How to set up MMA welding?

The basics of stick welding

Stick welding, also known as manual metal arc (MMA) welding refers to a welding method where a filler rod in the electrode holder serves as the welding electrode. The arc burns between the rod and the workpiece.

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Unlike other welding methods, the filler rod in MMA welding continuously shortens as the process develops. This is different from TIG and MIG/MAG welding where the torch distance from the workpiece must remain constant. During MMA welding, the electrode holder must be continuously moved toward the workpiece to maintain the correct distance between the electrode and the molten weld pool. This introduces certain challenges specific to MMA welding.

STICK WELDING APPLICATIONS INCLUDE UNDERWATER WELDING

MMA welding can be utilized in almost any condition, making it a highly versatile method in the welding industry. It’s frequently employed at installation sites where easy access to welding machines is critical, especially in outdoor environments.

Common applications of MMA welding include power plant pipeline welding and various other piping projects. It’s also a preferred method among hobbyists and small repair shops. Moreover, it’s suitable for underwater welding, using fillers designed specifically for subaqueous conditions.

STICK WELDING MACHINES ARE SMALL AND AGILE

MMA welding requires a power supply, a ground cable, and a welding cable equipped with an electrode holder. Unlike other welding techniques, MMA welding doesn’t need shielding gas since the electrode is coated with a material that creates shielding gas and slag over the molten weld pool. Many TIG welding machines are also compatible with MMA welding.

Modern small inverter power sources enhance mobility and accessibility. For instance, the power supply can be connected to a generator with long input cables, allowing the welding machine to be placed right next to the workpiece. Some of the smallest power sources available today weigh just 5 kg (10 lbs).

MMA welding is popular among hobbyists as it only requires a power source and filler electrode rods. There is no need for shielding gas, and the machines typically run on the electricity available from a standard household outlet.

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STICK WELDING USES FIXED-LENGTH ELECTRODES

A welding electrode is a fixed-length, straight welding wire coated with a filler material. The welding electrode has a fixing head with which it is attached to the electrode holder. The other end of the electrode has the ignition head with which the workpiece is stuck to ignite the arc. The quality or trade name of the electrode is indicated near the fixing head in the coating. Usually, also the AWS class ID is included.

The diameter of a welding electrode refers to the diameter of the metal rod inside the electrode. The purpose of the coating on the surface of the metal rod is to protect the welding event from the effects of the surrounding air, to produce slag to support the weld, and to make the creation of the arc easier.

KEEP THE ARC AS SHORT AS POSSIBLE FOR THE PERFECT STICK WELDING TECHNIQUE

Before welding, it is recommended to check the condition of the welding power source, the cables, electrode holder, and the grounding clamp. If the power source has a control panel and remote control, their functionality should also be reviewed. The quality and strength of the welding electrodes must be checked, and they must match the workpiece. The coating on the electrode must be intact.

The welding is started by sharply striking the bottom of the groove with the welding electrode. After this, move the welding electrode back to the beginning without stretching the arc, and move the electrode easily while monitoring the width of the molten weld pool. Move the welding electrode with the handle pointing forward. The boundary of the slag formed is visible after the molten weld. It must be behind the molten weld. The distance of the slag boundary from the molten weld can be adjusted with the welding current and the angle of the electrode holder.

Throughout the welding, concentrate on the length of the arc and keep it as short as possible. The length of the arc increases easily as the electrode decreases in size during the welding. The movement may be somewhat difficult to control at first but it is easy to get accustomed to.

When the welding electrode runs out, one needs to remove the slag from the previous weld and clean it with a steel brush. Ignite the next electrode slightly ahead of the previous weld and then move the welding electrode back to the previous weld and continue with the welding.

Turn off the welding electrode by moving it slightly back to the completed weld and then lifting the electrode straight away from the workpiece.

The MMA (Manual Metal Arc welding process was first developed in Russia in 1888 and comprised a bare metal welding rod. In the early 1900’s the coated electrode was introduced when the Kjellberg process was invented in Sweden. In the UK the Quasi arc method was introduced. The use of the coated electrode was slow due to the high production costs but the demand for higher integrity welds led to the process becoming increasingly used.

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The material is joined when an arc is created between the electrode and work piece melting the work piece and the electrode to form a weld pool. At the same time the electrode has an outer coating sometimes called electrode flux which also melts and creates a shield over the weld pool to prevent contamination of the molten pool and assist in establishing the arc.

This cools and forms a hard slag over the weld which then needs to be chipped away from the weld bead upon completion or before another weld bead is added. The process allows only short lengths of weld to be produced due to the electrode length before a new electrode needs to be inserted
in the holder. The quality of the weld deposit is highly dependent on the skill of the welder.
The power source provides a constant current (CC) output and can be either AC (alternating current) or DC (direct current).

The design of the MMA welding inverter is such that the operator extending arc length will reduce the welding current and shortening the arc length (reducing the arc voltage) will do the opposite i.e. increase the current. As a guide the voltage controls the height and width of the weld bead whilst the current controls penetration, therefore the welder manipulates the electrode to achieve a satisfactory weld.

The power used in the welding circuit is determined by the arc voltage and current.
The voltage (V) is determined by the electrode diameter and the distance between the electrode and work piece. The current within the circuit is dependent on the electrode diameter, the thickness of the materials to be welded and the position of the weld. Most electrode information will show details of current types to be used and optimum current range.

