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2. metals

WELDING
MACHINES
Brandon
AdendorffMachinery
Mart(PTY) Ltd
152 Rosettenville road
Springfield
Johannesburg
R.S.A
South Africa
(011) 683 8360
(011) 683 8114
9/5/2010
What is a welding machine? How does a welding
machine work? What different types of welding
machines do you get? What is duty cycle? What is the
difference between arc, mig, tig, gas and spot welding?
What type of welding machine should one use? These
are just a few types of questions you will be faced with
regarding welding and after this chapter you should have
learnt the basics and the technical specifications of our
product range we retail at Adendorff Machinery Mart.
WELDING
MACHINES
What is a welding machine?
Welding machine. This is the term used to describe the machine which converts 220-380 volt AC
(alternating current) electricity to welding voltage, typically 40-70 volts AC, but also a range of DC
(direct current) voltages. It generally consists of a large, heavy transformer, a voltage regulator
circuit, an internal cooling fan or oil cooled system, and an amperage range selector. The term
welder applies to a person doing the welding. A welding machine requires a welder to operate it.
What is duty cycle?
Duty cycle is a welding equipment specification which defines the number of minutes, within a 10
minute period, during which a given welder can safely produce a particular welding current.
For example: a 200 amp welder with a 60 % duty cycle must be “rested” for at least 4 minutes after 6
minutes of continuous welding. The less amperage draws one uses from the welder, the higher the
duty cycle. Failure to carefully observe duty cycle limitations can easily over stress a welder’s power
generation system contributing to premature welder failure. Many welders do not have internal
protection systems that prevent this sort of over stress, therefore leaving the task to the owner or
operator.
What is arc welding?
Arc welding, also known as manual metal arc welding (MMA) or stick welding, uses a welding power
supply to create an electric arc between an electrode and the base material to melt the metals at
the welding point. They can use either direct (DC) or alternating (AC) current, consumable or nonconsumable electrodes. The electrode rod is made of a material that is compatible with the base
material being welded and is covered with a flux that protects the weld area from oxidation and
contamination by producing CO2 gas during the welding process. There are generally two types of
arc welders available, namely: AC (alternating current), such as an air cooled or oil cooled AC welder
or a DC (direct current), such as an inverter welder which uses an air cooling system for cooling.
Furthermore, arc welding process is generally limited to welding ferrous metals, though specialty
electrodes have made possible the welding of cast iron, nickel, aluminium, copper and other metals,
which are non ferrous metals. The versatility of the method makes it popular in a number of
applications including repair work and construction.
What is mig welding?
Gas metal arc welding (GMAW), sometimes referred to by its subtypes metal inert gas (MIG) welding
or metal active gas (MAG) welding, is a semi-automatic or automatic arc welding process in which a
continuous and consumable wire electrode and a shielding gas are fed through a welding gun(mig
torch).Also known as a CO2 welder. A constant voltage, direct current power source is most
commonly used with GMAW, but constant current systems, as well as alternating current, can be
used. The most common gases used are carbon dioxide for general purpose welding. It is the
cheapest of the welding gases, and creates a good weld. On a MIG welder you can adjust the
voltage, amperage and speed at which the wire is fed through the welder. The tensioner on the
welding wire is variable as well. They will also have a valve to control the flow of gas, which will be
the flow meter on the gas bottle
.
It is also possible to use a MIG welder without shielding gas. This process is called flux core arc
welding (FCAW). Most welders have the option of switching the polarity of the welding arc for use
with flux cored wire. In this welding process the welding wire has a hollow core that is filled with
flux. Flux cored arc welding can be done outside, because there is no need to worry about the
shielding gas being blown away. The flux core wire has a hotter arc and therefore can be used to
weld thicker pieces of metal. The disadvantages of FCAW are that you have to remove and clean the
slag from the weld, similar to welding with a standard stick welder. Because of its hotter arc force, it
cannot generally be used to weld thinner sheet metal and other light metals. MIG welders can be
used to weld aluminium, tin, copper, zinc and brass and steel. There are dozens of different
compositions of MIG welding wire to choose from. When welding the non ferrous metals, it is
advisable to change the Teflon liner, which is situated inside the MIG torch. The reason for this is
that generally the welding wire used for this process is a lot softer, and tends to kink easily.
MIG welders are the ideal choice if you only want to buy one welder, and still be able to weld on a
variety of metals. If you want to start welding, a MIG welder would probably be your best choice for
a welder that is very versatile and easy to learn on
What is tig welding?
Tungsten inert gas (TIG) welding is basically a welding process that works with the help of a tungsten
electrode. TIG stands for Tungsten Inert Gas and is technically called Gas Tungsten Arc Welding or
GTAW. The process uses a non-consumable tungsten electrode that delivers the current to the
welding arc. A shielding gas, such as Argon gas is used to protect the weld area from atmospheric
contamination. A filler metal is normally used. TIG welding is most commonly used to weld thin
sections of stainless steel and non- ferrous metals such as aluminium, magnesium, and copper
alloys. The process grants the operator greater control over the weld than when comparing it to
procedures such as Mig and Gas welding. One can get two types of TIG welders, such as a DC (direct
current), which are generally used for the welding of ferrous types of metals and the other being the
AC/DC (alternating current, direct current) which can weld most types of metals, such as non-ferrous
and ferrous.
What is spot welding?
Spot welding is a process in which contacting metal surfaces are joined by the heat obtained from
resistance to electric current flow. Work pieces are held together under pressure exerted by
electrodes. The process uses two shaped copper alloy electrodes to concentrate welding current
into a small “spot” and to simultaneously clamp the sheets together. Forcing a large current through
the spot will melt the metal and form the weld. A spot welding machine normally consists of tool
and electrodes, which are mechanisms for making and holding contact at the weld. Tool holders
have two functions: to hold the electrode firmly in place and to support water hoses that provide
cooling of the electrodes. The attractive feature of spot welding is a lot of energy can be delivered to
the spot in very short time. That permits welding to occur without excessive heating to the rest of
the sheet. Spot welding is typically used for the welding of thin sheets of metal together, within a
range from 0.5 to 3 mm (0.020 to 0.12 inch). The amount of heat (energy) delivered to the spot weld
is determined by the resistance between the electrodes and the amplitude and duration of the
current. The amount of energy is chosen to match the sheet’s material properties, its thickness, and
type of electrodes. Applying too little energy won’t melt the metal or will make a poor weld.
Applying too much energy will melt too much metal, eject molten material, and make a hole rather
than a weld. Spot welding can be easily identified on many sheet metal goods, such as metal
buckets. Aluminium alloys can be spot welded, but their much higher thermal conductivity and
electrical conductivity requires higher welding currents. Therefore a larger spot welder is required
for the spot welding process of aluminium alloys. Weld times range from 0.01 seconds to 0.63
seconds, depending on the thickness of the metal, the electrode force and the diameter of the
electrodes themselves.
Now that you have basic understanding of the different types of
welding applications available and their differences, let us take a look
at the range of welder’s we retail at Adendorff Machinery Mart, with
their technical specifications on each unit.
Arc welder’s (air cooled) with AC
transformer (mma)
EWELAS/180
Description: 180 amp air cooled arc welder. AC transformer (BX6-180).MMA.
