How do I choose a welding machine?
Considering the variety of welding processes available, selecting the right one for your shop could be a confusing and difficult decision. In any manufacturing operation, matching the best process to the application can be the difference between profit and loss of a job.
Likewise, welding has many variables in terms of matching methods and materials. By properly selecting a welding process, many hours may be saved in production, repairs, polishing and grinding, or rejected welds.
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The object of welding, whether it's done on a production basis or occasionally, is the same: to produce a quality weld in the least amount of time. Welding quality is determined by the success one has in creating a weld that penetrates sufficiently, without pores, pockets or gaps. Good surface finish is also a factor.
In this article, we're going to look at the four most common welding processes. We'll briefly discuss what each brings to the job in terms of performance characteristics so you can better determine which welding process best fits your application.
Unfortunately, there is no single welding process suitable for all welding situations. For this reason, it is necessary to weigh the advantages and disadvantages of each welding process.
The most common welding processes used for fabricating metals are gas metal arc welding (MIG), flux-cored welding, gas tungsten arc welding (TIG) and shielded metal arc welding (stick electrode). To make an evaluation of the welding process most appropriate for the job at hand, the following factors should be considered:
- Type of material being welded,
- The thickness of the material,
- The welding position,
- Type of welding power source and the amount of currently available, and
- Time requirements.
Gas Metal Arc Welding (MIG) This process consists of feeding a bare metal filler wire_made of the same material being welded--in conjunction with a shielding gas through a handheld torch unit. The welding wire picks up the electric current supplied by a standard power source. On contact, it creates an arc that does the welding.
As the wire is fed from the unit to work, it functions as a continuous, consumable electrode, therefore requiring fewer starts and stops.
For routine joining applications, a MIG welder probably offers more advantages than any other welding process. Here's some advantages of MIG welding:
- It's the easiest welding process to learn. With a little practice, even a first-time MIG user can achieve a good-looking weld.
- Welds light gauge material or thick plate (with multiple passes).
- Welds all common metals_carbon steel, stainless steel and aluminium.
- Welding can be done in all positions, including overhead.
- There is no need to remove flux, as the shielding is provided by gas.
- High welding speeds can be obtained_up to four times faster than stick welding_reducing repair or construction time.
A power supply that gives direct current reverse polarity (DCRP) is recommended for use with the MIG welding process. Generally, welders use straight polarity current, which means the flow of electricity moves from the torch to the workpiece. In reverse polarity welding, current travels from the workpiece to the welding torch. For MIG welding, a DCRP current produces the best arc transfer and a smoother weld surface than other types of currents.
Special consideration is required when welding outdoors or in drafty areas with a MIG welder because air or drafts can blow the shielding gas from the weld puddle and cause porosity. The MIG welding process also requires more complex equipment, which is initially more costly. The following equipment and supplies are necessary for MIG welding:
- A power supply and welding cables,
- An electrode wire feeder/MIG welding gun system, and
- A gas cylinder with 75 per cent argon and 25 per cent CO2, plus hoses and regulators.
The same constant voltage equipment used for MIG welding also performs flux-cored welding. The difference is the wire that is used as an electrode. Rather than running a solid wire coupled with a shielding gas, flux-cored welding uses self-shielded wire with flux inside (some flux-cored wires require a shielding gas).
Cored wires are generally used on thicker material (4 mm and up) than the solid wires used with the MIG process. Advantages of flux-cored welding are:
- Less affected by drafts, so better suited for outdoor work.
- Works as well as stick welding on rusty or dirty material.
- Continuous wire feed, which minimizes starts and stops.
- Deep penetration for thick welding sections.
- Increased metal deposition (two or three times that of stick welding), which is beneficial for rough hardfacing (adding material to a workpiece).
- Can eliminate the need for a shielding gas bottle, which increases portability.
Porosity is a problem for welders. It often occurs in drafty areas when flux-cored welding with shielding gas. This difficulty can be overcome by using self-shielded, flux-cored wire. It performs similarly to a stick welder in such conditions, so windy conditions are less impactful on the weld.
