AOTAI MIG350MC User manual

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Dear Customer
This instruction manual will help you get to know your new machine. Read the manual
carefully and you will soon be familiar with all the many great features of your new
product. Meanwhile, please remember well safety rules and operate as instruction.
If you treat your product carefully, this definitely helps to prolong its enduring quality and
reliability things which are both essential prerequisites for getting outstanding results.
Production specification may change without advance notice.
The model you purchase is:
MIG350MC
Please find corresponding models from the "Contents".
Important:
Please take special note of safety rules and operate as instruction in case of damage
and serious injury.

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Safety Rules
“Danger”indicates an imminently hazardous situation which, if not avoided, will result in death or
serious injury.
“Warning!”indicates a possible hazardous situation which, if not avoided, could result in death or
serious injury. The possible hazards are explained in the text.
“Caution”indicates a possible hazardous situation which, if not avoided, may result in slight or
moderate injury.
“Note!”indicates a situation which implies a risk of impaired welding result and damage to the
equipment.
“Important!” indicates practical tips and other useful special-message. It is no signal word for a
harmful or dangerous situation.
Utilization for intended purpose only
•The machine may only be used for jobs as defined by the “Intended purpose”.
•Utilization for any other purpose, or in any other manner, shall be deemed to be “not in accordance
with the intended purpose”. The manufacturer shall not be liable for any damage resulting from such
improper use.
Safety signs
•All the safety instructions and danger warnings on the machine must be kept in legible condition, not
removed, not be covered, pasted or painted cover.
Safety inspection
•The owner/operator is obliged to perform safety inspection at regular intervals.
•The manufacturer also recommends every 3-6 months for regular maintenance of power sources.
Electric shock can kill
•Touching live electrical parts can cause fatal shocks or severe burns. The electrode and work circuit
is electrically live whenever the output is on. The input power circuit and machine internal circuits are
also live when power is on. In MIG/MAG welding, the wire, drive rollers, wire feed housing and all
metal parts touching the welding wire are electrically live. Incorrectly installed or improperly grounded
equipment is a hazard.
•Do not touch live electrical parts of the welding circuit, electrodes and wires with your bare skin or wet
clothing.
•The operator must wear dry hole-free insulating welding gloves and body protection while performs
the welding.
•Insulate yourself from work and ground using dry insulating protection which is large enough to
prevent you full area of physical contact with the work or ground.
•Connect the primary input cable according to rules. Disconnect input power or stop machine before
installing or maintenance.
•If welding must be performed under electrically hazardous conditions as follow: in damp locations or
wearing wet clothing; on metal structures such as floors, gratings, or scaffolds; when in cramped
positions such as sitting, kneeling, or lying; or in occasion when there is a high risk of unavoidable or
accidental contact with the work piece or ground. Must use additional safety precautions:
semiautomatic DC constant voltage (wire) welder, DC manual (Stick) welder and AC welder with
reduced open-load voltage.
•Maintain the electrode holder, ground clamp, welding cable and welding machine in good, safe
operating condition. Replace damaged part immediately.
Electric and magnetic fields (EMF) may be dangerous
•If electromagnetic interference is found to be occurring, the operator is obliged to examine any
possible electromagnetic problems that may occur on equipment as follow:
-mains, signal and data-transmission leads
-IT and telecoms equipment
-measurement and calibration devices
-Wearers of pacemakers
•Measures for minimizing or preventing EMC problems:
-Mains supply
If electromagnetic interference still occurs, despite the fact that the mains connection in accordance
with the regulations, take additional measures
-Welding cables
Keep these as short as possible
Connect the work cable to the work piece as close as possible to the area being welded.
Lay term well away from other cables.
Do not place your body between your electrode and work cables.

