Weldclass WeldForce WF-255MST User manual

WF-255MST
© Weldclass 2019 | E.&O.E. | Edition 2.2 1
Edition 2.2
OPERATING INSTRUCTIONS
IMPORTANT!
To qualify for full 36 month warranty, you must register within 30 days of purchase. See inside for details.
Read these Operating Instructions Completely before attempting to use this machine. Save this manual and
keep it handy for quick reference. Pay particular attention to the safety instructions we have provided for
your protection. Contact your distributor if you do not fully understand anything in this manual.

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2© Weldclass 2019 | E.&O.E. | Edition 2.2
Congratulations & thank you for choosing WeldForce!
The WeldForce range from Weldclass provides market leading value, features and durability. WeldForce
machines have been designed with emphasis on robust construction, with simple and functional operation.
Register Your Warranty Now
Standard warranty without registration is 24 months.
To qualify for an extended full 36 month warranty on your purchase you must register within 30 days of
purchase.
Please register your warranty now by going to:
www.weldclass.com.au/weldforcewarranty
You will need;
a) A copy of your purchase invoice / receipt.
b) Your machine serial number which can be found on the technical data plate on the back of the
machine, or on the outside of the box that your machine came in.

WF-255MST
© Weldclass 2019 | E.&O.E. | Edition 2.2 3
1CONTENTS...............................................................................................................................................3
2BASIC SPECIFICATIONS ............................................................................................................................8
3KNOW YOUR MACHINE.........................................................................................................................10
3.1 Machine Front ..............................................................................................................................10
3.2 Machine Side................................................................................................................................10
3.3 Machine Rear ...............................................................................................................................11
3.4 Control Panel................................................................................................................................11
3.5 LCD Readout.................................................................................................................................12
3.6 Symbols chart...............................................................................................................................13
4CONTROLS EXPLAINED..........................................................................................................................14
4.1 Weld Process Selection ................................................................................................................14
4.1.1 MIG Process: ............................................................................................................................14
4.1.2 Stick & TIG Process:..................................................................................................................14
4.2 MIG Program Selection ................................................................................................................15
4.3 Function Selection........................................................................................................................16
4.3.1 Pre-Gas Time (MIG)..................................................................................................................17
4.3.2 Post-Gas Time (MIG) ................................................................................................................17
4.3.3 Soft-Start Adjustment (MIG) ....................................................................................................17
4.3.4 Burnback Adjustment (MIG) ....................................................................................................17
4.3.5 Spot/Stitch Weld Time (MIG)...................................................................................................17
4.3.6 Stitch Weld Gap/Interval Time (MIG).......................................................................................17
4.3.7 Spool Gun On/Off (MIG) ..........................................................................................................18
4.3.8 Post-Gas Time (TIG)..................................................................................................................18
4.3.9 Slope Down Time (TIG).............................................................................................................18
4.3.10 Hot Start Adjustment (Stick) ................................................................................................18
4.3.11 Arc Force Adjustment (Stick)................................................................................................18
4.3.12 Optional VRD Function (Stick)..............................................................................................18
4.4 Trigger Mode Selection ................................................................................................................19
4.4.1 2T (Standard Trigger)................................................................................................................19
4.4.2 4T (Latch Trigger)......................................................................................................................19
4.4.3 SP (Spot/Stitch) ........................................................................................................................19
4.5 Inductance Control.......................................................................................................................20
4.6 Test Gas ........................................................................................................................................20
4.7 Feed Wire / Wire Inch ..................................................................................................................21
4.8 Job Memory .................................................................................................................................21
4.8.1 Save or Update a Job................................................................................................................21
4.8.2 Recall a Job...............................................................................................................................22

