MIG / MAG

MANUAL
RX 250 / RX 400

April, 2007
 INDEX:

About Mig. 3
Advantages of Mig. 3
Brief description of all parts. 4- 8
Setting welding current. 9
Problems and their solutions. 10
Cause of welding defects and
their solutions. 11
Technical information. 12
Circuit diagram of power source. 13
Circuit diagram o wire feeder. 14
Torch spare guidelines AK25-P 15
Torch spare guidelines 36KD-P 16
Installation guide. 17

2
 ABOUT MIG:
MIG (Metal Inert Gas) welding, also sometimes called GMAW (gas
metal arc welding), is a welding process that was originally developed
back in the 1940's. MIG welding is a semi automatic process in which a
relatively thin wire is feed through welding gun instead of using a flux
coated electrode. The wire fed continuously by a wire feeder from a coil
and a shielding gas is used as an alternate of flux, this mechanism gives
continuous non stop weld and many advantages comprising electrode
welding. Originally Argon was used for shielding the weld pool. This inert gas
acts as a shield, keeping air borne contaminants away from the weld zone.
Due to high cost of Argon, the weld process was modified by replacing
Argon with CO2, because this is active gas some amount of Mn and Si was
added to welding wire for cancelling the poor effect of CO2 on weld pool.
Today ‘s MIG wire is actually MAG(metal active gas ) wire. So, the name
MIG/MAG welding be famous.

ADVANTAGE OF MIG:

The primar y advantage of MIG welding is that it allows metal to be

welded much quicker, slag free and continuous than traditional welding
"stick welding" techniques. Some major advantages of MIG are listed
below:

* It produces long continuous welds.

* Welds much faster, 3 to 5 times faster.
* No slag formed during welding.
* No need to chip or brush welding.
* Clean weld with ver y little spatter.
* Easy machinable softer welds.
* No burn out at bead corners.
* Great metal filling speed.
* Ideal for thin metal welding.
* Good finish.

3
BRIEF DESCRIPTION OF ALL PARTS:
FRONT

1
2
3
4

5
7

6
8

9
11
13
10
14

12

15 16

17

19
18

20

4
BRIEF DESCRIPTION OF ALL PARTS:
REAR

31

32

33

34

35
36
37
38 39

40

5
1. POWER INDICATOR: It is placed in front of wire feeder shows the power is
on from power source and control cord to wire feeder has been
connected.

2. GAS CHECK: Press Gas check push button to check the flow of shielding
gas on conical nozzle and scaling on flow meter.

3. WIRE CHECK: Press Wire check push button to check the motor rotation
and for feeding wire in torch when you change an empty wire roll with
new one.

4. WIRE SPEED: This is knob to set a wire feed speed according to welding
volts and for control of welding current, To run motor fast or want to
increase in welding current rotate it clock wise and vice-versa. The
rotating device below knob is called potentio meter.

5. GAS PLUG: Connect the torch gas pipe here. When gas check or torch
trigger is pressed the gas comes from this plug and passes to welding
end of torch.

6. TORCH PLUG: This is base plug for the plug that is attached with torch,
make the connections by connecting these plugs. When you press
torch trigger the trigger switch works through this plug if this plug is not
connected torch switching will not work.

7 Feeder Motor: This is variable speed motor attached with a feed roll and
gearbox. It feeds wire at a constant speed set from wire speed knob.

8. CENTRAL ADAPTOR PM-3b: It’s the connector to connect welding torch,

Mig wire and welding current runs through this connector.

9. VOLT METER: By pressing OCV CHECK switch in front of power source, It

shows the open circuit volts of power source and when you do the
welding it shows welding volts.

10. AMPERE METER: It shows welding current during welding.

11. OCV CHECK: Press this toggle to check the set value of OCV(open
circuit volts).

12. POWER ON: Power on toggle switch. It is used for switching power source
control circuit and wire feeder ON or OFF. By switch off machine from
this switch does not mean the power is removed from power source, it
only cuts power of control circuit.
6
13. POWER LED: It shows power is connected to machine and POWER ON
toggle switch is set to on.

14. WELD LED: The weld led shows the status of welding volts, when OCV
CHECK toggle switch or torch trigger is pressed will glow.

15. COURSE CONTROL SWITCH: It is 3-POLE 4-WAY rotary switch, It’s one step
increment make increase in OCV about 5-Volts.

16. FINE CONTROL SWITCH: It’s function is same as course control switch, the
only difference is it’s step size, a step of it will only change in OCV about
2-Volts.

17. WIRE FEEDER TERMINAL: Terminal for connecting wire feeder welding
lead. It is positive terminal.

18. WORK TERMINAL: It is negative terminal and connected to workpiece or

work table through a work lead.

