Weldclass FORCE 200MST MK2 User manual

OPERATING INSTRUCTIONS
To qualify for full extended warranty, you must register within 30 days
of purchase. See inside for details.
IMPORTANT!
FORCE 200MST MK2

2
Congratulations & thank you for choosing Weldclass
The Force range from Weldclass provides market leading value, features and
durability. Force 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 warranty your purchase you must register within 30 days of
purchase.
Please register your warranty now by going to:
www.weldclass.com.au/warrantyregistration
You will need;
a. A copy of your purchase invoice / receipt.
b. Your machine serial number which can be found on the back of the
machine.
Using Gasless MIG Wire?
Weldclass Platinum GL-11 is Australia’s No.1 Gasless wire.
Welders right across Australia & beyond rate Platinum GL-11
as the most user-friendly, smoothest running gasless wire
on the market.
Talk to your Weldclass distributor today, or go to:
www.Weldclass.com.au/GL-11 Platinum GL-11

3
FORCE 200MST
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Contents
Know Your Machine
Controls Explained
Power Supply
Operating Environment
Welding Settings
Accessories & Spare Parts:
Care & Maintenance
MIG Basic Welding Guide
MIG Welding Troubleshooting
MMA (Stick) Basic Welding Guide
MMA (Stick) Troubleshooting
TIG Basic Welding Guide
TIG Welding Troubleshooting
Knowledge & Resources
Safety
Warranty

4
Specications
Output Power MIG: 40-200A
ARC/TIG: 30-170A
Duty Cycle MIG: 160A @ 60%
ARC/TIG: 130A @ 60%
MIG Wire Size 0.6, 0.8, 0.9, 1.0mm
MMA Electrode Size 1.6 – 4.0mm
TIG Tungsten Size 1.6 – 2.4mm
Spool Size 200mm (4.5kg or 5kg) & 300mm (15kg)
Input Power 240V, 15A

5
FORCE 200MST
2
1
3
4
567
8
9
10
11
Know Your Machine
1. MIG Torch Euro Connection
2. Spool Gun Connection Socket
3. Spool Gun Switch
4. LCD Current Meter
- Displays output current (amps) in real time
5. 5. LCD Voltage Meter
- Displays output voltage in real time
6. Welding Output Mode Switch
- Sets power source in MIG, MMA or Lift TIG
mode
7. Overload Indicator Lamp
8. Welding Voltage Adjustment Knob
- Adjusts welding voltage in MIG mode
9. MIG Wire Feed Speed Adjustment Knob/
Arc (Stick / TIG) Current Adjustment Knob
10. MIG Inductance Control Knob
11. Cooling Fan Inlet (obscured)
12. Positive (+) Welding Power Output
Connection Socket
13. Negative (-) Welding Power Output
Connection Socket
14. MIG Torch Polarity Connection Lead
15. Shielding Gas Inlet Connection
16. 240V AC Mains Power Input Lead
17. Power Switch
18. Wire Spool Holder
19. Wire Drive Inlet Guide
20. Wire Feed Tension Adjustment
21. Wire Feed Tension Arm
22. Wire Drive Roller Retainer
23. Wire Drive Roller (obscured)
18
19
20
21
22
23
17
16
15
12
13
14
Controls Explained
These indicate voltage and current (amperage) settings, both statically (before welding) and dynamically
(during welding). These are very sensitive, so it is not abnormal to observer some small uctuations on
them when the machine is at rest.
LCD Current & Voltage Display Meters

