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What is a Pulse MIG? A how & why guide to Pulse MIG welding
The how, what and why guide to pulse MIG welding -
Welders, Single-Phase Power, and Plugs: Your questions answered
Plus: Tips For Using Welders on 10A Single-Phase Power
What is a Pulse MIG? A how & why guide to Pulse MIG welding
What is Pulse MIG Welding?
Pulse MIG offers fast, high quality, low spatter and consistently great looking welds, with better thermal control vs. conventional MIG welders.
Pulse MIG is best known as a great process for welding aluminium, however it is also an excellent process for welding with steel, stainless-steel, and bronze wires. In many cases, Pulse MIG can achieve results that are comparable to TIG welding, but with superior speed and productivity.
In technical terms, Pulse MIG is a highly-controlled spray-transfer MIG process. Unlike the traditional 'short-circuit' MIG process, when pulse welding the filler metal is transferred from the wire to the weld pool, without the wire contacting the weld pool. The current alternates, or pulses, between a high peak current and a low background current at a frequency of up to several hundred times per second. With each pulse, the peak current pinches off a droplet of wire and propels it to the weld joint, while the background current maintains the arc at a low enough power level so that short-circuit can’t occur.
Why use Pulse MIG ?
Among other benefits, Pulse MIG is best known (or desired) because it offers;
- Lower heat = minimal distortion, reduced burn-through
- Reduced spatter: Spatter is significantly reduced, or even eliminated = Minimal cleanup
- Visually appealing welds = Added value to the finished product
- Higher deposition rates = Increased efficiency & faster travel speeds
- Tighter weld pool control = Ideal for out-of-position welding
- Reduced welding fumes = Safer & cleaner work environment
What metals can you weld with Pulse MIG ?
Pulse MIG is ideal for metals and applications where controlling heat is difficult when using standard MIG process, and/or where high weld quality and appearance is desired.
Pulse MIG welding Aluminium
Aluminium is a high thermal conductor (which means that heat is quickly transferred away from the weld pool), with a relatively low melting temperature. Pulse MIG process allows the operator much greater thermal control to apply enough heat for a successful weld, whilst avoiding distortion or burn-through.
Pulse MIG welding with Bronze wires (MIG brazing)
Bronze wires are typically applied at a temperate that is lower than the melting point of the parent material - where the materials are essentially "stuck" rather than welded together - and are commonly used on thin materials (eg car body panels) where low temperature welding is essential to avoid distortion. Also commonly used on galvanised or zinc-coated steels (up to 2mm thickness) because the weld metal does not rust and the lower application temperature prevents disturbance (evaporation) of the zinc coating. The ability to control and reduce heat makes pulse an ideal process for brazing wires.
Pulse MIG welding with Stainless-Steel
Because stainless-steel is a poor thermal conductor, heat is typically 'trapped' close to the weld zone. This can result in expansion/distortion and rust contamination due to concentrated carbon in the weld zone. The weld pool is comparitively sluggish with poor wetting/flow into parent metal. The pulse process allows stainless wires to be applied at lower temperatures to minimise distortion and imperfectons. Pulse MIG is especially beneficial for welding thin stainless material where it is often extremely difficult, if not impossible, to avoid warpage/distortion with conventional MIG process.
Pulse MIG welding mild steel
Mild-steel does not present the same "thermal challenges" as other metals like aluminium or stainless, so pulse does not necessarily offer the same advantages in this respect. For this reason, conventional MIG may be the most practical process for welding mild steel in many applications. That said, pulse will still offer reduces spatter levels and improved weld appearance in many applications, better control when welding thin materials, and higher-deposition rates for faster / more efficient welding (especially heavier materials).
What is Double-Pulse MIG ?
Also known as dual-pulse or pulse-on-pulse (PoP), this adds an additional pulse 'wave', where the current alternates (or cycles) between the main current level and a secondary current level. This effectively multiplies the benefits of single-pulse, with even better thermal control, weld quality and appearance.
Pulse MIG vs TIG Welding
TIG is traditionally the go-to process when there is a need to weld materials to a higher standard (quality and/or appearance) than conventional MIG. Aluminium and stainless-steel are commonly welded with TIG, as these materials are often used in projects where the finish of the final product is critical - for example; boats & marine, architectural fixtures, food handling equipment, etc.
The disadvantage of TIG is that it is a comparatively slow & inefficient process, which increases cost and processing time.
Enter Pulse MIG! Essentially, Pulse MIG offers;
- Weld quality and finish compariable or very close to TIG in many applications
- Superior speed and efficiency vs TIG
- Compared to TIG, typically requires less skill and is easier to learn, which reduces training time
While the TIG process will always have its place, Pulse MIG is certainly replacing TIG as the logical choice for many applications, especially production work.
Pulse MIG Weld Cycle, Settings & Adjustments
If you're new to Pulse MIG, one of your questions is likely going to be; What are the different parameters and adjustments involved with MIG pulse welding?
