CNC Lexicon
(We tried to eliminate as much engineer-speak as possible...)
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2-Axis
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• | The cutter moves side-to-side (X) and back and forth (Y), so it has two linear axes. |
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3-Axis
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• | The cutter moves side-to-side (X), back and forth (Y), and up and down (Z), so it has three linear axes. |
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4-Axis
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• | The cutter moves side-to-side (X), back and forth (Y), up and down (Z), and can rotate in one plane. |
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5-Axis
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• | The cutter moves side-to-side (X), back and forth (Y), up and down (Z) and can rotate in two planes. |
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A-Axis
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• | The three linear axes are X, Y and Z. When rotaion is added, these are the A, B and C axes. |
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Acceleration
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• | When the spindle is moved without a load, it doesn't do so at a single speed. It speeds up, then slows down. |
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Aggregate head
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• | A spindle that holds more than one tool. Most aggregates can work at angles other than just 0 and 90 degrees. |
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Angular (rotational) axis
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• | Rotation about a vector (line) that is at an angle other than 0 or 90 (one of the X, Y or Z planes). |
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ASCII
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• | The American Standard Code for Information Interchange - it's the most common format for text files. |
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ATC (automatic tool changing)
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• | A machine head that holds a number of tools (bits) so the CNC doesn't have to stop to change bits. |
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Axis (plural, Axes)
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• | A straight line. It usually describes the path that a cutter follows, or rotates around. |
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B-Axis
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• | The three linear axes are X, Y and Z. When rotaion is added, these are the A, B and C axes. |
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Bearing - roller
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• | Like a ball-bearing, but with cylinder-shaped rollers instead of spheres. |
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Bearing - thrust
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• | These are round ball or (usually tapered) roller bearings that are housed in a circular sandwich |
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Bore/Boring
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• | Boring technically describes making a drilled pilot hole larger by machining around its edges. |
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Bushing
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• | A hard sleeve or lining that protects something such as wiring, or maintains the shape of a hole. |
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C-Axis
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• | The three linear axes are X, Y and Z. When rotaion is added, these are the A, B and C axes. |
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CAD (computer aided design)
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• | A computer program that is used to draw cabinets, furniture and parts. |
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CAM (computer aided manufacturing)
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• | A computer program that tells the router bit where to go, based on a CAD drawing. It creates toolpaths. |
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Canned Cycle
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• | Little programs that tell the machine to repeat what it is doing (usually with another step in between). |
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Cartesian (or Rectangular) Coordinate
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• | This is the standard XYZ imaginery rectangle (2-axes) or cube (3-axes) that is used to describe movement. |
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Charge pump
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• | An electronic safety switch that disables the motors, as in when you're changing a tool. |
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Chuck
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• | Just like a drill chuck, it holds the tool. |
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Closed Loop
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• | It provides feedback that tells the operator if something is out of whack. |
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CNC (Computer Numeric Control)
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• | A drawing is converted into numbers that tell the router's cutting tool where to travel. |
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Collet
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• | A segmented sleeve/collar that goes around a tool shaft and allows the chuck to grip it. |
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Control/Control System
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• | Either a single path (with starting and ending coordinates), or a continuous loop. |
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Coordinate (co-ordinate)
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• | A point where two or more axes intersect. Basically, it's where you tell the tool to be. |
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Datum
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• | An imagined shape, point, line or other geometrical entity. Zero datum is your starting point. |
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DXF (Drawing eXchange Format)
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• | Invented by the creators of AutoCad, it's a graphics format that CAD programs use to save designs. |
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EIA standards
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• | The Electronic Industries Alliance and ISO have developed standards for G-Code to help make it universal. |
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Feed hold
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• | Stops the spindle moving along a toolpath, but allows it to continue spinning the bit. |
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Feed rate
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• | How fast the spindle moves. |
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FOR, FRO (feed rate override)
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• | Usually a dial that allows you to manually slow down the travel of the cutter, if it's bogging down. |
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G-Code (GCODE)
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• | The computer language that transforms a design into a series of instructions the CNC can follow. |
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Gantry
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• | A 'bridge' that slides the length of the table, and allows the spindle/router to move across the table. |
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Home, homing, zero
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• | The starting point, which is 0,0 on the X and Y axes. |
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HPGL
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• | Hewlett-Packard Graphics Language, an older control system originally designed for printing plotters. |
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Jogging
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• | Manually moving the spindle in a straight line to save time. It can be done with the control panel, too. |
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Jumps, jumped steps (see also missed step)
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• | Can happen because the travel speed (feed) is too fast, or the load (cut depth, bit diameter) is too heavy. |
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Limits, limit switches
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• | Two on each axis tell the machine where home is, and also where the boundaries of the table are. |
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Linear Scale
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• | Where the units are the same, as in 1-2-3-4 (as opposed to a geometric scale such as 2-4-16-256) |
