G-codes are also called preparatory codes, and are any word in a CNC program that begins with the letter 'G'. Generally it is a code telling the machine tool what type of action to perform, such as: There are other codes; the type codes can be thought of like registers in a computer (*) M codes control the overall machine, causing it to stop, start, turn on coolant, etc., whereas other codes pertain to the path traversed by cutting tools. Different machine tools may use the same code to perform different functions; even machines that use the same CNC control. A standardized version of G-code known as BCL is used, but only on very few machines. G-code files may be generated by CAM software. Those applications typically use translators called post-processors to output code optimized for a particular machine type or family. Post-processors are often user-editable to enable further customization, if necessary. G-code is also output by specialized CAD systems used to design printed circuit boards. Such software must be customized for each type of machine tool that it will be used to program. Some G-code is written by hand for volume production jobs. In this environment, the inherent inefficiency of CAM-generated G-code is unacceptable. Some CNC machines use "conversational" programming, which is a wizard-like programming mode that either hides G-code or completely bypasses the use of G-code. Some popular examples are Southwestern Industries' ProtoTRAK, Mazak's Mazatrol, Hurco's Ultimax and Mori Seiki's CAPS conversational software.Code Description G00 Rapid positioning G01 Linear interpolation G02 CW circular interpolation G03 CCW circular interpolation G04 Dwell G05.1 Q1. Ai Nano contour control G05 P10000 HPCC G10/G11 Programmable Data input/Data write cancel G17 X-Y plane selection G18 X-Z plane selection G19 Y-Z plane selection G20 Programming in inches G21 Programming in mm G28 Return to home position G30 2nd reference point return G31 Skip function (used for probes and tool length measurement systems) G33 Constant pitch threading G34 Variable pitch threading G40 Tool radius compensation off G41 Tool radius compensation left G42 Tool radius compensation right G43 Tool offset compensation positive G44 Tool offset compensation negative G45 Axis offset single increase G46 Axis offset single decrease G47 Axis offset double increase G48 Axis offset double decrease G49 Tool offset compensation cancel G53 Machine coordinate system G54 to G59 Work coordinate systems G54.1 P1 to P48 Extended work coordinate systems G73 High speed drilling canned cycle G74 Left hand tapping canned cycle G76 Fine boring canned cycle G80 Cancel canned cycle G81 Simple drilling cycle G82 Drilling cycle with dwell G83 Peck drilling cycle G84 Tapping cycle G84.2 Direct right hand tapping canned cycle G90 Absolute programming (type B and C systems) G91 Incremental programming (type B and C systems) G92 Programming of absolute zero point G94/G95 Inch per minute/Inch per revolution feed (type A system) G98/G99 Inch per minute/Inch per revolution feed (type B and C systems) G96/G97 Constant cutting speed (Constant surface speed)/Constant rotation speed (constant RPM)
G-Code, or preparatory code or function, are functions in the Numerical control programming language. The G-codes are the codes that position the tool and do the actual work, as opposed to M-codes, that manages the machine; T for tool-related codes. S and F are tool-Speed and tool-Feed, and finally D-codes for tool compensation.
The programming language of Numerical Control (NC) is sometimes informally called G-code. But in actuality, G-codes are only a part of the NC-programming language that controls NC and CNC machine tools. The term Numerical Control was coined at the MIT Servomechanisms Laboratory, and several versions of NC were and are still developed independently by CNC-machine manufacturers. The main standardized version used in the United States was settled by the Electronic Industries Alliance in the early 1960s. A final revision was approved in February 1980 as RS274D. In Europe, the ISO standard DIN 66025 is often used instead.
Due to the lack of further development, the immense variety of machine tool configurations, and little demand for interoperability, few machine tool controllers (CNCs) adhere to this standard. Extensions and variations have been added independently by manufacturers, and operators of a specific controller must be aware of differences of each manufacturers' product. When initially introduced, CAM systems were limited in the configurations of tools supported.
Today, the main manufacturers of CNC control systems are GE Fanuc Automation (joint venture of General Electric and Fanuc), Siemens,Mitsubishi, and Heidenhain, but there still exist many smaller and/or older controller systems.
Some CNC machine manufacturers attempted to overcome compatibility difficulties by standardizing on a machine tool controller built by Fanuc. Unfortunately, Fanuc does not remain consistent with RS-274 or its own previous versions, and has been slow at adding new features, as well as exploiting increases in computing power. For example, they changed G70/G71 to G20/G21; they used parentheses for comments which caused difficulty when they introduced mathematical calculations so they use square parentheses for macro calculations; they now have nano technology recently in 32-bit mode but in the Fanuc 15MB control they introduced HPCC (high-precision contour control) which uses a 64-bit RISC (reduced instruction set computer) processor and this now has a 500 block buffer for look-ahead for correct shape contouring and surfacing of small block programs and 5-axis continuous machining.
This is also used for NURBS to be able to work closely with industrial designers and the systems that are used to design flowing surfaces. The NURBS has its origins from the ship building industry and is described by using a knot and a weight as for bending steamed wooden planks and beams.
The programming language of Numerical Control (NC) is sometimes informally called G-code. But in actuality, G-codes are only a part of the NC-programming language that controls NC and CNC machine tools. The term Numerical Control was coined at the MIT Servomechanisms Laboratory, and several versions of NC were and are still developed independently by CNC-machine manufacturers. The main standardized version used in the United States was settled by the Electronic Industries Alliance in the early 1960s. A final revision was approved in February 1980 as RS274D. In Europe, the ISO standard DIN 66025 is often used instead.
Due to the lack of further development, the immense variety of machine tool configurations, and little demand for interoperability, few machine tool controllers (CNCs) adhere to this standard. Extensions and variations have been added independently by manufacturers, and operators of a specific controller must be aware of differences of each manufacturers' product. When initially introduced, CAM systems were limited in the configurations of tools supported.
Today, the main manufacturers of CNC control systems are GE Fanuc Automation (joint venture of General Electric and Fanuc), Siemens,Mitsubishi, and Heidenhain, but there still exist many smaller and/or older controller systems.
Some CNC machine manufacturers attempted to overcome compatibility difficulties by standardizing on a machine tool controller built by Fanuc. Unfortunately, Fanuc does not remain consistent with RS-274 or its own previous versions, and has been slow at adding new features, as well as exploiting increases in computing power. For example, they changed G70/G71 to G20/G21; they used parentheses for comments which caused difficulty when they introduced mathematical calculations so they use square parentheses for macro calculations; they now have nano technology recently in 32-bit mode but in the Fanuc 15MB control they introduced HPCC (high-precision contour control) which uses a 64-bit RISC (reduced instruction set computer) processor and this now has a 500 block buffer for look-ahead for correct shape contouring and surfacing of small block programs and 5-axis continuous machining.
This is also used for NURBS to be able to work closely with industrial designers and the systems that are used to design flowing surfaces. The NURBS has its origins from the ship building industry and is described by using a knot and a weight as for bending steamed wooden planks and beams.
Labels: Mechanical
Computer numerical control (CNC) is a computer "controller" that reads G-code and M-code commands and drives a machine tool, a powered mechanical device typically used to fabricate components by the selective removal of material. CNC does numerically directed interpolation of a cutting tool in the work envelope of a machine. The operating parameters of the CNC can be altered via the Master Control Unit (MCU) of the machine.
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