The degree to which an actuator is able to move to a specific commanded point. On the bullseye below, notice that all the holes are centered around the middle of the target, but the grouping is not very close together. Good accuracy does not require good repeatability. (see repeatability & accuracy)
Threaded screw and nut design which utilizes sliding surfaces between the two. Typical efficiencies are between 60-70%.
A mechanism for moving or controlling something indirectly instead of by hand.
Adjustable shock absorbers
Used on BC2 and BC3 band cylinders to decelerate heavy loads at high velocities. Tolomatic offers light and heavy duty shock absorbers. The sizing and selection software will automatically choose the correct shock absorber; either light duty or heavy duty as required. When shock absorbers are used on the cylinder internal cushions are not operational. Note: Shock absorber is most effective when stopping load at its center of gravity.
The temperature of the cooling medium, usually air, immediately surrounding the actuator or another device.
Protective treatment for aluminum that involves subjecting the metal to electrolytic action in a chemical bath, to create a protective film of aluminum oxide with a very smooth finish.
The drive function that determines the motor’s angular rotor position for commutation without the need for Hall Effect switches.
An option for band cylinders or linear slides that increases the load capacity of the cylinder as well as increasing the capacity of bending moment about the Y axis. Note: internal cushion will not work when auxiliary carrier ordered without piston, it will be necessary to add external shock absorbers.
Velocity calculations for all rodless cylinders need to differentiate between final velocity and average velocity. For example: Cycling a 100 inch BC3 model in one direction in one second yields an average velocity of 100 inches per second. To properly determine the inertia forces for cushioning, it is important to know the final (or impact) velocity. Rodless cylinders accelerate and decelerate at each end of the stroke. Therefore this acceleration must be considered. If final velocity cannot be calculated directly, a reasonable guideline is to use 2X average velocity.
Load where the force is acting along the axis of actuator (bearing) in any direction.
A bearing where the journal turns upon loose, hardened steel balls that roll easily in a race.
Screw and nut design utilizing a nut that contains one or more circuits of recirculating steel balls which roll between the screw and nut.
The name for a rodless cylinder using Tolomatic’s patented band retention system. Band cylinders feature a central slot. A band-type cylinder uses a bracket directly mounted to the cylinder piston to transmit force. The bracket passes between two bands which then seal the cylinder. The inner sealing band creates a tight metal to metal seal with the internal diameter of the cylinder bore. An outer dust band keeps dust and grit away from the sealing band. Elastomer strips provide a positive, non-magnetic lock. Tolomatic models include: BC2, BC3, BC4.
The IS Metric unit of pressure equal to one million Dynes per square centimeter. The Bar is used to measure both pneumatic and hydraulic pressure. One Bar is equal to 14.5038 pounds per square inch. It is also nearly equivalent to one atmosphere of pressure.
Base mounting linear slides may be accomplished by fastening directly to “T” slot nuts provided in the base of the slide or by using the base mounting.
Number of binary bits transmitted per second in a serial communication system.
Equivalent torque produced by a force displaced by a known distance from the carriage. (Ex. Mx, My, Mz, Fz)
Method of purging air from a brake system’s hydraulic lines and cylinders. Air is compressible and contaminates brake fluid. It is released via a “bleeder valve.”
Brake lining (friction material) attached to the backing plate with adhesive.
The ratio of braking force distributed between the front and rear wheels.
Brake disc (or rotor)
The basis of a disc brake system: a round metal disc which rotates with the road wheel and, in order to generate braking power, is clamped by a caliper holding two friction linings (pads).
Reduction (or complete loss) of braking performance, usually caused by too much heat in the system.
Sensation transmitted to the driver during a braking action via the brake pedal.
Liquid formulated specifically to be used in hydraulic brake systems.
Flexible rubber (or synthetic) hose used to join hydraulic brake components.
Rigid tubing which links various hydraulic components in a brake system.
Common name for Friction Material.
The component in a disc brake system which is fitted with brake lining and clamped against the brake disc to cause friction.
The minimum amount of force or pressure required to cause the initial movement of a given device such as a cylinder piston, a brake piston, or a rotary actuator through a full stroke.
Torque required to start an actuator in motion. In an electric actuator, this consists primarily of the torque to overcome the preload of the lead screw nut assembly and the static friction of the carrier bearings.
