CNC Glossary

By: Ivan Irons

CAD (Computer-aided design)Geometry authoring tool that involves software and sometimes special-purpose hardware. Current packages range from 2D vector based drafting systems to 3D solid and surface modellers.

CAM (Computer-aided manufacturing) Considered as an NC programming tool wherein 3D models of components generated in CAD software are used to generate CNC code to drive numerical controlled machine tools

CNC (computer numerical control)Refers specifically to a computer "controller" that reads G-code instructions and drives the machine tool.

CAD/CAM part programmingThe computer calculation and creation of a toolpath based on part geometry information created in CAD.

Canned cycleA predetermined machining sequence used to simplify programming.

Data Information processed as the basis for calculations. Database Computer storage that holds data and is searchable

Detail DrawingA drawing of a part giving a complete and exact description of its form, dimensions, and construction

DimensionThe desired measurement of a part

DocumentationA CAD process in which a part design is converted to a computer file or hard copy for reference and storage purposes.

Drawing Exchange FormatDXF. A standard storage format for personal computer-based CAD/CAM platforms

DriverThat portion of the electronic package that receives the stepping sequence from the translator and provides the switching of the windings in the stepper motor.

G-CodeCommon name for the programming language that controls NC and CNC machine tools

Geometric ModelingA modeling process in which a designer creates lines and text that represents the shape of a desired part. Geometric modeling is the first step in CAD.

GeometryThe measurement, properties, and relationships of the lines and points of an object that make up its shape

M CodeA code used to signal an action from a miscellaneous group of commands. M codes change cutting tools, turn on or turn off the coolant, spindle, or work piece clamps, etc.

Machine Control DataManufacturing instructions defined in CAM and enacted on a CNC machine.

Machine Control UnitA small, powerful computer that controls and operates a CNC machine

Machine ToolPowered mechanical device, typically used to fabricate metal components of machines by machining

Machining The selective removal of metal or material

Numerical ControlThe use of computers and special program instructions to execute the sequence of machining operations to make a part.

Part ProgramA series of numerical instructions used by a CNC machine to perform the necessary sequence of operations to machine a specific work piece.

Personal ComputerPC.

A computer designed for an individual user and commercial software. Desktops, laptops, and notebook computers are PCs.

PlotterA large printer used to print blueprints. These output devices support vector graphics, unlike dot matrix and laser printers.

Post ProcessorA software link in the CAD/CAM chain that communicates instructions from CAM to a CNC machine

Preliminary BlueprintA design representing the rough dimensions of a specific part

Primitives or PrimitiveBasic shapes such as cubes, spheres, cylinders, blocks, and cones that are combined in solid modeling to create a model of a part.

PrototypeThe original test model of a part

Raster ImageA form of graphics in which closely spaced rows of dots form an image on a computer screen. Also known as bit-mapped graphics.

RampingThe process of controlling the pulse frequency to accelerate or decelerate a stepper motor. Ramping increases the ability to drive larger loads at greater speeds by slowing the first series of pulses allowing the motor to overcome inertial loads and reduces overshooting by slowing the motor down more gradually than an unramped motor.

ScannerA computer device that converts hard copy drawings into digital form

SoftwareThe coded instructions, formulas, and operations that structure the actions of a computer

Solid ModelingA type of geometric modeling based on solids in which all visible surfaces of a part are shown. In addition, solid modeling describes interior volume, mass, and weight.

Sub-ProgramActing as a part programming shortcut, a part program sequence that is called on as needed. Also called a subroutine.

Surface ModelingA type of geometric modeling based on geometry only, in which all visible surfaces of a part are shown regardless of volume definition.

Step Angle The angular increment the motor shaft will turn each time the windings (coils) are energized. The angle is specified in degrees. For a 200 step per revolution motor the step angle will be 1.8 degrees.

Step per revolution The total number of steps to rotate the motor shaft 360 degrees. For CNC, 200 or 400 steps per revolution are usually used.

Stepper motorA device that translates electrical pulses into precise mechanical movement. The output shaft may deliver rotary or linear motion.

Title BlockA portion of a blueprint that contains information such as the company name, part name, part number, designer, scale, and material.

ToleranceA blueprint specification indicating an unwanted but acceptable deviation from a given dimension

ToolpathThe series of coordinate positions that determine the movement of a tool during a machining operation.

TranslatorAn electronic device that converts pulses into the correct switching sequence, which will operate the motor one step for each pulse received.

UnipolarA bifilar wound motor. The current flows only in one direction through each winding. Normally there are two winding per bobbin and eight bobbins per motor. Usually is a 5, 6 or eight wire motor. One or more common leads are used per winding. Has less torque than a bipolar stepper motor but is simpler to drive. Bipolar stepper motor- just two windings. The electronic controls reverse the current alternately between the coils. This motor has more torque but requires more electronic controls.

Vector GraphicsA form of graphics that uses geometric formulas to represent images. Vector graphic images are more easily manipulated than raster graphics when dealing with CNC.

Wire Frame ModelingA type of geometric modeling in which the edges of a part are represented by solid lines

Working DrawingA drawing of a part providing data for manufacturing

X-AxisAn axis that is left or right. All movement left of a zero point is minus (-X)Psychology Articles, all movement right of the zero point is plus (+X).

Y-axisAn axis that is at right angles to the X-axis and intersect the zero point of the X-axis. All movement further away from the zero point is plus (+Y). All movement closer than the zero point is minus (-Y).

Z-axisAn axis that is vertically perpendicular to the X-Y zero point. All movement above the zero point is positive (+Z) while all movement below the zero point is (-Z).


» More on Computers