This is best answered by looking at the typical pulse MIG 'wave' or weld cycle, as shown in this diagram:
As follows are the main 'components' of this cycle and the associated adjustments.
Note that most reputable pulse MIG machines have synergic control, where the Volts and Amps/Wire Speed are adjusted together automatically. For the sake of simplicity, we are going to refer to these collectively as "Current".
Start Current: Current level at start of the weld. Usually set as a % of the main current. When welding aluminium, typically this will be higher than the main current, to help break through the oxide layer for a clean start to the weld.
Start Current Time: Duration of start current.
Main Current: Main welding current/amps.
Secondary Current: Also known as Background Current, this applies to double-pulse only. Usually set as a % of main current. Typically this will be lower than the main current for a cooler weld pool.
End Current: Current level at the end of the weld. Usually set as a % of the main current. Typically this will be lower than the main current. End Current & End Slope work together to prevent/minimise 'craters' etc for a clean & aesthetic finish to the weld (also known as crater fill).
End Current Time: Duration of end current.
Start Slope Time: Duration of the gradual change in output from start current to main welding current
End Slope Time: Duration of the gradual change in output from main welding current to end current
Pulse Frequency: Used in double-pulse only. Adjusts the pulse 'cycle' (main current pulse, followed by secondary current pulse) frequency in Hz (cycles per second)
Pulse Balance: Used in double-pulse only. Adjusts the length (%) of the main current pulse within each cycle. Increasing this % means the main pulse will be longer and the secondary pulse will be shorter. Typically main current setting will be higher than secondary current, in which case increasing balance % will increase 'heat'.
Arc Length (also known as arc control or trim): Adjusts the distance from the end of the wire to the weld pool. If arc length is too short (longer wire stick out) the arc will be very 'crackly' and produce a lot of spatter. If too long this can make the weld black and cause porosity.
What to look for in a Pulse MIG welder
Pulse MIG can open up a lot of new opportunities for your workshop or fabrication business, and improve your productivity. However, pulse is much more complex and costly than conventional MIG, which makes it important to chose a machine that will give you the best results and return on your investment in the long term. Here's a few points to keep in mind;
Single-Pulse or Double-Pulse? Double-pulse takes the benefits of single pulse (weld quality, finish, etc) to a new level. Not all pulse MIGs will have double-pulse mode. Single pulse can be considered as an "entry level" option if you are learning or trialling pulse MIG, and will typically have fewer features and adjustments and will be simpler to operate. More experienced operators may prefer double pulse. Check the machine specs so you know what you're getting.
Track Record: It's a fact that when it comes to developing a truly functional and reliable Pulse MIG, many welder manufacturers have tried and failed. As they say 'nothing beats experience', and this is certainly true when it comes to pulse. So our best advice is to chose a proven machine from a well established manufacturer.
Simple vs Complex: Pulse welding can be less forgiving than conventional MIG and often it's the little things - for example a slightly loose connection, or an incorrect setting - that can make the difference between a happy result or a frustrating waste of time. It's easy to be wowed by a lot of features and options, but keep in mind that this also adds to the "list of things that can go wrong". The most reliable and user-friendly pulse machines are typically those with a comparitively simple design.
Controls: Sadly, it's not uncommon to find operators who have been lured by the benefits of pulse, but have found their machine difficult, confusing and time consuming to learn and operate. On the other hand, controls that are intuitive and easy to follow will maximise your welding time, and minimise down time.... and make it much easier to train new operators.
Wire feed system: With pulse, it is critical that wire feeding is 100% consistant and reliable. Reputable drive systems are often made by specialist manufacturers who then provide this componentry to welding machine manufacturers, so it pays to dig into the detail of where the drive system comes from and its track record. Robust build is important, but other less obvious aspects are also critical, such as whether the system is purely mechanical or does it electonically synchronise with other machine controls.
Push-Pull Ready? For industrial and manufacturing applications, a push-pull torch (typically 8m long) is a great way to extend the reach and portability of your machine, especially when welding aluminium where using conventional torches longer than 3m can be troublesome. In the case of push-pull torches, both the torch 'pull' motor and the machine 'push' motor must be synchronised - which means that the torch and the machine need to be compatible with each other. With this in mind, you'll not only want a machine that is "push-pull ready", but you also want to make sure that; a) there's a push-pull torch available specifically to suit the machine you're looking at, and b) the torch is a tried & tested quality design from an experienced manufacturer to ensure you get reliability and value from your investment.
Pulse MIG Options from Weldclass:
FURY Series: Affordable Pulse MIG, Stick, and TIG
FURY machines offer:
- Three FURY models to chose from: 165 MPST, 185 MPST, 205 MPST
- Pulse mode in all processes: MIG, Stick, and TIG
- Simple and easy-to-use controls
- Incredible value: Prices starting from $749 for packages that include bonus helmet and gloves