Advanced GMAW Applications 302

AC aluminum pulse welding

An advanced GMAW process that uses alternating current to weld aluminum. AC aluminum pulse has a lower heat input because of the alternating polarity of AC.

adaptive control

A feature of some advanced power sources monitors the arc and increases or decreases current in response to changes in the arc. Adaptive control is a form of waveform control.

adaptive control

A feature of some advanced power sources that monitors the arc and increases or decreases current in response to changes in the arc. Adaptive control is a form of waveform control.

alloy steels

A steel that contains intentionally added materials that change the property of the metal. Alloy steels are commonly made with manganese, molybdenum, and nickel.

alloys

A metal consisting of a mix of two or more elements, one of which must be a metal. Alloys can be used to make metal matrix composites.

alternating current

AC. Current that switches direction as it flows. Alternating current is typically not used for GMAW processes.

aluminum

A silver-white nonferrous metal that is strong, light, and thermally conductive. Aluminum is corrosion resistant, has a high strength-to-weight ratio, and has good weldability.

aluminum oxide

A thin film that forms on the surface of aluminum when it reacts with oxygen in the air. Aluminum oxide is often removed before welding.

arc length

The distance that electricity must travel from the tip of the electrode to the weld puddle. Longer arcs require more voltage.

argon

An inert gas commonly used as shielding for GMAW. Argon is much heavier than air, so it effectively shields the weld area.

automatic

A type of welding process in which a computer or a robot controls both the welding equipment and the weld variables. In an automatic process, the welder is responsible for setting and controlling the specialized settings for the computer or robot.

axial spray transfer

A type of metal transfer in which the metal at the end of the electrode melts into small, fine droplets that transfer to the weld puddle. Axial spray transfer creates a stable arc and little spatter.

axis

An imaginary straight line that passes through the center of an object. Robot movement is described in relation to axes.

background current

The lower nominal amperage of metal transfer with waveform control. Background current maintains the arc.

backing strips

A strip of metal located on the side opposite of the weld. Backing strips protect the back of the weld from atmospheric contamination and provide a surface for depositing the first layer of metal.

burnback time

An end option that controls how long weld output continues after the wire stops feeding. The burnback time option prevents the wire from sticking to the puddle and prepares it to start the next arc.

burnthrough

Excessive melt through or a hole in the base metal. Burnthrough may be caused by extremely high welding energy.

carbon dioxide

CO2. An active gas commonly used as shielding for GMAW. Carbon dioxide is inexpensive but yields a violent arc.

carbon steel

A common metal that consists of iron and carbon. Carbon steels are the most commonly welded metals.

chromium

A shiny, gray nonferrous metal that provides high corrosion resistance. Chromium is a common alloying element used in metals such as stainless steel.

chromium oxide

A protective film formed on the surface of stainless steel by the reaction of oxygen and chromium. Chromium oxide helps prevent corrosion.

constant current

CC. A power source that uses current that varies slightly with changes in voltage. Constant current power sources are often used in gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW).

constant voltage

CV. A power source that maintains a constant voltage setting while compensating for changes in amperage. Constant voltage power sources are typically used for GMAW.

consumable electrode

A device that conducts electricity from the contact tip to the arc and melts into the weld as a filler metal. Consumable wire electrodes are used in GMAW.

current

The flow of electricity through a circuit. Current is measured in amperes (or amps).

deposition rates

The rate at which filler metal melts off the electrode into the weld puddle. Deposition rates can be measured in pounds per hour or in grams per minute.

direct current

DC. Current that flows in one continuous direction. Direct current is typically used in GMAW.

direct current

DC. Current that flows in one continuous direction. GMAW typically uses direct current.

direct current electrode positive

DCEP. Current that always flows in one continuous direction with reverse polarity. With direct current electrode positive, electricity flows from the negative workpiece to the electrode.

drive rolls

Wheels that direct the wire electrode as it moves through a wire feeder. Drive rolls are specially designed for various types and sizes of wires.

duty cycle

The percentage of a ten-minute period that an electrical device can perform work before it must rest to prevent overheating. Welding guns are rated by their duty cycle.

electrode extension

The distance from the end of the contact tip to the end of the electrode. Electrode extension is also called stickout.

electrode liner

The insulated lining that surrounds the wire electrode. The electrode liner supports the electrode from the wire feeder to the contact tip.

ferrous

Containing iron. The most popular ferrous metal is steel.

