Manual and CNC Welding: A Complete Guide to MMA, MIG, TIG, Plasma and Automated Welding
Welding is one of the most important manufacturing processes used in engineering, fabrication, construction, automotive production and general industry. From repairing a steel gate to manufacturing pressure vessels or producing thousands of automotive components, there is a welding process suited to almost every application. In this post we will take a look at the different welding types available.
MMA, MIG, MAG, TIG, FCAW, plasma and resistance welding all have different advantages. The best choice depends on the material, thickness, required weld quality, production volume, available equipment and, importantly, the skill of the welder.
What are the main different welding types that you will encounter?
The most common welding processes used in engineering and fabrication include:
- MMA / Stick welding (SMAW)
- MIG welding (GMAW)
- MAG welding
- TIG welding (GTAW)
- Flux-cored arc welding (FCAW)
- Plasma arc welding (PAW)
- Submerged arc welding (SAW)
- Resistance spot welding
- Laser welding
- Robotic and CNC welding
MIG, MAG, MMA and TIG are particularly common in general engineering because they cover a very wide range of materials and applications.
MMA Welding
MMA, or Manual Metal Arc welding, is also known as stick welding or SMAW.
It uses a consumable electrode coated with flux. An electric arc is created between the electrode and the workpiece. The electrode melts and provides filler metal while the flux produces shielding gas and slag.
MMA is one of the simplest welding processes because the equipment is relatively compact and does not require a shielding-gas cylinder.
Advantages of MMA welding
MMA remains extremely useful despite the availability of more automated processes.
Its main advantages include:
- Relatively inexpensive equipment.
- Very portable.
- No shielding-gas cylinder is required.
- Suitable for outdoor welding.
- Can weld relatively dirty or rusty steel better than TIG – think patching a hole in a waste skip.
- Excellent for repair and maintenance.
- Suitable for carbon steel, stainless steel and many alloy steels.
- Long welding leads can be used.
- Particularly useful for structural and heavy fabrication.
Modern inverter MMA machines are considerably smaller and lighter than traditional transformer machines.
For example, the ESAB Rogue ES 181iP weighs only 6.8 kg and can produce up to 180 A for TIG and 170 A for MMA. ESAB specifies 170 A at a 20% duty cycle for MMA and 97 A at 60%.
Disadvantages of MMA
MMA is slower than MIG/MAG because the electrode must be replaced regularly. Effectively the length of a single pass is limited by the length of the stick that you are using.
The process also produces slag which must normally be removed between passes.
Other disadvantages include:
- Lower deposition rate than MIG/MAG.
- Electrode changes interrupt production.
- More difficult to automate.
- Greater variation between welders.
- More post-weld cleaning.
- More difficult to achieve attractive welds on thin sheet.
MMA can also generate relatively high levels of welding fume. HSE specifically identifies MMA as one of the welding processes requiring appropriate fume controls.
Typical MMA applications
MMA is particularly suitable for:
- Structural steelwork.
- Agricultural machinery.
- Heavy machinery repairs.
- Pipework.
- Outdoor fabrication.
- General maintenance.
- Construction.
- Repairing heavy steel components.
Typical MMA equipment cost
| Setup | Approximate UK cost |
|---|---|
| Hobby MMA machine | £100–£250 |
| Good light-industrial inverter | £300–£700 |
| Professional MMA machine | £700–£2,000+ |
| Electrodes | £3–£10/kg |
| Welding helmet | £50–£300 |
| Basic extraction | £200–£800+ |
Consumable cost is generally low, although electrode efficiency is lower than wire processes because some of the electrode becomes slag.
MIG and MAG Welding
MIG and MAG are both forms of gas metal arc welding (GMAW).
The major difference is the shielding gas.
MIG – Metal Inert Gas normally uses an inert gas such as argon.
MAG – Metal Active Gas uses an active gas or gas mixture, commonly argon/CO₂ mixtures or CO₂.
In everyday engineering workshops, the term MIG welding is frequently used to describe both processes.
Instead of replacing an electrode after every weld, the machine continuously feeds wire from a spool through the welding torch.
This makes MIG/MAG much faster than MMA for many applications.
Advantages of MIG/MAG
MIG/MAG is particularly attractive for production welding.
Advantages include:
- High welding speed.
- Continuous wire feed.
- High deposition rate.
- Relatively easy to learn.
- Excellent for fabrication.