British Thermal Unit (BTU)
The amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit.
Brushless DC Servo
Motor/drive that generates trapezoidal motor currents and trapezoidal back EMF in a brushless motor.
A widely used copolymer (artificial rubber) used for making seals. Buna-N seals should never be used with automotive brake fluid.
Cable cylinder repair kit
A sub-assembly consisting of two cable assemblies and the internal seals, (two piston seals, two cushion seals and two tube-sealing O-rings) required to keep a cable cylinder operational.
A type of clamp which grips a disc rotor to create friction and thereby generate stopping power
Caliper disc brake
A form of brake, used to retard, stop or hold action. The brake is called a “caliper” because it is mounted over a rotating disc to which it applies a friction member (puck) to slow, stop or hold the disc.
Moving part of a rodless actuator providing a mounting surface for a load.
Center of gravity
(Center of Mass) The point at which the entire weight of a body may be considered as concentrated so that if supported at this point the body would remain in equilibrium in any position.
The name given to the U-shaped cable connecting bracket on a Tolomatic cable cylinder.
Closed Loop (Feed Back)
System where the output is measured and compared to the input. If this system is capable of making corrections to minimize the difference it is classified as a servo.
Coefficient of friction
The measurement of friction of one object sliding across another. Symbolized by the Greek letter Mu (m) it is defined as the tangent of the angle of repose of a static body. The coefficient is expressed in decimal values (clean iron on clean iron is 1.0, while metal on solid rubber may range from 1.0 up to 4.0). When objects are wet, the coefficient of friction decreases.
Switching of drive voltage to the motor windings necessary to provide continuous rotation. A brush motor uses mechanical switching through a brush-bar contact. Brushless motors use separate devices such as Hall Sensors to sense the rotor position. This information is then processed by the drive to determine the switching sequence.
A series of code letters and numbers that Tolomatic uses to create built-to-order actuators.
Name given to the software that uses the configuration string to give instructions to the factory with correct specifications to create your built-to-order actuator.
Guided and supported in a particular direction, through the use of an external guidance and bearing system.
Another term for RMS torque. See RMS torque
Rotational speed of a lead screw at which the screw begins to oscillate or whip. This speed is dependent on the screw length and diameter.
Disc with friction surfaces which have been drilled with rows of holes to improve cooling, reduce weight and provide an escape route for dirt and gasses which can be wedged between the pads and disc. High-performance rotors can be both cross-drilled and slotted.
Curved vane disc
Ventilated rotor in which the cooling channels (or vanes) have been curved to increase their ability to pump out hot air and cool the disc. Curved vane rotors are more efficient than conventional ventilated rotors and, as a side benefit, tend to be stronger.
A means of slowing down a cylinder piston at the end of its stroke by forcing exhaust through a port with an orifice small enough to restrict the velocity at which the pressure fluid is exhausted.
A complete motion of actuator’s carrier or tooling plate from start to finish and back.
Total number of complete cycles in a specific period of time.
A metal-forming process similar to injection-molding for plastic. In Die-Casting, molten metal (usually aluminum) is injected into a mold under pressure.
The most popular and effective type of automotive brake. It uses a rotor (a round grey metal plate) which is squeezed by a caliper to create friction and thereby generate stopping power.
Disc thickness variation
A variation in thickness between two points on the friction surface of a disc rotor (usually caused by poor manufacture, poor machining or rubbing of the rotor against the caliper when the brakes are “off”).
Alternate term for Minimum Thickness.
Double-acting brakes apply pressure to pucks on each side of the disc. Both disc and brake may be fixed mounted.
Double-acting cable cylinder
Cable cylinder that applies equal force in two directions.
Double-purchase cable cylinder
Cable cylinder that uses additional cable and pulleys to double the velocity and stroke of cable cylinders.
A type of older – but still popular and effective – automotive brake in which a circular drum rotates around a set of brake shoes which are fixed to the hub and act on the drum by expanding.
Dual 180 carrier
Option for the BC3 that gives greater bending moments without using a larger actuator.
Option for BC2 with two magnets, one on each side of the carrier.
Part of Tolomatic’s patented band retention system, the external band.
Ratio of on time to total cycle time. Duty Cycle = On Time (On Time + Off Time)
A pause of motion within a move cycle.
Ratio of power output to power input
Part of a resistance weld gun that facilitates the high voltage current path to the part(s) being welded.