Code: EWELAS/180
Specifications:
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Input voltage / phase: 220 volt / 1
Current input: 27 amps – 43 amps
Current output: 70 amps – 180 amps
Voltage output: 20.8 volt – 25.2 volt
Welding rods recommended: 1 mm – 3 mm
Duty cycle: 20 % @ 180 amps
Dimensions (lhw) : 365mm x 300mm x 170mm
Weight:
Typical uses for this welding machine:
Looking for a simple to use arc welder for all those jobs around the home and in the garage? Well,
here is one which is ideal for the DIY enthusiast. Ideal for most arc welding applications. This welder
is exceptionally low priced which makes it invaluable around the house and workshop for general
repairs and light fabrication. Simple to operate. The welder does not come with welding cables, and
is recommended to purchase welding cables with a length of 2.5 mt, both electrode holder and
earth cable. (Please see ‘Guide for welding cable`, for the correct size of welding cables)
.
EWELAS/250
Description: 250 amp air cooled arc welder.AC transformer. MMA.
Code: EWELAS/250
Specifications:
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Input voltage / phase: 220 volt / 1
Current input: 30 – 60 amps
Current output: 82 – 250 amps
Voltage output: 21.2 – 30 volts
Welding rods recommended: 1 mm – 4 mm
Duty cycle: 20 % @ 250 amps
Dimensions (lhw) : 370mm x 310mm x 170mm
Weight:
Typical uses for this welding machine:
A step up from the basic home user model. Mainly used for the more professional and frequent
welder at home. Can also be used for light steel fabrication. This unit is ideal for doing those thicker
welds on metals, because of its high range of amperage for a single phase welder (250 amps). The
welder does not come with welding cables, and is recommended to purchase welding cables with a
length of 2.5 mt, both electrode holder and earth cable. (Please see ‘Guide for welding cable`, for
the correct size of welding cables)
Arc welder’s (oil cooled) with AC
transformer (mma)
EWELDO/130
Description: MAC-AFRIC 130 AMP oil bath arc (mma) welder.
Code: EWELDO/130
Specifications:
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Input voltage / phase: 220 volt / 1
Current input:
Current output: 90amps – 130amps
Voltage output:
Welding rods recommended: 1 mm – 3 mm
Duty cycle: 20 % @ 130 amps
Dimensions (lhw) : 260mm x 300mm x 230mm
Weight:
Typical uses for this welding machine:
This small, yet compact and easy to use welder is ideal for the DIY person. Mainly used for light steel
fabrication and general repair work around the home and workshop. This welder is equipped with an
easy to remove lid, which makes it easy for the refilling of the oil, and any general maintenance
needed to be done on the unit. Heavy duty robust design with a genuine copper transformer makes
this welder an invaluable welding machine for around the home and workshop. Make sure the oil
level is always at the correct level. (Use only welding transformer oil). The welder does not come
with welding cables, and is recommended to purchase welding cables with a length of 2.5 mt, both
electrode holder and earth cable. (Please see ‘Guide for welding cable`, for the correct size of
welding cables).
EWELDO/160
Description: MAC-AFRIC 160 amp oil cooled (mma) arc welder.
Code: EWELDO/160
Specifications:
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Input voltage / phase: 220 volt / 1
Current input: 19/20 amps
Current output: 90amps -160amps
Voltage output:
Welding rods recommended: 1 mm – 3 mm
Duty cycle: 20 % @ 160 amps
Dimensions (lhw) : 260mm x 330mm x 230mm
Weight:
Typical uses for this welding machine:
This small, yet compact and easy to use welder is ideal for the DIY person. Mainly used for light steel
fabrication and general repair work around the home and workshop. This welder is equipped with an
easy to remove lid, which makes it easy for the refilling of the oil, and any general maintenance
needed to be done on the unit. Heavy duty robust design with a genuine copper transformer makes
this welder an invaluable welding machine for around the home and workshop. Make sure the oil
level is always at the correct level. (Use only welding transformer oil). The welder does not come
with welding cables, and is recommended to purchase welding cables with a length of 2.5 mt, both
electrode holder and earth cable. (Please see ‘Guide for welding cable`, for the correct size of
welding cables).
EWELDO/190
Description: MAC-AFRIC 190 amp oil cooled arc welder.
Code: EWELDO/190
Specifications:
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Input voltage / phase: 220 volt / 1
Current input:
Current output:
Voltage output:
Welding rods recommended: 1 mm – 3 mm
Duty cycle: 20 % @ 190 amps
Dimensions (lhw) :
Weight:
Typical uses for this welding machine:
This welder is equipped with a robust handle and two wheels for easy manoeuvring of the unit and is
an easy to use welder. Ideal for the handyman, home craftsman and automotive enthusiast which
makes this welder a great choice for home DIY.Mainly used for light steel fabrication and general
repair work around the home and workshop. This welder is equipped with an easy to remove lid,
which makes it easy for the refilling of the oil, and any general maintenance needed to be done on
the unit. Heavy duty robust design with a genuine copper transformer makes this welder an
invaluable welding machine for around the home and workshop. Make sure the oil level is always at
the correct level. (Use only welding transformer oil). The welder does not come with welding cables,
and is recommended to purchase welding cables with a length of 2.5 mt, both electrode holder and
earth cable. (Please see ‘Guide for welding cable`, for the correct size of welding cables).
EWELDO/253
Description: MAC-AFRIC 250 AMP oil bath arc (mma) welder.
Code: EWELDO/253
Specifications:
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Input voltage / phase: 220 volt / 1
Current input:
Current output:
Voltage output:
Welding rods recommended: 1 mm – 4 mm
Duty cycle: 20 % @ 250 amps
Dimensions (lhw) :
Weight:
Typical uses for this welding machine:
This welder is equipped with a robust handle and two wheels for easy manoeuvring of the unit and is
an easy to use welder. Ideal for the DIY person and more frequent welder. Mainly used for light steel
fabrication and general repair work around the home and workshop. This welder is equipped with an
easy to remove lid, which makes it easy for the refilling of the oil, and any general maintenance
needed to be done on the unit. Heavy duty robust design with a genuine copper transformer makes
this welder an invaluable welding machine for around the home and workshop. Make sure the oil
level is always at the correct level. (Use only welding transformer oil). The welder does not come
with welding cables, and is recommended to purchase welding cables with a length of 2.5 mt, both
electrode holder and earth cable. (Please see ‘Guide for welding cable`, for the correct size of
welding cables).
EWELDO/252
Description: EEZI-STRIKE 220 AMP copper transformer oil bath arc welder
Code: EWELDO/252
Specifications:
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Input voltage / phase: 220 volt / 1
Current input: 29 AMPS
Current output: 50 – 220 amps
Voltage output: 60 volt (max)
Welding rods recommended: 1 mm – 4 mm
Duty cycle: 20 % @ 150 amps
Dimensions (lhw) : 300mm x 340mm x 300mm
Weight: 48 (kg)
Typical uses for this welding machine:
A general purpose arc welder that’s an ideal choice for numerous users. This welder has a heavy
duty robust design, which makes it a lifetime investment. Ideal for the more frequent welder. Ideal
for doing most general welding applications such as repair work and light steel fabrication. This
welder has a genuine cooper transformer, which makes it invaluable around the home and
workshop. Easy to use welder, with easy to turn and lock clamps for the welding cable lugs.
