Automation terms, in plain English
The words you will hear from drive manuals, fault codes and our technicians, explained simply.
A
- Absolute encoder
- An encoder that knows the exact shaft position as soon as it powers up, so the machine does not need to home first. Common on servo motors and robots.
- Encoder repair
- AC drive
- Another name for a variable frequency drive (VFD): it controls the speed of an AC motor by changing the frequency and voltage it receives.
- VFD repair
- Alarm code
- A number or short code a drive, CNC or PLC shows when it detects a problem. The same thing as a fault code.
- Fault Code Library
- Amplifier
- In motion control, the power stage that drives a servo motor. Many brands call a servo drive a servo amplifier.
- Servo drive repair
- Axis
- One direction of controlled motion on a machine, such as X, Y or Z on a CNC. Each servo axis usually has its own motor and drive module.
B
- Backlash
- Play or lost motion in gears, couplings or a ballscrew: the axis moves a little before the load follows. It shows up as position error and poor surface finish on CNC parts.
- Backlight
- The light source behind an HMI's LCD screen. When it fails the screen goes dark or very dim even though the panel is still running.
- HMI repair
- Backplane
- The board at the back of a PLC rack that carries power and data between the CPU and the I/O modules plugged into it.
- PLC repair
- Ballscrew
- A screw and nut with recirculating balls that turns a servo motor's rotation into precise straight-line motion. Used on most CNC axes.
- Battery-backed encoder
- An absolute encoder that keeps its multi-turn position with a small battery while the machine is off (common on Fanuc and Yaskawa systems). If the battery dies with power off, the axis must be re-referenced.
- Encoder repair
- Bearing
- The part that lets a motor shaft turn smoothly. Worn bearings cause noise, heat and vibration, and can damage the encoder over time.
- Bearing & shaft repair
- Brake (holding brake)
- A spring-applied brake built into many servo motors that holds a vertical axis in place when power is off. A failed brake can stop a machine from enabling.
- Brake repair
- Braking resistor
- A resistor that turns the energy from a decelerating motor into heat. If it is missing, too small or failed, the drive trips on DC link overvoltage.
- Brushes and commutator
- On a DC motor, carbon brushes slide on the commutator to feed current to the rotating armature. Brushes wear out and are replaced as part of normal maintenance.
- Motor repair
- Bus voltage (DC link)
- The DC voltage inside a drive, made by rectifying the incoming AC supply. Overvoltage and undervoltage faults usually refer to this.
- Fault Code Library
C
- Capacitor reforming
- Slowly bringing a drive that has been stored for a long time back up to voltage, so its DC link capacitors are not damaged at first power-up.
- CNC
- Computer numerical control: the controller that runs a machine tool's axes and spindle from a part program. Examples are Siemens SINUMERIK and Fanuc Series 0i / 30i.
- CNC control repair
- Commutation
- Switching current between a motor's windings in step with the rotor's position. In a servo motor this depends on the encoder being aligned correctly.
- Component-level repair
- Repairing a unit by finding and replacing the failed components on its boards, instead of swapping the whole unit or module.
- Contactor
- A heavy-duty relay that switches power to a motor or drive. Worn contacts can cause intermittent faults.
- Control board
- The board that holds a drive's or controller's processor and logic. It tells the power stage what to do.
- Controller card
- A plug-in electronic board that controls part of a machine or drive, such as a CPU, axis or interface card. Often the part that fails inside a larger unit.
- Controller card repair
- Cooling fan
- The fan that pulls air across a drive's heat sink. A worn or blocked fan is a common cause of overtemperature faults.
- CPU module
- The processor card of a PLC. It holds the program and runs the machine's logic, reading inputs and setting outputs.
D
- DC drive
- A drive that controls a DC motor's speed by adjusting the voltage on its armature, usually with a thyristor bridge. Still common on older presses, extruders and winders.
- VFD & drive repair
- DRIVE-CLiQ
- Siemens' digital connection between SINAMICS components: control unit, motor modules, line modules and motors with DRIVE-CLiQ encoders.
- Model Code Decoder
- Dynamic braking
- Stopping a servo motor quickly by shorting its windings through resistors when the drive is disabled or loses power.
E
- EMC filter
- A filter on a drive's supply that reduces the electrical noise the drive sends back into the mains and into nearby equipment.
- Encoder
- A sensor on a motor that reports shaft position and speed back to the drive. Servo motors cannot run accurately without it.
- Encoder repair
- Encoder alignment (offset)
- Setting the encoder's zero to match the motor's magnetic position. A misaligned encoder causes poor torque, overcurrent or a motor that will not run.
- Encoder repair
- EnDat
- Heidenhain's digital encoder interface. It sends absolute position and encoder data to the drive over a serial connection.
- EtherCAT
- A fast Ethernet-based fieldbus widely used for motion control, for example with Beckhoff and many servo drives.