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-Equipotential bonding
-Workpiece grounding (earthing)
-Shielding
Shield the entire welding equipment and other equipment nearby.
ARC rays can burn
•Visible and invisible rays can burn eyes and skin.
•Wear an approved welding helmet or suitable clothing made from durable flame-resistant material
(leather, heavy cotton, or wool) to protect your eyes and skin from arc rays and sparks when welding
or watching.
•Use protective screens or barriers to protect other nearby personnel with suitable, non-flammable
screening and/or warn them not to watch the arc nor expose themselves to the arc rays or to hot
spatter or material.
Fumes and gases can be dangerous
•Welding may produce fumes and gases, breathing these fumes and gases can be hazardous to your
health.
•When welding, keep your head out of the fume. If inside, ventilate the area at the arc to keep fumes
and gases away from the breathing zone. If ventilation is not good, wear an approved air-supplied
respirator.
•Work in a confined space only if it is well ventilated, or while wearing an air-supplied respirator.
•Welding fumes and gases can displace air and lower the oxygen level causing injury or death. Always
use enough ventilation, especially in confined areas, to insure breathing air is safe.
Welding and cutting sparks can cause fire or explosion
•When not welding, make sure the electrode circuit is not touching the work or ground. Accidental
contact can cause sparks, explosion, overheating, or fire. Make sure the area is safe before doing
any welding.
•Welding and cutting on closed containers, such as tanks, drums, or containers, can cause them to
blow up. Make sure proper steps have been taken.
•When pressure gas is used at the work site, special precautions are required to prevent hazardous
situations.
•Connect work cable to the work as close to the welding zone as practical to prevent welding current
from passing too long and creating fire hazards or overheat.
•Wear oil-free protective garments such as leather gloves, heavy shirt, cuffless trousers, high shoes,
and a cap. Wear ear plugs when welding out of position or in confined places. Always wear safety
glasses with side shields when in a welding area.
•Be attention that welding sparks and hot materials from welding can easily go through small cracks
and openings to adjacent areas and start a fire. Remove fire hazardous from the welding area, if not
possible, cover them thoroughly. Do not weld where flying sparks can strike flammable material and
where the atmosphere may contain flammable dust, gas, or liquid vapors (such as gasoline).
•Protect yourself and others from flying sparks and hot metal. Remove any combustibles from
operator before perform any welding.
•Keep a fire extinguisher readily available.
•Empty containers, tanks, drums, or pipes which have combustibles before perform welding.
•Remove stick electrode from electrode holder or cut off welding wire at contact tip when not in use.
•Apply correct fuses or circuit breakers. Do not oversize or bypass them.
Cylinder can explode if damaged
•Pressure gas cylinders contain gas under high pressure. If damaged, a cylinder can explode. Since
gas cylinders are normally part of the welding process, be sure to treat them carefully.
•Cylinders should be located away from areas where they may be struck or subjected to physical
damage. Use proper equipment, procedures, and sufficient number of persons to lift and move
cylinders.
•Always install cylinders in an upright position by securing to a stationary support or cylinder rack to
prevent falling over or tipping.
•Keep a safe distance from arc welding or cutting operations and any other source of heat, sparks, or
flame.
•No touching cylinder by welding electrode, electrode holder or any other electrically “hot” parts. Do
not drape welding cables or welding torches over a gas cylinder.
•Use only correct compressed gas cylinders, regulators, hoses, and fittings designed for the process
used; maintain them and associated parts in good condition.
•Use only compressed gas cylinders containing the correct shielding gas for the and properly
operating regulators designed for the gas and pressure used. All hoses, fittings, etc. should be
suitable for the application and maintained in good condition.
•Open the cylinder valve slowly and keep your head and face away from the cylinder valve outlet.
•Valve protection caps should be kept in place over valve expect when the cylinder is in use or
connected for use.
Hot parts can burn
•Do not touch hot parts with bare hand or skin.
•Ensure equipment is cooled down before perform any work.

