INSTRUCTIONS for
These INSTRUCTIONS are for experienced operators. If you
are not fully familiar with the principles of operation and safe
practices for arc welding equipment we urge you to read our
booklet Precautions and Safe Practices for Arc Welding,
Cutting and Gouging, Form 52-529. Do NOT permit untrained
persons to install, operate or maintain this equipment. Do NOT
attempt to install or operate this equipment until you have read
and fully understand these instructions. If you do not fully
understand these instructions contact your supplier for further
information. Be sure to read the Safety Precautions on page 2
before installing or operating this equipment.
F-12-728-C
February, 1995
MIG-28A*
WIRE FEEDER
SPECIFICATIONS
Torch Capacity (100% duty) .................................. 250 amps DC
Torch Weight, approx ..... 3 Ibs. 1.4 kg, (less wire; service lines)
Control Weight, approx ........................................ 16 lbs. (7.2 kg)
Primary Power Required.....................115 volts, 50/60 Hz, 1 ph.
Wire Feed Speed Range .................. 79-709 ipm (33-300 mm/s)
Wires Accommodated ....................... 030- through .045-in. hard
.030- through 1/16-in. soft
Dimensions, in.
Torch Control
Length ........... 15 (381 mm) Length. ..............14.7 (373 mm)
Width ........... 3-1/4 (82 mm) Width .................10.7 (272 mm)
Height ............. .8 (203 mm) Height ................ 10.2 (260 mm)
Handle Dia ....... .1-3/4 mm)
I. INTRODUCTION
The MIG-28A Wire Feeder can be used for either short
arc or spray arc welding with a constant potential (CP) or
a constant current (CC) power supply. A flip of a selector
switch readies the control for use with either type of
welding power. The control operates from a 115 volt AC
50/60 Hz power source.
The MlG-28A consists of two basic units: an SEC-7A
Control and an ST-23 Torch. This instruction booklet
covers the installation and operation of the complete
MIG-28A (torch and control). For installation of torch
accessories and torch maintenance, refer to Form 14353, ‘Instructions for ST-23A Mig Welding Torch’.**
A. DESCRIPTION
The SEC-7A Control contains a solid state governor to
F-12-728-C
maintain wire feed rate for constant potential welding,
and to regulate arc voltage for constant current welding.
Most of the control circuits in the SEC-7A are incorporated on one printed circuit board which is mounted
inside the control for easy access and removal.
The control circuitry contains a dynamic brake which
quickly stops wire feed, to eliminate freezing of wire in the
weld puddle for the vast majority of conditions. In addition, an optional Anti-Stick Kit is also available for the
SEC-7A to adjust the amount of wire burnback after wire
feed stops, to further prevent any freezing of welding wire
in the weld puddle.
The ST-23 Torch is an air cooled, spool-on-gun type
manual mig welding torch with a maximum current capacity of 250 amperes DC continuous duty. The torch
contains a complete gearmotor in the handle which pulls
the welding wire from a 4-in. diameter spool, mounted in
a molded case on the rear of the torch, and delivers it to
the torch nozzle. The case is molded from a rugged,
flame retardant, glass-reinforced polyester compound.
II. SETTING UP THE MIG-28A
A. EQUIPMENT SUPPLIED
The MIG-28A (Series A) is available in a welding outfit
under P/N 19163. Contents of the outfit are listed in Table
1.
Be sure this information reaches the operator.
You can get extra copies through your supplier.
POWER CABLE / GAS CONNECTIONS
PRINTED CIRCUIT BOARD
WELD POWER
SELECTOR SWITCH
CONSTANT
POTENTIAL
WIRE INCH RELAY
TORCH SWITCH RELAY
Fig. 1 - Interior View of SEC-7A Control
Table 1 - Contents of MIG-28A Outfit, P/N 19163
Description Qty. Part No.
SEC-7A Control 1 2075159
ST-23A Torch/30-ft. service lines 1 19164
Control Cable, 6-ft., 6-cond., 19 pin 1 36618
Gas Hose, 12-1/2-ft. 1 40V77
Contact Tip (.030" Hard & Soft) 3 996994
Contact Tip (.035" Hard & Soft) 3 996995
Contact Tip (3/64" Soft & .045" Hard) 3 996999
Contact Tip (1/16" Soft) 3 996997
Feed Roll (.030" & .035" Hard & Soft) 1 636343
Torch Liner (.030 & .035 Wire) 1 19166
No. 8 Nozzle Std. Duty 3 999471
No. 10 Nozzle Std. Duty 2 999472
B. REQUIRED COMPANION EQUIPMENT AND
ACCESSORIES
1. R-5007 Argon Regulator-Flowmeter, P/N 998124.
2. 2/0 Welding Cable (customer supplied) in suitable
lengths to connect the power supply to the control and
workpiece. Terminal lug with fiber cover, P/N 81F64,
is available for connecting the cable to the power
supply.