EWELDO/141
Description: STRIKE 140 AMP OIL COOLED ARC WELDER (MMA)
Code: EWELDO/141
Specifications:
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Input voltage / phase: 220 volt / 1
Current input: 15 amps
Current output: 40 – 140 amps
Voltage output: 65 volts
Welding rods recommended: 1 mm – 3 mm
Duty cycle: 20 % @ amps
Dimensions (lhw) : 265mm x 240mm x 240mm
Weight:
Typical uses for this welding machine:
This old fashioned yet reliable welder is ideal for the DIY enthusiast for around the home. This
welder is ideal for general welding repair and light steel fabrication work. This welder is low priced
which makes it invaluable for around the home, and is an easy to use welder. Make sure the oil level
is always at the correct level. The oil level must be at the level of 170mm. (Use only welding
transformer oil). The welder does not come with welding cables, and is recommended to purchase
welding cables with a length of 2.5 mt, both electrode holder and earth cable. (Please see ‘Guide for
welding cable`, for the correct size of welding cables).
EWELDO/221
Description: STRIKE 220 AMP OIL COOLED ARC (MMA) WELDER
Code: EWELDO/221
Specifications:
1) Input voltage / phase: 220 volt / 1
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Current input: 28 amps
Current output: 50 – 220 amps
Voltage output: 75 volts
Welding rods recommended: 1 mm – 4 mm
Duty cycle: 20 % @ 110 amps
Dimensions (lhw) : 285mm x 360mm x 265mm
Weight: 34 kg
Typical uses for this welding machine:
This old fashioned yet reliable welder is ideal for the DIY enthusiast for around the home and the
workshop. This welder is ideal for general welding repair and light steel fabrication work. This welder
is low priced which makes it invaluable for around the home, and is an easy to use welder. Make
sure the oil level is always at the correct level. The level for the oil must be at 190mm. (Use only
welding transformer oil). The welder does not come with welding cables, and is recommended to
purchase welding cables with a length of 2.5 mt, both electrode holder and earth cable. (Please see
‘Guide for welding cable`, for the correct size of welding cables).
EWELDO/251
Description: STRIKE 250 AMP OIL COOLED ARC (MMA) WELDER.
Code: EWELDO/251
Specifications:
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Input voltage / phase: 220 volt / 1
Current input: 29 amps
Current output: 50 – 250 amps
Voltage output: 75 volts
Welding rods recommended: 1 mm – 5 mm
Duty cycle: 20 % @ 135 amps
Dimensions (lhw) : 285mm x 360mm x 265mm
Weight: 47 kg
Typical uses for this welding machine:
This old fashioned yet reliable welder is ideal for the DIY enthusiast and the more frequent welder
for around the home and the workshop. This welder is ideal for general welding repair and light steel
fabrication work. This welder is low priced which makes it invaluable for around the home, and is an
easy to use welder. Make sure the oil level is always at the correct level. The oil level must be at
190mm. (Use only welding transformer oil). The welder does not come with welding cables, and is
recommended to purchase welding cables with a length of 2.5 mt, both electrode holder and earth
cable. (Please see ‘Guide for welding cable`, for the correct size of welding cables).
DC (direct current) arc inverter welder
(mma)
Introduction:
The MAC-AFRIC D.C. STICK INVERTER range consists of 160 amp, 200amp, output capacity welding
machines, all suitable for use on 220 volt input supply and generally used for maintenance
applications. For production use we have a 250 amp and a 300 amp suitable for use on 380 volt
input supply. All units are rated at 60% duty cycle, are lightweight and have low amperage
capabilities (i.e. 20 to 30 amps depending on the unit).
INVERTER welding machines are state of the art technology and makes use of solid state switching
and rectification and filtration of the input voltage to produce very stable D.C. voltage and current.
The input line voltage can either be single phase (220 volt or three phases 380/525 volt). Solid state
control circuits are incorporated to provide excellent arc characteristics and line voltage
compensation.
IMPORTANT FEATURES
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Lightweight portability is one of the main features to be considered when purchasing a
welding machine for use on a specific range of applications.
Input voltage covers all power input supplied in South Africa.
The components can absorb up to 15% under or over line voltage variations.
Inverters produce a stronger, more concentrated, smooth and state arc with excellent
striking and re-striking capabilities.
Inverters are ideally suited and versatile for use on all commercially available ferrous
and non-ferrous metals. It will weld electrodes of different specifications, including basic
(low hydrogen) and cellulosic types. Fine adjustment through the current range allows
for precision welding on complex alloys.
The stick Inverters (no high frequency facility) can be used for scratch start D.C. T.I.G.
welding using straight (Negative -) electrode polarity when T.I.G. welding ferrous (steel)
metals.
On thin metals using mild steel electrodes, the polarity can be reversed i.e. electrode
negative (-) and ground (earth) (+). This allows for less burn through possibilities.
The Inverters are fitted with an overload protection switch that is activated once the
components reach overheating levels or the duty cycle is exceeded.
PROVENTATIVE MEASURES AND MAINTENANCE
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Inverters should be used in dry environments, with humidity levels of 90% max.
The ambient room temperature should be between 10 to 40 ºC.
The Inverter should not be used in rain or drizzle.
Do not use the Inverter in corrosive areas.
The cooling fan fitted to the Inverter needs to keep the unit cooled to required limits,
therefore, the intake air vents must not be obstructed, always clean and not within 0.3
meter to the nearest object. The WARRANTY of the Inverter allows for the operator to
6.
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9.
remove the cover to blow out excessive dust and metal dust particles (using dry
compressed air with reasonable pressure level) that may damage the electrical
components. However, the WARRANTY will be null and void if any component is
changed or altered. Care should be taken that the cover is fitted back correctly as this
can influence the correct air flow.
The duty cycle of the Inverter should not be exceeded.
The input voltage should always be within the + - 15% under of over allowable constant
supply. Using input power cable exceeding 15 meters may cause the voltage to drop
below this level and may damage the electronic components. When the overload
protection device is activated (front indicator light will come on) the Inverter will switch
off and the power will only be re-activated (front indicator light off) for further welding
once the component temperature reaches safe levels. The cool down time may vary
according to the conditions under which the Inverter is used.
Prevent water or steam from entering the Inverter. Should this happen, remove the
power supply from the mains and dry properly.
Inverters should not be used using power generators unless expensive voltage equalizers
are fitted. The electronic components fitted to Inverters cannot absorb the excessive
voltage variations found with this type of power supply.
EWELDS/160
Description: Mac- Afric 160 amp DC inerter welder (mma)
Code: EWELDS/160
Specifications:
1) Input voltage / phase: 220 volt / 1
2) Current input: 23 amps – 30 amps
3) Current output: 20 – 160 amps
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Voltage output: 26.4 volts
Welding rods recommended: 1 mm – 3.2 mm
Duty cycle: 60 % @ 160 amps
Dimensions (lhw) : 290x132x203
Weight: 8 (kg)
Includes: earth clamp and electrode holder
Typical uses for this welding machine: Ideal for the DIY enthusiast around home and the workshop
for repair work and light steel fabrication work. Can also use this welder as a DC (scratch) TIG
welder, by adapting an external TIG torch and argon gas bottle with flow meter. It will weld stainless
steels, alloy steels, carbon steels, copper and other metals. It can weld electrodes of different
specifications, including basic and cellulosic as well as aluminium electrodes.