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•If touching hot parts is needed, use proper tools and/or wear heavy, insulated welding gloves and
clothing to prevent burns.
Flying metal or dirt can injure eyes
•When welding, chipping, wire brushing, and grinding can cause sparks and flying metal. It can hurt
your eyes.
•Remember wear appropriate safety glasses with side shields when in welding zone, even under your
welding helmet.
Noise can damage hearing
•Noise from some processes or equipment can damage hearing.
•Remember wear approved ear protection to protect ears if noise level is high.
Moving parts can injure
•Stay away from moving parts such as fans.
•Stay away from pinch points such as drive rolls.
•Keep all doors, panels, covers, and guards closed and securely in place.
•Have only qualified persons remove doors, panels, covers, or guards for servicing and maintenance.
•Reinstall doors, panels, covers, or guards when servicing and maintenance is finished and before
reconnecting input power.
Overuse can cause overheating
•Use machine follow duty cycle. Reduce current or reduce duty cycle before starting to weld again.
•Allow cooling period.
•Do not block or filter airflow to unit.
Static can damage PCB
•Always wear wrist straps before touching PCB or parts.
•Use proper static-proof bags and package to store or move PCB.
Safety markings
•Equipment with CE-markings meets the basic requirements of the Low-Voltage and Electromagnetic
Compatibility Guideline (e.g. relevant product standards according to EN 60 974).
Safety markings
•The equipment with the CCC mark meets the basic requirements stipulated in the Chinese standards
GB / T15579.1-2013 and GB / T8118.
Safety markings
•This marking means that the product is certified for both the U.S. and Canadian markets, to the
applicable U.S. and Canadian standards. The preferred location of the indicators is as shown.

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Contents
1-GENERAL REMARKS.................................................................................................................................................. 6
1-1 Power source features.................................................................................................................................... 6
1-2 Functional principle......................................................................................................................................... 6
1-3 Output characteristics..................................................................................................................................... 7
1-4 Duty cycle..........................................................................................................................................................7
1-5 Applications...................................................................................................................................................... 8
1-6 Warning label....................................................................................................................................................8
2-VERSIONS BRIEFS...................................................................................................................................................... 9
3-BEFORE COMMISSIONING....................................................................................... 错误！未定义书签。
3-1 Utilization for intended purpose only............................................................ 错误！未定义书签。
3-2 Machine installation rules...............................................................................错误！未定义书签。
3-3 Power source connection...............................................................................错误！未定义书签。
3-4 Welding cables instruction............................................................................. 错误！未定义书签。
4-MIG350MC....................................................................................................................................................................12
4-1 System components..................................................................................................................................... 12
4-2 Basic equipments for welding......................................................................................................................12
4-3 Control panel.................................................................................................................................................. 13
4-4 Interface.......................................................................................................................................................... 15
4-5 Installation.......................................................................................................................................................17
4-6 welding process installation......................................................................................................................... 19
4-7 Technical data................................................................................................................................................20
4-8 Dimension.......................................................................................................................................................21
4-9 Disassembly and reassembly......................................................................................................................21
5-WIREFEEDER..............................................................................................................................................................23
6-TROUBLE SHOOTING...............................................................................................................................................24
7-CARE AND MAINTENANCE..................................................................................................................................... 25

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1-GENERAL REMARKS
1-1 Power source features
This series welding machines apply IGBT soft switch inverter technology; the power source enjoys highly stable welding
voltage against the fluctuation of power grid and arc length change. The internal control system achieves precise control
of welding process to ensure optimal welding results.
Features and benefits:
Enjoy reasonable static characteristic and sound dynamic characteristic
Less spatter due to the advanced waveform control technology
Continuous adjustment of welding current and voltage with wide range
2 step / 4step
Perfect functions of starting arc and reducing melting ball while stopping arc
Multiple security functions
Compact design, installed wire feeder, needle roller bearing design, stable wire feeding
Energy saving
Polarity conversion plug/socket design, easy for solid wire and FCAW welding switch
VRD function
1-2 Functional principle
This series of power sources adopt IGBT soft switch inverter technology to improve the dynamic response rate and make
the machines with small size and light weight. The control circuit's closed-loop control makes the power source enjoy
strong ability against power grid fluctuation and perfect welding performance. The schematic diagram is as shown in Fig.
1-2-1:
Fig. 1-2-1: Schematic diagram