Device attached to the end of an electrode. This is a replaceable/consumable item that contacts the metal parts being welded.
Device used to provide relative position and velocity information to a drive or controller by sensing mechanical motion and providing a corresponding pulse rate as output.
The process used in resistance spot welding to position or “float” the welding gun relative to the work piece prior to each resistance weld cycle within the weld schedule.
Shock absorbers of some sort used to decelerate the load on a rodless cylinder in cases where the load is too heavy to make use of the cylinder’s internal cushions.
Stops used on the outside of a vane-type rotary actuator to limit the rotation of the unit short of the unit’s full cycle.
Mounting style for Float-A-Shaft® standard series.
When traveling in a straight horizontal line, the vertical deviation above or below the horizontal plane of travel of the carrier.
Method of mounting single acting caliper disc brake that allows the force of the brake to be applied to both sides of the disc.
An option for use in applications where the load is not guided and supported by the Tolomatic actuator, or when compensating for nonparallelism.
A mounting plate that attaches a cylinder head to mount the cylinder to a flat surface at a 90° angle.
An agency or influence that if applied to a free body results chiefly in an acceleration of the body and sometimes in elastic deformation and other effects.
Resistance to relative motion between two bodies in contact, such as steel sliding on steel.
Material which is pushed against a disc by a shoe or caliper to generate friction.
Any of the surfaces designed to rub together in a brake system to create friction and therefore stopping power.
Hall-effect D.C. switch
A magnetically controlled transistor switch controlling DC power. It has no moving parts and theoretically unlimited contact life.
A metal component mounted at each end of a rodless pneumatic cylinder. With a cable cylinder, the head has a pulley, ports, mounting holes and provides sealing. On a Band Cylinder, the head provides tube sealing, fluid ports and mounting holes.
The process whereby braking components rid themselves of heat caused by friction. The heat in a disc system is mostly dissipated into the surrounding air. Dissipation can be accelerated by various forms of ventilation.
Shiny dark areas on a rotor caused by extreme heat.
Pattern found on the surface of a disc which has been poorly machined.
Maximum external torque that can be applied to a stopped, energized motor without causing the rotor to rotate.
A means of attaching a sprocket, pulley or disc to a shaft.
The delivery system of a modern braking set-up. It uses fluid to transmit the force applied at the pedal to activate the disc calipers.
A characteristic whereby something tends to absorb water. Brake fluid is hygroscopic.
A unit of measure of torque. It is derived from a given force in pounds acting at a given radius in inches (pounds multiplied by inches = inch-pounds). An inch-pound is 1/12th of a foot-pound. Inch-pounds may be converted to the IS Metric equivalent of Newton-meters by multiplying them by 0.1129848. Newton-meters may be converted to inch-pounds by multiplying them by 8.850748.
A positional move referenced from the current position.
Measure of an object’s resistance to change in motion that is a function of the object’s mass and shape.
If the reflected inertia of the load is equal to the rotor inertia of the motor, the system will operate optimally for efficiency and dynamic performance.
A type of bearing material used in Float-A-Shafts® for applications with lower torque requirements.
A demountable machinery part, which, when assembled into a keyseat, provides a positive means for transmitting torque between two other machine parts.
An axially-located groove in the length of a shaft along which a key may be located.
The ability to do work based on motion. It is found by multiplying half the mass by the square of the velocity.
Linear travel of a lead screw nut or carriage for every one full rotation of the lead screw expressed in inches per rev.
A switch that is actuated by some part or motion of a machine or equipment to alter the electrical circuit associated with it.
A rodless cylinder using the same patented band retention system as the band cylinder. The Linear Slide uses a wider extrusion with steel shafts and bearings for additional load support. Tolomatic model: LS
A mass or weight supported by the carrier (rodless cylinders) or tooling plate (rod type cylinders). (Ex. Fz)
An option available for the BC4 the long carrier increases the My and Mz moment load capacity. It also gives a larger mounting surface and virtually eliminates chatter for vertical cantilever loads.
Magnetic coupling force
The force created between the piston magnets and moving carrier. (measured in pounds)
Magnetically coupled actuator
Rodless cylinder and slides featuring a magnetic couple between the piston and moving carrier.
Braking system which does not use power-assistance to magnify the pedal effort.