Basic helpful hints:
When using a long extension cable, in order to prevent voltage from dropping, a larger diameter
cable is suggested. If the extension cable is too long, it may affect the performance of the power
system, so we suggest you use a configured length, (10 meters, 2.5 mm inner core, 25 amps).
Make sure the cooling fan of the machine is not blocked or obstructed, otherwise, the duty cycle will
be affected and the performance of the welder.
Correctly connect the cables, by putting the earth cable plug into the socket marked “-“negative
polarity and the electrode holder socket into the socket marked “+” positive polarity, and fasten it
clockwise.
EWELDS/200
Description: Mac – Afric 200 amp DC inverter welder.
Code: EWELDS/200
Specifications:
1) Input voltage / phase: 220 volt / 1
2) Current input: 24 amps to 33 amps
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Current output: 20 – 200 amps
Voltage output: 21 volt – 28 volt (DC)
Welding rods recommended: 1 mm – 4 mm
Duty cycle: 60 % @ 200 amps
Dimensions (lhw) : 290x132x203
Weight: 8 (kg)
Typical uses for this welding machine: Ideal for the DIY enthusiast around home and the workshop
for repair work and light steel fabrication work. Can also use this welder as a DC (scratch) TIG
welder, by adapting an external TIG torch and argon gas bottle with flow meter. It will weld stainless
steels, alloy steels, carbon steels, copper and other metals. It can weld electrodes of different
specifications, including basic and cellulosic as well as aluminium electrodes.
Basic helpful hints:
When using a long extension cable, in order to prevent voltage from dropping, a larger diameter
cable is suggested. If the extension cable is too long, it may affect the performance of the power
system, so we suggest you use a configured length, (10 meters, 2.5 mm inner core, 25 amps).
Make sure the cooling fan of the machine is not blocked or obstructed, otherwise, the duty cycle will
be affected and the performance of the welder.
Correctly connect the cables, by putting the earth cable plug into the socket marked “-“negative
polarity and the electrode holder socket into the socket marked “+” positive polarity, and fasten it
clockwise.
EWELDS/250
Description: MAC – AFRIC 250 amp DC inverter welder.
Code: EWELDS/250
Specifications:
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Input voltage / phase: 380 volt / 3
Current input:
Current output:
Voltage output:
Welding rods recommended: 1 mm – 3 mm
Duty cycle:
Dimensions (lhw) :
Weight:
Typical uses for this welding machine:
EWELDT/207
Description:
Code: EWELDT/207
Specifications:
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Input voltage / phase: 380 volt / 3
Current input:
Current output:
Voltage output:
Welding rods recommended: 1 mm – 3 mm
Duty cycle:
Dimensions (lhw) : 490mm x 380mm x 200mm
Weight:
Typical uses for this welding machine:
EWELDS/300
Description:
Code: EWELDS/300
Specifications:
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Input voltage / phase: 380 volt / 3
Current input:
Current output:
Voltage output:
Welding rods recommended: 1 mm – 3 mm
Duty cycle:
Dimensions (lhw) : 565mm x 525mm x 310mm
Weight:
Typical uses for this welding machine:
Related products for ARC (mma) welders:
EWELDA/205 (2.5 mm PHAMODI STEEL WELDING ELECTRODES) 5 KG.
EWELDA/315
DC (direct current) TIG inverter
welder’s
Introduction:
GAS TUNGSTEN ARC WELDING (GTAW)
TUNGSTEN INERT GAS (T.I.G.) WELDING
E, as shown in figure 1-1 above. For direct current reverse polarity “DCRP reverse (+)” the
connections are the opposite i.e. the electrons flow from the plate to the electrode, as shown in
figure 1 – 2 above.
In negative polarity welding, the electrons exert a considerable heating effect on the plate. In
positive polarity welding the electrode acquires this extra heat which then tends to melt off the end
of the electrode. In the case of DCSP (-) approximately 70% of the heat is developed at the work
piece and 30% at the electrode, so the electrode tip will not melt and will maintain the conical shape
when used within the recommended current range. For any given welding current, DCRP (+) requires
a larger diameter electrode than DCSP (-). These opposite heating effects of DCRP (+) and DCSP (-)
influence not only the welding action but also the shape of the weld obtained (see weld result
drawing). One other effect of DCRP (+) welding should be considered namely the so – called plate
cleaning effect which occurs. The exact reason for this surface cleaning action is not known. The
electrons and gas ions tend to remove the surface oxides and scale usually present.
When using a DC welder without high frequency facility, the arc can be stuck on the work piece or
on a piece of copper or steel (scratch start) and then carried to the weld starting point. Do not use a
carbon block for starting the arc as the electrode becomes contaminated causing the arc to wander.
The T.I.G. torches used in this case has a mechanical gas valve on the torch that is opened manually
by the operator before striking the arc.
When using a welder fitted with high frequency facility it eliminates the need for touching the work
piece as the high frequency is automatically turned on to assist in establishing the arc and is
automatically turned off as soon as the arc is established. The welder also has a solenoid valve that
opens to allow gas flow when triggered on the torch and shuts off after the trigger is released. If
water cooler is fitted to the system a water cooled torch is required and water flow is continuous
while the circulator pump is running.
ALTERNATING CURRENT (AC) WELDING
In alternating current (AC) welding, the welding current circuit is hooked up to the “straight (-)
polarity terminal. The high frequency facility on these AC/DC type welders jumps the gap between
electrode and the work piece, burns through the tough oxide skin during the “reverse polarity phase
- positive (+)” of the AC cycle and creates a clean path for the welding current that follows. The
depth of penetration results from the heat produced during the electrode negative (-) portion of the
AC cycle. Because cleaning action is inherent in electrode positive welding, any oxide film on the
work is broken up during the electrode-positive portion of the AC cycle. Zirconiated tungsten
electrodes are generally used when welding aluminium due to being able to carry slightly higher
currents and have a longer life than pure tungsten electrodes. The AC welders with high frequency
facilities are normally fitted with solenoid valves that regulate the gas flow through torch trigger
activation. If water cooler is fitted to the system a water cooled torch is required and water flow
through the torch is continuous while the circulator pump is running.
APPLICATIONS
The main feature of the GTAW (T.I.G.) process is the high quality welds achieved on almost all
commercially available metals and alloys. Freedom of contamination from the atmosphere is
achieved especially on critical alloys where small amounts of oxygen, nitrogen and carbon can cause
embrittlement and loss of corrosion resistance. The process is ideal for welds on thin material, root
passes and small parts where quality and finish is important. The ability of adding filler metal
independently of the arc current, that can be operated at very low amperages, with very little
spatter loss and with a stable arc, is a strong consideration especially on small thin walled parts.
The only disadvantages of the T.I.G. process is the greater skill required by the operator and the low
rate of filler metal being applied.
TECHNIQUES
The technique of manually feeding the filler wire into the weld puddle is illustrated in the drawing
above. The filler rod end should not be moved out of the inert gas shielding area of the torch. This is
to prevent the hot end from oxidizing with the resultant contamination in the weld pool, when it is
dipped into it. Pre-flow of gas before the arc is established and post-flow after the weld is completed
also prevents oxidation and allows the filler alloy to wet and flow properly. At the end of the weld
the current should be decreased gradually to avoid a crater forming with the possibility of crater
crack developing. Adding a small amount of filler metal at the end of the weld, just before the arc is
extinguished, is good practice. Many joints of thin material can be joined without adding filler
material by fusing them together such as corner joints, edge joints etc. On establishing the arc, the
torch is moved at a constant speed to the end of the weld.