- Suitable for thin and medium-thickness sheet.
- Easy to mechanise.
- Suitable for robotic welding.
- Less slag than MMA.
- Excellent productivity.
The process can also use different wire types and shielding gases to suit mild steel, stainless steel and aluminium.
For example, R-Tech’s MIG180 is specified for thin automotive work and fabrication up to approximately 6 mm steel, with a current range starting around 30 A. The manufacturer currently lists it at around £690 including VAT.
Disadvantages of MIG/MAG
MIG/MAG machines are more complicated than MMA machines.
The operator needs to manage:
- Wire feed speed.
- Welding voltage.
- Shielding gas.
- Contact tip condition.
- Torch position.
- Gas flow.
- Wire diameter.
The process is also more vulnerable to wind because the shielding gas can be blown away. This can result in poor quality porus welds.
This makes conventional MIG/MAG less convenient for exposed outdoor work.
Materials suitable for MIG/MAG
MIG/MAG can be used on:`
- Mild steel.
- Low-alloy steel.
- Stainless steel.
- Aluminium.
- Some nickel alloys.
The choice of wire, shielding gas and welding parameters is important.
Typical MIG/MAG equipment cost
| Setup | Approximate UK cost |
|---|---|
| Hobby MIG machine | £250–£600 |
| Light industrial MIG | £600–£1,500 |
| Professional MIG/MAG | £1,500–£5,000+ |
| Industrial pulse MIG | £4,000–£15,000+ |
| Wire | £3–£10/kg |
| Shielding gas | £30–£100+ per cylinder/refill depending on size and contract |
| MIG torch consumables | £10–£50+ |
For production work, the consumable cost per metre of weld can be substantially lower than MMA because wire feed is continuous and there is less interruption.
TIG Welding
TIG, or Tungsten Inert Gas welding, is also known as GTAW.
Unlike MMA and MIG, the tungsten electrode does not normally become part of the weld. Instead, it creates the arc while separate filler rod can be added by the operator.
TIG uses an inert shielding gas, normally argon.
TIG is famous for producing exceptionally clean and precise welds.
Advantages of TIG
TIG is often the first choice when weld appearance and control are critical.
Advantages include:
- Excellent weld quality.
- Very precise heat control.
- Minimal spatter.
- Excellent appearance.
- Suitable for very thin material.
- Excellent for stainless steel.
- Excellent for aluminium when using AC TIG.
- Suitable for nickel alloys.
- Excellent for pipework.
- Excellent for aerospace and specialist fabrication.
Disadvantages of TIG
The main disadvantage is speed.
TIG is considerably slower than MIG/MAG, particularly when welding thicker material.
The operator also needs significantly more skill.
The joint must be extremely clean because contamination can easily affect the weld.
Disadvantages include:
- Higher labour cost.
- Slower deposition rate.
- Greater operator skill required.
- More expensive equipment.
- Shielding gas required.
- Sensitive to contamination.
- Less economical for thick-section production welding.
TIG is therefore often used for the root pass of a weld, with a faster process such as MIG/MAG or submerged arc welding used for subsequent passes on thicker sections.
TIG equipment cost
| Setup | Approximate UK cost |
|---|---|
| Basic DC TIG | £300–£700 |
| Good AC/DC TIG | £700–£1,800 |
| Professional TIG | £1,500–£5,000+ |
| Industrial AC/DC TIG | £5,000–£15,000+ |
| Tungsten electrodes | £2–£10 each |
| TIG filler rod | £5–£20/kg |
| Argon | £30–£100+ per cylinder/refill |
| TIG torch consumables | £10–£100+ |
As an example, R-Tech’s 171 TFT AC/DC TIG machine is currently listed around £1,548 including VAT and is advertised for steel and aluminium up to approximately 5 mm.
Flux-Cored Arc Welding
FCAW, or Flux-Cored Arc Welding, is similar to MIG welding but uses a hollow wire containing flux.
There are two broad forms:
- Gas-shielded flux-cored wire.
- Self-shielded flux-cored wire.
Self-shielded FCAW is particularly useful for outdoor fabrication because it does not necessarily require an external shielding-gas supply.
Advantages
- High deposition rates.
- Excellent penetration.
- Good for thicker materials.
- Suitable for structural fabrication.
- Self-shielded versions can be used outdoors.
- Easily mechanised.
- Suitable for robotic applications.
