10 Questions You Should to Know about dc welding machine

Whether you're an experienced welder or just learning to stick weld, these tips will help improve your welding skills.

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Stick welding advice for beginners

Shellfish can make you a better welder. Simply think about CLAMS: current setting, length of arc, angle of electrode, manipulation of the electrode and speed of travel. If you're just learning the stick process, technically called shielded metal arc welding (SMAW), remembering these five points will improve your welding technique.

Take a minute to review the following stick welding advice, especially if you've never struck an arc or are still debating which machine to buy.

What type of stick welder works best for all-around use?

A welder with an AC/DC output, whether it&#;s an electric arc machine like the Miller® Thunderbolt® or a gas engine drive like the Bobcat&#; welder/generator.

DC welding offers advantages over AC for most stick applications, including: easier starts; fewer arc outages and sticking; less spatter/better looking welds; easier vertical up and overhead welding; easier to learn; and a smoother arc. DC reverse polarity (electrode positive) provides about 10 percent more penetration at a given amperage than AC. Conversely, DC straight polarity (electrode negative) welds thinner metals better.

Does an AC output have any advantages?

Yes, it&#;s a good option if you need to weld on material that's become magnetized from friction, such as when hay, feed or water constantly rub against a steel part. A DC output won't work because of arc blow, where the magnetic field blows the molten filler metal out of the weld puddle. Because an AC output alternates between polarities, it enables you to weld magnetized parts.

How big of machine do I need?

A 225- to 300-amp stick machine handles almost anything the average person will encounter. Most stick welding procedures require 200 amps or less. To weld material thicker than 3/8 inch, simply make multiple passes.

I see the word "duty cycle" on product spec sheets? What does that mean?

Duty cycle is the number of minutes out of a 10-minute cycle a welder can operate. For example, the Thunderbolt creates a 200-amp DC output at 20 percent duty cycle. It can weld continuously at 200 amps for two minutes and then must cool for eight minutes to prevent overheating.
Duty cycle and amperage are inversely proportional. Operating at 90 amps, the Thunderbolt has a 100 percent duty cycle, meaning you can weld without stopping. This inversely proportional rule is true of all Miller machines but does not apply to all machines made by other companies.

What type of rod should I use for hardfacing?

Hardfacing rods can provide impact resistance, abrasion resistance or both depending on the application. Because the type of rod required depends on the type of soil or aggregate in your area, contact your local welding supply distributor and ask their opinion. If you don't know a distributor, call 1-800-426- and the operator can automatically connect you to the nearest Miller distributor. You can also locate distributors through http://www.millerwelds.com/wheretobuy/.

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What type of rod should I use for general welding on steel?

Common electrodes used for general work include , , , and , each of which has specific properties: electrodes penetrate deeply, while electrodes penetrate less. For much better bead appearance and work on higher strength steels (say for a hitch), use a rod. For better penetration on thick material, grind the joint to a 30-degree bevel (leave a nickel-width land on the bottom of the groove) and make multiple passes. Alternatively, make the first pass with a rod, then make a cap pass with a . The rod is perhaps the easiest to use. Also known as a drag rod, this electrode's thick flux automatically maintains the correct arc length, which allows you to drag the rod directly along the work piece.

Do I have to remove rust or oil before welding?

Stick welding is more forgiving on unclean conditions, but it never hurts to clean parts with a wire brush or grind off excess rust. If you prepare well and have average welding ability, you can make a sound weld. However, even great welding skill cannot overcome poor preparation, as it can lead to cracking, lack of fusion and slag inclusions.

Stick welder settings

Now that you're ready to weld, remember CLAMS. Bringing all these points together in one moment of welding may seem like a lot to think about, but it becomes second nature with practice so don't get discouraged! Stick welding got its name not because the electrode looks like a stick, but because everyone sticks the rod to the workpiece when learning how to weld.

Current setting

The correct current, or amperage, setting primarily depends on the diameter and type of electrode selected. For example, a 1/8-inch rod runs well from 75 to 125 amps, while a 5/32-inch rod welds at currents up to 220 amps. The side of the electrode box usually indicates operating ranges. Select an amperage based on the material thickness, welding position (about 15 percent less heat for overhead work compared to a flat weld) and observation of the finished weld. Most new welding machines have a permanent label that recommends amperage settings for a variety of electrodes and material thicknesses.

Length of arc

The correct arc length varies with each electrode and application. As a good starting point, arc length should not exceed the diameter of the metal portion (core) of the electrode. Holding the electrode too closely decreases welding voltage. This creates an erratic arc that may extinguish itself or cause the rod to freeze, as well as produces a weld bead with a high crown. Excessively long arcs (too much voltage) produce spatter, low deposition rates, undercuts and sometimes porosity.

Many beginners weld with too long of an arc, so they produce rough beads with lots of spatter. A little practice will show you that a tight, controlled arc length improves bead appearance, creates a narrower bead and minimizes spatter.

Angle of travel

Stick welding in the flat, horizontal and overhead positions uses a drag or backhand welding technique. Hold the rod perpendicular to the joint and tilt the top of the electrode in the direction of travel approximately 5 to 15 degrees. For welding vertical up, use a push or forehand technique and tilt the top of the rod 15 degrees away from the direction of travel.

Manipulation

Each welder manipulates or weaves the electrode in a unique style. Develop your own style by observing others, practicing and creating a method that produces good results for you. Note that on material 1/4 inch and thinner, weaving the rod typically creates a bead that is wider than necessary. In many instances, plain, straight-ahead travel works fine.

To create a wider bead on thicker material, manipulate the electrode from side to side creating a continuous series of partially overlapping circles, or in a Z-shaped, semi-circle or stutter-step pattern. Limit side-to-side motion to two and a half times the diameter of the electrode core. To cover a wider area, make multiple passes or stringer beads.

When welding vertical up, focus on welding the sides of the joint and the middle will take care of itself. Pause slightly at the side to allow the far side of the bead to cool and the weld puddle to catch up and to ensure solid tie-in to the sidewall. If your weld looks like fish scales, you moved forward too quickly and didn't hold long enough on the sides.

Speed of travel

The proper travel speed produces a weld bead with the desired contour (or crown), width and appearance. Adjust travel speed so that the arc stays within the leading one-third of the weld pool. Slow travel speeds produce a wide, convex bead with shallow penetration. Excessively high travel speeds also decrease penetration, create a narrower and/or highly crowned bead, and possibly undercuts.

A few last words of advice. Always remember that you need a good view of the weld puddle. Otherwise, you can't ensure you're welding in the joint, keeping the arc on the leading edge of the puddle and using the right amount of heat (you can actually see a puddle with too much heat roll out of the joint). For the best view, keep your head off to the side and out of the smoke so you can easily see the puddle.

Also remember that you learn through mistakes. There's no shame in grinding out bad welds. In fact, professional welders create perfect welds by recognizing imperfections, grinding them out and rewelding.

While tig gets a lot of press it really is way down on my list of got to have tools. I havnt DC tig anything in 30 years or more and its not that I cant or don't have a machine but the modern wire feed has really taken over as the workhorse in a small shop. Its not that it cant be tig welded but I just don't need to.
IMOP a shop needs a stick machine. One of the things that keeps the AC side is that it can actually run larger electrodes but its not really a deal for home or maintenance. I may have used AC once for some exotic alloy issue but I could take the knob off set to DCRP. This is what is used in piping and construction, I am sure ine can find some exception but 13 and 14 are still around soley due to the AC machine and used by part timers, I do know a couple guys that do use them well but they are rather limited and an Ironworker, Pipefitter or Boilermaker could go a whole career without using one.

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