CHARACTERISTICS OF THE GAS TUNGSTEN ARC (T.I.G.) WELDING PROCESS FOR ALUMINIUM (ALL AT
SAME CURRENT)
Process
GAS TUNGSTEN ARC WELDING PROCESS
Characteristics
AC
DC ELECT. NEG.
DC ELECT. POS.
(ELECT. -, WORK +)
(ELECT. +, WORK -)
Current
Alternating
Flows electrode to work
Flows work to electrode
Arc heat concentration
50% each cycle (balanced
power source)
70% at work
30% at work
30% at electrode
70% at electrode
Higher current with
Larger electrode required.
Effects of heat concentration
Electrode current capacity
slightly less than DCEN (-
smaller electrode.
Wide and shallow penetration
Medium penetration,
greater than DCEP (+) and
less than DCEN (-)
Narrow and deep
penetration of arc heat
into base metal.
Much lower welding speed
than DCEN (-)
Midrange welding speed
Welding speed 125mm
p.m. +
(125 mm/pm +)
Helium increases
penetration and speed.
Argon gives best cleaning.
Arc Stability
Stable (balanced AC or with
continuous high frequency)
Stable
Stable
Cleaning action of arc and /
or gas
Good with Argon, on
positive portion of cycle
None. However, DCEN (-)
welds can be done with
Helium
Continuous – excellent with
Argon. DCEP (+) has best
cleaning action of the three,
but penetration is poorest.
Size of Tungsten Electrode
Medium ((2.5mm (3/32″) at
125 amp))
Small ((1.6mm (1/16″) at
125 amp))
Large ((4.0mm (¼″) at 125
amp))
Applications
General purpose manual
and automatic welding
Automatic
Thin sheet welding and also
for root pass on pipe
Maximum work thickness
3,.2mm (⅛″) full
penetration
4.0 – 12.0mm (¼″ to ¾″)
Very thin – below 1.5mm
(full penetration)
POWER SOURCES
DC Rectifier or Inverter power sources without high frequency facility can be used for scratch start
DC welding. The connection is torch power cable to the negative (-) connection of the machine and
earth cable to the positive (+) connection. The machine has no solenoid gas valve and gas flow is
controlled manually by the operator by turning the knob, mounted on the torch, to the required
volume.
DC Rectifier or Inverter power sources with high frequency facility are used for automatic arc
ignition T.I.G. welding. The connection can be either electrode positive (+) or negative (-) as
described below. These machines are fitted with a contactor and a means of controlling arc current
as well as a solenoid valve for automatic gas flow control by the welder. The control of arc current
can either be pre – set at the machine or through current control mounted on the torch or by using a
foot control unit. These machines normally also have pre – set control of gas flow before starting the
arc and gas flow off after completing the weld. An additional feature can be included to pulse the
weld which allows root pass welds, welds on thin material and overhead welds to be made with less
chance of melt through.
AC / DC Rectifiers or Inverter power sources with high frequency facility is the most versatile
machine used for T.I.G. welding of all ferrous (steel) based metals including non – ferrous metals i.e.
Aluminium, Copper, Nickel etc. The DC welding side is as per the above comments. For AC welding
the high frequency is on continuously and the power supply can vary the positive and negative half
cycles of AC current to favour either cleaning action or penetration. This feature is useful for welding
aluminium where adjustments must be made based on the thickness and cleanliness of the joint.
Current and gas flow control is as per above.
DIRECT CURRENT (D.C.) T.I.G. WELDING
In direct current welding (D.C.), the welding current circuit may be hooked up as either “straight –
negative (-)” or “reverse - positive (+)” polarity. The D.C. welder connection for direct current
straight polarity “DCSP negative (-)” welding is electrode negative and work piece positive. In other
words, the electrons flow from the electrode to the work piece.
EWELDT/162
Description:
Code: EWELDT/162
Specifications:
1)
2)
3)
4)
5)
6)
7)
8)
Input voltage / phase: 220 volt / 1
Current input:
Current output:
Voltage output:
Welding rods recommended: 1 mm – 3 mm
Duty cycle:
Dimensions (lhw) : 370mm x 260mm x 160mm
Weight:
Typical uses for this welding machine:
EWELDT/204
Description:
Code: EWELDT/204
Specifications:
1)
2)
3)
4)
5)
6)
7)
8)
Input voltage / phase: 220 volt / 1
Current input:
Current output:
Voltage output:
Welding rods recommended: 1 mm – 3 mm
Duty cycle:
Dimensions (lhw) : 370mm x 260mm x 160mm
Weight:
Typical uses for this welding machine:
EWELDT/180
Description:
Code: EWELDT/180
Specifications:
1)
2)
3)
4)
5)
6)
7)
8)
Input voltage / phase: 220 volt / 1
Current input:
Current output: 20 amps – 180 amps
Voltage output:
Welding rods recommended: 1 mm – 3 mm
Duty cycle
Dimensions (lhw) : 410mm x 330mm x 180mm
Weight:
Typical uses for this welding machine:
EWELDT/250
Description:
Code: EWELDT/250
Specifications:
1)
2)
3)
4)
5)
6)
7)
8)
Input voltage / phase: 380 volt / 3
Current input:
Current output:
Voltage output:
Welding rods recommended: 1 mm – 3 mm
Duty cycle:
Dimensions (lhw) : 490mm x 380mm x 200mm
Weight:
Typical uses for this welding machine:
AC/DC (Alternating/Direct current) TIG
inverter welder’s
Introduction:
AC/DC inverter TIG welders are generally used for various types of metal welding. These units have
HFS (High frequency start) which enables it to weld non-ferrous metals, such as aluminium. These
units can also weld metals from the group of ferrous types, such as mild steel, stainless steel, ECT.
These units also have the capability to do Arc (MMA) welding, DC, as well. Just simple change of the
switch, TIG or MMA, will enable the process required.
When TIG welding, argon gas must be used, for shielding purposes of the weld. These units have
many important features, such as:
1) PREFLOW- gas flow before TIG welding
2) PEAK CURRENT- welding current
3) BASIC CURRENT- penetration
4) SLOPE DOWN- welding current slowly drops off
5) ARC FORCE- high current at start and drops to set current
6) PULSE FREQUENCY- intensity of the pulse
7) PULSE DUTY- speed of the pulsation
.
8) CLEANING AREA WIDTH- controls width of the arc and
penetration.
9) GAS AFTER FLOW- gas flow after TIG welding to cool tungsten
rod.
These units come standard with the following accessories:
1)TIG torch
2) Earth clamp
3) Argon flow meter
4) Foot pedal.
EWELDT/201
Description: THERMAMAX 200 amp AC/DC TIG inverter welder
Code: EWELDT/201
Specifications:
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
12)
13)
14)
Input voltage / phase: 220 volt / 1
Current input: 14.6 amp – 20.7 amp
Current output: 10 amp – 200 amp
Voltage output: 10.4 volts – 18 volts
TIG rods recommended: ZIRCONIATED
Duty cycle: 60 % @ 200 amps / 100 % @ 154 amps
Dimensions (lhw) : 493x330x320
Weight: 20 (kg)
Power usage: 3.2 KV.A – 4.6 KV.A
Welding thickness (mm) : 10
Arc leading: HF vibration
Input frequency (HZ) : 50/60
Output frequency (HZ) : 60
Arc force: 0 – 100 amps
Typical uses for this welding machine:
This unit is ideal for most types of metal applications, such as non-ferrous and ferrous types of
metal. Ideal for thin sheet metal welding for the DIY enthusiast and workshop operator. Used mainly
for the repair on alloy metals and aluminium, and mild steels in the automotive industry. Processes
for this machine include- aluminium TIG, steel and others, stick (MMA).