Importantly, the material used to fill flux cored wires can be custom formulated to match the base metal, which helps produce a better weld. This can also make flux-cored welding less sensitive to rust and scale on the welded piece than other processes.
Between its MIG and flux-cored capabilities, a wire welder can perform most tasks a stick welder can do, and often more efficiently. While a good quality wire welder costs $450 to $2,000 (depending on its size), the costs for wire and gas are much less than that for stick welding rods. Coupled with the ability to weld aluminium and sheet metal, a wire welder can pay for itself very quickly.
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Gas Tungsten Welding (TIG) This process uses a non consumable tungsten electrode and shielding gas that protects the welding area from contamination. TIG welding can be done in all positions, including overhead. Its concentrated heat and precise control of the arc allows thin material (0.01 inch) to be welded. The advantages of TIG welding are:
- Precise welding on thin materials is easily accomplished, plus there is less distortion overall.
- Provides the highest quality work (x-ray quality) when required, as well as highly aesthetic weld beads.
- Allows the welder to adjust heat input while welding by using a foot or hand amperage control.
- Fine hard-facing_for mould and die work_can be performed.
- Welds steel, aluminium and other metals with just a single gas, argon.
- There is no spatter nor flux to remove.
Power supply for TIG typically uses alternating current (AC) for aluminium and magnesium, or direct current straight polarity (DCSP) for steel, stainless steel and various other alloys. AC/DC switchable power units are available to accommodate a variety of workpiece materials.
Although TIG welding is a relatively slow process, compared with wire-feed MIG or flux-cored, it provides high-quality welds. However, it also requires greater operator skill level than the other processes.
Because there is no spatter nor flux created from a TIG weld, it is an ideal option for applications where cosmetic appearance is important. The following equipment is necessary for TIG welding:
- A power supply, welding cables and TIG torch.
- A water supply with the water inlet and outlet hoses (water is unnecessary if the system is air-cooled),
- Non Consumable tungsten electrodes, and
- An inert-gas cylinder and gas supply, plus hoses and regulators.
TIG welding produces quality welds. Because of the variety of materials that it is capable of welding, it is considered one of the most widely used processes for precision and cosmetic work. Another factor to consider is that TIG machines also have stick welding capabilities (TIG/stick welders). While costing more than MIG or stick-only welders, a single TIG/stick machine gives the user great flexibility.
Shielded Metal Arc Welding (Stick) This process uses a consumable, flux coated electrode containing mild steel, stainless steel, cast iron or various other alloys. These electrodes are selected to match the base material being welded.
Other than the power source, electrode holder and work clamp, no other equipment is required. The advantages of stick welding are:
- Can be performed in any position and hard-to-reach locations. However, it's less appropriate for overhead welding.
- Can be used outdoors because drafts do not affect the weld.
- Most materials can be stick welded.
- Least expensive to get started.
- More forgiving than MIG when welding on dirty or rusty metal. Even so, it is always advisable to scrape or grind off paint, rust, and other debris; welding on the cleanest material possible produces a stronger weld.
Some limits of stick welding are:
- Welding thin materials (less than 18-gauge steel) may be difficult or impossible.
- Marginal for welding aluminium. It takes a high degree of operator skill to weld aluminium with the stick process.
- You must clean the slag off the weld.
- Stick is a slower process than MIG.
If you plan to purchase a stick welder, an AC/DC welder power supply is best. For most applications, DC reverse polarity welding offers advantages over AC. These include easier starts; fewer arc outages and sticking; less spatter (better-looking welds); easier out-of-position welding; simpler learning curve, and better welds on relatively thin materials.
What's The Deal With Duty Cycle? One way of classifying the "size" of welding power sources measures how much amperage can be generated in a given "duty cycle." Duty cycle is the number of minutes, out of a 10-minute cycle, a welder can operate.
For example, one of Miller's AC/DC units (Shopmaster 200) can deliver 200 amps of AC, constant current power, at a 40 per cent duty cycle. That means it can weld continuously at 200 amps for four minutes. It must cool down during the remaining six minutes to prevent overheating.