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4© Weldclass 2019 | E.&O.E. | Edition 2.2
4.9 Error/Over Temperature Indicator Light.......................................................................................22
5POWER SUPPLY .....................................................................................................................................23
5.1 Electrical Connection....................................................................................................................23
5.1.1 Setting machine to 15A Input Mode........................................................................................23
5.1.2 Setting machine back to Full Output Mode .............................................................................23
5.2 Extension Leads............................................................................................................................23
5.3 Generator Use ..............................................................................................................................24
5.3.1 Generator Size..........................................................................................................................24
5.3.2 Generator Quality & Warranty Limitations..............................................................................24
5.3.3 3 Golden Rules of Generator use.............................................................................................24
6OPERATING ENVIRONMENT..................................................................................................................25
6.1 Location........................................................................................................................................25
6.2 Ventilation....................................................................................................................................25
7BASIC OPERATION.................................................................................................................................26
7.1 MIG Welding.................................................................................................................................26
7.1.1 Fitting Wire Spool – 270/300mm Diameter (15kg)..................................................................26
7.1.1 Fitting Wire Spool – 200mm Diameter (5kg)............................................................................27
7.1.2 Loading Wire Feeder................................................................................................................28
7.1.3 Gasless Welding Setup .............................................................................................................29
7.1.4 Gas MIG Welding Setup ...........................................................................................................30
7.1.5 Additional Setup for MIG welding with aluminium .................................................................31
7.1.6 Spool Gun Setup.......................................................................................................................31
7.1.7 Adjusting Settings for MIG Welding in Manual Mode (Program 0)..........................................32
7.1.8 Adjusting Settings for MIG Welding in Synergic (Auto) Mode .................................................32
7.2 Stick (MMA) Welding Operation ..................................................................................................33
7.3 Lift TIG Operation.........................................................................................................................34
8ACCESSORIES, SPARE PARTS & CIRCUIT DIAGRAMS..............................................................................35
8.1 MIG Torch and Spares: .................................................................................................................35
8.2 TIG Torch and Spares (Optional Extra): ........................................................................................36
8.3 Optional Accessories....................................................................................................................37
8.4 Drive Rollers: ................................................................................................................................37
8.5 Machine Spare Parts: ...................................................................................................................38
8.6 Primary Schematic Circuit Diagram..............................................................................................40
9CARE & MAINTENANCE.........................................................................................................................41
9.1 Keep your Welding Machine in Top Condition.............................................................................41
9.2 Storing the Welder .......................................................................................................................41
10 GENERAL GUIDE TO WELDING .........................................................................................................42
10.1 Duty Cycle Rating .........................................................................................................................42
10.2 Choosing a Welding Process – MIG, Stick or TIG?........................................................................42

WF-255MST
© Weldclass 2019 | E.&O.E. | Edition 2.2 5
10.2.1 The Stick (MMA) Process .....................................................................................................42
10.2.2 The TIG Process....................................................................................................................43
10.2.3 The MIG Process ..................................................................................................................43
10.3 Joint Preparations.........................................................................................................................44
11 MIG BASIC WELDING GUIDE.............................................................................................................46
11.1 MIG Basic Welding Techniques.....................................................................................................46
11.2 Gas Metal Arc Welding (GMAW)..................................................................................................46
11.3 Flux Cored Arc Welding (FCAW) ...................................................................................................46
11.4 Position of MIG Torch...................................................................................................................47
11.5 Distance from the MIG Torch Nozzle to the Work Piece..............................................................47
11.6 Travel Speed .................................................................................................................................47
11.7 MIG Welding (GMAW) Variables..................................................................................................48
11.7.1 Preselected Variables...........................................................................................................48
11.7.2 Primary Adjustable Variables...............................................................................................48
11.7.3 Secondary Adjustable Variables...........................................................................................48
11.8 Establishing the Arc and Making Weld Beads ..............................................................................50
11.9 MIG Voltage & Wire Speed Settings.............................................................................................50
11.9.1 Setting Wire Speed/Amperage.............................................................................................50
11.9.2 Setting Voltage.....................................................................................................................50
11.9.3 Changing to a different welding wire...................................................................................50
11.9.4 How to determine correct Wire Speed/Voltage Setting ......................................................51
11.10 Suggested Settings for Typical MIG Applications .....................................................................51
11.11 Welding wire Size Selection .....................................................................................................51
11.12 MIG Welding Troubleshooting .................................................................................................52
11.12.1 Porosity Problems................................................................................................................52
11.12.2 Wire Feed Problems.............................................................................................................53
11.12.3 Weld Quality Problems ........................................................................................................54
12 STICK (MMA) BASIC WELDING GUIDE ..............................................................................................56
12.1 Size of Electrodes .........................................................................................................................56
12.2 Storage of Electrodes ...................................................................................................................56
12.3 Electrode Polarity.........................................................................................................................56
12.4 Effects of Stick (MMA) Welding on Various Materials..................................................................56
12.4.1 High Tensile and Alloy Steels................................................................................................56
12.4.2 Manganese Steels................................................................................................................56
12.4.3 Cast Iron...............................................................................................................................56
12.5 Types of Electrodes ......................................................................................................................57
12.5.1 MILD STEEL: .........................................................................................................................57
12.5.2 CAST IRON:...........................................................................................................................57
12.5.3 STAINLESS STEEL: .................................................................................................................57