Disadvantages
- Produces slag.
- More fumes than some MIG applications.
- Wire can be more expensive.
- Requires more post-weld cleaning than MIG.
- Self-shielded wire can produce considerable smoke and spatter.
FCAW is common in heavy fabrication, construction and structural steelwork.
Plasma Arc Welding
Plasma welding is related to TIG but constricts the arc through a small orifice to produce a concentrated plasma jet.
This produces a narrow, high-energy arc.
Plasma welding can provide:
- Excellent penetration.
- High precision.
- Narrow heat-affected zones.
- Good repeatability.
- High-quality welds.
It is particularly useful for specialised industrial applications, including aerospace, precision manufacturing and automated welding.
The disadvantages are higher equipment costs, more complicated setup and greater operator training requirements.
Plasma welding should not be confused with plasma cutting, which is a separate process.
Submerged Arc Welding
SAW, or Submerged Arc Welding, is primarily an industrial production process.
The arc is hidden beneath a layer of granular flux.
Because the arc is submerged, the process can operate at very high welding currents and deposition rates.
Where is SAW used?
Typical applications include:
- Pressure vessels.
- Structural beams.
- Large pipes.
- Shipbuilding.
- Heavy machinery.
- Long straight welds.
- Large fabricated structures.
SAW is generally unsuitable for small one-off jobs because the equipment is relatively large and the process is normally mechanised.
However, for large production runs it can be extremely economical.
Resistance Spot Welding
Resistance welding works differently from arc welding.
Two or more sheets are clamped between electrodes and a large electrical current is passed through the joint.
Electrical resistance generates heat and creates a weld nugget.
Spot welding is particularly common in automotive manufacturing, if you look at a car or a van you will usually be able to see evidence of spot wleding holding bodywork together.
Advantages
- Very fast.
- Highly repeatable.
- Easily automated.
- Low consumable usage.
- Excellent for sheet metal.
- Suitable for high-volume production.
- Relatively little fume compared with many arc processes.
HSE notes that resistance spot welding tends to produce considerably less fume and spatter than many other welding processes.
Its main limitation is that it is primarily suited to overlapping sheet-metal joints rather than general fabrication.
Laser Welding
Laser welding uses a concentrated laser beam to melt the material.
It can produce extremely narrow welds with relatively low heat input.
Modern laser welding systems can be highly automated and can offer excellent repeatability.
Applications include:
- Automotive components.
- Electronics.
- Medical equipment.
- Battery manufacturing.
- Precision engineering.
- Aerospace components.
The major disadvantage is equipment cost.
A professional laser welding system can cost tens of thousands of pounds, with industrial automated systems potentially costing considerably more.
Laser welding also requires careful consideration of laser safety, guarding and operator protection.
Manual Welding vs CNC and Robotic Welding
Manual welding still has an important place in industry.
It is particularly useful when:
- Production quantities are low.
- Components vary significantly.
- Access is difficult.
- Repairs are required.
- Parts are large.
- Components cannot easily be fixtured.
Automated welding becomes more attractive as production volume increases.
A CNC or robotic welding system can control:
- Torch movement.
- Welding speed.
- Current.
- Voltage.
- Wire feed.
- Arc length.
- Welding sequence.
- Position.
Robotic MIG/MAG welding is particularly common because continuous wire feed makes automation relatively straightforward.
A robot does not necessarily make welding cheaper, however.
The capital cost of the robot, welding power source, fixtures, safety guarding, programming and integration can be substantial.
For low-volume work, a skilled manual welder can often be considerably more economical.
For high-volume production, however, automation can dramatically reduce the cost per component.
Duty Cycle Explained
When comparing welding machines, duty cycle is one of the most important specifications to understand.
A duty cycle describes how long a machine can operate at a particular output during a defined period, usually 10 minutes.
For example:
200 A at 40% duty cycle
means the machine can weld at 200 A for approximately four minutes in a ten-minute period before requiring cooling time.
It does not mean the machine can only be used for four minutes every ten minutes under all circumstances. Lower welding currents normally permit substantially longer operating times.
For example, the ESAB Rogue EMP 210 PRO is rated at:
- 210 A at 30% duty cycle.
- 136 A at 60%.
- 105 A at 100%.
It can operate continuously at the lower output without exceeding its thermal rating.
For a hobbyist welding for a few minutes at a time, a low duty-cycle machine may be perfectly adequate.