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1-3 Output characteristics
Fig. 1-3-1: Output characteristics
1-4 Duty cycle
Duty cycle is percentage of 10 minutes that a machine can weld at rated load without overheating. If overheats,
thermostat(s) will open, output stops. Wait for fifteen minutes for the machine to cool down. Reduce amperage or duty
cycle before welding.
NOTE! Exceeding duty cycle can damage unit and void warranty.
Fig. 1-4-1: Duty cycle

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1-5 Applications
The MIG power source can be used with solid and flux-cored welding wire for welding carbon steel, alloy steel etc. The
power source is designed for the following recommend areas:
The power source is designed for the following recommend areas:
Automobile and components supply industry
Chemical plant construction
Boiler and pressure vessel
Shipyards
Power plant construction
Vehicle manufacturing
Machinery industry
Others
1-6 Warning label
The warning label is affixed onto the top of the power source, and it must not be removed or painted over.
Fig. 1-6-1: Warning label

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2-VERSIONS BRIEFS
Professional welding of special materials requires special welding parameters. Different models of the power sources are
matched to different weldings.
MIG 350MC
MIG350MC series is designed in accordance with the industrial standard. It has constant voltage (CV) and constant
current (CC) characteristics, also has 3 different welding processes: GMAW (MIG), SMAW (STICK) and Simple TIG.

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3-BEFORE COMMISSIONING
Warning! Operating the equipment incorrectly can cause serious injury and damage. Do not use the functions
described here until you have read and completely understood “safety rules”.
3-1 Utilization for intended purpose only
The power source may only be used for CO2/MAG, FCAW,STICK,TIG,GOUGING. Utilization for other purposes, or in any
other manner, shall be deemed to be "not in accordance with the intended purpose". The manufacturer shall not be liable
for any damage resulting from such improper use.Operate, inspect and maintain should follow all the instructions given in
this manual.
3-2 Machine installation rules
According to test, protection degree of this power source is IP21S (optional IP23S). However, the internal key
components must be protected from direct soaking.
Warning! A machine that topples over or falls from its stand can cause injury. Place equipment on an even,
firm floor in such a way that it stands firmly.
The venting duct is very important for safety protections. When choosing the machine location, make sure it is possible for
the cooling air to freely enter and exit through the louvers on the front and back of machine. Any electro conductive
metallic dust like drillings must not be allowed to get sucked into the machine.
3-3 Power source connection
- The power source is designed to run on the voltage given on the nameplate.
- The mains cables and plugs must be mounted in accordance with the relevant technical standards.
- The power supply sockets that come with power source are designed to use strictly according to the marked voltages.
Note!Inadequately dimensioned electrical installations can lead to serious damage. The mains lead, and its
fuse protection, must be dimensioned in accordance with the local power supply. The technical data shown on
the nameplate shall apply.
3-4 Welding cables instruction
When welding, please pay attention to the followings:
a. The welding cables should be kept as short as possible;
b. If extended cable is used, please do as shown in Fig. 3-4-1.

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Wrong
Coil the excess ground cable and welding cable in same
direction respectively.
Correct
Straighten the ground cable and welding cable and make
them close to each other.
Bundle the ground cable and welding cable together, running
the wires close to the ground.
Correct
When the excess cables are only be used by rolling up, coil
the cables to two windings inreverse direction and overlap
them.
The number of turns for A is same as the number for B.
Handle the welding cable and ground cable according to
above-mentioned method.
Fig. 3-4-1: Welding cables instruction