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6© Weldclass 2019 | E.&O.E. | Edition 2.2
12.6 Suggested Settings for Typical Stick (MMA) Applications ............................................................57
12.7 MMA Welding Techniques ...........................................................................................................58
12.7.1 A Word for Beginners...........................................................................................................58
12.7.2 The Welder...........................................................................................................................58
12.7.3 Striking the Arc.....................................................................................................................58
12.7.4 Arc Length............................................................................................................................59
12.7.5 Rate of Travel .......................................................................................................................59
12.8 Making Welded Joints ..................................................................................................................60
12.8.1 Butt Welds............................................................................................................................60
12.8.2 Fillet Welds...........................................................................................................................61
12.8.3 Vertical Welds ......................................................................................................................62
12.8.4 Overhead Welds...................................................................................................................63
12.9 MMA (Stick) Troubleshooting.......................................................................................................64
13 TIG BASIC WELDING GUIDE..............................................................................................................66
13.1 TIG Electrode Selection and Preparation .....................................................................................66
13.1.1 Electrode Polarity.................................................................................................................66
13.1.2 Preparing Tungsten for DC Electrode Negative (DCEN) Welding .........................................67
13.1.3 Shielding Gas for TIG Welding..............................................................................................68
13.1.4 Typical TIG Welding Settings................................................................................................68
13.2 TIG Welding Troubleshooting.......................................................................................................69
14 KNOWLEDGE & RESOURCES.............................................................................................................70
15 SAFETY..............................................................................................................................................70
15.1 Store and Retain this Manual.......................................................................................................70
15.2 Important Safety Information ......................................................................................................70
15.3 Welding Operation .......................................................................................................................70
15.4 Welding Safety Instructions & Warnings......................................................................................72
15.4.1 Personal Safety.....................................................................................................................73
15.4.2 Arc Rays can Burn Eyes and Skin..........................................................................................73
15.4.3 Noise Can Damage Hearing .................................................................................................73
15.4.4 Work Environment Safety....................................................................................................74
15.4.5 Electricity Can Kill.................................................................................................................74
15.4.6 Fumes And Gases.................................................................................................................75
15.4.7 Fire & Explosive Risks...........................................................................................................76
15.4.8 Sparks & Hot Metal..............................................................................................................76
15.4.9 Gas Cylinders........................................................................................................................77
16 WARRANTY.......................................................................................................................................78
16.1 Warranty period...........................................................................................................................78
16.2 Warranty Includes and Covers......................................................................................................78
16.3 Warranty Excludes / Does Not Cover ...........................................................................................78

WF-255MST
© Weldclass 2019 | E.&O.E. | Edition 2.2 7
16.4 Warranty Conditions ....................................................................................................................79

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8© Weldclass 2019 | E.&O.E. | Edition 2.2
Description
WeldForce WF-255MST
Part Number
WF-06167
Dimensions of Power Source (L x W x H)
680 x 250 x 480mm (including handle)
Weight of Power Source
26.5kg
Standard
AS 60974.1
Power Supply
240V +/- 15% 50hz Single Phase
(See further information under section 5 of this manual)
Factory Fitted Supply Plug Rating
15A
Output Terminals
Dinse™ style 35-50
Protection Class
IP23
MIG Welding
MIG Wire Spool Size
200mm (5kg) & 300mm (15kg)
MIG Wire Sizes
0.6, 0.8, 0.9, 1.0, 1.2mm
Stick (MMA) Welding
MMA Electrode Size
1.6 – 4.0mm
TIG Welding
TIG Tungsten Size
1.6 – 2.4mm
Table 1

