Rtech MIG251 User manual

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R-TECH MIG251
MIG WELDER
OPERATION INSTRUCTIONS
Version 2023-11

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Thank you for selecng the R-Tech MIG251 Digital Inverter MIG Welder.
The MIG251 Digital has many benets over tradional MIG welders, including EASY SETUP,
innite power control and spool gun opon for easy aluminium welding.
We want you to take pride in operang our MIG251 Digital as much pride as we have taken in
making this product for you. Please read all informaon in this manual before operaon
PLEASE EXAMINE CARTON AND EQUIPMENT FOR DAMAGE IMMEDIATELY
When this equipment is shipped, tle passes to the purchaser upon receipt from the courier. Con-
sequently all claims for material damaged in shipment must be made by purchaser against the
transportaon company used.
Please record your equipment idencaon below for future reference. This informaon can be found
on data plate at rear of machine.
Product: MIG251 Digital MIG Welder
Serial No.
Date of Purchase
Where Purchased
Whenever you request replacement parts or informaon on this equipment please always supply
informaon you have recorded above
Pay parcular aenon to the safety instrucons we have provided you for your protecon The level of
seriousness to be applied to each secon is explained below
This statement appears where the informaon must be followed exactly to avoid serious per-
sonal injury.
CAUTION
This statement appears where the informaon must be following to avoid a minor personal inju-
ry or damage to this equipment.

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Introducon
The R-Tech MIG251 welder is a member of our eld acclaimed family of welding machines.
Premium features include
Digital screen with EASY SET
35% Industrial duty cycle
Inverter power source - more ecient
Quite fan cooling system
Spool gun opon
MMA Sck welder
Lightweight and portable
Euro type torch ngs for easy torch tment/replacement
EASY SETUP MIG and MMA
Professional MIG weld sengs built in using 0.6/0.8/1.0mm wire, ux cored wire and MMA sengs
for 6013/7018 electrode.
Simple to use easy navigaon - no complicated menus - all sengs on single screen.
Trim control to ne tune weld power and wire speed.
MANUAL MIG MODE
Innite welding voltage to allow ne tuning of weld characteriscs
2T, 4T Trigger modes
Burnback control
Spool gun facility - Easy aluminium welding
Welding Capability – Duty Cycle
The R-Tech MIG251 Digital is rated at 250 Amps at 35% duty cycle on a ten minute basis.
If the duty cycle is exceeded a thermal protector will shut machine o unl the machine cools.

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Safety Precauons
Read enre secon before starng installaon.
Warning!
Electric Shock can kill – Only qualied personnel should perform this installaon. Turn o input power at
the fuse box before working on this equipment. Do not touch electrically live parts. Always connect the
machine to an earthed mains supply as per naonal recommended standards.
Select suitable locaon
Place the welder where clean cooling air can freely circulate in and out of the front & rear louver vents.
Dirt, dust or any foreign material that can be drawn through vents into welder must be kept to a mini-
mum. Failure to observe these precauons can result in excessive operang temperatures which can lead
to plant failure.
Grinding
Do not direct grinding parcles towards the welder.
An abundance of conducve material can cause plant failure.
Transport & unloading
Never underesmate the weight of equipment, never move or leave suspended in the air above people.
Use recommended liing/handling equipment at all mes.

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Electrical installaon
WARNING ELECTRIC SHOCK CAN KILL
Electric Shock can kill – Only qualied personnel should perform this installaon. Turn o input power at
the fuse box before working on this equipment. Do not touch electrically live parts. Always connect the
machine to an earthed mains supply as per naonal recommended standards.
Machine grounding and Interference Protecon
This welder must be grounded to earth. See naonal electrical codes for proper grounding methods.
The high frequency generator being similar to a radio transmier may cause interference to radio, TV and
other electronic equipment. These problems may be the result of radiated interference.
Proper grounding methods can reduce or eliminate this.
Radiated interference can develop in the following ways
1. Direct interference from welder power source
2. Direct interference from the welding leads
3. Direct interference radiated from feedback into power lines
4. Interference from re-radiaon by un-grounded metallic objects.
Keeping these contribung factors in mind, installing equipment as per following instrucons should
minimize problems.
1. Keep the welder input power lines as short as possible and enclose as much of them as possible in met-
al conduit or equivalent shielding. There should be a good electrical contact between this conduit and
ground (Earth).
2. Keep the work and electrode leads as short as possible. Tape the leads together where praccal.
3. Be sure the torch and earth leads rubber coverings are free from cuts and cracks that allow welding
power leakage
4. Keep earth lead connecon to work in good condion – Clean area on workbench where earth clamp is
situated on a regular basis.