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4-MIG350MC
4-1 System components
This series of machines can be equipped with many different accessories and can be used in various special sites with
different configurations.
Fig. 4-1-1: System components
4-2 Basic equipments for welding
Basic equipments are needed for normal welding. Below are the lists:
MIG/MAG welding
-Power source
-Ground cable
-MIG/MAG welding torch
-CO2 gas regulator, gas hose, gas cylinder (to supply the machine with shielding gas)
-Welding wire
STICK
-Power source
-Ground cable
-Electrode holder
-Electrode
TIG
-Power source
-Ground cable
-TIG torch

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-Gas regulator, gas hose, gas cylinder (to supply the machine with shielding gas)
-Welding wire
4-3 Control panel
The functions on the control panels are all arranged in a very logical way. The various modes and parameters needed for
welding are easy to select by pressing the appropriate button; parameters are easy to be adjusted by rotating encoder.
Synergic adjustment makes the complicated operation much easier.
Note! Some described parameters in this manual may be slightly different from the power source, some
identification may be slightly different from power source identification, but the manner of working is the same.
Warning! Operating the equipment incorrectly can cause serious injury and damage. Do not use the functions
described here until you have read and completely understood all content of this manual.
Fig. 4-3-1 Control panel
1.Welding current displayer
- MIG:When in open load, the wire feeding speed relative value (0~100) is displayed; during welding, display the actual
welding current value.
- Stick, TIG:When in open load, display the preset welding current value; during welding, display the actual welding
current value
2.Welding voltage displayer
- MIG:When in open load, display the preset welding voltage value; during welding, display the actual welding voltage
value.
- Stick, TIG:Display the actual welding voltage both in open load and during welding.

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3.Power indicator
Indicate whether the welding machine is power on or not.
4.Protection indicator
During normal welding, the indicator lights off;
Indicator lights up and machine will automatically stop working if the power source overheats. Do not cut off the power
supply if machine come into overheat protection mode. Keep the fan running until the machine inner temperature recovers
to normal and the overheat protection indicator lamp is off, and then start welding after 20 minutes later.
5.Welding current adjustment knob
- MIG/MAG: it is used to preset wire feeding speed (0-100).
-Stick/TIG: it is used to preset welding current, range is 20~350A.
6.Inductance /arc force adjustment knob
- MIG/MAG, FCAW: it is used to change the welding stability, penetration and spatter.
When decrease inductance, there will be stiff, stable arc, smaller penetration and more spatter; when increase inductance,
there will be soft arc, bigger penetration, less spatter;
- Stick: it is used to adjust the arc force current value;
- TIG: inactive.
7.Welding voltage adjustment knob
When standby, it is used to preset welding voltage; during welding, it is used to adjust the actual welding voltage.
8.Welding process selection switch
Below are the selectable welding processes:
- MIG
- STICK
- TIG
9.Torch trigger control mode(2T/4T)
2-T:It is mainly used for short weld seam welding;
4-T:This mode is mainly used for long weld seam welding and process that needs crater filler welding.
Symbols
Fig. 4-3-2: Press torch trigger Fig. 4-3-3: Hold torch trigger Fig. 4-3-4: Release torch trigger
2-step mode
In this mode, press torch trigger for normal welding, release torch trigger to stop welding. It is mainly used for short
welding seam.

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Fig. 4-3-5: 2-step mode
4-step mode
After pressing torch trigger and successfully start arc, then you can release trigger for normal welding. When re-press
trigger, then turn into crater filler standard (crater filler standard is the same with welding standard) preset on front panel,
release trigger to stop welding. This mode of welding is mainly used for long welding seam.
Fig. 4-3-6: 4-step mode
4-4 Interface
Fig. 4-4-1: Interface
1. Euro-type connector (+)
In MIG mode: connect to welding torch.