- EtherNet/IP
- The Ethernet-based industrial network used by Allen-Bradley (Rockwell) PLCs, drives and I/O.
- Exchange unit
- A tested replacement unit you get in exchange for your failed one, usually at a lower price than buying a refurbished unit outright.
- Exchange program
F
- Feedback cable
- The cable that carries encoder or resolver signals from the motor to the drive. Damaged feedback cables are a common cause of encoder faults.
- Custom cables
- Fieldbus
- The network that connects a PLC or CNC to drives, I/O and other devices, such as PROFIBUS, PROFINET, EtherNet/IP or EtherCAT.
- Firmware
- The software stored inside a drive, CNC or PLC. The firmware version often has to match the rest of the machine for a replacement to work.
- Following error
- The difference between where a CNC or motion controller commands an axis to be and where it actually is. If it gets too big the control raises an alarm.
- Fault Code Library
G
- Ground fault (earth fault)
- Current leaking to earth through damaged insulation in a motor, cable or drive. Drives trip on it to protect people and equipment.
- Fault Code Library
H
- Heat sink
- The finned metal block that carries heat away from a drive's power transistors (IGBTs). Dust build-up on it causes overheating.
- Hiperface
- SICK's encoder interface that combines analog sine/cosine signals with a digital data channel. Used on many servo motors.
- HMI
- Human-machine interface: the touch screen or operator panel used to run and monitor a machine.
- HMI repair
- Homing (reference point)
- Moving an axis to a known reference position after power-up so the control knows where it is. Needed with incremental encoders.
I
- I/O module
- A PLC card that connects inputs (sensors, switches) and outputs (valves, lights) to the controller.
- PLC repair
- IGBT
- Insulated-gate bipolar transistor: the power switch in most modern drives. Shorted IGBTs are one of the most common drive failures.
- Incremental encoder
- An encoder that counts pulses as the shaft turns. It only knows position relative to where it started, so the axis usually has to home after power-up.
- Industrial PC
- A rugged computer built for machines and control cabinets, often with a built-in touch screen.
- Industrial PC repair
- Inertia ratio
- The load's inertia divided by the motor's inertia. A high ratio makes a servo axis harder to tune and can cause vibration.
- Insulation resistance test
- A test that puts a high DC voltage between a motor's windings and its frame to check the insulation. Often called a megger test, after the instrument.
- Motor rewinding
- Inverter
- The output stage of a drive that turns DC back into variable-frequency AC for the motor. Also used as another name for a whole VFD.
- IP rating
- Ingress protection rating (IEC 60529). The first digit rates protection against dust, the second against water: IP65 means dust-tight and protected against water jets.
L
- Ladder logic
- The most common PLC programming language. It looks like an electrical relay diagram, with contacts and coils on rungs.
- Light curtain
- A safety sensor that sends a row of light beams across an opening and stops the machine when any beam is broken.
- Safety equipment
- Line module
- The supply unit in a modular drive system (for example SINAMICS S120) that feeds the DC bus shared by several motor modules.
- Line module repair
- Line reactor (choke)
- A coil fitted on a drive's supply or output to limit current spikes, reduce harmonics and protect the drive.
- Linear motor
- A motor laid out flat so it moves a carriage in a straight line directly, with no ballscrew or belt.
- Linear motor repair
M
- Model code (order number)
- The full part number of a drive or motor. Each section stands for an option such as size, speed, encoder, brake or shaft.
- Model Code Decoder
- Motion controller
- A controller that coordinates several servo axes so they move together along a programmed path.
- Motion controller repair
- Motor module
- In a modular drive system, the power unit that drives one or two servo motors from the shared DC bus.
- Servo drive repair
- Multi-turn encoder
- An absolute encoder that counts full revolutions as well as the position within one turn, so it knows the axis position over many turns.
N
- Nameplate
- The label on a drive or motor with its model, serial number and ratings. A clear photo of it is the fastest way to identify a part.
- Part Checker
O
- Obsolete part
- A part the manufacturer no longer makes or supports. Repair or a refurbished unit is often the only way to keep the machine running.
- Legacy & obsolete parts
- OEM
- Original equipment manufacturer: the company that built the machine or made the part, such as the machine builder or the drive brand.
- Overcurrent fault
- A fault raised when the drive measures more current than allowed. Causes range from a shorted motor or cable to a failed power stage or wrong tuning.
- Fault Code Library
- Overtemperature fault
- A fault raised when a drive's heat sink or a motor's temperature sensor reads too hot. Often caused by fans, dirty filters or overload.
- Fault Code Library
- Overvoltage fault
- A fault raised when the drive's DC link voltage gets too high, usually while a motor is decelerating and returning energy to the drive.
- Fault Code Library
P
- Parameters
- The settings stored in a drive or controller: motor data, limits, tuning and I/O. Always back them up before a unit is removed.