WF-255MST
© Weldclass 2019 | E.&O.E. | Edition 2.2 9
This table applies when utilizing the factory fitted 15A plug – Refer to 5.1
Effective Input Current (I1eff)
15A
Maximum Input Current (I1max)
30A
MIG Welding
Welding Current Output
40 – 200A
Welding Voltage Output
16 – 24V
Wire Feed Speed (m/min)
1.5 – 16.5
Duty Cycle
200A / 24.0V @ 25%
145A / 21.3V @ 60%
110A / 19.5V @ 100%
Nominal Open Circuit Voltage
65V
Stick (MMA) Welding
Welding Current Output
10 – 200A
Duty Cycle
200A / 28.0V @ 25%
130A / 25.2V @ 60%
100A / 24.0V @ 100%
Nominal Open Circuit Voltage
VRD on 65V / VRD off 13.5V
TIG Welding
Welding Current Output
10 – 200A
Duty Cycle
200A / 18.0V @ 35%
155A / 16.2V @ 60%
120A / 14.8V @ 100%
Nominal Open Circuit Voltage
65V
Table 2
This table applies when upgraded plug fitted rated at 25A – Refer to 5.1
Effective Input Current (I1eff)
21A
Maximum Input Current (I1max)
38A
MIG Welding
Welding Current Output
40 – 250A
Welding Voltage Output
16 – 26.5V
Wire Feed Speed (m/min)
1.5 – 18
Duty Cycle
250A / 26.5V @ 35%
195A / 23.8V @ 60%
150A / 21.5V @ 100%
Nominal Open Circuit Voltage
VRD on 68V / VRD off 13.5V
Stick (MMA) Welding
Welding Current Output
10 – 250A
Duty Cycle
250A / 30.0V @ 30%
180A / 27.2V @ 60%
140A / 25.6V @ 100%
Nominal Open Circuit Voltage
68V
TIG Welding
Welding Current Output
10 – 250A
Duty Cycle
250A / 20.0V @ 35%
195A / 17.8V @ 60%
150A / 16.0V @ 100%
Nominal Open Circuit Voltage
68V
Table 3
For full machine specifications, refer to technical data plate on back of machine – or go to:
www.Weldclass.com.au/WF-255MST

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10 © Weldclass 2019 | E.&O.E. | Edition 2.2
3.1 Machine Front
1. Carry Handle
2. Control panel
3. Positive (+) Welding Power Output Connection Socket
4. MIG Torch Euro Connector
5. Spool Gun/TIG torch Interface Connector
6. TIG Torch Gas Connector
7. Negative (-) Welding Power Output Connection Socket
8. MIG Torch Polarity Change Tail
3.2 Machine Side
9. Spool Post
10. Spool Nut
11. Spool Lock Pin
12. Wire Inlet Guide
13. Left Wire Feed Tension Adjustment Lever
14. Left Wire Feed Tension Arm/Top Roller
15. Left Drive Roller
16. Left Drive Roller Retainer Knob
17. Centre Wire Guide Tube
18. Right Drive Roller Retainer Knob
19. Right Drive Roller
20. Outlet Wire Guide Tube
21. Right Wire Feed Tension Arm/Top Roller
22. Right Wire Feed Tension Adjustment Lever
Figure 1
Figure 2
4
3
5
6
7
2
1
8
11
20
14
12
13
16
10
9
15
19
21
22
18
20

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© Weldclass 2019 | E.&O.E. | Edition 2.2 11
3.3 Machine Rear
23. Mains Power Switch
24. 240V AC Mains Power Input Lead
25. Gas Inlet Connection
3.4 Control Panel
26. MIG Program Selection Button (P)
27. Function Selection Button (Fn)
28. Process Indicator Lights
29. Process Selection Button (Process)
30. Gas Test Button (Test Gas)
31. Left Selection Knob (Voltage Dial)
32. Right Selection Knob (Wire Speed/Amperage Dial)
33. Wire Feed/Load Button (Feed Wire)
34. Trigger Mode Selection Button (Trigger)
35. Trigger Mode Indicator Lights
36. Job Recall Button
37. Job Save Button
38. Right LCD Readout
39. Left LCD Readout
Figure 4
29 34
26
27
28
30
31
32
33
35
36
37
38
39
23
25
24
Figure 3