The engine-room of a brake system, where the force applied at the pedal is converted into hydraulic pressure.
Maximum dynamic Load
Load of constant magnitude acting in one direction that results in a nominal life (travel) of a linear motion actuator (component).
Maximum static Load
Maximum load of constant magnitude acting in one direction that a static actuator (component) can withstand without permanent deformation.
Type of drive that proportions the current in a step motor’s windings to provide intermediate positions between full steps. Advantages over full and half stepping include smoothness of rotation and higher position resolution.
The thickness at which a disc rotor must be discarded. Through wear and machining a disc rotor becomes thinner over time; as a result it becomes less able to dissipate heat and more prone to warping and other problems. The minimum thickness is usually determined by the vehicle manufacturer.
Modified standard products
Tolomatic can easily accommodate your special needs. Our standard products are often customized with extra mounting holes, different materials and other requests. This can often be done within our normal 5 day production time. We welcome modifications as well as completely new custom products.
Rotational forces applied to the carrier equal to the linear force applied (weight) multiplied by the distance between the location of the force (center of gravity) and the surface center of the carrier. Typically expressed as yaw (Mz), pitch (Mx) and roll (My).
Definition of an objects position and velocity relationships in time during a move.
A type of roller bearing where the journal turns on small-diameter, hardened needle-like rollers which roll easily in a metal race.
Friction material which uses no asbestos, thereby being easier on public health (breathing asbestos dust can cause the disease asbestosis).
A ring of synthetic rubber with a circular cross-section, used as a gasket or seal.
Motion control system where no position or velocity signals are provided for correction. Typically, stepper systems run as open loop systems.
Transmission of a signal from one device to another with a light source (emitted) and sensor (received), in order to avoid direct electrical contact.
Industry term for a component supplied with a new vehicle or as an official replacement part. Known as OEM or “Original Equipment Manufacturer” parts, they are not necessarily produced by the vehicle-maker in question.
Effect where a disc is no longer true to its original shape, as a result of either warping, inconsistent wear or other damage. This can cause pulsing, grabbing, additional noise and lowered performance.
Metric versions of the BC2, BC3, BC4 and LS have the choice of parallel port and taper port.
A term which refers to the relationship between the two friction surfaces on a disc brake rotor.
A sliding component moved by fluid pressure. It usually consists of a short, solid metal cylinder within a cylindrical vessel in which it moves back and forth.
Number of revolutions required by a leadscrew to move the nut or carrier one inch, expressed in revs/per inch.
(Programmable logic controller) is an industrial digital computer that is used to control machines and processes by continuously monitoring analog and digital inputs and making decisions based on custom programs.
In pneumatic units, the area to make connection to air lines that supply power to the actuator. In electrical units: a connecting unit between a data link and a device.
Pounds per square inch (PSI)
A measurement of pressure in the American system. By way of comparison, the weight of the atmosphere (one atmosphere) is 14.7 pounds per square inch, at sea level. It is used to express pressure in both pneumatic and hydraulic-powered systems. In the IS Metric system, pressure is measured in Bars. To covert PSI to Bars, take the PSI figure and multiply it by 0.0689476.
Hydraulic control designed to stop the rear wheels from locking up (rear wheels become “light” under heavy braking and therefore more likely to skid).
An LED-equipped device for sensing end-of-stroke on cylinder slides. Proximity sensors supply either a sourcing signal or a sinking signal to a device such as a programmable logic controller.
A sheave or small wheel with a grooved rim used with a cable cylinder to change the direction and point of application of the pulling force generated by the cylinder’s piston.
Tendency of a vehicle to pull to one side under braking.
Uneven or stutter-like force transmitted through the brake pedal during braking, usually caused by problems with disc rotors or linings.
Pulse Width Modulation is a method of controlling current in the windings of a motor by on-off switching of transistors to vary the duty cycle.
A sealing ring of synthetic rubber which has 4 spacing lobes and is capable of sealing in two directions.
Load where the force is acting perpendicular to the axis of actuator (bearing) in the direction of actuator (bearing).
Tolomatic’s Form A Reed Switch is an LED-equipped 0.5 ampere switch consisting of ferromagnetic blades brought into contact when a magnet passes nearby. Reed switches are used for signalling position only.
Characteristic of a motor to act as a generator when the CEMF (counter electromotive force) is larger than the drive’s applied voltage.