6
Adequate ventilation is required to provide proper
cooling for the 200MST. Ensure that the machine is
placed on a stable level surface where clean cool air
can easily ow through the unit. The 200MST has
electrical components and control circuit boards
which may be damaged by excessive dust and dirt,
so a clean operating environment is essential.
The MIG voltage control is essentially the power in
the welding arc that sets the heat. The wire speed
feed simply controls the rate at which the welding
wire is fed into the weld pool.
For any voltage position setting, there will be a
specic corresponding ‘sweet spot’ in the wire
feeding speed that will give the smoothest and
most stable welding arc. The correct wire feeding
speed for a given voltage setting is aected by
welding wire type and size, shielding gas, welding
material and joint type.
It is recommended to set the welding voltage as
desired and then slowly adjust the wire speed until
the arc is smooth and stable. When reaching this
point, if the penetration/ heat input is too much/
not enough, adjust the voltage setting and repeat
the process. If the operator is not able to achieve a
smooth and stable arc with the desired heat input
for the weld, it is likely that a change in wire size
and/or shielding gas type is required (assuming all
other factors are correct).
A chart with recommended settings using this
machine for common welding applications is
located on the underside 0f the wire feeder cover
door and further on in this manual.
MIG Welding Mode
The current control knob sets the target welding
output current for either mode selected. The
voltage knob has no eect in MMA or TIG mode.
MIG Inductance Control - Inductance adjustment
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, useful for thicker weld joints. Less
inductance will create a narrow more focused arc.
This eect can also be used to ne tune the arc to
produce less splatter. Wire speed, wire size and
type, shielding gas will all change the eect that
the inductance setting has on the welding arc. As
a general rule, CO2 based shielding gas will weld
more smoothly with increased inductance, while
argon shielding gas will perform better with less
inductance. Inductance setting will have no eect
on MIG spray transfer process (as opposed to short
circuit process), MMA or TIG welding process.
MMA/ Lift TIG Welding Mode
MIG Voltage & MIG Wire Speed / MMA
& Lift TIG Current Control Knobs
Lights when duty cycle is exceeded and thermal
protection is activated. When thermal protection
is activated, welding output will be disabled until
machines cools suciently and overload indicator
lamp goes out. Also may activate with inverter
circuit failure issues.
Overload Indicator Lamp
LiftTIGisanarcignitionsystemforbasicTIGwelding
that removes the need to ‘scratch’ start or strike the
tungsten on the work piece to start the arc, which
can have a negative eect on the weld quality due
to tungsten contamination. Lift arc starting works
by gently touching the tungsten on the work piece
and then lifting it o. The control circuit will sense
when the tungsten is removed from the work piece
and send a pulse of electricity through the torch
that will cause the TIG arc to initiate.
Lift TIG Mode
Power Supply
The Force 200MST is designed to operate on a 15A
240V AC power supply.
Electrical Connection
This machine has a wide input power variation
tolerance (~170-265V), allowing it to operate o
generator power.
Generator size should be not less than 8kva. Avoid
using poor, low quality generators as these have
the greatest risk of power spikes etc. A suitable
quality generator should have a THD (total harmonic
distortion) rating of not more than 6%. Most
reputable generator supplier will be able to specify
the THD ratings on their product.
Generator Use
If an extension cord must be used, it should be
minimum cable core size 2.5mm2. Using extension
leads of over 20m is not recommended.
Extension Leads
Operating Environment

7
FORCE 200MST
1. Fitting Wire Spool
1.1 Open the wire feeder compartment door.
Remove the wire spool holder (18) by
threading it anticlockwise. If using 5kg/ D.200
spool, check that the 5kg spool spacer sleeve
is tted to the spool holder. Fit the wire
spool to spool holder, ensuring that the wire
exits the spool towards the wire feeder from
bottom the spool.
1.2 To replace the spool holder, set the spool
brake tension by adjusting the spool tension
adjustment hex screw in the middle of the
spool holder. Clockwise to increase spool
brake tension and anti- clockwise to decrease.
The spool brake tension should be set so
that the spool can rotate freely, but does not
continue to rotate once the wire feed stops.
This may need to be adjusted as the wire is
used up and the spool weight decreases.
WARNING!
Excessive spool brake tension will cause wire
feeding issues and aect welding performance
as well as premature failure/ wear of wire feed
components. Insucient brake tension will
cause the spool to ‘freewheel’ and the welding
wire will unravel from the spool (known as a
‘birds nest’)
1.3 Feed the wire from the spool through the wire
drive inlet guide (19) into the wire feeder.
2. Loading Wire Feeder
2.1 Release the wire feed tension arm (21) by
pivoting the wire feed tension adjustment
lever (20) towards you from the vertical
‘locked’ position.
2.2 Check the wire drive roller (23) groove
matches the selected MIG wire type and
size. The drive roller will have two dierent
sized grooves; the size of the groove in use
is stamped on the side of the drive roller.
For ux cored ‘soft’ wire, such as that used in
gasless MIG welding, the drive roller groove
has a serrated prole (known as knurled).
For solid core ‘hard’ MIG wire, the drive roller
groove used has a ‘v’ shaped prole. For
Aluminum solid core ‘soft’ MIG wire, the drive
roller required has a ‘u’ shaped groove. If
necessary, remove and change the drive roller
by unthreading the drive roller retainer (22).
Once the correct drive roller (23) is selected
and tted and the drive roller retainer (22)
is secured in place, manually feed the wire
through the wire drive inlet guide (19),
through the drive roller groove and into the
outlet wire guide tube. Ensuring that the wire
is correctly seated in the drive roller groove,
replace the wire feed tension arm (21) and
lock it into place by pivoting the wire feed
tension adjustment lever (20) back to the
vertical position.
2.3 Adjusting wire feed tension. This is
accomplished by winding the knob on the
tension adjustment lever (20). Clockwise will
increase tension, anticlockwise will decrease
drive tension. Ideal tension is as little as
possible, while maintaining a consistent wire
feed with no drive roller slippage.
2.4 Check all other causes of excess wire feeding
friction causing slippage rst, such as;
incorrect/worn drive roller, worn/damaged
torch consumables, blocked/damaged torch
wire guide liner, before increasing wire feed
tension. There is a number scale on the
tension adjustment lever (20) to indicate the
adjustment position. The higher the number
indicated, the higher the tension that is set.
WARNING!
Before changing the feed roller or wire spool,
ensure that the mains power is switched o.
WARNING!
The use of excessive feed tension will cause
rapid and premature wear of the drive roller, the
support bearing and the drive motor/gearbox.
2.5 Connect the MIG Torch Euro Connector to the
MIG torch Euro connection socket (1) on the
front of the machine. Secure by rmly hand
tightening the threaded collar on the MIG
Torch connector clockwise.
2.6 Check that the correct matching MIG wire,
drive roller (23) and MIG torch tip are tted.
2.7 Connect the machine to suitable mains power
using the mains input power lead (16). Switch
the mains power switch (17) to ‘on’ to power
up the machine. Set the welding mode switch
(6) to ‘MIG’ position.
Basic Operation - MIG Welding