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Electrical installaon cont.
Input Connecons
Make sure the voltage, phase and frequency of input power is as specied on machine rang
plate located at rear of machine.
Have a qualied electrician provide suitable input power as per naonal electrical codes. Make
sure machine is earthed / grounded.
Make sure fuse or circuit breaker is correct rang for machine. Using fuses or circuit breakers
smaller than recommended will result in ‘nuisance’ shut o from welder inrush currents even if
welding at low amperages.
Failure to follow these instrucons can cause immediate failure within the welder and void ma-
chines warranty.
Turn the input power OFF at the mains switch & fuse box before working on this equipment. Have
a qualied electrician install & service this equipment.
Allow machine to sit for 5 minutes minimum to allow the power capacitors to discharge before
working inside this equipment. Do not touch electrically live parts
The MIG251 Digital MIG Welder requires a 240V 50/60Hz supply. It requires a 32A supply.
It comes with a 2.5 metre mains cable aached.
Connect wires according to naonal coding.
Brown wire – Live
Blue wire – Neutral
Green/Yellow Wire – Earth (Ground)
Connecng to an Engine Driven Generator
If connecng this machine to an engine driven generator please ensure the following
Minimum Generator KVA Output – 7.0 KVA connuous Generator to be ed with AVR
(automac voltage regulaon) DO NOT USE ON A GENERATOR WITHOUT AVR
Connecng to a generator without the above minimum requirements
will invalidate your warranty.

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Input 240V AC 50/60Hz Input amperage 32A
Gross weight 20 KG
Dimensions 600L x 270W x 480H (mm)
Insulaon IP21S
MIG Current range MIG 30A - 250A
No load voltage 80VDC
Duty cycle 35% @ 250A
Trigger modes Manual mode 2T,4T
MIG EASY SET Wire diameter 0.6, 0.8, 1.0mm
Material thickness selector 0.8, 1.0, 1.5, 2.0, 3.0, 4.0, 5.0, 6.0, 8mm
MIG Manual mode Welding voltage 13.0 - 27V
Wire feed speed 1.5 - 15.0 m/min
Spool gun opon Yes
Burnback control 0.0s - 2.0s
Wire diameter 0.6, 0.8, 1.0mm
MMA EASY SET Electrode size 2.5, 3.2, 4.0mm
Electrode type 6013, 7018
Material thickness 1.5 - 10.0mm (See page 19)
MMA Manual mode Amperage range 20 - 200A
Electrodes Mild / Stainless Steel / Dissimilar
Technical specicaons

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Connecons
Front panel connecons
MIG mode + posive
connector for earth
lead for gasless ux
cored wire only.
MMA mode - connect
electrode holder.
7 pin socket for
spool on gun.
MIG mode - connect
earth lead (negave)
when welding with
GAS.
MMA mode - connect
Earth lead
Euro torch connector. Connect Euro type MIG torch to euro torch connector, align torch connector to machine con-
nector and then turn retaining ring clockwise to secure. Ensure torch is secured ghtly to avoid weld power problems

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Rear panel connecons cont..
Gas connector & Extra earth connecon
3/8 BSP male connector
for gas input
Extra earth connecon, used if you experience
local interference (not normally used)
On/O
switch
Mains input cable - comes
with 2.5m cable ed.