19. WIRE FEEDER CONTROL PLUG: Connect one side Plug of 3 Core
connection lead here and other plug on the back of wire feeder.
Through these connection power is provided to wire feeder and to
make control between wire feeder and power source.

20. AIR VENT: This is out-let for cooling air at bottom of machine, keep the
surface clean below it, to prevent air blockage

31. WIRE SPOOL PIN: This pin is for fixing wire spool. Note that it could not
rotate freely, a tensioning spring is placed inside it.

32. CONTROL PLUG: A already mentioned connect control lead plug here.
33. GAS IN-LET: Connection for shielding gas.
34. HOLDER CABLE IN-LET: A welding cable has gone inside from here to
give positive current for torch. It’s other end is connected to Wire feeder
terminal.

35. HEATER PLUG: Connection for CO2 heater plug.

36. FUSE FOR CONTROL TRANSFORMER: This is fuse holder and a fuse inside
in protects control transformer from faulty conditions.

37. FUSE FOR FAN: Fuse for cooling fan.

7
38. FUSE FOR HEATER: To protect heater supply from short circuit, in caseif
heater cable or heater gets faulty.

39. COOLING FAN: Give forced air in machine to cool DIODES and MAIN
TRANSFORMER.

40. SUPPLY COVER: It protects surrounding from touch with terminal strip
behind it. After connecting power supply place the cover back in its
original position.

8
Setting welding current:
MIG RX 250
STEP NO. OCV WELDING WELDING
COURSE FINE VOLTS CURRENT
1 1 22.8 18 60
1 2 23.7 18.3 65
1 3 24.7 18.5 70
1 4 25.7 18.9 75
2 1 26.3 19.3 85
2 2 27.6 19.5 95

* The values shown in table are only for guidelines.

2 3 28.7 19.8 105

Actual value may differ from table.

2 4 29.9 20.6 115
3 1 30.9 21.5 130
3 2 32.5 22 145
3 3 34.3 22.5 160
3 4 36.1 23 175
4 1 37.4 23.5 190
4 2 39.7 24 210
4 3 42.0 25 230
4 4 44.5 26 250

MIG RX 400
STEP NO. OCV WELDING WELDING
COURSE FINE VOLTS CURRENT
1 1 27.5 20.0 100
1 2 28.5 20.3 130
1 3 29.5 21.2 140
1 4 30.8 21.5 160
2 1 31.6 21.4 180
2 2 32.9 22.3 200
2 3 34.3 23.8 200
2 4 35.8 23.9 220
3 1 36.8 23.6 250
3 2 38.4 24.4 260
3 3 40.2 26 280
3 4 42.3 26.9 300
4 1 43.8 27.6 320
4 2 46.1 29.6 340
4 3 48.8 30.7 360
4 4 51.5 32.4 380
9
 PROBLEMS & THEIR Solutions:
Problem Cause Solutions
1. Power indicator does not One phase or all three Check power supply status
glow. phases of power are then check fuses then
missing. check supply cable &
connection strip at back
of machine.

2. Wire feeder’s power Three core control cable Replace control cable.
indicator does not glow or damage.
it is not functioning. Melted fuse of PCB. Replace Fuse.
Faulty PCB. Replace PCB.

3. Torch switch does not Dust in torch switch or Wash the torch switch with
work, But wire & gas Push loose connection of torch a oil based cleaning
buttons on wire feeder are plug. agent or replace switch.
working. Replace torch plug.

By pressing torch switch

4. Gas does not come. Gas cylinder empty or Check step by step all
Heater does not heat up or causes and replace the
Pressure regulator faulty or faulty component.
gas pipe blocked or faulty
solenoid valve.
5. Wire dose not come. Wire coil jam or Pressure Grease wire spool or set
lever loose or Motor not appropriate pressure on
running. wire by adjusting pressure
lever then check motor if
faulty replace it else
replace PCB.
6. Current does not come. Breakage of control Find breakage area and
cable. repair it or replace it with
new cable.

7. While setting voltage from Loose wire on switch. Tighten the loose wire.
rotary switches, voltage Damaged contacts of Replace rotary switch.
variation is not linear. switch.

*We provide this information to guide only a certified engineer, There is always risk of electric shock during
repair please don’t do it your self, always get services from a professional engineer or company.
10
 Cause of Welding defects and their solution’s:
Welding defect Cause Solutions
1. Black burned welding Improper shielding gas. If gas heater does not
bead. heat up replace it or
increase gas flow, shield
welding area from air flow.
Faulty shielding gas. Replace gas cylinder with
a cylinder from different
lot.