Duty cycle and amperage, however, are inversely proportional. Reducing amperage increases duty cycle. Operating at 130 amps, the same power supply has a 100 per cent duty cycle_it can weld continuously at this amperage level. At the other end of the power curve--operating at 300 amps--it has about a 20 per cent duty cycle. This is effectively two minutes' welding out of 10.
With the duty cycle in mind, consider that thin metals require less amperage than thick metals. For example, to MIG-weld 18-gauge steel in a single pass takes roughly 70 amps. Welding 1/4-inch steel in a single pass requires roughly 180 amps.
The phrase in a single pass is the key. Because a series of thin passes can be made to weld thicker material per pass, less amperage is required. However, multiple passes take more time. And, you may still exceed the machine's duty cycle, spending even more time waiting than welding.
What Size Welder Should You Consider?
There is no universal welding power supply. Each unit has an effective working range. Here's a general summary of which size welders match up best with a given application.
For light repair work on steel, stainless steel and aluminum_from sheet metal to material 3/16 inch thick--a 130-amp MIG or TIG unit with a 20 or 30 per cent duty cycle can perform many of the welding jobs required.
For heavier repair or fabrication jobs, consider a MIG or TIG unit with at least 200 amps and a duty cycle 40 per cent or higher. Remember, you need to have sufficient amperage to ensure proper penetration of the root (first) pass. You cannot make up for a poor root pass with subsequent passes.
By properly considering the many factors of your application, and examining the advantages that each welding process offers, selecting the right welding power source can be a simplified and profitable decision.
The world of welding is fascinating—especially, to a DIY enthusiast or an aspiring welder who has just begun to learn the trade—with its wide range of products and accessories available for use on the market. There is a wide assortment of welding accessories that can be selected—ranging from MIG welders, TIG welders and stick welders to oxyacetylene welders. There are also several other high-end welding machines that are relatively more expensive in comparison with the more common TIG and MIG ones; these high-end welding machines are, however, often driven by fuel-fed engines in order for them to be used off the electric grid with equal convenience.
What factors should you consider when determining a budget?
You may already have an estimated budget in mind.
The type of welder you purchase should be suited for the specific functions you require as well as the projects you will work on the most. Think about your end goal and consider opportunities to expand the usefulness of your welder. Will you want more power or amperage in the future?
It is important to take note of the varying amperage and power requirements as well as the duty cycle necessary to achieve the most effective and economical operational results for the projects you're looking to complete.
In addition to the cost of the welder itself, don't forget to include costs for the accessories and supplies you'll need to operate your new welder. This includes welding protection (helmet, gloves, jacket, etc.) as well as gas and consumables.
Don't feel rushed into making a purchasing decision right now. Take some time to define your needs. If you have questions or something is unclear, Miller can answer any questions you have about welding processes, benefits, limitations and machine operation. When you're ready to match a specific model with the task, hobby or business — Miller can suggest the model or product that is the best for you.
Miller has provided quality welders since 1929. When you're ready to buy, we'd be honoured if your first welder was a Miller® welder.
If you are an aspiring welder, it would best if you understood the different types of welding equipment to better your prospects for employment. If you are able to decide on which welding model would be more compatible for a particular project, you will better your chances of being appointed as a supervisor or project assistant by an employer.
Assess the nature of the metal
Usually, welding is done only on carbon steel. Carbon steel has the ability to handle the excess heat that any novice welder might accidentally apply to the metal. It is, thus, compatible with a majority of the welding machines available for use. Stainless steel is well suited for storing beverage or edible items because of its ability to resist corrosion.
It is compatible with the usual TIG or MIG welding machine and does not require as much amperage to operate as does carbon steel when being welded. Aluminium needs an almost uniform supply of heat to keep the weld pool from drying out owing to its high heat-conductive capacity. However, the high input of heat often results in deformation of the workpiece.
Thus aluminium requires more complex welding machines, such as the MIG machine equipped with the ability to perform pulse welding, in order to be conjoined optimally well. A better choice for welding aluminium would be a high-end TIG welding machine. It would be, thus, best that you assess the metal that you wish to conjoin before selecting a welding machine.