For production welding, duty cycle becomes much more important.
Welding Equipment: Hobby, Light Industrial and Professional
The cheapest welding machine is not necessarily the cheapest welding setup.
A complete welding workstation may require:
- Welding power source.
- Torch or electrode holder.
- Earth/return lead.
- Gas regulator.
- Gas cylinder.
- Welding wire or electrodes.
- Welding helmet.
- Gloves.
- Welding jacket.
- Extraction.
- Welding screen.
- Workbench.
- Clamps and fixtures.
- Grinder.
- Cleaning equipment.
Hobby setup: approximately £500–£1,000
A basic hobby setup might include:
- 160–200 A inverter welder.
- MMA capability.
- Basic MIG capability.
- Auto-darkening helmet.
- Gloves and jacket.
- Basic clamps.
- Hand tools.
This is suitable for occasional repairs, brackets, garden machinery and light fabrication.
Light-industrial setup: approximately £1,500–£4,000
A small engineering workshop might invest in:
- 200–300 A MIG/MAG machine.
- MMA capability.
- TIG capability where required.
- Gas cylinder and regulator.
- Quality auto-darkening helmet.
- Welding bench.
- Welding screens.
- Mobile fume extraction.
- Grinding and preparation equipment.
At this level, equipment reliability and duty cycle become much more important.
Professional workshop: £5,000–£20,000+
A professional fabrication shop may require:
- 300–500 A MIG/MAG.
- Pulse MIG.
- TIG AC/DC.
- MMA.
- Water-cooled torches.
- Industrial gas supply.
- Fume extraction.
- Welding positioners.
- Fixtures.
- Welding tables.
- Inspection equipment.
- Welding procedure documentation.
A high-end multiprocess machine can combine several processes in one system. For example, Fronius’ iWave Multiprocess PRO supports TIG, plasma, MIG/MAG and MMA from one platform.
Example Professional Welding Machines
ESAB Rogue EMP 210 PRO
The Rogue EMP 210 PRO is an excellent example of a portable multi-process machine.
It provides:
- MIG.
- MAG.
- Flux-cored welding.
- TIG.
- MMA.
- MIG brazing.
It produces up to 210 A and is rated at 30% duty cycle at maximum MIG/TIG output.
Its relatively compact size makes it suitable for maintenance, repair and light industrial fabrication.
Best suited to: small fabrication shops, maintenance departments and workshops that need several processes from one machine.
ESAB Rogue ET 181iP
The Rogue ET 181iP is a portable TIG/MMA machine weighing approximately 8.7 kg.
It offers:
- High-frequency TIG start.
- TIG pulse.
- MMA.
- Up to 180 A TIG.
- 230 V operation.
- 25% TIG duty cycle at 180 A.
- 100% duty cycle at 90 A.
Best suited to: stainless-steel fabrication, maintenance, pipework and workshops where portability and TIG quality are more important than MIG productivity.
ESAB Warrior Edge 500 DX
At the other end of the scale is the Warrior Edge 500 DX.
This is a genuine industrial machine capable of:
- MIG/MAG.
- TIG.
- MMA.
- 500 A output.
- 60% duty cycle at 500 A.
- 100% duty cycle at 400 A.
- Three-phase operation.
At 85 kg, this is not a machine intended for carrying around a garage.
It is designed for serious industrial fabrication and high-output welding.
Best suited to: heavy fabrication, structural steel, production welding and demanding industrial applications.
How Much Does Welding Really Cost?
The cost of welding is more complicated than the price of the welder.
A useful way of calculating welding cost is:
Total welding cost = labour + electricity + shielding gas + consumables + preparation + finishing + equipment depreciation
For manual welding, labour is often the largest cost.
This is why a process with cheap consumables is not automatically the cheapest process.
For example, TIG may use relatively inexpensive filler rod, but the welding speed is low. MIG wire may cost more per kilogram, but a skilled operator can deposit metal much faster.
This is one reason MIG/MAG is so widely used in production environments.