2. Proper color good welding Poor quality welding wire. Replace wire with an old
but some fine holes like lot of wire or change its
needle holes in welding. brand.

3. Weld bead raise (hollow Dust, oil or cutting oil on Clean the job.
from inside) in-between or job.
probably at the end of
welding.

4. Low penetration. Wrong selection of If you are using argon

shielding gas. mixed gas, use Co2
shielding gas.
Low welding current. Increase welding current.

5. Thin sheet burns during Wrong selection of Use Argon mixed gas
welding. shielding gas. instead of Co2.
High welding current. Set the welding current to
a relative lower value, if it
is not possible increase
the welding speed.

11
TECHNICAL INFORMATION:

MODEL
ITEM
RX 250 RX 400
Rated input voltage 400 400
MAIN TR ANSFORMER

Supply voltage _ 10%

415 + _ 10%
415 +
Rated frequency 50 50
Phase 3 3
Rated power 9.5/7.8 19.4/17.5
Rated duty cycle 60 60
OCV 22~45 28~54
Output current 50~250 80~400
Type of transformer Double star Double star
Insulation class Class H Class H
Required MCB 16 Amp. 3P 25 Amp. 3P
Supply Cable 1.5 mm2 or 3/20 2.5 mm2 or 7/22
Welding Lead 25 mm2 35 mm2
Cooling Fan 220V AC 80W 220V AC 80W
Main Contactor 220V AC 150W 220V AC 150W
Heater 16 Amp. Coil24V AC 16 Amp. Coil24V AC
OCV Selector Switches 3P 4W 16Amp. 3P 4W 25Amp.
Diodes 150 N 40 150 N 40
Fuses Control Tr. 2.5 Amp 2.5 Amp
Fan 1 Amp 1 Amp
Heater 1 Amp 1 Amp
PCB 78C 5 Amp. 5 Amp.
Feeder Motor 24V DC 24V DC
Solenoid Valve 24V DC 24V DC

* NOTE : The information provided above may different from actual.

12
CIRCUIT DIAGRAM OF MIG RX 250 POWER SOURCE
P1/3 P2/3 P3/3

L3 B 1
415-V 2
L2 Y Sw1 (½3( C Sw1 (½3( Sw1 (½3(
415-V R 3
L1
Cont.1 4

A1

A2
1
2
C
3
F1 Sw2 (½3( Sw2 (½3( Sw2 (½3(
5Amp. 4

Sw 4

3 PIN HCL PLUG (1)

(TO WIRE FEEDER) P1/3 P2/3 P3/3
Tr. 1
3 1
26-V
L1 +
F2 2
Q0
HEATER PLUG (2)
220-V M1 _
F3 3 1 M2
300-A
_ 50-V
2 x 2Amp. AUTO +
Sw 3 2 Tr. 2
Tr. 3 +
Q1

Shunt (75m V/300 Amp. )

13
FAN 1
 CIRCUIT DIAGRAM OF MIG RX 250 WIRE FEEDER.
SOHAL 78 (PCB)

CN1 CN2 CN3 CN4 CN5

+ 3 PIN PLUG
( TO POWER SOURCE)
3 1
P.B. (WIRE) P.B.
(GAS)
Arm.
2

Pot. 4K7 T. Sw.

1 Amp.

SOLENOID VALVE
COIL.

14
TORCH SPARE GUIDELINEs:

MIG TORCH SOHAL AK25-P

28 M8
4 Nozzle Spring
8

M6

M8

M6 M8

90 80 1
Contact Tip Contact Tip Swan Neck
0.8 or 1.2mm Holder

M 10x1

Torch Body Plastic 7

10 Ergo Handel with trigger

Trigger 18
15

102 Gas Nozzle

57

120 Liner Insulated

Power Cable 3m 40

Adaptor Nut 58
Central
59 Adaptor
PM-3
M 10x1

Gas Hose

42 Torch Plug

15
TORCH SPARE GUIDELINEs:

MIG TORCH SOHAL 36KD-P

Contact Tip
Holder
28
80
8

M6

M8
32.5
M6 28 1 Swan Neck
M8
16

90
Contact Tip 70
0.8 or 1.2mm
Gas Diffuser

M 10x1

10 Ergo Handel with trigger

Trigger 18
16

105 Gas Nozzle

84

120 Liner Insulated

Power Cable 3m 40

Adaptor Nut 58
Central
59 Adaptor
PM-3
M 10x1

Gas Hose

42 Torch Plug

16
 INSTALLATION GUIDE FOR MIG RX 250 / 400

17
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