EWELDT/205
Description: THERMAMAX 250 amp AC/DC TIG inverter welder
Code: EWELDT/205
Specifications:
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
12)
13)
14)
Input voltage / phase: 380 volt / 3
Current input: 16 amps
Current output:10 amps - 250 amps
Voltage output:
TIG rods recommended: ZIRCONIATED
Duty cycle: 60 % @ 250 amps
Dimensions (lhw) : 560x365x355
Weight: 30 (kg)
Power usage: 6.3 KV.A
Welding thickness (mm) : 12
Arc leading: HF vibration
Input frequency (HZ) : 50/60
Output frequency (HZ) : 60
Arc force: 0 – 100 amps
Typical uses for this welding machine:
This unit is ideal for most types of metal applications, such as non-ferrous and ferrous types of
metal. Ideal for thin sheet metal welding for the DIY enthusiast and workshop operator. Used mainly
for the repair on alloy metals and aluminium, and mild steels in the automotive industry. Processes
for this machine include- aluminium TIG, steel and others, stick (MMA).
Related products:
MIG (GMAW) welder’s
Introduction:
GAS METAL ARC WELDING (GMAW)
METAL INERT GAS WELDING (M.I.G.)
GAS METAL ARC WELDING (GMAW) (M.I.G) PROCESS
Gas metal arc welding, commonly known as M.I.G., welding consists of various components as
indicated in the drawing above. The system uses continuous small diameter solid wire and an
externally supplied gas or mixtures of gasses. The shielding gas can be Helium, Argon, Carbon
dioxide or mixtures thereof.
M.I.G. welding is suitable for use on all major commercial metals i.e. Low Carbon, Low and High Alloy
Steels, Stainless Steels, High Strength quenched and tempered steels, Aluminium, Magnesium,
Copper, Titanium, etc. With these various metals the welding techniques and weld procedures may
vary widely.
Carbon – Dioxide or Argon – Oxygen mixtures are suitable as shielding gasses on low carbon and low
alloy steels, whereas pure inert
gas (Argon –
Helium) is used when welding high alloyed steels and alloys of Aluminium, Magnesium, Copper,
Titanium, Stainless Steel and the Nickel Based alloys.
Welding is either semi-automatic, using a hand-held torch (manual) through which the wire is fed
automatically, or fully-automatic equipment can be used.
Metal transfer achieved using the M.I.G. process is done by one of two methods, namely, “spray arc”
or short circuiting (globular). With spray arc, drops of molten metal detach from the wire and move
through the arc column to the work piece. With the short circuiting method, metal is transferred to
the work piece when the tip of the wire contacts the molten metal.
In short – circuit welding (globular), lower current, low voltages and small diameter wire is used and
the metal is transferred with each short – circuit rather than across the arc as in spray arc welding.
This method results in low heat input with the minimum of distortion and used on thin or poor fitups and bridging wide gap applications.
Spray arc M.I.G. welding produces a very hot, high voltage arc and gives a higher deposition rate
than short circuit welding. The spray arc method is normally recommended for thicker sections
requiring heavy single or multi-pass applications where deposition rate is important.
Gas Metal Arc (M.I.G.) welding is done with Direct Current (D.C.) rectifier power sources, using
reverse polarity, wire positive (+) and this provides a stable arc, smooth metal transfer, relatively low
spatter loss and good weld bead.
Some manufacturers also provides Spot Welding features on their equipment which replaces either
riveting or where T.I.G. spot welding is not suitable such as in joining Aluminium or on poor fit-ups
and where cleanliness requirements are not as important or on thicker materials.
As with all welding processes, the correct setup and maintenance of M.I.G. welding equipment is
vitally important to ensure continuous automatic feeding and successful weld deposits. This equally
applies to the M.I.G. torch and ensuring that the torch system is clean, with no obstructions and
current carrying parts, that are relatively inexpensive, are replaced frequently. It is also good
practice to have the torch cable as straight as possible to ensure continuous successful wire feeding.
When welding non-ferrous metals i.e. Aluminium, Copper or Nickel alloys it is highly recommended
to use a separate torch specifically for these alloys, than the one used on steel alloys, and that the
torch cable length is as short as possible and kept as straight as possible.
EWELML/105
Description: MAC-AFRIC light duty mig welder
Code: EWELML/105
Specifications:
1)
2)
3)
4)
5)
6)
7)
8)
Input voltage / phase: 220 volt / 1
Current input: 8.2 amps – 15 amps
Current output: 35 amps – 90 amps
Voltage output: 15.7 volts – 18.5 volts
Welding wire size recommended: 0.6mm and 0.8mm
Duty cycle: 10 % @ 90 amps.
Dimensions (lhw) : 425 mm x 415 mm x 225 mm
Weight:
Typical uses for this welding machine:
EWELML/150
Description:
Code: EWELML/150
Specifications:
1) Input voltage / phase: 220 volt / 1
2) Current input:
3)
4)
5)
6)
7)
8)
Current output:
Voltage output:
Welding rods recommended: 1 mm – 3 mm
Duty cycle:
Dimensions (lhw) :
Weight:
Typical uses for this welding machine:
EWELML/195
Description:
Code: EWELML/195
Specifications:
1)
2)
3)
4)
5)
6)
7)
8)
Input voltage / phase: 220 volt / 1
Current input:
Current output:
Voltage output:
Welding rods recommended: 1 mm – 3 mm
Duty cycle:
Dimensions (lhw) :
Weight:
Typical uses for this welding machine:
Related products:
EWELMH/160
Description:
Code: EWELMH/160
Specifications:
1)
2)
3)
4)
5)
6)
7)
8)
Input voltage / phase: 220 volt / 1
Current input:
Current output:
Voltage output:
Welding rods recommended: 1 mm – 3 mm
Duty cycle:
Dimensions (lhw) :
Weight:
Typical uses for this welding machine:
EWELMH/190
Description:
Code: EWELMH/190
Specifications:
1)
2)
3)
4)
5)
6)
7)
8)
Input voltage / phase: 220 volt / 1
Current input:
Current output:
Voltage output:
Welding rods recommended: 1 mm – 3 mm
Duty cycle:
Dimensions (lhw) :
Weight:
Typical uses for this welding machine:
EWELMH/250
Description:
Code: EWELMH/250
Specifications:
1)
2)
3)
4)
5)
6)
7)
8)
Input voltage / phase: 220 volt / 1
Current input:
Current output:
Voltage output:
Welding rods recommended: 1 mm – 3 mm
Duty cycle:
Dimensions (lhw) :
Weight:
Typical uses for this welding machine:
EWELDT/202
Description:
Code: EWELDT/202
Specifications:
1)
2)
3)
4)
5)
6)
7)
8)
Input voltage / phase: 220 volt / 1
Current input:
Current output:
Voltage output:
Welding rods recommended: 1 mm – 3 mm
Duty cycle:
Dimensions (lhw) :
Weight:
Typical uses for this welding machine:
Related products:
EWELSP/025
Description:
Code: EWELSP/025
Specifications:
1)
2)
3)
4)
5)
6)
7)
8)
Input voltage / phase: 380 volt / 3
Current input:
Current output:
Voltage output:
Welding rods recommended: 1 mm – 3 mm
Duty cycle:
Dimensions (lhw) :
Weight:
Typical uses for this welding machine:
PLASMA ARC CUTTING
EWElDP040
Description: MAC-AFRIC CUT 40 PLASMA CUTTER
Code: EWELDP/040
Specifications:
1)
2)
3)
4)
5)
6)
7)
8)
Input voltage / phase: 220 volt / 1
Current input:
Current output:
Voltage output:
Thickness of metal capabilities:
Duty cycle:
Dimensions (lhw) :
Weight:
Typical uses for this plasma cutter:
The Plasma Arc Cutting system employs the use of an electric arc and a pressurized volume of
ionized air forced through a small orifice (TIP) fitted between the electrode in the plasma torch and
the work piece to be cut. This constricted, high speed and high temperature plasma arc stream cuts
through metal in a concentrated localized area and the molten metal is blown away by the high
velocity arc and air steam.
