g-code

CNC Glossary

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

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

Canned cycle
A 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 Drawing
A drawing of a part giving a complete and exact description of its form, dimensions, and construction

Dimension
The desired measurement of a part

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

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

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

GCODE
Common name for the programming language that controls NC and CNC machine tools

Geometric Modeling
A 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.

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

M Code
A 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 Data
Manufacturing instructions defined in CAM and enacted on a CNC machine.

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

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

Machining
The selective removal of metal or material

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

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

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

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

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

Preliminary Blueprint
A design representing the rough dimensions of a specific part

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

Prototype
The original test model of a part

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

Ramping
The 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.

Scanner
A computer device that converts hard copy drawings into digital form

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

Solid Modeling
A 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-Program
Acting as a part programming shortcut, a part program sequence that is called on as needed. Also called a subroutine.
Surface Modeling
A 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 motor
A device that translates electrical pulses into precise mechanical movement. The output shaft may deliver rotary or linear motion.

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

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

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

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

Unipolar
A 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 Graphics
A 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 Modeling
A type of geometric modeling in which the edges of a part are represented by solid lines

Working Drawing
A drawing of a part providing data for manufacturing

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

Y-axis
An 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-axis
An 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).

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Rapid Prototyping

Prototyping can be referred to as method of getting virtual 3D model printed onto a 2D object. Rapid Prototyping falls in the category of ‘rapid prototyping’ technology. The function typically performed by 3D printers is that of printing consecutive layers on the previous ones for building up a 3D object. It is easier, more affordable, and faster to use 3D printers as compared to other technologies related to additive fabrication.

Technologies: Initially, production of a prototype required a lot of man-hours, tools, and experienced labor. For instance, after designing a novel Street Light Luminaire digitally, drawings used to be sent to accomplished craftsmen where the paper design used to be followed with utmost pains and a 3D Printing used to be formed in wood through the utilization of the entire shop that is full of costly tools and working machinery. One can easily make out that this process consumed a lot of time. Moreover, the skillful labor was not all that cheap. These shortcomings necessitated the need of rapid prototyping.

Inkjet Printing System is one variation of 3D Printing. It involves binding of fine powder layers (resins, cornstarch, or plaster) by the way of printing a gum from inkjet print head as per the shape of every cross-section as spotted by the CAD file. This is the only technology allowing full color prototypes to be printed. The school of thought is that this is the quickest method.

On the other hand, the liquids are fed by these machines. Photopolymer is one of such kind. These machines make use of UV (ultraviolet) flood lamp. It is mounted in print head for curing each layer on its deposition. A new technology called Fused Deposition Modeling uses a nozzle to deposit molten polymer layer by layer to the supported structure. The other approach is Selective Fusing of Print Media in the granular bed. Here, the media that has been unfused supports thin walls and overhangs in the piece which is being produced, thereby reducing need for temporary auxiliary supports for the work piece.

Ultimately, 3D Micro fabrication technique having a photo polymerization of 2-photons might be used to make ultra small features. Here, the preferred 3D object gets traced out by a completely focused laser in a gel block. The curing of gel into a solid takes place only in places where laser had been focused, owing to photo excitation’s non-linear nature. The gel that is left out gets washed away.

Resolution: Resolution is measured in terms of layer thickness. The X-Y resolution is given in dpi. 100 microns is the characteristic layer thickness. The X-Y resolution is compatible with laser printers. Diameter of the particles, i.e. 3D dots is around 50-100 microns.

Applications: Standard applications are inclusive of design visualization, metal casting, CAD/prototyping, architecture, geospatial, education, healthcare, retail/entertainment, etc. Off late, 3D printing technology is being used in artistic expressions. Its biotechnological applications include bio-printing, computer-aided Tissue engineering, and organ printing.

Self-replication: The main purpose behind using 3D printing technology is its ability to replicate itself. RepRap is one such printer. It has the ability to print plastic parts and circuit boards. It is believed to print metals in future.

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