The technique of slowing or stopping a drive by regeneration.
A ratio that indicates the amount of water vapor in the air. It is usually expressed as a percentage. At any temperature, it is the amount of water vapor in the air, divided by the amount that would be present at saturation.
The degree to which an actuator can return to a reference location. Notice on the bullseye on the next page that the holes are close together, however the grouping is far from the bullseye. Repeatability can be thought of as how tight of a grouping can be made. Unidirectional repeatability, measured by approaching a position from a single direction, hides errors caused by backlash and hysteresis effects. Bidirectional repeatability, measured by approaching a position from opposing directions, includes these effects, and provides a more meaningful specification.
Repeatability and accuracy
The measure of how close to a programmed point the actuator can come, and how close it gets to that same point again. The repeatability of industrial actuators is usually much better than the accuracy. Notice on the bullseye below that the points are centered around the middle of the target and are grouped close together. This is good accuracy and repeatability.
Chamber connected to the master cylinder (usually by hoses) and used for storing hydraulic fluid.
Resistance spot welding (RSW)
Resistance Welding is the coordinated application of electric current and mechanical pressure in the proper magnitudes and for a precise period of time to create a coalescent bond between two base metals. Weld electrodes are used to conduct the electric current to the base metals as they are forged together.
The smallest position increment that can be achieved.
A feedback device consisting of a stator and rotor that provides position and velocity information to the drive for commutation.
Reverse radial load
Load where the force is acting perpendicular to the axis of actuator (bearing) in the direction opposite from actuator (bearing).
RMS (Root Mean Square)
An industry-accepted standard for measuring the smoothness of a surface finish. Under a microscope, all surface finishes have peaks and valleys. The more peaks and valleys, the rougher the finish and the higher the RMS value. The smaller the RMS number, the smoother the finish.
In an intermittent application, this is the torque provided to generate equivalent motor heating to one operating in a steady state. Trms= where: Ti= Torque during interval i and ti= Time of interval i
Industry-accepted standard for definition of hardness.
A cylinder using a rod attached to its piston to transmit force.
An actuator that contains the stroke within the cylinder itself.
An anti-friction device consisting of a journal which rests on free-rolling, hardened cylinders in a race.
Alternative name for brake disc.
A standard for data communication that defines voltages and time requirements for information to be transferred on a single line in sequential format.
Rotors which are warped or out-of-true have excess “run-out”, meaning the surface varies or wobbles as it rotates around a fixed point.
A diagram of a circuit in which symbols illustrate circuit components.
An object used to retain air pressure, water, hydraulic fluid or oil in a vessel. In the Tolomatic product line, seals are made of an elastomer, which is any of a variety of synthetic rubber compounds.
The stainless steel strip which is part of Tolomatic’s patented band retention system, the internal band.
System that compares the output of a device (by monitoring position, velocity, and/or torque) with the desired outcome and makes corrections to minimize the difference.
Motor used in closed loop systems where feedback is used to control motor position, velocity, and/or torque, usually expected to have high torque/inertia ratio.
The practice of confining the electrical field around a conductor to the primary insulation of the cable by putting a conducting layer over and/or under the cable insulation. (External shielding is a conducting layer on the outside of the cable insulation. Strand or internal shielding is a conducting layer over the wire insulation.)
A self contained hydraulic device commonly used on rodless cylinders, rodless slides and rod cylinder slides to decelerate heavy loads at high velocities.
The event, phenomenon, or electrical quantity that conveys information from one point to another.
Single end porting
Single end porting simplifies air hook up, allows running air lines to just one end of the actuator. Unless otherwise specified single end porting is factory installed on the right side of the actuator. Available for the BC3 and BC4.
Single-acting brakes have piston and puck on “live side” and a non-actuated puck on the “dead side”. Since only one side applies force to the disc, a means to allow movement of the disc or caliper must be provided.
Single-acting cable cylinder
Cable cylinder that applies force in one direction and uses gravity (generally) to return to home position.
Constant non-zero velocity portion of a motion profile.
Type of disc brake rotor which has a series of slots or grooves across its friction surfaces. These are designed to improve the bite of the pads and break down the build-up of gas and dirt which can occur between pad and rotor. High-performance rotors can be both slotted and cross-drilled.