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2. Polarity conversion plug
It is used to connect with polarity conversion socket. Only when they connect well, welding torch can work.
In MIG mode use solid wire: it is used to connect with output terminal (+);
In MIG mode use Flux core wire: it is used to connect with output terminal (-).
3. Welding machine output terminal (-)
In MIG mode flux cored wire: it is used to connect with polarity conversion plug;
In TIG (GTAW): it is used to connect with torch plug;
In STICK (SMAW): it is used to connect with ground cable.
4. Welding machine output terminal (+)
In MIG mode solid wire: it is used to connect with polarity conversion plug;
In TIG (GTAW): it is used to connect with ground cable;
In STICK(SMAW): it is used to connect with welding cable.
5. Spool gun control socket
6. Circuit breaker
The function of circuit breaker is to protect welding machine and operator by automatic trip to turn-off power
supply when overload or short circuit happens to the power source. Normally, the switch flipped to upward means
power-on. To start or stop the welding machine is done by the mains switch in the distribution box. Please do not
take this circuit breaker as the power switch.
7. Power cord
8. Fan
9. Gas inlet
Connect with gas cylinder by gas hose
10. Name plate
11. Wire spool axle
For bearing the standard-size wire spool
12. wire test
13. Torch selection(spool torch/push torch)
14. Wire feeding device
15. Swivel wheel
16. Fixed wheel

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4-5 Installation
Warning! An electric shock can be fatal. If the machine is plugged into the mains electricity supply during
installation, there is high risk of very serious injury and damage. Do not use the functions described here until
you have read and completely understood “safety rules” in the beginning.Only carry out work on the machine
when
- the mains switch is on turn-off position,
- the machine is unplugged from the mains.
● Installation environment requirements
1. It should be placed indoors without direct sunlight, rainproof, low humidity and less dust. The ambient air temperature
range is -10℃~+40℃.
2. The inclination to the ground should not exceed 10°.
3. There should be no wind in the welding station, if any, it should be covered.
4. The welding machine is more than 20cm away from the wall, and the distance between the welding machine is more
than 10cm.
5. When using water-cooled welding torch, pay attention to anti-freezing.
●Power supply and cable requirement
Please note the size of fuse and circuit breaker in the table below are for reference only.
Table4-5-1: Power supply and cable requirement
Note! Welding machine must be taken special design if it is powered by generator, please contact with manufacturer if
you have such needs.
●Connections of Power cord and distribution box
Warning! -Avoid hot-line work
- Operating by professional electrician
- Avoid connecting two power sources to one breaker
- Please refer to Table 4-5-1 to check if standard of input voltage, breaker and input cable is suitable
Model
350
Power supply
3 phase, AC380/400V±10%, 50/60Hz
Electricity grid min.
power (KVA)
Power grid
17
Generator
30
Input protection(A)
Fuse
30
Circuit breaker
32
Cable size (mm²)
Power cord
≥4
Output cable
50
Protective GND wire
≥4

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Fig. 4-5-1: Connections of power cord and distribution box
●Gas cylinder installation
1. Stand the gas cylinder on the trolley and secure it by fixing the cylinder
strap around a point in the top third of the cylinder-but never around the
neck of the cylinder.
2. Take the protective cap off the gas cylinder.
3. Gently turn the gas-cylinder value anticlockwise, and blow off any dust and
dirt.
4. Screw the pressure regulator onto the gas cylinder and tighten it.
5. Connect the shielding-gas connector to the pressure regulator.
Fig. 4-5-2: Gas cylinder installation
●Mounting the torch
To ensure normal welding, please make sure that the wire diameter, contact tip, welding torch, welding wire tube are
matched to each other.. Choose wire feeding tubes according to wires of different diameters and materials.
- Steel wire hose is suitable for hard wire, such as carbon steel wire, stainless steel wire.
For installation of steel wire feed hose
Fig. 4-5-3: Installation for steel wire feed tube

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Note!If the wire hose is too tight or too loose, it will increase resistance for wire feeding and cause wire
feeding unstable.
4-6 welding process installation
Warning! Operating the equipment incorrectly can cause serious injury and damage. This part is about
operating. Do not use the functions until you have read and completely understood content of this manual.
●MIG welding process installation
Fig. 4-6-1: Installation for MIG
●STICK welding process installation
Fig. 4-6-2: Installation for STICK