8
3. Gasless Welding Operation
3.1 Connect the earth cable quick connector to
the positive welding power output socket
(12). Connect the earth clamp to the work
piece. Contact with the work piece must be
rm contact with clean, bare metal, with no
corrosion, paint or scale at the contact point.
3.2 Connect the MIG power connection lead (14)
to the negative welding power output socket
(13). Note if this connection is not made,
there will be no electrical connection to the
welding torch!
3.3 Set the welding voltage adjustment
knob (8), wire speed control knob (9) and
inductance control knob (10) to the desired
positions. You are now ready to weld!
4. Gas MIG Welding Operation
NOTE: Gas MIG welding will require a gas cylinder.
(Argon mix or CO2)
4.1 Connect the earth cable quick connector to
the negative welding power output socket
(13). Connect the earth clamp to the work
piece. Contact with the work piece must be
rm contact with clean, bare metal, with no
corrosion, paint or scale at the contact point.
4.2 Connect the MIG power connection lead (14)
to the positive welding power output socket
(12). Note if this connection is not made,
there will be no electrical connection to the
welding torch!
4.3 Connect the gas regulator to a gas cylinder
(not included with machine) and connect the
gas hose from the regulator to the gas inlet on
the rear of the machine (12). Ensure all hose
connections are tight. Open gas cylinder valve
and adjust regulator, ow should be between
10-25L/min depending on application. Re-
check regulator ow pressure with torch
triggered as static gas ow setting may drop
once gas is owing.
4.4 Set the welding voltage adjustment
knob (8), wire speed control knob (9) and
inductance control knob (10) to the desired
positions. You are now ready to weld!
MIG welding with aluminium provides a
unique challenge, due to the low column
strength and surface friction of the wire.
This causes the wire to deform more as it is
pushed through the feed mechanism and the
torch wire delivery liner, greatly increasing
friction. Because good MIG welding results
are dependent on a smooth wire feed, certain
changes must be made to the wire feed
system to minimise friction caused issues.
For a standard ‘push’ fed torch, a length of
no longer than 3m cable should be used, as
well as the torch feed liner must be changed
to a special Teon/PVC liner, rather than the
conventional steel liner. Also the correct
style drive roller must be used and specic
Aluminium rated torch contact tip (or a
standard tip in one size oversize, e.g 0.8mm
aluminium wire, use standard 1.0mm contact
tip). For this reason, it is quite common
for operators to have an extra MIG torch
specically set up for aluminium use, if the
machine is used for welding steel as well.
Anotheroption to overcome the friction issues
is using a spool gun, which will give better
results than a 3m push torch when welding
aluminium. The Weldforce 200MST is spool
gun capable, refer following section for use
with a spool gun on the Weldforce 200MST.
5. Spool Gun Operation
NOTE: Spool Gun is an optional extra for the
Weldforce 200MST.
The spool gun is a very useful addition to a
MIG welder. It can be used for all types of MIG
welding, but it has two primary advantages over
2.8 You are now ready to feed the wire through
the torch. With the wire feeder cover open,
pull the trigger of the MIG torch to check that
the wire is feeding smoothly through the
feeder and into the torch.
2.9 Set the wire feeding speed knob (9) to
maximum. With the torch tip removed from
the torch and the torch laid out as straight as
possible, depress MIG torch trigger until the
wire feeds out through the end of the MIG
torch. Replace the tip on the MIG torch and
trim o any excess wire.
MIG welding with Aluminium and other soft
wires.
For tips and tricks on setting up the 200MST for
MIG welding Aluminium, go to:
www.weldclass.com.au/alumig