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12 © Weldclass 2019 | E.&O.E. | Edition 2.2
3.5 LCD Readout
40. Power On Indicator Light
41. Error/Over Temperature Indicator Light
42. Spool Gun Mode Indicator Light
43. MIG Program Selection Indicator Light
44. Voltage Setting Indicator Light
45. Inductance Setting Indicator Light
46. Seconds Setting Indicator Light
47. Wire Speed Setting Indicator Light
48. Material Thickness Setting Indicator Light
49. Amperage Setting Indicator Light
50. Job Save/Recall Selection Indicator Light
51. VRD Indicator Light
43
40 41 42
44 45 46
47 48
49 50
Figure 5
51

WF-255MST
© Weldclass 2019 | E.&O.E. | Edition 2.2 13
3.6 Symbols chart
I
Power On
O
Power Off
Power On
Indication
Fault Indication
Caution / Hazard
Read Instruction
Manual
MIG Function
TIG Function
Stick/MMA
Function
Material Thickness
Wire Feed
Amperage (current)
output
Voltage output
Variable
Inductance
Increase/Decrease
Save Settings
Recall Settings
Single phase
Inverter power
source DC
MIG (GMAW)
Function
Stick/MMA
(SMAW) Function
TIG (GTAW)
Function
Power Supply
Connection
Single Phase
Direct Current (DC)
–
Negative
+
Positive
Hertz (cycles/sec)
Duty Cycle
Amperage
(Current)
Voltage
Table 4

4.1 Weld Process Selection
1. Press ‘Process’ button (29) until the desired Welding Process Indicator Light (28) is lit.
4.1.1 MIG Process:
In Manual MIG mode (Program 0) – before welding the Left Selection Knob (31) adjusts target voltage
output and the Right Selection Knob (32) adjusts Target Wire Speed (m/min). During welding, Left LCD
Readout (39) will display actual weld voltage and Right LCD Readout (38) will display actual amperage
output.
In Synergic (Auto) MIG mode (Programs 1-20) – before welding the Left Selection Knob adjusts voltage
(31) (which will change the performance from the automatic program) and the Right Selection Knob (32)
adjusts target amperage output. Right Selection Knob can be pressed to toggle to adjust Material
Thickness instead of Amperage. During welding, Left LCD Readout (39) will display actual weld voltage
and Right LCD Readout (38) will display actual amperage output.
4.1.2 Stick & TIG Process:
Before welding the Left Selection Knob (31) is disabled and the Right Selection Knob (32) adjusts target
amperage output. During welding, Left LCD Readout (39) will display actual weld voltage and Right LCD
Readout (38) will display actual amperage output.
Figure 6
1

WF-255MST
© Weldclass 2019 | E.&O.E. | Edition 2.2 15
4.2 MIG Program Selection
(Only available in MIG process mode)
1. Press ‘P’ button (26 - MIG Program Selection Button)
2. Rotate Right Selection Knob (32) to choose program (refer to chart below)
3. Press ‘P’ button (26)
NOTE: Program ‘0’ is traditional Manual MIG mode which allows you to manually adjust volts and
wire speed.
MIG Program Chart
Program
Wire Size
Wire Type
Shielding Gas
0
Manual (Non-Synergic)
1
0.6mm
Solid Steel
Mixed (Argon + CO2)
2
0.8mm
3
0.9mm
4
1.0mm
5
1.2mm
6
0.6mm
Solid Steel
CO2
7
0.8mm
8
0.9mm
9
1.0mm
10
1.2mm
11
0.8mm
Flux Cored Steel
Gasless or Gas
12
0.9mm
13
1.0mm
14
1.2mm
15
0.8mm
Stainless Steel
Mixed or Argon
16
0.9mm
17
1.0mm
18
1.2mm
19
0.8mm
Silicone Bronze (CuSi)
Argon
20
0.9mm
21
0.8mm
Aluminium
Argon
22
0.9mm
23
1.0mm
24
1.2mm
Table 5
Figure 7
2
1, 3

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16 © Weldclass 2019 | E.&O.E. | Edition 2.2
4.3 Function Selection
1. Press ‘Fn’ button (27)
2. Rotate Left Selection Knob (31) to select Function (refer to chart below)
3. Rotate Right Selection Knob (32) to adjust parameter for the chosen Function
4. If desired, press ‘Fn’ (27) button to exit the Function setting
Figure 8
Functions Chart
Display
Drive Roller
Symbol
MIG MODE
PrG
Pre-Gas Time (sec)
PoG
Post-Gas Time (sec)
SFt
Soft Start Adjustment
bUb
Burnback Adjustment
SPt
Spot/Stitch Weld Time (sec)
GAP
Stitch Weld Gap/Interval Time (sec)
SPo
Spool Gun (On/Off)
TIG MODE
PoG
Post-Gas Time (sec)
SLo
Slope Up Time (sec)
STICK (MMA) MODE
Hot
Hot Start Adjustment
ArC
Arc Force Adjustment
Table 6
1, 4
2
3