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Wire feed assembly, wire reel holder & gasless wire
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1 - Wire reel retainer. Screw in to retain wire roll adaptor onto wire reel.
2 - Wire Feed Drive Assembly. To change roller size release retaining screw, remove roller and turn
roller around and slide onto sha making sure the right size groove is in line with wire and ret re-
taining screw. The MIG251 comes ed with a dual rollers 0.6/0.8mm & 0.8/1.0mm.
3 - Roller tensioner - This sets the pressure of rollers, the best way to adjust tension is to slacken o
pressure so that MIG welding wire does not feed, slowly adjust pressure unl wire feeds
smoothly, you should be able to stop wire feeding by holding wire and it should slip on rollers.
If you have too lile pressure wire will slip when welding causing unwanted Burn back into ps or
errac weld beads size.
4 - When using gasless wire, move internal cable to negave connector – This then makes the torch
negave, you would then connect Workpiece earth lead to + posive connector on front of machine
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Front panel
Digital Colour Screen with easy to navigate menu system
EASY SET mode - pre-programmed weld sengs MIG & MMA
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3456
7 8
910
1 - Wire feed speed - Turn to change seng in small steps, press and turn to change in larger steps
2 - Welding voltage - Turn to change seng in small steps, press and turn to change in larger steps
3 - SELECT buon - Press to cycle through four welding modes
4 - Le arrow buon - use to scroll le in menus
5 - Right arrow buon - use to scroll le in menus
6 - EASY SET buon - press to enable / disable EASY SET mode
7 - Wire feed speed display
8 - Welding voltage display
9 - Wire diameter display - EASY SET
10 - Work thickness display - EASY SET

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Controls and sengs
The MIG251 features 4 main operang modes
MIG in EASY mode
MIG in Manual mode
MMA (STICK) in EASY mode
MMA (STICK) in Manual mode
MIG EASY MODE - With gas
R-Tech Easy mode takes the guesswork out of MIG welding. You normally had to enter wire speed and
welding voltage to weld on manual welders, we have done this for you.
You simply select the following from easy to understand screen.
Wire diameter
Material thickness
The machine will set main welding voltage and wire feed speed
Press select buon to required gas being used 95% Arg/Co2 or 20% Arg/Co2
TO ENTER EASY MODE - PRESS EASY SET BUTTON ON FRONT PANEL
Press le arrow to switch between 0.6mm, 0.8mm and 1.0mm wire diameter, the selected size will ash
Now press right arrow to switch between material thickness, the selected size will ash
EASY SET MIG 0.6mm wire
The above image shows 0.6mm wire selected, you then have material thickness opons of
0.8mm, 1.0mm, 1.2mm, 1.5mm, 2.0mm

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EASY SET MIG 0.6mm connued
Once you have selected 0.6mm wire size and material thickness the suggested wire speed
and voltage will be shown in the display, you are now ready to weld.
If you want to ne tune the weld characteriscs to suit your personal preference.
You can trim the wire speed by 1 m/min by turning wire speed knob.
You can trim the welding voltage by +/- 1V by turning welding voltage knob.
EASY SET MIG 0.8mm wire
The above image below shows 0.8mm wire selected, you then have material thickness opons of
0.8mm, 1.0mm, 1.5mm, 2.0mm, 2.5mm, 3.0mm, 3.5mm and 4.0mm
Once you have selected 0.8mm wire size and material thickness the suggested wire speed
and voltage will be shown in the display, you are now ready to weld.
If you want to ne tune the weld characteriscs to suit your personal preference.
You can trim the wire speed by 1 m/min by turning wire speed knob.
You can trim the welding voltage by 1V by turning welding voltage knob.
EASY SET MIG 1.0mm wire
With 1.0mm wire selected, you then have material thickness opons of
1.5mm, 2.0mm, 3.0mm, 4.0mm, 5.0mm, 6.0mm, 8.0mm

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Once you have selected wire size and material thickness the suggested wire speed
and voltage will be shown in the display, you are now ready to weld.
Material thickness opons of 0.8mm wire
1.0mm, 1.5mm, 2.0mm, 3.0mm and 4.0mm
If you want to ne tune the weld characteriscs to suit your personal preference.
You can trim the wire speed by 1 m/min by turning wire speed knob.
You can trim the welding voltage by +/- 1V by turning welding voltage knob.
Material thickness opons of 0.9mm wire
1.5mm, 2.0mm, 3.0mm, 4.0mm and 5.0mm
Material thickness opons of 1.0mm wire
1.5mm, 2.0mm, 3.0mm, 4.0mm, 5.0mm, 6.0mm,8.0mm
MIG EASY MODE - Gasless wire (Flux cored)
Press select buon to Flux-Cored indicator.
TO ENTER EASY MODE - PRESS EASY SET BUTTON ON FRONT PANEL
Press le arrow to switch between 0.8mm,0.9mm & 1.0mm wire diameter, the selected size will ash
Now press right arrow to switch between material thickness, the selected size will ash