- Parameter backup
- Phase loss
- One of the three supply phases is missing or weak. Drives detect it and trip to avoid damage.
- Fault Code Library
- Planetary gearbox
- A compact gearbox with gears arranged around a central sun gear. Commonly fitted to servo motors to raise torque and lower speed.
- Gearboxes
- PLC
- Programmable logic controller: the industrial computer that runs a machine's sequence and logic.
- PLC repair
- Power supply unit
- The unit that turns incoming mains power into the DC voltages a control system needs, such as 24 V DC.
- Power supply repair
- Pre-charge circuit
- The resistor and relay that slowly charge a drive's DC link capacitors at power-up. If it fails, the drive may not power up or may trip on undervoltage.
- PROFIBUS
- A fieldbus widely used with Siemens PLCs, drives and I/O. PROFINET is its Ethernet-based successor.
- PROFINET
- The Ethernet-based industrial network used with Siemens SIMATIC and SINAMICS equipment and many other brands.
- Proximity sensor
- A sensor that detects metal or other objects without touching them. Used to sense positions, parts and end of travel.
- Sensors
- PTC / KTY sensor
- Temperature sensors built into motor windings. A PTC switches to high resistance when hot; a KTY gives a reading that rises with temperature.
R
- Rack
- The frame that holds a PLC's power supply, CPU and I/O modules, connected through the backplane.
- PLCs & I/O
- Rectifier
- The input stage of a drive that turns incoming AC into DC for the DC link.
- Refurbished
- A used unit that has been inspected, repaired where needed, cleaned and tested before it is sold again.
- Shop Parts
- Regen (regenerative) unit
- A unit that returns energy from a braking motor back to the mains supply instead of burning it off as heat in a braking resistor.
- Resolver
- A rugged analog position sensor used on some servo motors instead of an encoder. Common on older and high-temperature applications.
S
- Safe Torque Off (STO)
- A safety function that removes power to the motor so it cannot make torque. If the STO inputs are not wired or are open, the drive will not enable.
- Safety controller repair
- Safety relay
- A relay module that monitors e-stops, guard doors and light curtains and safely shuts the machine down when one is triggered.
- Safety equipment
- Serial number
- The unique number of one individual unit. Two units with the same part number have different serial numbers.
- Servo drive
- The unit that controls a servo motor's torque, speed and position using feedback from the motor's encoder.
- Servo drive repair
- Servo motor
- A motor with built-in position feedback, controlled by a servo drive for precise motion.
- Servo motor repair
- Servo tuning
- Setting a servo drive's gains so the axis responds fast without overshooting or vibrating.
- Soft starter
- A device that ramps up an AC motor's voltage at start to reduce inrush current and mechanical shock. Unlike a VFD, it does not control speed while running.
- Soft starter repair
- Solenoid valve
- An electrically operated valve that switches air or hydraulic oil to cylinders and actuators.
- Pneumatics & hydraulics
- Spindle drive
- The drive or amplifier that powers a machine tool's spindle motor and controls its speed.
- CNC control repair
- Spindle motor
- The motor that turns the cutting tool or workpiece on a machine tool. Usually driven by a spindle drive or amplifier.
- Motor repair
- Stepper motor
- A motor that moves in fixed steps, usually without position feedback. Common on smaller axes, feeders and indexers.
- Stepper motor repair
- Surplus
- Unused or lightly used stock, often left over from a project or a plant's spares. Inspected before it is listed.
- Shop Parts
T
- Teach pendant
- The handheld control unit used to jog, program and run an industrial robot.
- Robotics repair
- Test jig
- A test setup that runs a unit under real operating conditions on our bench: drives with a motor, motors under drive control.
- How we work
- Test report
- The record of how a repaired unit was tested before it left our bench. Every repair we ship comes with one.
- Thyristor (SCR)
- A power semiconductor used in DC drives and soft starters to control how much of each AC cycle reaches the motor.
- Torque constant (Kt)
- How much torque a servo motor makes per amp of current. Listed on the motor's data sheet.
- Touch screen (digitizer)
- The touch-sensitive layer on an HMI. Resistive screens respond to pressure; capacitive screens respond to a finger. Dead or drifting touch is a common HMI fault.
- HMI repair
- Turnaround time
- How long a repair takes once the quote is approved. Ours is typically 24 to 72 hours.
U
- Undervoltage fault
- A fault raised when the drive's DC link voltage drops too low, often from a weak supply, a phase loss or a failed pre-charge circuit.
- Fault Code Library
V
- VFD
- Variable frequency drive: controls an AC motor's speed by changing the frequency of its supply. Also called an AC drive or inverter.
- VFD repair
W
- Winding
- The coils of copper wire in a motor's stator. Damaged insulation between windings causes ground faults and overcurrent trips.
- Motor rewinding