fixtures

A customized device that is used to position and hold a workpiece in place. Fixtures are used with hard automated welding.

flat-position

The welding position used to weld from the upper side of the joint. In flat-position welding, the face of the weld is horizontal.

frequency

A measurement of the number of times a waveform repeats in one second. Frequency is measured in Hertz (Hz).

frost line

A border around an aluminum bead where the aluminum oxide has been blasted off. Frost lines indicate that a bead was welded properly.

gantry

A bridge-like overhead structure with a platform for supporting equipment such as a crane. Gantries may be used to move robot manipulator arms for welding.

gas metal arc welding

GMAW. An arc welding process in which a bare wire electrode and shielding gas are fed to the weld through a welding gun. Gas metal arc welding is also referred to as MIG/MAG welding.

globular transfer

A type of metal transfer in which the metal at the end of the electrode melts into a large ball and drops to the workpiece. Globular transfer deposits large amounts of metal into the weld puddle.

GMAW

Gas metal arc welding. An arc welding process in which a bare wire electrode and shielding gas are fed to the weld through a welding gun. GMAW is also referred to as MIG/MAG welding.

hard automation

The use of mechanized devices to automate a process using only linear movements. Hard automation is also known as fixed automation because it is designated to one specific task.

helium

An inert gas commonly used as shielding for GMAW. Helium is much lighter than air and can escape the weld area quickly.

inches per minute

ipm. The rate at which the wire electrode feeds through the welding gun. Wire feed speed is measured in inches per minute or millimeters per minute (mm/min).

interface control panel

A device that connects the robot control computer to the power source in a robotic welding system. The interface control panel allows the computer to control the other devices.

keyboard programming

Teaching a robot to perform an operation by programming the computer, with or without moving the arm. Keyboard programming can be performed offline or online.

lead-through programming

Teaching a robot to perform an operation by controlling its movements with a teach pendant. Lead-through programming is the most common method.

nonferrous

Not containing iron. Common nonferrous metals include aluminum and copper.

out-of-position

Welding positions that are not classified. Out-of-position welds are often done with electrodes that have smaller diameters to prevent spillage.

overshoot

The part of a waveform during which current increases above peak current. Overshoot increases pinching forces.

peak current

The higher nominal amperage of metal transfer with waveform control. Peak current helps form and pinch the molten metal.

physical properties

A characteristic of material that describes how it responds to forces other than mechanical ones. Physical properties include a metal's magnetic, thermal, and electrical attributes.

pinch current

The part of a waveform during which current increases in order to squeeze or pinch a molten droplet off the electrode. A pinch current may also be peak current.

polarity

Having two oppositely charged poles, one positive and one negative. Polarity determines the direction in which current flows.

positioner

The component that holds and moves the workpiece in a robotic welding system. Positioners increase the manipulator's range.

postflow time

An end option that controls gas shielding after welding stops. Postflow time determines how long gas flows after the welding output ends.

precision pulse transfer

An advanced GMAW process in which metal droplets form on the electrode one at a time at a fixed frequency. Precision pulse provides more control and consistent transfer than traditional pulse.

preflow time

A start option that controls gas shielding before welding begins. Preflow time determines how long gas flows after the trigger is pulled but before the wire feeding begins.

pulse spray transfer

A type of metal transfer in which one droplet of metal forms on the end of the electrode at a time. Pulse spray transfer is also known as GMAW-P.

push-pull wire feed system

A wire drive system that consists of two motors: one that pushes the electrode from the feeder and another that pulls the electrode. Push-pull systems are often used when welding aluminum.

ramp-up

The part of a waveform during which current increases. The speed of ramp-up affects the stiffness of the arc.

Rapid X

An advanced GMAW process that combines aspects of pulse spray and STT. Rapid X uses an extremely short arc length, which reduces spatter significantly more than RapidArc.

