stand to side of valve,

and open valve slightly. Gas flow

blows dust and dirt from valve.

Close valve.

7 Cylinder

8 Regulator/Flowmeter

Install so face is vertical.

9 Gas Hose Connection

Fitting has 5/8-18 right-hand

threads. Obtain and install gas

hose.

10 Flow Adjust

Typical flow rate is 20 cfh (cubic feet

per hour). Check wire manufactur-

er’s recommended flow rate.

11 CO

Adapter

12 O-Ring

Install adapter with O-ring between

regulator/flowmeter and CO

cylinder.

ssb3.1* 6/93 − ST-154 623 / ST-158 697-A

Tools Needed:

5/8, 1-1/8 in

To Gas

Regulator/

Flowmeter

Gas

11 12

Argon Gas Or

Mixed Gases

Figure 3-2. Typical Regulator/Flowmeter Installation

OM-157 066 Page 5

3-3. Gun Polarity And Range Selector

WARNING

ELECTRIC SHOCK can kill.

• Do not touch live electrical parts.

• Turn Off welding power source, and disconnect input power before inspecting or installing.

swarn1.1 2/93

1 Polarity Changeover Label

2 Wire Drive Assembly

3 Positive (+) Output Terminal

4 Negative (−) Output Terminal

Always read and follow wire man-

ufacturer’s recommended polarity.

5 Range Selector

Arc voltage is fine tuned using Volt-

age switch (see Figure 4-2). See

rear cover for settings.

6 Range Label

Move bar for desired range.

7 Circuit Breaker CB1 (see

Section 5-2).

8 Pilot Light (see Section 5-2)

Close door.

Ref. ST-153 874-A

Tools Needed:

3/4, 11/16 in

HIGH RANGE

LOW RANGE

S-153 070

Shown As Shipped − Set For Electrode

Positive (DCEP) For Solid Steel Or

Aluminum Wires (GMAW Process).

Wire Drive Assembly Lead

To Positive (+) Output Terminal

Work Clamp Lead To

Negative (−) Output Terminal

GUN POLARITY

CHANGEOVER CONNECTIONS

Reverse Lead Connections − For Electrode

Negative (DCEN) For Flux Cored Wires

(FCAW Process). Drive Assembly

Becomes Negative

S-144 449-C

Figure 3-3. Gun Polarity Connections And Range Selector Location

3-4. Installing Drive Rolls And Welding Gun

1 Pressure Adjustment

2 Pressure Assembly

3 Drive Roll

4 Securing Screw

Install correct drive roll for wire size

and type using supplied screws.

5 Wire Drive Assembly

6 Gun Securing Knob

7 Gun End

Loosen securing knob. Insert gun

end through opening until it bottoms

against drive assembly. Tighten

knob.

8 Gun Trigger Plug

Insert into receptacle, and tighten

threaded collar.

Close pressure assembly. Close

door.

ST- 154 621 / Ref. ST-154 624

Tools Needed:

Figure 3-4. Gun Connections

OM-157 066 Page 6

3-5. Connecting Input Power

WARNING

ELECTRIC SHOCK can kill.

• Do not touch live electrical parts.

• Turn Off welding power source, and disconnect input power before inspecting or installing.

• Have only qualified persons install unit.

• Installation must meet National Electrical Code and all other codes.

swarn3.1 2/93

A. Positioning Jumper Links

Jumper links allow operation on dif-

ferent input voltages and are

factory set for the highest input volt-

age.

Check input voltage available at

site.

1 Input Voltage Label

Look at jumper links and compare

link position with applicable label.

2 Screw

3 Access Door

To change link position, remove

screw and pivot door up.

4 Input Voltage Jumper Links

Location

Move links to match input voltage.

For example, use 200 volts position

when 200 volts input power is avail-

able.

Close door and secure with screw.

Close side door.

ssb5.1* 2/92 / Ref. ST-154 626-A / Ref. ST-154 628-A

Tools Needed:

3/8 in

200 VOLTS

230 VOLTS

S-153 980

Door In Open Position

Figure 3-5. Input Voltage Jumper Links Location

S-0092-G

OM-157 066 Page 7

B. Connecting Input Power

Have only qualified persons make

this installation.

1 Line Disconnect Device Of

Proper Rating

2 230 Volts AC Wall Receptacle

3 Input Conductors

4 Grounding Conductor

Select size and length using

Table 3-1. Conductor rating must

comply with national, state, and

local electrical codes.

Install and connect grounding

conductor and input conductors in

conduit or equivalent between wall

receptacle and deenergized line

disconnect device.

Connect grounding conductor first,

then line input conductors.

Be sure grounding conductor goes

to an earth ground.

5 Overcurrent Protection

Select type and size using

Table 3-1. Install into deenergized

line disconnect device (fused dis-

connect switch shown).