Welding Materials
The material being welded has a major influence on process selection.
| Material | MMA | MIG/MAG | TIG | Resistance | Laser |
|---|---|---|---|---|---|
| Mild steel | Excellent | Excellent | Excellent | Excellent | Excellent |
| Stainless steel | Excellent | Excellent | Excellent | Good | Excellent |
| Aluminium | Limited | Excellent | Excellent | Good | Excellent |
| Cast iron | Good | Possible | Possible | Poor | Limited |
| Nickel alloys | Good | Good | Excellent | Limited | Excellent |
| Copper | Limited | Possible | Excellent | Good | Good |
| Galvanised steel | Possible | Excellent | Possible | Good | Possible |
These are broad guidelines rather than guarantees. Material grade, thickness, joint design, cleanliness and welding specification all affect the result.
Welding Safety and Ventilation
Welding should never be treated as simply a matter of putting on a helmet and switching on the machine.
There are serious risks from welding fumes, UV radiation, fire, hot metal, electricity, compressed gases and confined spaces.
The UK Health and Safety Executive states that all welding fume can cause lung cancer, and welding fume is subject to the COSHH Regulations.
Welding fume extraction
Good ventilation is essential.
The preferred approach is to capture welding fume at source, rather than allowing it to spread throughout the workshop.
This is normally achieved using local exhaust ventilation (LEV).
Examples include:
- Mobile extraction arms.
- Fixed extraction hoods.
- On-torch extraction.
- Welding booths.
- Enclosed automated cells.
HSE specifically recommends LEV wherever reasonably practicable and identifies on-torch extraction as a particularly effective option for some MIG welding applications.
General room ventilation alone should not automatically be considered an adequate substitute for source extraction.
LEV systems also need appropriate maintenance and examination. HSE states that ventilation control equipment must be examined and tested at appropriate intervals, with 14-month intervals specified in relevant COSHH guidance.
TIG welding is not fume-free
TIG produces relatively little visible particulate fume compared with some other processes, but this does not mean it is harmless.
HSE highlights ozone as a particular concern when TIG welding stainless steel and aluminium.
Other welding hazards
A proper welding risk assessment should also consider:
- UV radiation.
- Arc eye.
- Infrared radiation.
- Burns.
- Molten metal.
- Fire.
- Explosions.
- Electric shock.
- Compressed gas cylinders.
- Grinding dust.
- Noise.
- Confined spaces.
- Contaminated coatings.
- Galvanised coatings.
- Paint and surface treatments.
Welding screens should protect other workers from arc radiation, while appropriate gloves, protective clothing and welding helmets should be selected for the process. HSE recommends suitable welding filters and protective clothing to control UV, infrared radiation and spatter.
7
Which Welding Process Should You Choose?
There is no single welding process that is best for every application.
As a general guide:
Choose MMA when:
- Portability is important.
- You are working outdoors.
- Material is relatively thick.
- The work is repair or maintenance.
- Low equipment cost is important.
Choose MIG/MAG when:
- Productivity is important.
- You are welding mild steel regularly.
- You need high deposition rates.
- You are fabricating brackets, frames or machinery.
- You want to automate the process.
Choose TIG when:
- Weld appearance is important.
- You are welding stainless steel or aluminium.
- Material is thin.
- Heat control is critical.
- High-quality welds are required.
Choose FCAW when:
- High deposition rates are required.
- You are welding structural steel.
- Outdoor welding is required.
- Thick material is involved.
Choose resistance welding when:
- You are producing large quantities.
- The components are sheet metal.
- High repeatability is required.
- Automation is desirable.
Choose robotic/CNC welding when:
- Production volumes are high.
- Components are consistent.
- Welding paths can be standardised.
- Repeatability is important.
- Labour cost is significant.
Final Thoughts
Choosing a welding process is ultimately a balance between weld quality, production speed, material, equipment cost, consumables and labour.
MMA remains one of the most versatile and affordable processes for repair work and heavy fabrication. MIG/MAG offers an excellent combination of speed, productivity and relatively straightforward operation. TIG provides outstanding control and weld quality, particularly on stainless steel and aluminium.
For high-volume manufacturing, automated MIG/MAG, resistance welding, laser welding and other mechanised processes can dramatically improve consistency and production rates.
The most expensive welding machine is not necessarily the best choice. A £10,000 machine may be completely unnecessary for occasional repair work, while a £500 machine could be a false economy in a production environment where high duty cycle, reliability and repeatability are essential.
The right approach is to start with the component, material, thickness, joint design and production volume, then select the welding process and equipment around those requirements.
For professional welding work, safety should be considered at the same time as productivity. Effective fume extraction, appropriate PPE, welding screens, training and a suitable risk assessment are essential parts of a modern welding facility.