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MIG Manual mode
In manual MIG mode you have full control of welding wire feed speed, welding voltage,
2T/4T trigger opons, Burnback control and spool on gun operaon.
Use select buon to select 95% ARG Mode, ensure EASY SET is o, the following screen will be shown.
Set wire feed speed using le side knob, adjustable between 1.5 - 15 m/min.
Set welding voltage using right side knob, adjustable between 13v - 27v.
2T & 4T Trigger control
You can select between 2T and 4T trigger opons by pressing le or right arrow buons unl 4T is ashing,
then use le knob to turn from o/on.
2T - Press trigger to start weld, release to nish weld.
4T - Press and release trigger to start weld, To nish weld press and release trigger.
This is commonly know as trigger latching.

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Burnback control
Burnback is how long the welding power will connue aer wire feed has stopped, this stops the wire
from scking to workpiece when weld nished, if Burnback is set too long you can experience wire burning
back to p.
You can adjust Burnback by pressing le or right arrow buons unl Burnback is ashing, then use le
knob to adjust from 0s to 2.0s
For most applicaons a seng of 0.3s is advised.
Spool on Gun opon
For best results when welding aluminium we recommended using a spool on gun as shown in image below
You can select spool gun funcon by pressing le or right arrow buons unl SPOOL is ashing, then use
le knob to switch from o/on. When switched on the internal wire feed is disabled.
Disconnect standard MIG torch and connect spool gun to euro connector and 7 pin plug to machine
Note: Pure argon is required when welding aluminium.

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MMA (STICK) EASY
R-Tech EASY SET mode takes the guesswork out of MMA welding. You normally had to enter
required amperage to weld on manual welders, we have done this for you.
You simply select the following from the easy to understand screen.
Electrode Type 6013 or 7018
Electrode diameter
Material thickness
The machine will set main welding amperage required.
Press select buon so MMA mode is illuminated.
TO ENTER EASY MODE - PRESS EASY SET BUTTON ON FRONT PANEL
Press le arrow to switch between electrode type and electrode size, the selected electrode type and size
will ash.
Now press right arrow to switch between material thickness, the selected size will ash.
Once you have selected electrode type and size and material thickness, the required welding amperage
will show in display as image below. You are now ready to weld.
090
You can trim the welding amperage by using le control knob + /- 10 amps to suit your personal
welding travel speed / weld bead.

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MMA (STICK) EASY cont..
Note: When in MMA mode the welding terminals are constantly LIVE.
Ensure electrode / electrode holder are not touching workpiece / earth when switching to MMA mode.
MMA EASY SET SETTINGS.
Electrode Type Electrode Size Material thickness
6013 2.5mm 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0mm
6013 3.2mm 3.0, 4.0, 5.0, 6.0, 8.0mm
6013 4.0mm 4.0, 5.0, 6.0, 8.0, 10mm
7018 2.5mm 3.0, 4.0, 5.0, 6.0mm
7018 3.2mm 4.0, 5.0, 6.0, 8.0mm
7018 4.0mm 5.0, 6.0, 8.0, 10mm
Image below shows 6013, 3.2mm electrode with 3.0mm material thickness selected and using
le control knob the welding amperage has been increased from 80A to 87A using trim funcon as
indicated by arrow.

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To change welding amperage use le side control knob to required amperage.
Range is 20 - 200 amps.
MMA (STICK) Manual mode
Note: When in MMA mode the welding terminals are constantly LIVE.
Ensure electrode / electrode holder are not touching workpiece / earth when switching to MMA mode.
To enter MMA manual mode, use select buon to move indicator to MMA then ensure EASY SET is turned
o. You will see the following screen.