6 Input Power Plug

Turn off unit Power switch, and con-

nect plug to wall receptacle.

ssb2.2 1/94 − Ref. ST-154 619-A / Ref. ST-149 405-B

4 3

34 3

For Plug Connection

Tools Needed:

Figure 3-6. Input Power Connections

Table 3-1. Electrical Service Requirements*

Input Voltage

200 230

Input Amperes At Rated Output

46 40

Recommended Standard Fuse Or Circuit Breaker Rating In Amperes

70 60

Input Conductor Size In AWG/Kcmil

8 8

Max Input Conductor Length In Feet (Meters)

89 (27) 117 (36)

Grounding Conductor Size In AWG/Kcmil

8 10

These values are calculated from the 1993 edition of the National Electrical Code (NEC).

1 Recommended fuse or circuit breaker size is that closest to 150% of rated input amperage of the welding power source. Article 630-12(a) of NEC

allows fuse or circuit breaker sizing up to 200% of rated input amperage.

2 Input conductor size is for insulated copper wire with 75°C rating with not more than three single current-carrying conductors in a cable or raceway

(Table 310-16 of NEC).

3 Maximum length is to prevent more than a 3% voltage drop between service entrance and input terminals of the welding power source (Articles

210-19(a) and 215-2(b) of NEC).

4 The grounding conductor shall be colored or identified as specified in the NEC. Grounding conductor size for copper wire is not required to be larger

than input conductor (Article 250-95 of NEC).

OM-157 066 Page 8

3-6. Installing Wire Spool And Adjusting Hub Tension

Turn Off unit.

1 Wire Spool

2 Gun Contact Tip

If necessary, cut welding wire off at

contact tip, and retract wire onto

spool and secure.

3 Retaining Ring

4 Compression Spring

Remove ring and pull off spool.

Compression spring is used with 8

in (200 mm) spools.

5 Hub

6 Hub Pin

Slide spool onto hub so wire feeds

off bottom. Turn spool until hub pin

fits hole in back of spool. Reinstall

retaining ring.

7 Hub Tension Nut

Grasp spool in one hand and turn

while using a wrench to adjust hub

tension nut. When a slight force is

needed to turn spool, tension is set.

Thread welding wire (see Section

3-7). Close door.

Ref. ST-154 626-A / Ref. ST-072 573-B

Tools Needed:

15/16 in

Figure 3-7. Installing Wire Spool And Adjusting Hub Tension

3-7. Threading And Feeding Welding Wire

WARNING

CYLINDERS can explode if damaged.

• Keep cylinders away from welding and other

electrical circuits.

• Never touch cylinder with welding electrode.

• Always secure cylinder to running gear, wall, or

other stationary support.

ELECTRIC SHOCK can kill.

• Do not touch live electrical parts.

The welding wire, drive rolls, drive assembly, and all

metal parts touching the welding wire are electrically

live when welding or feeding wire using gun trigger.

WELDING WIRE can cause puncture

wounds.

• Do not press gun trigger until instructed to do so.

• Do not point gun toward any part of the body, other

people, or any metal when threading welding wire.

HOT SURFACES can burn skin.

• Allow gun to cool before touching.

swarn5.1 10/91 / swarn2.1 9/91

OM-157 066 Page 9

ST-800 739 / ST-154 251 / S-0627-A

1 Wire Spool

2 Welding Wire

3 Inlet Wire Guide

4 Pressure Adjustment Knob

5 Pressure Assembly

6 Drive Roll

7 Outlet Wire Guide

8 Gun Conduit Cable

Lay gun cable out straight.

3 6 7

Pull and hold wire; cut off end.Open pressure assembly.

6 in

(150 mm)

Hold wire tightly to keep it

from unraveling.

Push wire thru guides into gun;

continue to hold wire.

Close and tighten pressure assembly,

and let go of wire.

Tighten

Set switch.

Press gun trigger until wire

comes out of gun. Reinstall

contact tip and nozzle.

WOOD

Feed wire to check drive roll pressure.

Tighten knob enough to prevent slipping.

Cut off wire.

Close and latch door.

Remove gun nozzle

and contact tip.

Figure 3-8. Threading And Feeding Welding Wire

OM-157 066 Page 10

SECTION 4 − OPERATION

WARNING

ELECTRIC SHOCK can kill.

• Always wear dry insulating gloves.

• Insulate yourself from work and ground.

• Do not touch live electrical parts.

• Keep all panels and covers securely in place.

FUMES AND GASES can be hazardous

to your health.

• Keep your head out of the fumes.

• Ventilate area, or use breathing device.

• Read Material Safety Data Sheets (MSDSs) and

manufacturer’s instructions for material used.

WELDING can cause fire or explosion.