9
FORCE 200MST
a conventional ‘push’ wire feeder. The main
advantage is that distance that the wire has to
travel from the spool to the welding tip is very short,
compared with a conventional torch. This greatly
reduces the wire feeding friction and improves
the wire feed speed smoothness and consistency,
thus the welding quality is greatly improved. This
is especially so with ‘soft’ wires such as Aluminium.
It is dicult to get Aluminium to feed smoothly in
welding machines equipped with standard design
wire feeders, even with special torch liners and
short torch lengths.
The second advantage is that the gun can allow
the use of the small D100 wire spools at a distance
from the power source (This distance is only
limited by the length of the spool gun lead). This
is advantageous for high cost wire, that is not used
commonly such as Stainless Steel or MIG brazing
wire. It saves the outlay cost for a much more
expensive, larger D200 spool.
5.1 Connect the earth cable quick connector to
the negative welding power output socket
(13). Connect the earth clamp to the work
piece. Contact with the work piece must be
rm contact with clean, bare metal, with no
corrosion, paint or scale at the contact point.
5.2 Connect the MIG power connection lead (14)
to the positive welding power output socket
(12). Note if this connection is not made,
there will be no electrical connection to the
welding torch!
5.3 Connect the spool gun Euro Connector to
the MIG torch Euro connection socket (1) on
the front of the machine. Secure by rmly
hand tightening the threaded collar on the
MIG Torch connector clockwise. Connect
the spool gun interface plug to the spool
gun connection socket (2). Set the spool gun
switch (3) to ‘on’ position.
5.4 Connect the gas regulator to a gas cylinder
(not included with machine) and connect the
gas hose from the regulator to the gas inlet on
the rear of the machine (15). Ensure all hose
connections are tight. Open gas cylinder valve
and adjust regulator, ow should be between
10-25 l/min depending on application. Re-
check regulator ow pressure with torch
triggered as static gas ow setting may drop
once gas is owing.
5.5 Set the welding voltage adjustment knob (8),
wire speed control knob (9) and inductance
control knob (10) to the desired positions.
You are now ready to weld!.
6. ARC/ MMA Welding Operation
6.1 Connect the earth cable quick connector to
the negative welding power output socket
(13) Connect the earth clamp to the work
piece. Contact with the work piece must be
rm contact with clean, bare metal, with no
corrosion, paint or scale at the contact point.
6.2 Insert an electrode into the electrode holder
and connect the electrode holder and work
lead to the positive welding power output
socket (12).
NOTE: This polarity connection conguration is valid
for most GP (General Purpose) MMA electrodes. There
are variances to this. If in doubt, check the electrode
specications or consult the electrode manufacturer.
6.3 Connect the machine to suitable mains power
using the mains input power lead (16). Switch
the mains power switch (17) to ‘on’ to power
up the machine. Set the welding mode switch
(6) to ‘ARC’.
6.4 Select the required output current using the
current control knob (9). You are now ready to
weld!
7. Lift TIG Operation
NOTE: Lift TIG operation requires an optional valve
control TIG torch, argon gas cylinder & regulator.
7.1 Connect the earth cable quick connector to
the positive welding power output socket
(12). Connect the earth clamp to the work
piece. Contact with the work piece must be
rm contact with clean, bare metal, with no
corrosion, paint or scale at the contact point.
7.2 Insert TIG torch power connection into the
negative welding power output socket
(13). Connect valve TIG torch gas line to the
regulator, ensuring all connections are tight.
7.3 Open gas cylinder valve and adjust regulator,
ow should be between 5-10 l/min depending
on application. Re-check regulator ow
pressure with torch valve open as static gas
ow setting may drop once gas is owing.
7.4 Connect the machine to suitable mains power

10
Accessories & Spare Parts:
The MIG Torch supplied with the 200MST is a BZL 25
(Binzel 25 style) model. To view parts for this torch, go to:
www.weldclass.com.au/BZL25parts
The compatible TIG torch for this machine is Weldclass
9/17 torch with valve. To view parts for this torch, go to:
www.weldclass.com.au/TigTorch917v
For machine parts, go to www.weldclass.com.au/machines or contact your Weldclass distributor
MIG Torch Spare Parts:
TIG Torch (Optional Extra):
Machine Spare Parts:
Welding Settings
using the mains input power lead (16). Switch
the mains power switch (17) to ‘on’ to power
up the machine. Set the welding mode switch
(6) to ‘Lift TIG’.
7.5 Select the required output current using the
current control knob (9). You are now ready to
weld!
7.6 Select the required output current using the
current control knob (9). You are now ready to
weld!
NOTE: The Weldforce 200MST is a DC (Direct Current)
output welder only, this means that it is unable to TIG
weld reactive metals such as Aluminium alloys and
Brass (which require AC output). DC TIG output is
suitable for steel, stainless steel and copper.
Use chart as guide only, as optimal settings will vary with weld joint type and operator technique.
Cells left blank not recommended combination for effective welding results.
*Inductance adjustment controls the rate of the welding current rise and fall as the welding wire contacts the workpiece (known as a
short circuit). In some respects, inductance is like adjusting the nozzle on a garden hose. Low inductance = wide, smooth, fluid arc, can
reduce spatter and improve weld appearance. High inductance = narrow, focused, crisp arc which can increase spatter levels, but in
some applications (especially thinner materials) allows a tighter ‘pin point’ weld bead. Wire speed, wire size and type, shielding gas will all
change the effect that the inductance setting has on the welding arc. Inductance setting will have no effect on MIG spray transfer process
(as opposed to short circuit process), MMA or TIG welding process.
MIG Welding Parameter Material Thickness / Settings
Welding
Material Wire Type Polarity Wire Size Drive Roller Type Torch Liner Shielding Gas
1.6mm 2.0mm 3.0mm 5.0mm 8.0mm 10.0mm
Settings Key: Voltage / Wirespeed
Mild
Steel
Gasless Torch (-)
Earth (+)
0.8mm
Knurled
Groove Blue
N/A
1/2 3/2 3.5/4 5/5 - -
0.9mm Red 2/2 2/2 3.5/4 5/4 5/5 6.5/6
Solid Steel Torch (+)
Earth (-)
0.6mm ‘V’
Groove
Blue
Mixed
(Argon +
CO2)
3/5.3 4/6 - - - -
0.8mm 2/5.3 4/6 5/10 - - -
0.9mm Red 3/3 3/5 5/8 6/8 6/9 7/9