The Plasma Arc Cutting process is capable of cutting and gouging most Ferrous (steel) and NonFerrous (Aluminium, Copper etc) metals producing a clean narrow cut width (determined by the tip
orifice size) and smoother surfaces. The process is more portable, cuts faster and cleaner than the
gas cutting (oxy/fuel) process, requiring no pre-heat, and with the added advantage of being able to
cut Stainless Steel and Non-Ferrous metals (oxy/fuel cannot) cleanly and effectively, using less
cumbersome equipment. The process can be used with either a hand held torch or on automated
systems.
The Plasma Power source has drooping current characteristics, using higher voltages than standard
welding machines and the torches are well insulated to protect the operator against the high
voltages present.
The majority of Plasma Arc Cutters today have high frequency arc starting features meaning that non
base metal contact is used as opposed to machines without high frequency that require scratch start
to initiate the arc.
Hand cutting torches using stand-off guides (determines tip distance from work piece) enables the
operator to rest the torch on the work piece and by using a template or straight edge is able to cut
straight or profile edges cleanly and accurately. The torch can also be used for gouging by changing
the tip to a gouging tip that enables the operator to angle the torch to + - 30 degrees as opposed to
the 90 degree used when cutting.
Long (extended) tips can be fitted for maximum visibility giving a clear view of the cut to be
made either in the stand-off or drag position. The tips contain an orifice which constricts the
plasma arc. The tips come in various orifice sizes and also gradually wear with use and must
be replaced when the arc cut becomes too wide.
Due to the alloying denseness and higher electrical resistance of Stainless Steel the
thickness of cut achieved per cutting machine capacity is considerably lower than steel. All
manufactures of Plasma Arc Cutting equipment indicate the cutting capacity when cutting
various metals.
When cutting a circle the cut is started at the plate leading edge towards the circle edge or a hole is
pierced in the centre of the circle and cut towards the circle edge. On piecing the hole through the
plate the torch is angled at + - 30º and once pieced the torch is raised to a 90º position.
PROBLEM SHOOTING AND MAINTENANCE
1.
The operating voltages for Plasma Arc Cutting can reach 400 volt D.C. and most systems
incorporate safety features that prevent the operator from coming into contact with the
high voltage. Before using the system the operator must ensure that the torch cable is
not damaged or punctured and that the electrode, tip and shield cup is fitted correctly,
securely and in good condition. All access panels must be closed at all times when the
power is connected.
2.
It is recommended that periodic cleaning using dry compressed air, of the interior of the
power source is done to ensure that metal containing dust does not damage the
electronic components. When this is done the power to cutter must be disconnected
first for you own safety.
3.
Fumes and gases produced by the Plasma Arc Cutting can be hazardous to health and
must be avoided. Use the necessary respiratory protection masks or respirators when
cutting in unventilated or confined areas.
4.
Sparks from the Plasma Arc Cutting can be a fire hazard and all combustible material and
solvents should be kept away from the cutting area.
5.
The Plasma Arc emits intense, visible, infrared and ultraviolet radiation which can be
harmful to the eyes and skin. The same eye and skin protection normally used for GTA
(T.I.G.) welding at the equivalent current range should be used.
6.
Water vapour and oil introduced into the highly concentrated constricted arc can
damaged the electrode, tip and shield cup and depending on the severity of the water or
oil “explosion” within the arc, damage to the entire torch head is possible. It is
recommended that the water/oil trap fitted to the air supply system of the cutting
machine is cleaned at regular intervals. Should water/oil still persist, it is recommended
that a second water/oil trap be installed at the compressor outlet.
TROUBLESHOOTING GUIDE ON WELDING EQUIPMENT
PROBLEM
Welder will not start
Welder starts but blows
fuse
CAUSE
REMEDY
Power switch not turn on
Place power switch to “ON” position
Supply line fuse blown
Replace fuse (Check cause first)
Power circuit dead
Check input voltage
Overload relay tripped
Cool down unit (remove cause)
Loose or broken power, electrode or ground lead
Replace, tighten or repair
Wrong voltage
Check input voltage per manual
Polarity switch not centered (AC - DC)
Centre switch on +, -, or AC or DC
Open circuit to switch
Repair
Short circuit in electrical components of welder
Check connections and lead insulation
Fuse to small
Check manual for correct fuse size
Proper air ventilation obstructed.
Make sure that all case ventilation
openings free and clean
Cooling fan not working
Replace or repair leads and connections
Overloading – welding in excess of rating
Operate at rated load & duty cycle
Current to low
Check recommended current for electrode
type and size
after welding begins
Welder welds but soon
stops welding
Variable & sluggish arc
Low line voltage
Check input line voltage
Welding cables to small
Check recommended cable sizes
Poor earth, electrode or control circuit connection
Check all connections. Clean or replace
Current setting is to high
Check recommended setting according to
electrode type or size
Polarity setting is wrong
Check recommended polarity. Try
reversing polarity or change electrode
Polarity switch won’t work
Contacts worn, rough and pitted from improper
switch while welder is under load
Replace switch. Never operate switch while
welder is under load.
Welder will not switch off
Line switch has failed mechanically
Replace switch
Arcing at earth clamp
Loose connection or weak clamp spring
Tighten connection or replace earth clamp.
Positive and firm earth = good welds
Electrode holder becomes
hot
Loose connection, loose jaw, loose electrode
clamping, inadequate duty cycle of holder
Tighten cable connection to holder or
replace holder with correct duty cycle size
Electrical shock when
touching welder
Frame not grounded
See welder instruction manual for proper
grounding procedure of welder covers.
Welding cables hot
Incorrect duty cycle of cable
Check recommended cable size according
to welders manual.
Welding arc is load and
spatters excessively
CONSEQUENCES RESULTING FROM
INCORRECT USE OF WELDING ACCESSORIES
ELECTRICAL CONDUCTIVITY OF METALS
Electrical conductivity is the efficiency of a metal in conducting electrical current. The conductivity of
electrolytic tough pitch copper (ETP) is 101% of the International Annealed Copper Standard (IACS).