• Do not weld near flammable material.

• Watch for fire; keep extinguisher nearby.

• Do not locate unit over combustible surfaces.

• Do not weld on closed containers.

• Allow work and equipment to cool before handling.

ARCING can damage switch.

• Do not change Voltage switch position while

welding.

Arcing inside switch can damage contacts, causing

switch to fail.

ARC RAYS can burn eyes and skin;

NOISE can damage hearing.

• Wear welding helmet with correct shade of filter.

• Wear correct eye, ear, and body protection.

MOVING PARTS can cause injury.

• Keep away from pinch points such as drive rolls.

• Keep all doors, panels, covers, and guards closed

and securely in place.

MAGNETIC FIELDS FROM HIGH CUR-

RENTS can affect pacemaker operation.

• Pacemaker wearers keep away.

• Wearers should consult their doctor before going

near arc welding, gouging, or spot welding opera-

tions.

WELDING CURRENT can damage elec-

tronic parts in vehicles.

• Disconnect both battery cables before welding on a

vehicle.

• Place work clamp as close to the weld as possible.

See Safety Precautions at beginning of manual for ba-

sic welding safety information.

swarn6.2 8/92

Wear the following while welding:

1 Dry, Insulating Gloves

2 Safety Glasses With Side

Shields

3 Welding Helmet With Correct

Shade Of Filter (See ANSI

Z49.1)

sb3.1 1/94

123

Figure 4-1. Safety Equipment

OM-157 066 Page 11

1 Wire Speed Control

Use control to set wire feed speed.

2 Wire Speed Low Range/Full

Range Switch

For better control of wire speed use

Low Range when wire speed is be-

tween minimum and 350 ipm.

3 Voltage Switch

Use switch and Range Selector

(see Section 3-3) to set arc voltage.

Step 6 of Low range and Step 1 of

High range overlap.

4 Pilot Light

5 Power Switch

Use switch to turn unit On and Off.

The pilot light comes on when unit

is turned on.

6 Work Clamp

Use wire brush or sandpaper to

clean metal at weld joint area.

Connect work clamp to clean,

paint-free location on workpiece, as

close as possible to weld area.

Ref. ST-154 622-A / Ref. ST-155 398 / Ref. ST-154 251

Tools Needed:

Figure 4-2. Controls

OM-157 066 Page 12

SECTION 5 − MAINTENANCE & TROUBLESHOOTING

WARNING

ELECTRIC SHOCK can kill.

• Do not touch live electrical parts.

• Turn Off welding power source, and disconnect

input power before inspecting, maintaining, or

servicing.

HOT PARTS can cause severe burns.

• Allow cooling period before maintaining or servicing.

MOVING PARTS can cause injury.

• Keep away from moving parts.

• Keep away from pinch points such as drive rolls.

Maintenance and troubleshooting to be performed only

by qualified persons.

swarn8.2* 2/93

5-1. Routine Maintenance

Turn Off all power before maintaining.

6 Months

Clean

Drive

Rolls

3-4

3 Months

14-Pin Cord

Gas Hose Gun Cable

− −

Replace

Cracked

Parts

Replace

Unreadable

Labels

Blow Out

Gun

Casing

− −

Clean

Nozzle

And Check

Contact Tip

Each Spool Of Wire

Clean

And

Tighten

Weld

Terminals

3-1

See

Section

5-4

Blow Out

Vacuum

Inside

− −

During Heavy Service,

Clean Monthly

Figure 5-1. Maintenance Schedule

OM-157 066 Page 13

5-2. Overload Protection

READ SAFETY BLOCKS at start of

Section 5 before proceeding.

WARNING

A. Circuit Breaker CB1

Ref. ST-153 874-A

1 Circuit Breaker CB1

2 Pilot Light

If CB1 opens, pilot light goes out,

and wire feed stops. Check gun lin-

er for blockage or kinks, and check

for jammed wire, binding drive gear,

or misaligned drive rolls. Allow a

cooling period before resetting

CB1.

Figure 5-2. Circuit Breaker CB1

B. Fuses F1 And F2

Turn Off unit and disconnect input

power.

1 Fuse F1 (See Parts List For

Rating)

F1 protects the 115 volts ac winding

of transformer T1. If F1 opens, all

weld output stops and pilot light PL2

goes out.

2 Fuse F2 (See Parts List For

Rating)

F2 protects the 24 volts ac winding

of transformer T1. If F2 opens, all

weld output stops.

Ref. ST- 154 629-A

Figure 5-3. Fuse Location

C. Overheating

minutes

When overheated, thermostat

opens, output stops, and cooling

fan keeps running.

Let fan run for

15 minutes.

Start welding.

ssb10.1 1/94 − Ref. ST-157 072

Figure 5-4. Overheating

OM-157 066 Page 14

5-3. Wire Drive Assembly Maintenance

READ SAFETY BLOCKS at start of

Section 5 before proceeding.

