CNC Definitions

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As with any area there tends to be a set of terms and jargon that goes along with it.  Presented here are several that relate to CNC as well as a few that are related to CAD as this tends to run hand in hand with CNC.


A-Axis The axis of circular motion of a machine tool member or slide about the X-axis. Values along the A-axis are degrees of rotation about the X-axis.
Axis A principal direction along which the relative movements of a tool or work piece occur. Three linear axes, occurring at 90 degree angles from each other, named X, Y and Z.

The plural form of "axis" is Axes pronouced [ak-seez]

Backlash A relative movement between interacting mechanical parts as a result of looseness.
B-Axis The axis of circular motion of a machine tool member or slide about the Y-Axis.
Bezier Curve Polynomial used to describe complex curves and surfaces. The location of midpoints controls the shape of a Bezier curve.
Cartesian Coordinates A three dimensional system whereby the position of a point can be defined with reference to a set of axes at right angles to each other.
C-Axis The axis of circular motion of a machine tool member or slide about the Z-axis. C-axis values are degrees of rotation about the Z-axis.
Cloud of Points
aka Point Cloud
A set of x-y-z coordinates obtain from a 3D scanner or digitizer. The data can then be turned into a continuous surface and used in a 3D model. Often used in reverse engineering applications.
Computer Aided Design (CAD) The use of computers to assist in the creation and modification of a design, most commonly, designs with a heavy engineering content. Usually refers to drafting and modeling software.
Computer Aided Engineering (CAE) The use of computers in design, analysis, and manufacturing of a product, process, or project. Sometimes refers more narrowly to the use of computers only in the analysis stage.
Computer Aided Manufacturing (CAM) The use of computers to assist in the creation or modification of manufacturing control data, plans, or operations. Sometimes refers more specifically to the programming of numerical controlled (NC) machines.
Cutter Diameter Compensation (CDC) A system in which the programmed tool path may be altered to compensate for cutter diameter differences.
CNC Computerized Numerical Control.
Cutter Offset The distance from the part surface to the axial center of a cutter (the radius of the cutter).
Cutter Path The path defined by the center of the cutter.
Downtime Time during which equipment is inoperable because of faults.
Dots/inch (dpi) The resolution of a hardcopy device or graphics display.
Drawing Exchange Format (DXF) A file format for CAD drawings used to transfer CAD data from one system or program to another, especially those files created by Autodesk Inc.
Dwell Time A timed delay of programmed or established duration used in specific machining operations.
DWG format (DWG) The file format for native AutoCAD drawing files
Feed Rate A programmed or manually established rate of movement of the cutting tool into the work piece for the required machining operation.
Feed Rate Override A variable manual control function that allows the control system to increase or reduce programmed feed rates.
G Code Active Preparatory Function-An NC word addressed by the letter G and followed by a numeric value, G Codes are flags that when executed by the machine control unit, initiate axis motions, plane changes, feed rate changes, etc.
Hewlett-Packard Graphics Language (HPGL) A format for graphics printing, especially of CAD data, developed and used by Hewlett-Packard Co. And emulated by many others. This format is sometimes used to exchange CAD data among systems.
Interpolation A function of a control whereby data points are generated between given coordinate positions.
Jig A device used most often for machining operations to hold a base part in a specified orientation or position relative to a known point.
Jog A control function that momentarily operates a drive into the machine.
Mirror Image The reversal of plus and minus values along an axis. Mirror imaging is used to make a left-handed part from a right-handed tool path.
Numerical Control (NC) The technique of controlling a machine or process by using command instructions in coded numerical format.
Offset A displacement in the axial direction of the tool equal to the difference between the actual tool length and the programmed tool length.
Parametric A capability of 2D and 3D modeling systems in which the user defines dimensions and constraints to which the model must conform. Alterations are then automatically reflected in related areas. Strictly speaking, parametrics work in only one direction, i.e., altering entity A will affect entity B, but not vice-versa. In practice, however, most systems allow the changes to operate in either direction.
Pixel For "picture element," the smallest definable dot of graphics data. Typically used in the description of graphics processors, displays, and monitors.
Plug In A software extension for programs that adds specific functionality.  Often a means for 3rd party developers to add functions to an existing software product.
Point Cloud A set of x-y-z coordinates obtained from a 3D scanner or digitizer. The data from an "ordered" point cloud can then be turned into a continuous surface and used in a 3D model. Often used in reverse engineering applications.
Rapid Prototyping (RP) Various manufacturing processes that accept 3D CAD files, slice the data into cross-sections, and construct layers from the bottom up, bonding one on top of the other, to produce physical prototypes for engineering purposes, prototypes; and patterns for hard tooling.
Raster A method of defining 2D graphic data with black-and-white or colored dots as opposed to vector data. Raster data resolution is typically defined by the number of pixels or dots/inch.
Stereolithography (SL) A rapid prototyping (RP) process. A Stereolithography machine focuses an ultraviolet (UV) light onto the surface of a vat filled with liquid photopolymer. The light beam, moving under computer control, draws each layer of an object onto the surface of the liquid. Wherever the beam strikes the surface, liquid changes to solid. 3D parts are built from the bottom up, one layer at a time; when the part is finished, it is exposed to UV light for curing.
Surface Modeling A 3D modeling method of describing geometry by its surfaces. Typically used where surface shape is critical, for example, automobile body panels. Surface modeling software generally provides many functions for creating, editing, and evaluating surfaces.
Tool Path The path the tool travels through in order to work material
Vector A method of defining 2D or 3D graphics by lines, arcs, circles, etc. in contrast to raster data.
Wire Frame A geometric model that describes 3D geometry by outlining its edges, similar to a "stick figure."


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