11
FORCE 200MST
Care & Maintenance
MIG Basic
Welding Guide
The Weldforce 200MST does not require any
special maintenance, however the user should
take care of the machine as follows:
• Regularly clean the ventilation slots.
• Keep the casing clean.
• Check all cables before use.
• Check electrode holders, work lead/clamps and
welding torches before use.
• Replace worn electrode holders and earth
clamps, which do not provide a good connection.
• Replace worn torch consumable parts in a timely
manner.
• Replace worn wire drive components in a timely
manner.
• Use a soft cloth or brush to clean electrical
components. Do not use liquid cleaning
products, water or especially solvents.
• Do not use compressed air to clean electrical
components as this can force dirt and dust
further into components, causing electrical short
circuits.
• Check for damaged parts.
Two dierent welding processes are covered in
this section (GMAW and FCAW), with the intention
of providing the very basic concepts in MIG
welding, where a welding gun is hand held, and
the electrode (welding wire) is fed into a weld
puddle, and the arc is shielded by a gas (GMAW) or
ux cored wire (FCAW).
Keep your Welding Machine in Top
Condition
MIG Basic Welding Techniques
If damaged, before further use, the welder must be
carefully checked by a qualied person to
determine that it will operate properly. Check for
breakage of parts, mountings and other conditions
that may aect its operation.
Have your welder repaired by an expert. An
authorised service centre should properly repair a
damaged part.
This appliance is manufactured in accordance with
relevant safety standards. Only experts must carry
out repairing of electrical appliances, otherwise
considerable danger for the user may result.
Use only genuine replacement parts. Do not use
modied or non-genuine parts.
When not in use the welder should be stored in the
dry and frost-free environment.
WARNING!
Before performing cleaning/maintenance,
replacing cables / connections , make sure the
welding machine is switched o and
disconnected from the power supply.
Storing the Welder

12
Gas Metal Arc Welding (GMAW)
This process, also known as MIG welding, CO2
welding, Micro Wire Welding, short arc welding,
dip transfer welding, wire welding etc., is an electric
arc welding process which fuses together the parts
to be welded by heating them with an arc between
a solid continuous, consumable electrode and the
work.
Shielding is obtained from an externally supplied
welding grade shielding gas. The process is
normally applied semi automatically; however the
process may be operated automatically and can
be machine operated. The process can be used
to weld thin and fairly thick steels, and some non-
ferrous metals in all positions.
Flux Cored Arc Welding (FCAW)
This is an electric arc welding process which
fuses together the parts to be welded by heating
them with an arc between a continuous ux lled
electrode wire and the work. Shielding is obtained
through decomposition of the ux within the
tubular wire. Additional shielding may or may
not be obtained from an externally supplied gas
or gas mixture. The process is normally applied
semi automatically; however the process may be
applied automatically or by machine.
It is commonly used to weld large diameter
electrodes in the at and horizontal position and
small electrode diameters in all positions. The
process is used to a lesser degree for welding
stainless steel and for overlay work.
The angle of MIG torch to the weld has an eect on
the width of the weld.
The welding gun should be held at an angle to the
weld joint. (See Secondary Adjustment Variables
below).
Hold the gun so that the welding seam is viewed at
all times. Always wear the welding helmet with
proper lter lenses and use the proper safety
equipment.
CAUTION!!
Do not pull the welding gun back when the arc is
established. This will create excessive wire
extension (stick-out) and make a very poor
weld.
The electrode wire is not energized until the gun
trigger switch is depressed. The wire may therefore
be placed on the seam or joint prior to lowering
the helmet.
GMAW Process
(Fig 1-1) Shielding Gas
Molten Weld Metal
Nozzle
Electrode Arc
Base Metal
Weld Metal
FCAW Process
(Fig 1-2) Nozzle
(Optional)
Flux Cored
Electrode
Arc
Base
Metal
Weld Metal
Slag
Molten
Slag
Molten Metal
Shielding Gas
(Optional)
Push Vertical Drag Pull
Position of MIG Torch
(Fig 1-3)
(Fig 1-4) 5oto 15o
Longitudinal Angle
Direction of Travel
90oTransverse
Angle
(Fig 1-5)
5oto 15o
Longitudinal Angle 30oto 60o
Transverse
Angle
Direction
of Travel