WARNING

Turn Off unit and disconnect input

power.

1 Wire Spool

2 Gun Contact Tip

Cut welding wire off at contact tip.

Retract wire onto spool and secure.

3 Drive Roll Alignment Bolt

Turn in or out until groove lines up

with wire guide.

4 Drive Roll

5 Wire Inlet Guide

Remove guide by pressing on

barbed area or cutting off one end

near housing and pulling it out of

hole. Push new guide into hole from

rear until it snaps in place.

6 Pressure Roll Arm

7 Cotter Pin

8 Pin

9 Screw

10 Bearing

Remove bearing as shown. Install

new bearing and secure with screw.

Reinstall arm onto pin and secure

with cotter pin.

Thread welding wire (see Section

3-7). Close door.

Ref. ST-154 626-A / SA-145 763 / ST-154 633

Tools Needed:

910 6

Incorrect

Correct

Alignment

Figure 5-5. Wire Drive Assembly Maintenance

OM-157 066 Page 15

5-4. Gun Maintenance

READ SAFETY BLOCKS at start of

Section 5 before proceeding.

WARNING

FLYING METAL CHIPS AND DIRT can cause injury and damage equipment.

• Point gun away from people and in a safe direction when blowing out with compressed air.

swarn10.1 10/91

Turn Off unit and disconnect input

power.

1 Wire Spool

Cut welding wire off at contact tip.

Retract wire onto spool and secure.

2 Gun Securing Knob

Loosen knob and remove gun and

trigger plug.

3 Nozzle

4 Contact Tip

5 Contact Tip Adapter

6 Head Tube

7 Setscrew

8 Wire Outlet Guide

Disassemble gun as shown.

9 Liner

Pull liner from this end. Blow gun

casing out with compressed air.

Insert new liner into gun casing.

The liner end covered with clear

tubing goes to the head tube.

Reinstall guide so that 1/8 in (3 mm)

of liner sticks out. Hand tighten

guide, and then tighten two full turns

more.

Cut liner off so that 1/2 in (13 mm)

sticks out of head tube. Trim clear

tubing off 1/4 in (6.3 mm) from end

of liner.

Tighten setscrew to secure liner in

head tube. Overtightening set-

screw crushes liner and causes

wire feed problems.

Reassemble gun.

Reinstall gun (see Section 3-4).

Thread welding wire (see Section

3-7). Close door.

Ref. ST-154 624 / ST-145 478-C / Ref. ST-150 438-A

Tools Needed:

3/8 in

Figure 5-6. Gun Maintenance

OM-157 066 Page 16

5-5. Troubleshooting

READ SAFETY BLOCKS at start of

Section 5 before proceeding.

WARNING

Welding Trouble Remedy Section

No weld output; wire does not feed. Secure power cord plug in receptacle. 3-5

Reset circuit breaker CB1. Replace fuse F1 and/or F2. 5-2

Replace building line fuse or reset circuit breaker if open. 3-5

Secure gun trigger plug in receptacle or repair leads, or replace trig-

ger switch.

3-4

No weld output; wire does not feed; fan

motor continues to run and pilot light is

off.

Thermostat open (overheating). Allow fan to run; the thermostat will

close when the unit has cooled.

5-2

No weld output; wire feeds. Connect work clamp to get good metal to metal contact. Figure 4-2

Replace contact tip. 5-4

Low weld output. Connect unit to proper input voltage or check for low line voltage. 3-5

Wire Drive/Gun Trouble

Electrode wire feeding stops during

welding.

Straighten gun cable and/or replace damaged parts. 5-4

Adjust hub tension. 3-6

Adjust drive roll pressure. 3-7

Replace contact tip if blocked. 5-4

Clean or replace wire inlet guide or liner if dirty or plugged. 5-3, 5-4

Replace drive roll or pressure bearing if worn or slipping. 5-3

Secure gun trigger plug in receptacle or repair leads, or replace trig-

ger switch.

3-4

Check and replace F1 and/or F2. 5-2

Check and clear any restrictions at drive assembly and liner. 5-3, 5-4

Have nearest Factory Authorized Service Station check drive

motor.

− −

SECTION 6 − ELECTRICAL DIAGRAMS

SB-155 419

Figure 6-1. Circuit Diagram For Welding Power Source

Page is loading ...

Miller AUTO ARC 255 Owner's manual

Brand: Miller

Model: AUTO ARC 255

Category: Welding System

Type: Owner's manual

This manual is also suitable for

KE629034

Download PDF

report

Miller AUTO ARC 255 Owner's manual

This manual is also suitable for

Miller AUTO ARC 255 Owner's manual

Related papers

Other documents