MMA welding power sources which can TIG weld are often referred to as drooper’s or drooping characteristic power sources. They are typically basic selector type, magnetic amplifier control or engine driven units with a robust design as they are often required to work in extreme conditions.
The characteristic of the output shape gave rise to the term “drooper”.

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Modern welding inverter power supplies however can overcome these problems and provide excellent characteristic and performance as the curve can be controlled electronically for each process.

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The small relatively cheap AC sets are generally used in the DIY or small maintenance functions and some larger AC sets often oil cooled may be used in heavier industry but the DC output set are now the most common in use.

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Electrode manufacture means that not all DC electrodes can operate on AC power sources but AC electrodes can operate on both AC and DC. Direct current (DC) is the most commonly used mode. Control of AC units tends to be moving iron core or switched transformers.

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DC output power sources can be used on many material types and can be obtained in wide current ranges. Controls of these units vary from moving iron core control to the latest inverter designs. Inverter design has brought many advantages as they are:

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• Very lightweight and portable compared to their predecessors
• Very energy efficient power supply and offer energy cost savings

• Able to provide higher outputs for lower inputs
• High levels of control and performance

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In general it is preferable to weld in the flat or horizontal position. When welding in position is required such as vertical or overhead it is useful to reduce the welding current compared to the horizontal position. For best results in all positions maintaining a short arc, uniform movement and travel speed in addition to consistent feeding of the electrode are required.

What makes up the MMA (Stick) System?

The Welding Inverter Power Source

The welding inverter power source selected should have sufficient power to melt the electrode and weld material with enough capacity to maintain the arc voltage. 

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The MMA (Stick) welding process typically requires high current (50-350 Amps) at relatively low voltage (10-50 Volts). The MMA welding electrodes are designed to operate on different types of output power and voltage and you should always read the manufacturers data.

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All welding electrodes can be used on direct current (DC) but not all on alternating current (AC). Some AC electrodes also have certain voltage requirements. When used in the DC mode the electrode lead should be connected to the polarity recommended by the electrode manufacturer, in most cases this will be electrode positive polarity but there are electrodes that use electrode negative polarity. The power source operates with a “no load” or “open circuit voltage” present when no welding arc is struck. This no load voltage rating is defined in the standard EN 60974-12012 (EN 60974) in accordance with the welding environment or risk of electrical shock.The power source may have a voltage reduction device (VRD) fitted either internally or externally.

The Electrode Holder and Welding Cables

The Electrode Holder and Welding Cables

​The electrode holder clamps the end of the electrode with conductive clamps built into its head. These clamps operate either by a twist action or spring-loaded clamp action (crocodile type).

The clamping mechanism allows for the quick release of the remaining unused electrode end (stub end).

To ensure the maximum welding efficiency the electrode has to be firmly clamped into the holder, otherwise poor electrical contact may cause arc instability through voltage fluctuations and overheating of the holder.

The welding cable is connected to the holder either mechanically, crimped or soldered.

Electrode holders should conform to IEC 60974-11.

Welding Cable

Welding cable diameter is generally selected on the basis of welding current level. The higher the current and duty cycle,
the larger the diameter of the cable to ensure that it does not overheat (see relevant standard). If welding is carried out some distance from the power source, it may be necessary to increase cable diameter to reduce voltage drop.

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The Welding Electrode

The welding electrode consists of a core material of the material type i.e. steel or stainless steel etc. which provides the weld filler metal. This is covered by an outer coating called a flux which helps in creating the arc and shields the arc from contamination with what is called slag.

Types of Flux/Electrodes

The stability of the arc, depth of penetration, metal deposition rate and positional features are significantly influenced by the chemical composition of the flux coating on the electrode. Electrodes can be divided into three main types:

• Basic
• Cellulosic

• Rutile

Basic Welding Electrodes

Basic welding electrodes contain a high proportion of calcium carbonate (limestone) and calcium fluoride (fluorspar) in the coating. This makes their slag coating more fluid than rutile coatings - this is also fast-freezing which assists welding in the vertical and overhead position. These electrodes are used for welding medium and heavy section fabrications where higher weld quality, good mechanical properties and resistance to cracking (due to high restraint) are required.

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Features:

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• Low hydrogen weld metal

• Requires high welding currents/speeds

• Poor bead profile (convex and coarse surface profile)

• Slag removal difficult

   

When these electrodes are exposed to air moisture pick-up is rapid. Because of the need for hydrogen control these electrodes should be thoroughly dried in a controlled temperature drying oven.
Typical drying time is one hour at a temperature of approximately 150oC to 300oC but you should always consult the manufacturer data before use.

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After controlled drying, basic and basic/rutile electrodes must be held at a temperature between 100oC and 150oC to help protect them from re-absorbing moisture into the coating. These conditions can be obtained by transferring the electrodes from the main drying oven to a holding oven or a heated quiver at the workplace.

Metal Powder Electrodes

Metal powder electrodes contain an addition of metal powder to the flux coating to increase the maximum permissible welding current level. Thus, for a given electrode size, the metal deposition rate and efficiency (percentage of the metal deposited) are increased compared with an electrode containing no iron powder in the coating.

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