13
FORCE 200MST
Distance from the MIG Torch Nozzle
to the Work Piece
The electrode wire stick out from the MIG Torch
nozzle should be between 10mm to 20mm. This
distance may vary depending on the type of joint
that is being welded.
Travel Speed
The speed at which the molten pool travels
inuences the width of the weld and penetration
of the welding run.
MIG Welding (GMAW) Variables
Most of the welding done by all processes is on
carbon steel. The items below describe the welding
variables in short-arc welding of 24gauge (0.024”,
0.6mm) to ¼” (6.4mm) mild sheet or plate. The
applied techniques and end results in the GMAW
process are controlled by these variables.
Preselected Variables
Preselected variables depend upon the type
of material being welded, the thickness of the
material, the welding position, the deposition rate
and the mechanical properties.
These variables are:
• Type of electrode wire
• Size of electrode wire
• Type of gas
• Gas ow rate
Primary Adjustable Variables
These control the process after preselected
variables have been found. They control the
penetration, bead width, bead height, arc stability,
deposition rate and weld soundness.
These variables are:
• Arc Voltage
• Welding current (wire feed speed)
• Travel speed
Secondary Adjustable Variables
These variables cause changes in primary
adjustable variables which in turn cause the
desired change in the bead formation. They are:
1. Stick-Out (distance between the end of the
contact tube (tip) and the end of the electrode
wire). Maintain at about 10mm stick-out
2. Wire Feed Speed. Increase in wire feed speed
increases weld current. Decrease in wire feed
speed decreases weld current.
3. Nozzle Angle. This refers to the position of the
welding gun in relation to the joint. The transverse
angle is usually one half the included angle
between plates forming the joint. The longitudinal
angle is the angle between the centre line of the
welding gun and a line perpendicular to the axis
of the weld. The longitudinal angle is generally
called the Nozzle Angle and can be either trailing
(pulling) or leading (pushing).
Vertical Fillet Welds (Fig 1-6)
10o
Longitudinal Angle
Direction of Travel
10oto 20o
Longitudinal Angle
30oto 60o
Transverse
Angle
30oto 60o
Transverse
Angle
Direction of Travel
(Fig 1-7)
5oto15o
Longitudinal
Angle
30oto 60o
Transverse
Angle
Electrode Stick-Out
(Fig 1-8)
Gas Nozzle
Tip to
Work Distance
Contact Tip (Tube)
Electrode Wire
Actual
Stick-Out
Transverse & Longitudinal
Nozzle Axes (Fig 1-9)
Longitudinal Angle
Transverse Angle
Axis of Weld

14
Whether the operator is left handed or right
handed has to be considered to realize the eects
of each angle in relation to the direction of travel.
Establishing the Arc and Making
Weld Beads
Before attempting to weld on a nished piece of
work, it is recommended that practice welds be
made on a sample metal of the same material as
that of the nished piece.
The easiest welding procedure for the beginner to
experiment with MIG welding is the at position.
The equipment is capable of at, vertical and
overhead positions.
For practicing MIG welding, secure some pieces of
16 or 18 gauge (1.5mm or 2.0mm) mild steel plate
(150 x 150mm). Use (0.8mm) ux cored gasless
wire or a solid wire with shielding gas.
Setting of the Power Source
Power source and Current (Wire Speed) setting
requires some practice by the operator, as the
welding plant has two control settings that have
to balance. These are the Current (Wire Speed)
control and the welding Voltage Control.
The welding current is determined by the Current
(Wire Speed) control, the current will increase with
increased Current (Wire Speed), resulting in a
shorter arc. Less Current (Wire Speed) will reduce
the current and lengthen the arc. Increasing the
welding voltage hardly alters the current level,
but lengthens the arc. By decreasing the voltage,
a shorter arc is obtained with a little change in
current level.
When changing to a dierent electrode wire
diameter, dierent control settings are required.
A thinner electrode wire needs more Current
Nozzle Angle, Right Handed Operator
(Fig 1-10)
Direction of Travel
Leading or “Pushing”
Angle (Forward Pointing)
Trailing or “Pulling”
Angle (Backward Pointing)
90o
(Wire Speed) to achieve the same current level.
A satisfactory weld cannot be obtained if the
Current (Wire Speed) and Voltage settings are not
adjusted to suit the electrode wire diameter and
the dimensions of the work piece.
If the Current (Wire Speed) is too high for the
welding voltage, “stubbing” will occur as the wire
dips into the molten pool and does not melt.
Welding in these conditions normally produces a
poor weld due to lack of fusion. If, however, the
welding voltage is too high, large drops will form
on the end of the wire, causing spatter. The correct
setting of voltage and Current (Wire Speed) can be
seen in the shape of the weld deposit and heard by
a smooth regular arc sound.
Electrode Wire Size Selection
The choice of Electrode wire size and shielding gas
used depends on the following:
• Thickness of the metal to be welded
• Type of joint
• Capacity of the wire feed unit and power
source
• The amount of penetration required
• The deposition rate required
• The bead prole desired
• The position of welding
• Cost of the wire

15
FORCE 200MST
MIG Welding
Troubleshooting
The general approach to x Gas Metal Arc Welding
(GMAW) problems is to start at the wire spool then
work through to the MIG torch. There are two main
areas where problems occur with GMAW, Porosity
and Inconsistent wire feed.
When there is a gas problem the result is usually
porosity within the weld metal. Porosity always
stems from some contaminant within the molten
weld pool which is in the process of escaping
during solidication of the molten metal.
Contaminants range from no gas around the
welding arc to dirt on the workpiece surface.
Porosity can be reduced by checking the following
points.
WARNING!
Wire Jam Troubleshooting
• If wire jam occurs when the torch becomes hot, this is often because the heat causes the wire and the tip
to expand (which shrinks the hole in the tip). Using a slightly oversize tip can prevent this – eg: for 0.9mm
wire, use a 1.0mm tip.
• Do NOT over-tighten the drive roll tension – this will accelerate wear of the drive system, may distort the
wire & will cause further wire feed problems.
• Refer to page 15-16 for more troubleshooting tips.