A patented method of installing seals in cable cylinder heads without using tools. It includes a plastic washer, which, when pulled into a cable cylinder head cable port, snaps into a groove and holds the seal arrangement in place.
Disc rotor with solid metal between the two friction surfaces.
Solid state devices
Electronic components that control electron flow through solid materials (e.g., transistors, diodes, or integrated circuits).
Pedal which feels spring-like, perhaps due to the presence of air in the hydraulic system.
Maximum torque available at zero speed.
Motor which translates electrical pulses into motion, where the pulse rate controls velocity and position.
System ability to maintain accuracy when subject to disturbance.
When traveling in a straight horizontal line, the side to side deviation within the horizontal plane of travel of the carrier.
The distance that the carrier and its load will move on the actuator.
A transient variation in the current or potential at a point in the circuit.
Total friction area contacted by the pads during one revolution of the rotor.
Located on the carrier or piston magnets are needed for switches to sense position of carrier. On the BC3 and BC4 the switch magnet is a standard feature, attached to the piston. On the BC2 and LS the switch magnet is only included if switch is ordered. Magnets are easily inserted into carrier for field retrofitting.
Switch magnets dual
The BC2 optionally can have dual switch magnets, one on each side of the carrier.
For intermediate support, tube support brackets can be mounted to the BC2, BC3, and BC4 models. For the BC3 and BC4 the T-Nuts, that are needed for the brackets, must also be ordered.
Metric versions of the BC2, BC3, BC4 and LS have the choice of parallel port and taper port.
The greatest longitudinal stress a substance can bear without permanent deformation.
A threaded device attached to the end of a cable cylinder assembly for convenience in making connections and adjustments. One terminal is attached to the piston, while the other is attached to the bracket (clevis).
Measurement of linear force.
Device that physically machines (re-shapes) the cap (tip) electrode to like new shape & condition to extend the cap life while providing quality welds.
A specified allowance for error from a desired or measured quantity.
Measurement of force producing rotation.
Torque generated in a DC motor per ampere applied to the windings.
Track cable cylinder
A cable cylinder with hardened ground shafts and a guided carrier within linear bearings, giving the cylinder the ability to guide and support moderate work loads.
A velocity vs time profile that is characterized by total move time split evenly for acceleration, deceleration and velocity.
Triac AC reed switch
These switches are designed for signaling end-of-stroke position to devices such as programmable controllers. They can be used to operate ac relays and solenoids if a protection circuit is used and if current and voltage limits are observed.
A velocity vs time profile that is characterized by equal time for acceleration and deceleration.
Due to the nature of loads and aluminum extrusions tube deflection will occur if cylinder (linear slide) is supported only on the ends without tube supports at recommended intervals along length of cylinder.
Optional accessory for band cylinders and linear slides (base mount) to prevent tube deflection.
A synthetic rubber component with lips along its inner and outer circumferences giving a cross-section the appearance of the letter “U”. When under pressure, the lips flare out, providing a tight seal in one direction and minimal drag from the non-pressurized side.
U.S. Standard: A system of weights and measures based on the pound and inches. Metric: A decimal system of weights and measures based on the kilogram and meter.
A class of drives that sense motor current in each individual motor phase and resolves these readings into two current vectors. One vector is the torque producing current and other is the waste current. The current control algorithm then works to drive the non-torque-producing component to zero. This results in a high bandwidth torque response over the full speed range without the phase lag and tolerance issues that place older drive technologies.
Disc rotor which has a series of fins (or cooling passages) between the two friction surfaces to aid in heat dissipation.
A DuPont Chemical Co. trademark for a fluorocarbon rubber used in high temperature applications. At Tolomatic, Viton® is used for seals in high temperature situations and for brakes designed to be operated with non-flammable hydraulic fluids such as phosphate-ester.
Unit of electromotive force. It is the difference of potential required to make a current of one ampere flow through a resistance of one ohm.
Back EMF generated by a DC motor usually in units of volts per 1000 rpm.
The maximum voltage at which a given device may be safely maintained during continuous use in a normal manner. It is also called working voltage.
A unit of power or a rate of doing work. The power dissipated by a one ohm resistor with one ampere of current is one watt.
Description of molten metal that is created during the resistance spot weld process by high current being applied through the electrodes to the metal being thermally joined.
Six or seven axis servo driven industrial robot that carries and positions the spot weld gun to the weld location.