Establish the ideal amperage
The cost of a welding machine is partly dependent on the amount of current it can generate; thicker metals usually require more current in order for them to be welded properly. It is thus best that you pay ample attention to the thickness of the fixtures as well as the base metals you'd be required to work with for a project.
Take, for instance, thick structural steel and a pipe having a thickness greater than half an inch; you would require either a stick welding machine or a high-end MIG welding machine to weld these effectively.
To weld thin metals, on the contrary, you would require more sensitive welding machines which would provide just the right amount of heat to form the weld. In this respect, welding aluminium becomes almost the same as does welding a relatively thinner metal.
Choose an ideal site for welding.
The site where you'd be performing the welding also helps in arriving at a suitable welding machine. When welding indoors, you could plug in your machine to 115 volt AC machine, a 220-240 volts AC supply. A 115 volt supply is the regular supply that any commercial or domestic facility receives. Most elementary welding machines operate at this voltage. The machine could work in single-phase or work as a three-phase device.
Refer to the specs sheet
Referring to the specs sheet can help you understand several things critical to differentiating a good welding machine from another. For instance, a specs sheet can help you gauge how much of continuous welding a machine can perform in ten minutes. Duty cycle is representative of the number of minutes that you can weld per a standard interval of ten minutes. Exceeding the duty cycle may heat the machine, damaging its internal circuitry.
Analyze compressed-gas requirements, if any
Different welding processes call for the use of different compressed gases. Oxygen, argon and carbon dioxide are the most popularly used compressed gases across several welding procedures.
What are the common mistakes to avoid while choosing a welding machine?
Purchasing any machinery for your company is a huge investment and one that could be the difference between success and failure. Choosing a welding machine is no different. Now, there are many articles and guides out there that tell you how to choose a welding machine and what steps to take, but today we're going to talk about the common mistakes that you should avoid making and why.
You don't know what type of welding machine you're looking for
When you are setting out to choose a welding machine, you really have to think about what type of machine is the best fit for your business as there are several different options: the MIG Welder (Gas Metal Arc Welder), the TIG Welder (Gas Tungsten Welder) and the Stick Welder (Shielded Metal Arc Welder) are just three of the options available. These machines have their own uses and purposes and to avoid a very costly error, you really must get to know these different types of machine and work out which one is best suited for you and your needs. So, don't forget to do your research!
You forgot to look at the extra expenses
If you're going to purchase a welding machine, don't forget that there is a chance that there could be extra expenses. For example, with the TIG welders, you will have to buy a lot of add-on items like a power supply, welding cables, TIG torch, etc. This is perhaps not the option for those with a limited budget. If you have a budget, you may want to look into the MIG welder or a stick welder. It is really important not to forget about the extra expenses as you do not want to purchase a more expensive welding machine and forget about the expensive add-ons that you must buy to accompany it!
You're focusing on the bottom line.
We all want to save money where it can be saved but skimping on the type of welder you purchase is not where you should start. In the long run, purchasing a cheaper welding machine could be detrimental to your business. Cheaper welders are not designed to handle tough weld jobs, and if you purchase one, you risk them breaking or lacking the power needed to complete tough jobs. If you are looking for power and quality, you really must spend a little more. However, it could save you money long-term as you will not need to pay for repairs or shell out more money for another machine later on. When it comes to welding machines, you get what you pay for.
You are looking for a used machine.
This is another option that may be cheaper, but it is not very satisfactory in the long run! Although, it may be advisable to test the waters with a used model especially when you are making a long-term investment, picking the right machine the first time around can save a lot of headaches (and cash). When you purchase a used welding machine, you risk it falling in the middle of a big job, or it lacks the power to make two pieces of the metal meet. To sum up, purchasing a used welding machine may help you to make ends meet in the short term but it is not a long term solution!
You're scared to ask for help.
When you are selecting a welding machine, even if this isn't your first foray into choosing a machine, you must be able to ask for help. Each kind of welding machine has its limitations, its own purposes, its benefits, its drawbacks; each fits a different type of welding project, a different type of welding company and if you want to choose the one that will be the best fit for you, you should consult a professional. Don't be scared to ask for help in order to make the right decision for you!