Other metals compare as follows:
ALUMINIUM
(99.9%)
65%
ALUMINIUM ALLOYS
35%
MILD STEEL
15%
STAINLESS STEEL (300 SERIES) 2.5%
WELDING CABLE
The first item on both sides of the welding machine (power source) is the cable required for
conveying the electrical current. The cable from the welding machine to the electrode holder carries
the current to the electrode via the electrode holder to the arc and on to the work piece. The cable
from the welding machine to the work piece is the earth cable and completes the circuit from work
piece back to the welding machine.
The electrical conductors of the cable are fine strands of copper (preferred) or aluminium. The
quality, size and length of the conductors are extremely important to ensure the efficiency, success
and quality of welding. The insulating material of rubber or synthetic rubber over the copper strands
provides adequate insulation and flexibility needed. The size of cable used depends on the current
(amperage) to be carried and the total length of the electrical circuit. The longer the circuit, the
larger the size of the conductors needed to prevent voltage drop and the dissipation of energy by
resistance heating within the conductor. DAMAGED INSULATION, BROKEN CONDUCTORS INSIDE THE
INSULATION, TO SMALL CONDUCTORS CARRING THE CURRENT WILL CAUSE HEAT BUILD UP, COPPER
SCALING, WITH THE RESULTANT POOR CONDUCTIVITY AND WELDING EFFICIENCY.
ELECTRODE HOLDERS
The electrode holder is a clamping device that grips the welding electrode between the jaws that
conducts the current through the electrode to the work piece. Electrode holders are rated according
to their current carrying capacity. By choosing the correct rated size holder and cable, that the cable
connection to the holder is sound and the metal used by the manufacturer on the holder’s
body/jaws, carrying the current, has good electrical conveying and gripping properties, will ensure
that the electrode holder does not overheat. Quality electrode holders have good handle and jaw
insulation and the screws holding these parts are well recessed thereby protecting the welder from
electrical shock or accidentally touching the work piece causing a short circuit. THE EFFICIENCY,
COMFORT AND WELD QUALITY PRODUCED BY THE WELDER GREATLY DEPENDS ON THE QUALITY OF
THE ELECTRODE HOLDER AND SOUND CONNECTING SYSTEM.
EARTH (GROUND) CLAMP
Proper earth (ground) of the system cannot be over emphasized to its importance in achieving
quality and efficient welding. The earth completes the electrical circuit back to the welding machine.
Any resistance i.e. earth not firm enough or insufficient cross sectional area surface contact in
relation to the cable size will cause electrical resistance, voltage drop will occur with the resultant
heat build up in the cable and earth clamp and poor arc characteristics. Since the conductivity of
copper is almost 7 times that of mild steel, the cross sectional area of any common steel grounding
bar should be at least 7 times the cross section of the welding cable conductor. It is good practice to
ensure that the area of earth contact is adequate, free from scale, rust, oil, grease, oxides, or dirt
that would act as areas of insulation. PROPER EARTH IN ALL WELDING SYSTEMS IS A PRE-REQUISITE
IN OBTAINING GOOD ARC CHARACTERISTICS AND WELD QUALITY.
CABLE CONNECTORS
Connecting the current conducting welding cable to either the welding machine or extending the
length of welding cable is normally done by either using cable lugs or cable connectors. Again the
cross sectional area and soundness of the connection of the cable to these connectors is important
in assuring good electrical flow and reducing the possibility of resistance, heat build up, voltage drop
and poor arc characteristics. ADEQUATE AND UNINTERUPTED ELECTRICAL FLOW ENSURES GOOD
ARC CHARACTERISTICS AND WELD QUALITY.
WELDING SAFETY CHECKLIST
HAZARD
SEVERITY
PRECAUTION
FACTORS
SUMMARY
Electric shock
Wetness
can kill you
Welder in or on
Insulate welder from work piece and ground using dry insulation. Rubber mat or dry
wood.
Wear dry, whole free gloves. (Change if damaged)
work piece
Do not touch electrically “hot” parts or electrode with bare skin or wet clothing.
Confined space
Electrode holder
If wet area and welder cannot be insulated from work piece use a stick welder
with voltage reducing device.
and cable insulation
Fumes & gases
can be
dangerous
Confined areas
Use ventilation or exhaust or respirators to keep air breathing zone clear, comfortable.
Positioning of welder’s
head
Use helmet and positioning of head to minimize fumes in breathing zone.
Do not weld unless ventilation is adequate.
Lack of general
ventilation
Electrode types i.e.,
manganese, chrome, etc
Provide additional ventilation where special ventilation requirements are called for.
Use special care when welding in confined areas.
Read warnings on electrode container or material safety data sheets to access level of
Base metal coatings,
galvanized, paint, etc
Air contamination during welding and type of respiratory equipment recommended.
Welding sparks
can cause fire or
explosion
Containers which have
held combustible or
Do not weld on containers that have held combustible materials. Check carefully before
welding.
flammable materials
Remove flammable materials from welding area or shield from sparks - heat.
Keep a fire extinguisher in the immediate area.
Wear fire retardant clothing and safety cap. Use earplugs for overhead welding.
Arc rays can burn Process: gas shielded
eyes and skin
arc is the most severe
Select the correct filter lens suited for the process you are using and that provides you
with the best eye comfort and safety.
Always use a helmet giving most facial area protection.
Provide non-flammable shielding to protect other operators in the vicinity.
Wear correct protective clothing that protects your skin while welding.
Confined space
Metal enclosure
Carefully evaluate adequacy of ventilation especially where electrode requires special
ventilation or where gas may displace breathing air.
Wetness
Restricted entry
Heavier than air gas
If basic electric shock precautions cannot be followed to insulate welder from work and
electrode, use stick welder fitted with voltage reduction device.
Provide welder and his helper with easy method of retrieval from outside enclosure in
case of emergency.
Welder inside or on work
piece
General work
Cluttered areas
Keep hoses, cables, materials, and tools, steel sections, organized.
area hazards
Indirect ground (earth)
connections
Connect earth cable as close as possible to area where welding is being performed. Do
not allow alternate circuits through scaffolds, hoist chains, building framework, other
ground leads or separate work pieces.
Use properly insulated and grounded equipment.
Always disconnect power supply to equipment when servicing or repairing.
Electrical Equipment
Use in open, well ventilated areas.
Refuel with engine switched off.
Engine driven
equipment
Keep all necessary guards/covers on machine.
If using as auxiliary power ensure that proper earth/grounding is achieved.
Never touch gas cylinders with the electrode.
Never lift a machine with the cylinder attached
Gas cylinders
Keep cylinders in the upright position and chained for support.
GUIDE FOR WELDING CABLE P.V.C. COVERING
COLOR
CONDUCTOR
I.D. OF
NOMINAL
P.V.C.
AREA mm2
100%
85%
60%
30%
GREEN
16
135
145
175
245
BLUE
25
180
195
230
GREY
35
225
245
RED
50
285
BROWN
70
YELLOW
BLACK
+ - CURRENT IN AMPS FOR DUTY CYCLE OF:
MAXIMUM
APPROX.
OVERALL
MASS
DIA. mm
KG/100m
300
11.5
216
300
400
13.0
350
290
410
500
14.5
470
310
370
520
635
16.5
639
355
385
460
650
795
19.0
814
95
430
470
560
700
900
21.5
1108
120
500
540
650
910
1120
25.0
1420
20%