Our Sites

How to pick a welding power source

From GMAW to SMAW, it starts with welders taking a closer look at current and future needs

Welding power source

DIY welders should consider investing in a SMAW machine that has a hot start feature, which produces more amperage at the start and will help prevent your electrode from sticking when striking an arc.

Welding is frequently thought of as an intimidating trade. But choosing the right welding power source can be equally intimidating and overwhelming. Whether you’re new to welding or want to upgrade your machine, it can be difficult to know what to look for.

For those new to welding, have little experience, or do it only part time, it’s important to understand how you intend to use the power source. What is the average thickness of the material you’ll be welding? Will you be working indoors, outdoors, or a combination of both? Will you need a power source dedicated to one welding process or do you need a multiprocess machine? Taking a realistic look at what you intend to do with the machine will help you find one that fits your needs and avoid overspending for capabilities that you don’t need.

Most welders can be classified into one of three categories: the do-it-yourselfers (DIY), farmers/ranchers, and general contractor. The following recommendations will help guide your decision and break down welding technology and applications.

DIY Welding Power Sources

Welders who fall into the DIY category typically weld on small-scale repair projects in their garage, like lawn mowers, metal art, go-carts, small tractors, and automobile restoration. Welding in a garage environment typically means that machine portability isn’t a huge factor.

Most DIYers use mostly shielded metal arc welding, also known as stick welding, or flux-cored arc welding (FCAW) so they don’t have the expense of the shielding gas. However, if you’re adventurous and want to improve your skills or learn other processes, consider a multiprocess machine that can do FCAW, gas metal arc welding (GMAW), stick welding, and gas tungsten arc welding (GTAW).

Typical DIY welders will not weld material thicker than ¼ inch, which means at least 100 amps of welding output and 20 amps for plasma cutting output are sufficient. This can usually be found with 110- to 120-V machines. If you need more power for the occasional thicker material, consider a machine that is capable of both 110 to 120 V and 208 to 240 V. Carefully choose a machine that will make the most of your input power.

Fifteen years ago all DIY power sources were transformer machines because they were inexpensive. The market has changed and is moving toward inverter-based machines because they are much more power-efficient and usually have slightly higher output and duty cycles. Choosing an inverter FCAW machine will give you more features; a smoother arc; and allow infinite voltage and wire feed adjustments, which makes learning and setup easier.

Stick welding is a great process for welding materials like steel, stainless steel, cast iron, and hardfacing. An added benefit is it doesn’t require shielding gas, which can reduce your initial investment. Look for a SMAW machine that has a hot start feature, which produces more amperage at the start and will help prevent your electrode from sticking when striking an arc.

Consider purchasing both 3⁄32- and 1⁄8-in.-dia. electrodes for a 120-V machine, which will allow you to weld sheet metal up to ¼ in. thick. Sometimes you can find a 5⁄64-in. electrode, which is ideal for welding thin sheet metal. A large-diameter electrode, like 5⁄32 in., is not recommended for 120-V machines because it will produce poor penetration and you likely won’t have enough amperage output to strike an arc.

Remember that some rods such as E6013 and E7014 run on low amperages and are simple to strike and learn with. Some brands of electrodes are formulated to run better on low-voltage welding machines, so try a couple different brands to see what runs best on your machine.

A common misconception when choosing a wire for GMAW is that larger-diameter wires like 0.035 in. are better, but this is not the case for 120-V machines. Most entry-level wire-feed machines recommend that you use 0.030-in. wire, which is the better choice. Wire with a small diameter will have a more consistent arc, wider sweet spot, better current density, and better penetration while being able to weld a wide array of material thicknesses, including sheet metal up to ¼ in.

If you need to weld away from your garage, consider choosing a generator. Most 120-V machines can run off a high-quality, 4,000-W continuous generator if it produces clean power (less than 5% total harmonic distortion). Make sure the power source manufacturer says it’s a generator-friendly welding machine before you attempt to use one.

Welding Power Sources for the Farm or Ranch

The requirements of farm and ranch welders are similar to those of DIYers, but they weld more frequently and on larger equipment and thicker materials. In addition, portability is important as they often conduct repair welding in the field.

About 15 to 20 years ago, most farmers and ranchers wanted a dedicated stick welding machine, which offered reliability and was easy to use outdoors. Deciding between stick and GMAW is no longer a problem, though, because machine manufacturers now produce several good multiprocess machines for under $1,500. These machines can do FCAW, stick, GMAW, and GTAW, giving you more versatility and better overall value. It is much easier to switch between processes with the newer machines than it is with some of the older power sources. If you fall into the farmer/rancher category, try to find a machine that makes it easy to switch between stick and GMAW (the TIG process is not as common for this industry).