RapidArc

An advanced GMAW process that combines aspects of pulse spray and STT. RapidArc reduces spatter and makes faster travel speeds possible.

robot controller

The computer that controls the movement of robotic components in a robotic welding system. The robot controller is programmed by an operator.

robot manipulator

The component that holds and moves the torch in a robotic welding system. The robot manipulator has sensing devices to provide feedback to the computer about its location, speed, distances traveled, and, often, any unintended contact.

robotic welding

A type of automated welding that uses robots to move an arc. Robotic welding is a specialized form of soft automation.

robots

A mechanized device that can be programmed to manipulate materials, parts, tools, and other devices to perform a variety of tasks. Robots are multifunctional and reprogrammable.

run-in WFS

A start option that controls wire feed speed at the beginning of welding. Run-in WFS determines the speed of the wire from when the trigger is pulled to when the arc is established.

seam trackers

Sensory devices used to locate and adapt to seams or joints in a workpiece. Seam trackers are used for robotic welding when repeatedly accurately locating joints is impractical.

semi-automatic

A type of welding process in which the power source maintains a uniform arc and a wire feeder controls the wire feed speed of the electrode. In semi-automatic welding, the welder is responsible for controlling the position of the welding gun as well as the direction and speed of travel.

shielding gas

A gas that protects the weld puddle and arc from reacting negatively with the atmosphere. GMAW shielding gas is supplied to the power source and flows through the welding gun.

short circuit

A circuit in which current takes a shorter, unintended path between two conductors, interrupting the intended flow of electricity. A short circuit causes excess current flow.

short circuit transfer

A type of metal transfer in which the electrode produces a short circuit and high current when it touches the workpiece. Short circuit transfer's high current level causes a violent transfer of metal, which creates the weld.

smut

A black soot made of aluminum and manganese oxide that may form on aluminum base metals. Smut is expected in some locations, but excess smut indicates a problem.

soft automation

The use of reprogrammable mechanized devices to automate a task. Soft automation includes robotic processes.

spool gun

A type of wire feeder that consists of a self-contained gun, which feeds filler wire from spools mounted on the gun. Spool guns are mainly used for smaller diameter, softer wires, such as aluminum.

stainless steel

A type of steel that contains more than 11% chromium and exhibits excellent corrosion resistance. Stainless steel is one of the metals most commonly welded with GMAW.

stainless steels

A type of steel that contains more than 11% chromium and exhibits excellent corrosion resistance. Stainless steel is one of the metals most commonly welded with GMAW.

stepoff

The part of a waveform during which current goes from tail-out to background current. Stepoff reduces spatter.

STT

Surface Tension Transfer. An advanced GMAW process that uses a specialized form of short circuit transfer and adaptive control. STT relaxes the surface tension of the puddle to improve transfer.

surface tension

An effect within the surface layer of a liquid that causes that layer to behave as an elastic sheet. Surface tension prevents a weld puddle from flowing away from the weld.

Surface Tension Transfer

STT. An advanced GMAW process that uses a specialized form of short circuit transfer and adaptive control. STT relaxes the surface tension of the puddle to improve transfer.

synergic control

A feature of some advanced power sources that calibrates all welding parameters in response to one setting. Synergic control devices allow the welder to set wire feed speed (WFS) and then adjust all other variables accordingly.

tail-out

The part of a waveform during which current decreases. The speed of tail-out affects average current and puddle fluidity.

teach pendant

A device used to control a robot during programming. Teach pendants may have control buttons, a joystick, or a touch screen.

thermal conductivity

A material's ability to conduct heat. Thermal conductivity depends on the material's structure and temperature.

thermal expansion

An increase in a metal's dimensions in response to heat. Thermal expansion varies for different metals.

trim

A value used to control arc length in synergic processes. Trim represents all welding parameters combined.

voltage

The electrical force or pressure that causes current to flow in a circuit. Voltage and arc length are directly proportional in GMAW.

walk-through programming

Teaching a robot to perform an operation by physically guiding the manipulator. Walk-through programming is easy but inaccurate.

waveform

A visual representation of how current behaves over time. Waveform can be controlled to achieve certain arc characteristics.

waveform control

A feature of some advanced power sources that increases or decreases current to achieve different arc and weld characteristics. Waveform control helps transfer metal cleanly and minimize spatter.

weld backing

A substance located opposite the weld that protects the weld from atmospheric contamination. Weld backing may be in the form of metal backing strips or inert gas.

wet-in

The phenomenon in which a liquid filler metal spreads and adheres to a solid base metal in a thin continuous layer. Wet-in can decrease spatter.

WFS

Wire feed speed. The rate at which the wire electrode is fed through the welding gun. WFS determines amperage and the amount of heat in the arc in GMAW.

wire feed speed

WFS. The rate at which the wire electrode is fed through the welding gun. Wire feed speed determines amperage and the amount of heat in the arc in GMAW.