16
Other weld problems can be reduced by checking the following points.
Wire feeding problems can be reduced by checking the following points.
(Replace liner)
(Replace liner)

17
FORCE 200MST
MMA (Stick) Basic
Welding Guide
Flat Position,
Down Hand Butt Weld
(Fig 1-11)
Flat Position,
Gravity Fillet Weld
(Fig 1-12)
Horizontal Position,
Butt Weld
(Fig 1-13)
Horizontal-Vertical
(HV) Position
(Fig 1-14)
Vertical Position,
Butt Weld
(Fig 1-15)
Vertical Position,
Fillet Weld
(Fig 1-16)
Overhead Position,
Butt Weld
(Fig 1-17)
Overhead Position,
Fillet Weld
(Fig 1-18)
Size of Electrodes
The electrode size is determined by the thickness
of metals being joined and can also be governed
by the type of welding machine available. Small
welding machines will only provide current
(amperage) to run smaller sized electrodes.
For thin sections, it is necessary to use smaller
electrodes otherwise the arc may burn holes
through the job. A little practice will soon establish
the most suitable electrode for a given application.
Storage of Electrodes
Always store electrodes in a dry place and in their
original containers.
Electrode Polarity
Electrodesaregenerallyconnectedtotheelectrode
holder with the electrode holder connected
positive polarity.
The work lead is connected to the negative polarity
and is connected to the work piece. If in doubt
consult the electrode data sheet.
Eects of MMA(Stick) Welding
on Various Materials
High Tensile and Alloy Steels
The two most prominent eects of welding these
steels are the formation of a hardened zone in
the weld area, and, if suitable precautions are not
taken, the occurrence in this zone of under-bead
cracks. Hardened zone and underbead cracks in
the weld area may be reduced by using the correct
electrodes, preheating, using higher current
settings, using larger electrodes sizes, short runs
for larger electrode deposits or tempering in a
furnace.
Manganese Steels
The eect on manganese steel of slow cooling from
high temperatures causes embrittlement. For this
reason it is absolutely essential to keep manganese
steelcool during welding by quenching after each
weld or skip welding to distribute the heat.
Cast Iron
Most types of cast iron, except white iron, are
weldable. White iron, because of its extreme

18
Joint Preparations
In many cases, it will be possible to weld steel
sections without any special preparation. For
heavier sections and for repair work on castings,
etc., it will be necessary to cut or grind an angle
brittleness, generally cracks when attempts are
made to weld it. Trouble may also be experienced
when welding white-heart malleable, due to the
porosity caused by gas held in this type of iron.
Copper and Alloys
The most important factor is the high rate of heat
conductivity of copper, making pre-heating of
heavy sections necessary to give proper fusion of
weld and base metal.
Types of Electrodes
Arc Welding electrodes are classied into a number
of groups depending on their applications.
There are a great number of electrodes used for
specialised industrial purposes which are not
of particular interest for everyday general work.
These include some low hydrogen types for high
tensile steel, cellulose types for welding large
diameter pipes, etc. The range of electrodes dealt
with in this publication will cover the vast majority
of applications likely to be encountered; are all
easy to use.
between the pieces being joined to ensure proper
penetration of the weld metal and to produce
sound joints. In general, surfaces being welded
should be clean and free of rust, scale, dirt, grease,
etc. Slag should be removed from oxy-cut surfaces.
Typical joint designs are shown in Figure 1-19.
MILD STEEL :
E6011 - This electrode is used for all-position welding or
for welding on rusty, dirty, less-than- new metal. It has
repair or maintenance work.
E6013 - This all-position electrode is used for welding
clean, new sheet metal. Its soft arc has minimal spatter,
moderate penetration and an easy-to-clean slag.
E7014 - All positional, ease t o use electrode f or u se on
thicker steel than E6013. Especially suitable for sheet metal
E7018 - A low-hydrogen, all-position electrode used when
quality is an issue or for hard-to-weld metals. It has the ca-
pability of producing more uniform weld metal, which has
better impact properties at low temperatures.
CAST IRON:
ENI-CL - Suitable for joining all cast irons except white
cast iron.
STAINLESS STEEL:
E318L-16 - High corrosion resistances. Ideal for dairy
work etc.
Open Square Butt Joint
(Fig 1-19a)
Gap varies from1.6mm (1/16”)
to 4.8mm (3/16”) depending on plate thickness
Single Vee Butt Joint
(Fig 1-19b) Not less than 45˚
Single Vee Butt Joint
(Fig 1-19c) Not less than 70˚
1.6mm (1/16”) max.
1.6mm (1/16”)
Double Vee Butt Joint
(Fig 1-19d) Not less than 70˚
1.6mm (1/16”) max.
1.6mm (1/16”)
Lap Joint (Fig 1-19e)
Fillet Joint (Fig 1-19f)