WF-255MST
© Weldclass 2019 | E.&O.E. | Edition 2.2 17
4.3.1 Pre-Gas Time (MIG)
Pre-Gas (or Pre-Flow) setting is adjustable from 0 – 2 seconds. This controls the period shielding gas will
flow for when the torch is triggered before the arc starts. This purges the weld zone of atmospheric gas
which could contaminate the weld before the weld starts. In most common welding applications pre-gas is
not critical and can be set to 0.
4.3.2 Post-Gas Time (MIG)
Post-Gas (or Post-Flow) setting is adjustable from 0 – 5 seconds. This controls the period of time the
shielding gas continues to flow after the arc has stopped. This protects the weld area from contamination
while it is still hot enough to react with atmospheric gases, after the weld is finished/trigger is released. In
most common welding applications post-gas is not critical and can be set to 0.
4.3.3 Soft-Start Adjustment (MIG)
Soft-Start setting is adjustable on a scale 0 – 5. Sometimes known as ‘hot start’ or ‘slow feed’. When a weld
is started, the workpiece and the wire will be ‘cold’ compared to welding temperature. This can cause an
uneven and poor start to the weld using the voltage and wire feed speed selected as optimal once the arc
is established. This setting slows the wire speed down at the start of the weld which improves the weld
starting performance. If you find the wire ‘bumping’ the workpiece before the arc is fully established try
increasing Soft-Start setting.
4.3.4 Burnback Adjustment (MIG)
Burn-back setting is adjustable on a scale 0 – 5. Burnback adjustment controls the short period of time that
the wire feed will continue to run for after the main welding current stops. If the wire feed and current is
stopped at exactly the same time, the wire will still be hot and will ‘burn’ back and stick to the welding tip.
If this problem is happening, increasing the burnback adjustment will cause the wire feeder to run for longer
after the arc has stopped. If the burnback adjustment is excessive, after a weld has stopped, the operator
will be left with excess ‘stick out’ wire length from the torch tip that will require correcting before starting
the next weld.
4.3.5 Spot/Stitch Weld Time (MIG)
This setting will ONLY be accessible when Trigger Mode is set to ‘Spot Welding’.
Spot/Stitch Weld Time setting is adjustable from 0 – 5 seconds. This controls the length of time for the weld.
When the trigger is pulled the machine will weld for the set time and then stop. This is great for producing
very precise weld size or ensuring consistent weld size/length when spot welding, tacking or stitch welding.
4.3.6 Stitch Weld Gap/Interval Time (MIG)
This setting will ONLY be accessible when Trigger Mode is set to ‘Spot Welding’ (see 4.4 Trigger Mode
Selection).
Stitch Weld Gas/Interval Time setting is adjustable from 0 – 5 seconds. This controls the length of time
between welds. So when trigger is held on the machine will weld for the ‘Spot/Stitch’ time then it will stop
for the ‘Stitch Weld Gap/Interval’ time and repeat this until the trigger is released. This is great for producing
a very consistent stitch weld or multiple tack welds.
TIP! If you are only doing individual ‘Spot’ welds (single welds, no repeat) it is
suggested to set this Stitch Weld Gap time to maximum and release the trigger before
the weld repeats.