The material thickness most often used in this category is between sheet metal and up to ½ in. thick. This means you will need a 200-amp welding output and 40-amp plasma cutting output to achieve good results. Multiple or dual-voltage machines can dramatically improve your flexibility to weld in various locations and are high on the recommended list of features.

Transformer machines are more commonly used among farmers and ranchers because of the reliability, repairability, and familiarity factors. Although you’re more likely to find a transformer machine on a farm, inverter machines are beginning to take their place.

Inverter machines weigh a lot less—65% to 75% less to be exact—than transformers and are easier to repair. A typical 250-amp transformer machine can weigh up to 220 lbs., but an inverter machine with a similar output may weigh 50 lbs.

Warranty repair time averages 25 to 35 minutes for an inverter machine and 45 to 60 minutes for a transformer machine, assuming the entire printed circuit board on an inverter needs to be replaced.

Lastly, most farmers and ranchers have an oxyacetylene setup for heating and cutting metals or fixing broken cast-iron parts. If you don’t have an oxyacetylene setup, consider adding a plasma cutter. Plasma cutters are safe and require only clean and dry compressed air to make quality cuts. These machines are typically priced around $1,000 and allow you to cut material up to ½ in. thick.

Welding Power Sources for General Contractors

There’s a difference between a welding contractor who welds all day, every day and a general contractor who welds occasionally. The general contractor category is dedicated to those who might weld for the purposes of building maintenance, HVAC, stainless steel kitchen fabrication, metal fencing or stairs, or other metal landscaping structures. Versatility and portability are the most important factors for welders who fall into this category.

Most general contractors work with thin metals that rarely exceed ½ in., which means a welding machine with up to 200 amps for welding and 40 amps for plasma cutting is best. Look for a dual-voltage machine so you can weld in various locations, and look for an inverter machine, which is light and versatile.

If you weld mostly on steel or stainless steel, consider a multiprocess machine with direct current (DC) output that allows you to use either GMAW or stick. A multiprocess machine adds versatility and allows you to switch between FCAW, GMAW, stick, and GTAW. A trimix gas is often recommended for welding stainless with GMAW, but that can be a bit expensive. The stick process for welding stainless may be cheaper. Common stainless electrodes are E308L, E309L, and E316L. For stainless work, for instance in a food processing environment where the weld toe transitions must be perfect, try GTAW using a dedicated stick/GTAW machine with pulse controls.

If you need to weld aluminum, make sure your multiprocess machine is spool gun-capable. Precision aluminum GTAW on thin structural frames (such as motorbikes and some boat applications) will likely require a dedicated GTAW machine with alternating current (AC) output. For aluminum GTAW, you will want the ability to adjust balance, frequency, and pulse controls. You may have heard the term wave form controls. This is a nice feature for very specific applications, but it also adds complexity and expense. For a general contractor, a dual-voltage machine that operates off 110 to 120 V or 208 to 240 V is a must.

Most contractors need to cut metal on a regular basis. Efficiency is essential, so consider a plasma cutter that has a clean-cut capability of up to ½ in. thick. If you are in a bind and working on ¾ in., you can typically sever-cut 3⁄4 in. with a plasma cutter that is rated for ½ in.

Plasma consumables can be expensive, so keep that in mind when evaluating various machines. The No. 1 problem with plasma machines is dirty or oily air, so make sure to filter and dry the air and never use an oil bath compressor. Finding a dry, ultraquiet compressor that has a built-in dryer and filter is your best option. Treat your plasma torch carefully as there are moving parts inside that can easily get gummed up or damaged. Replacing a damaged or nonfunctioning plasma torch head is a common occurrence, and most manufacturers do not warranty the torch or head.

Before You Buy a Welding Power Source

One of the most important elements to consider when shopping for a new machine is the warranty and certification. Odds are, you will need good warranty and technical support during the life of your machine. Be sure to purchase a machine from a reputable company and brand.

In addition, purchasing a certified machine (CSA and ETL certified) ensures the machine meets UL safety standards, which are applicable in the U.S. and Canada (note: CE certified is not). Beware there are machines sold in the U.S. and Canada without these certifications, and uncertified products are not tested or verified by a third party.

Jason Mahugh is director of engineering and technical service at Forney Industries, 2057 Vermont Drive, Fort Collins, CO 80525, 800-521-6038, jmahugh@forneyind.com.

About the Author

Jason Mahugh

Director of Engineering

800-521-6038