19
FORCE 200MST
MMA Welding Techniques
- A Word for Beginners
For those who have not yet done any welding, the
simplest way to commence is to run beads on a
piece of scrap plate. Use mild steel plate about
6.0mm thick and a 3.2mm electrode.
Clean any paint, loose scale or grease o the plate
and set it rmly on the work bench so that welding
can be carried out in the down hand position. Make
sure that the Work Lead/Clamp is making good
electrical contact with the work, either directly or
through the work table. For light gauge material,
always clamp the work lead directly to the job,
otherwise a poor circuit will probably result.
The Welder
Place yourself in a comfortable position before
beginning to weld. Get a seat of suitable height
and do as much work as possible sitting down.
Don’t hold your body tense. A taut attitude of
mind and a tensed body will soon make you feel
tired. Relax and you will nd that the job becomes
much easier. You can add much to your peace of
mind by wearing a leather apron and gauntlets.
You won’t be worrying then about being burnt or
sparks setting alight to your clothes.
Place the work so that the direction of welding
is across, rather than to or from, your body. The
electrode holder lead should be clear of any
obstruction so that you can move your arm freely
along as the electrode burns down. If the lead is
slung over your shoulder, it allows greater freedom
of movement and takes a lot of weight o your
hand. Be sure the insulation on your cable and
electrode holder is not faulty; otherwise you are
risking an electric shock.
Striking the Arc
Practice this on a piece of scrap plate before going
on to more exacting work. You may at rst
experience diculty due to the tip of the electrode
“sticking” to the work piece. This is caused by
making too heavy a contact with the work and
failing to withdraw the electrode quickly enough.
A low amperage will accentuate it. This freezing-
on of the tip may be overcome by scratching the
electrode along the plate surface in the same way
as a match is struck. As soon as the arc is established,
maintain a 1.6mm to 3.2mm gap between the
burning electrode end and the parent metal. Draw
Corner Weld
(Fig 1-19g)
Tee Joints
(Fig 1-19h)
Edge Joint
(Fig 1-19i)
Plug Welds
(Fig 1-19j)

20
Arc Length
The securing of an arc length necessary to produce
a neat weld soon becomes almost automatic. You
will nd that a long arc produces more heat.
A very long arc produces a crackling or spluttering
noise and the weld metal comes across in large,
irregular blobs. The weld bead is attened and
spatter increases. A short arc is essential if a high
quality weld is to be obtained although if it is too
short there is the danger of it being blanketed by
slag and the electrode tip being solidied in. If this
should happen, give the electrode a quick twist
back over the weld to detach it. Contact or “touch-
weld” electrodes such as E7014 Stick electrodes
do not stick in this way, and make welding much
easier.
Rate of Travel
After the arc is struck, your next concern is to
maintain it, and this requires moving the electrode
tip towards the molten pool at the same rate as it is
melting away. At the same time, the electrode has
to move along the plate to form a bead.
The electrode is directed at the weld pool at about
20º from the vertical. The rate of travel has to be
adjusted so that a well-formed bead is produced.
If the travel is too fast, the bead will be narrow and
strung out and may even be broken up into
individual globules. If the travel is too slow, the
weld metal piles up and the bead will be too large.
Making Welded Joints
Having attained some skill in the handling of an
electrode, you will be ready to go on to make up
welded joints.
A. Butt Welds
Set up two plates with their edges parallel, as
shown in Figure 1-21, allowing 1.6mm to 2.4mm
gap between them and tack weld at both ends. This
is to prevent contraction stresses from the cooling
weld metal pulling the plates out of alignment.
Plates thicker than 6.0mm should have their mating
edges bevelled to form a 70º to 90º included angle.
This allows full penetration of the weld metal to
the root. Using a 3.2mm E7014 Stick electrode
at 100 amps, deposit a run of weld metal on the
bottom of the joint.
Do not weave the electrode, but maintain a steady
rate of travel along the joint sucient to produce a
well-formed bead. At rst you may notice a
tendency for undercut to form, but keeping the arc
length short, the angle of the electrode at about
20º from vertical, and the rate of travel not too fast,
will help eliminate this.
The electrode needs to be moved along fast
enough to prevent the slag pool from getting
ahead of the arc. To complete the joint in thin
plate, turn the job over, clean the slag out of the
back and deposit a similar weld.
the electrode slowly along as it melts down.
Another diculty you may meet is the tendency,
after the arc is struck, to withdraw the electrode so
far that the arc is broken again. A little practice will
soon remedy both of these faults.
20o
1.6mm (1/16”)
Striking an Arc
(Fig 1-20)
Tack Weld
Butt Weld
(Fig 1-21)
Electrode
20o- 30o
Tack Weld
Weld Build Up Sequence
(Fig 1-22)