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18 © Weldclass 2019 | E.&O.E. | Edition 2.2
4.3.7 Spool Gun On/Off (MIG)
This setting turns activates or deactivates Spool Gun mode. See separate section for full explanation of
spool gun operation. The Spool Gun indicator light (42) will be illuminated when Spool Gun Mode is turned
on.
4.3.8 Post-Gas Time (TIG)
Pre-Gas (or Post-Flow) setting is adjustable from 0 – 5 seconds. This controls the period of time the shielding
gas continues to flow after the arc has stopped. This protects the weld area from contamination while it is
still hot enough to react with atmospheric gases, after the weld is finished/trigger is released.
4.3.9 Slope Down Time (TIG)
Slope-Down time setting is adjustable from 0 – 10 seconds. When the trigger is released, the welding
current will reduce gradually over the time selected down to 0. This allows the operator to complete the
weld without leaving a ‘crater’ at the end of the weld pool.
4.3.10 Hot Start Adjustment (Stick)
Hot Start setting is adjustable from 0 – 10. Hot start provides extra power when the weld starts to
counteract the high resistance of the electrode and workpiece as the arc is started. It makes igniting the
electrode easier and prevents it from sticking when cold.
4.3.11 Arc Force Adjustment (Stick)
Arc Force setting is adjustable from 0 – 10. Sometimes called ‘Dig’ or ‘Arc Control’. A Stick welder is designed
to produce constant output current (CC). This means with different types of electrode and arc length; the
welding voltage varies to keep the current constant. This can cause instability in some welding conditions
as Stick welding electrodes will have a minimum voltage they can operate with and still have a stable arc.
Arc Force control boosts the welding power if its senses the welding voltage is getting too low. The higher
the arc force adjustment, the higher the minimum voltage that the power source will allow. This effect will
also cause the welding current to increase. 0 is Arc Force off, 10 is maximum Arc Force. This is practically
useful for electrode types that have a higher operating voltage requirement or joint types that require a
short arc length such as out of position welds.
4.3.12 Optional VRD Function (Stick)
This function is disabled by default. To have this feature enabled please contact your WeldForce
distributor.
When enabled, VRD function reduces the welding machines’ open circuit voltage (OCV, or no-load
voltage) to a much safer level of approximately 13.5V. OCV is the voltage measured across the positive
and negative terminals when welding is not in progress.
The VRD function will turn on full welding power/voltage when the resistance between the electrode and
work piece is less than 200 Ohms (i.e. metal to metal contact).
When the VRD function is active, the VRD Active Indicator Light (51) is illuminated.
Figure 9

WF-255MST
© Weldclass 2019 | E.&O.E. | Edition 2.2 19
4.4 Trigger Mode Selection
1. Press ‘Trigger’ button (34) until the desired Trigger Mode Light is lit
Figure 10
4.4.1 2T (Standard Trigger)
2T is available for MIG & TIG processes.
2T stands for Two Touch or ‘Standard Trigger’ mode. In this mode the trigger is pulled and held on to
start welding, when the trigger is released, the welding stops.
4.4.2 4T (Latch Trigger)
4T is available for MIG & TIG processes.
4T stands for Four Touch or ‘Latching’ mode. The trigger is pulled once and released to welding and then
pulled and released again to stop the welding. This function is useful for longer welds as the trigger is
not required to be held on continuously and thus reduced operator fatigue.
4.4.3 SP (Spot/Stitch)
SP is only available for MIG process.
Spot Welding trigger mode is used for Spot, Tacking or Stitch welding. It allows you to set fixed times for
welding time and interval between welding and automatically repeats this process until the trigger is
released.
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20 © Weldclass 2019 | E.&O.E. | Edition 2.2
4.5 Inductance Control
Inductance setting is adjustable on scale of -5 to +5.
This setting changes the MIG waveform to simulate changing the inductance of the welding circuit.
Inductance controls the rate of the current rise and fall as the welding wire contacts the workpiece (known
as a short circuit).
More inductance increases the short circuit time and decreases the short circuit frequency rate. This causes
a wider and more penetrating arc, often with better edge wetting, useful for thicker weld joints.
Less inductance will create a narrow more focused arc. This effect can also be used to fine tune the arc to
produce less spatter. This is often effective on thin materials.
Wire speed, wire size and type, shielding gas will all change the effect that the inductance setting has on
the welding arc. Inductance change will have no practical effect on MIG spray transfer process (as opposed
to short circuit process).
To adjust inductance (only applied in MIG modes):
1. Press ‘Left Selection Knob’ (31) down. Inductance Setting Indicator Light (45) should illuminate.
2. Rotate ‘Left Selection Knob’ (31) to increase or decrease inductance setting. (Normal setting is
‘0’)
Figure 11
4.6 Test Gas
The ‘Test Gas’ button (30) works in both MIG and TIG process modes.
This simply opens gas flow (without feeding wire or giving arc voltage) to allow user to check that there is
sufficient gas flow coming out of the torch nozzle.
Figure 12
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