3. Gas Hose Coupling, P/N 11N17 permits you to extend
gas hose by ordering additional hose (40V77).
4. One of the following types of power supplies:
a. A D.C. Rectifier-Type Constant Potential Power
Supply (such as VI-206, VI-300, VI-450, etc.) as
shown in Figure 2.
b. A D.C. Generator or D.C. Rectifier-Type Constant
Current Power Supply which does not have a built-
CONSTANT
CURRENT
SWITCH ON P/C BOARD
P.C. Board location of
SLOW INCH DOWN TRIMPOT
(See Section IV-D-2.)
TRANSFORMER
in contactor. For this type unit, a 300 Amp. Secondary Contactor Assembly (P/N 677333) will be required to interrupt the welding current between the
SEC-7A Control and the power source as shown in
Figure 3. (Refer to Form 12-825 for complete
installation instructions.)
c. A D.C. Rectifier-Type Constant Current Power
Supply that contains a built-in contactor with a
115-volt coil. This type unit can be operated directly from the SEC-7 control as shown in Figure 4.
d. A Heliarc 306/Heliarc 350 AC/DC Power Supply may
also be used; however, in this case an Adaptor Kit
(P/N 995313) will be required. (Refer to Form 12324 for complete installation instructions.)
5. Standard Welders Helmet with proper shade of
glass. A No. 12 glass should be used for currents
of 75 to 200 amperes.
C. OPTIONAL ACCESSORIES
1. Torch Control Cable Extension Assy., (30-ft.) P/N
636968. Used to extend the length of the torch cables
(see Fig. 5)
2. Torch Power and Gas Extension Adaptor, P/N 993457.
This adaptor is used in conjunction with extension
636968 above. Both parts enable you to extend the
torch service lines up to 60-ft. (See Fig. 5.)
3. Control Adaptor Cable (3-ft., 6-cond.) P/N 996736.
Required to connect the control to any power supply
which does not contain a remote contactor receptacle.
4. Control Extension Cable (25-ft.) P/N 996738. Used to
extend the control to power supply cable (see Fig. 2).
3
5. Anti-Stick Kit, P/N 2075076. Kit permits precise adjustment of amount of burnback after wire feed stops,
to eliminate freezing of wire in weld puddle. For
installation refer to Section III-B
III. INSTALLATION
A. HOSE AND ELECTRICAL CONNECTIONS
B. ANTI-STICK KIT
All components of the Anti-Stick Kit are mounted on a PC
board connected to the anti-stick potentiometer. To
install the kit simply insert potentiometer through knockout on back panel. Then with hardware provided tighten
potentiometer, and install knob. For electrical connections refer to Figure 10.
CAUTION: Be sure the Main Line Switch (MLS) on the
IV. ADJUSTMENTS AND OPERATION
control cabinet and the power supply are OFF
before making any connections.
Depending on the type of power supply used, make the
necessary cable and hose connections in accordance
with one of the following interconnection diagrams.
A. SHIELDING GAS FLOW
The torch trigger switch controls the flow of shielding gas
set by the flowmeter. To check the flow, first deenergize
the control by placing the Main Line Switch (MLS) in the
OFF position. Then depress the torch switch. After
Fig. 2 - Interconnection Diagram for Constant Potential
Welding
Fig. 3 - Interconnection Diagram for Constant Current
making the necessary adjustments to the flowmeter,
place the Main Line Switch in the ON position.
B. TORCH CONTROLS
Power Supplies without Built-in Contactor.
Wire feed power is provided by the permanent-magnet
Fig. 4 - Interconnection Diagram when using a Con-
stant Current Power Supply/Built-in Contactor.
type DC motor in the ST-23A torch. Wire may be inched
by pressing the button on the bottom of the torch handle
CAUTION: Do not allow metal-to-metal contact between the wire feeder (control) cabinet and a metal surface
connected in any way to a welding ground. Without insulation, a poor work lead connection may create a
difference in potential that sends part of the welding current through the safety ground wiring in the control
cable and wire feeder, resulting in burnout of that wiring and/or damage to wire feeder circuitry. If safety
ground burns out, the operator may be exposed to 115 V. shock hazard.
GAS
NOTE:
For Internal power cable & gas hose
connections, See Fig. 3
P2
SEC-7A
FRONT
TORCH POWER
CABLE (30 ft.)
ST-23A TORCH
REGULATOR/FLOWMETER
6 ft. CONTROL CABLE12-1/2 ft. GAS
HOSE-40V77
TORCH CONTROL
CABLE (30 ft.)
SEC-7A
BACK
P1
2/0 WELDING CABLE
(Customer Supplied)
GRD.
996739 (Provided)
25 ft. EXTENSIONS
CABLE - 996738
Optional
WORK
Fig. 2 - Interconnection Diagram for Constant Potential Welding
4
CONSTANT POTENTIAL
POWER SUPPLY
(Customer Supplied)
Loading...