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Linear/Linear Axis
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• | A straight line, as opposed to a rotary exis that describes a circle or arc of a circle. |
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M-Code
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• | G-Code tells the machine what to do and M-Code (Miscellaneous Code) essentially makes it happen. |
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Machining Center
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• | A CNC (usually with an automatic toolchanger), where the tool moves and the workpiece stays put. |
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MCU (Machine Control Unit)
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• | It reads code and tells the machine what to do. |
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MDI (Manual data input)
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• | This is where the machine allows you to manually change/override a setting, such as the spindle RPMs. |
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Missed step (see also jumps)
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• | Where the spindle skips a small step, and this can lead to cuts in the wrong place or a shut-down. |
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Momentum
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• | The forward progress of the spindle, fueled by weight and speed. |
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Offset/preset
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• | A distance from 'home', so that a second part can be milled without the tool returning home. |
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Open Loop
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• | There is no feedback that tells the operator if something is out of whack. |
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Open or Closed Loop
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• | Open - no feedback. Closed - gives feedback (tells the operator what's happening) |
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Optic Code/Optical Encoder
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• | This is a sensor that 'sees' movement and tells the operator about the tool's position, velocity and direction. |
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Origin
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• | 0,0 on the XYZ axes. Also called home position, grid zero, and machine origin. |
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Pass
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• | An incremental cut: the tool removes waste in steps to avoid too much stress. |
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Path - Continuous
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• | Also called contouring, this is a path that can follow more than a single direction, e.g. a curve. |
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Path - Toolpath
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• | Where the tool is told to travel between points. |
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PID
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• | A proportional-integral-derivative is one way in which the machine delivers feedback about its progress. |
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Point-to-point
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• | An earlier, simpler version of a CNC. (Some machinists will argue that P2P still has relevance.) |
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Rapid
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• | When the cutter leaves the work and moves to another location, you can tell it to do so rapidly to save time. |
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Resolution
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• | The unit of measurement used to determine minimum travel increments. (e.g., 1/1000"). |
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Righthand Rule
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• | With your right hand palm up, the thumb and index finger form an L showing the X and Y axes respectively. |
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Rotational Axis
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• | These are imaginary axes (A, B and C) around which a tool - or a part - tilts or rotates. |
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Run-out (runout)
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• | This is where the tool (and it's sometimes the spindle) is no longer true, so it spins at a small angle. |
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Safe-Z
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• | A resting Z (vertical) setting where the tip of the cutter is safe - it doesn't touch anything. |
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Servo _DC
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• | A cool-running, efficient, quiet alternative to steppers, they're a little more tempermental. Runs on DC. |
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Servo - AC
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• | A cool-running, efficient, quiet alternative to steppers, they're a little more tempermental. Runs on AC. |
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Servo - Hydraulic
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• | A cool-running, efficient, quiet alternative to steppers, they're a little more tempermental. Runs on hydraulics. |
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Spindle
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• | The chuck and motor that holds the tool. Akin to the motor on a handheld router. |
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Spindle speed
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• | Usually describes the fastest speed that the tool can revolve, or else the variable speed setting. |
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Spoil Board (spoilboard)
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• | A waste sheet (usually MDF) that is attached to the bed and then milled flat and parallel to the gantry. |
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Stepover (step-over), Overlap
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• | How far the tool cuts across its previous path when making the next cut, balancing time and quality. |
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Stepper motor
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• | Less expensive but also less efficient than servo, with bearings instead of brushes, it runs hotter and can skip. |
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STL
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• | A file format used in more complex three-dimensional milling. |
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Surface (verb)
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• | To flatten. To reveal a new, fresh, flat surface. |
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Tool Path
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• | The route the tooling will travel. |
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Toolholder (tool holder, tool-holder)
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• | A device that holds several tools so that there is minimal downtime between changing them. |
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Tooling - Ball End Mill
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• | A bit with a round (spherical) cutting tip, also called a ball nose end mill, is durable and delivers a smooth cut. |
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Tooling - Drill
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• | A bit that drills vertical holes, and can often mill horizontally too. |
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Tooling/Cutting Tool
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• | The router bit or other cutter. |
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Travel
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• | The combined movement across the gantry and along the bed. |
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Vac clamp, Vacuum Hold-down
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• | One of myriad small pads, pods, clamps and other pneumatically activated hold-down systems. |
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Vector
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• | A line. The start and end are located as XYZ coordinates. |
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Velocity
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• | The speed at which the cutter moves across/through the workpiece. |
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VFD (Variable Frequency Drive)
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• | Allows an AC motor to run at different speeds. |
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XYZ
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• | X is side to side, Y is back to front and Z is up and down. |
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