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G code/ What is G code/ How to run a CNC
發佈時間 2020.03.05 / 下午02:53

G code/ What is G code/ How to run a CNC

G-code is a language in which people tell computerized machine tools how to make something. The "how" is defined by g-code instructions provided to a machine controller (industrial computer) that tells the motors where to move, how fast to move, and what path to follow. This intruction can be used on differnet brand machine like DMG Mori, Mazak, Okuma, Doosan, or any other brands machine. It also fit into horiozontal machine(HMC), vertical machine(VMC), turning & lathe, boring mill, 5-axis machines or even mill-trun machines.

 

The two most common situations are that, within a machine tool such as a lathe or mill, a cutting tool is moved according to these instructions through a toolpath cutting away material to leave only the finished workpiece and/or, an unfinished workpiece is precisely positioned in any of up to 9 axes around the 3 dimensions relative to a toolpath and, either or both can move relative to each other. The same concept also extends to noncutting tools such as forming or burnishing tools, photoplotting, additive methods such as 3D printing, and measuring instruments.

 

Code

Description

Milling
( M )

Turning
( T )

Corollary info

G00

Rapid positioning

M

T

On 2- or 3-axis moves, G00 (unlike G01) traditionally does not necessarily move in a single straight line between start point and end point. It moves each axis at its max speed until its vector quantity is achieved. Shorter vector usually finishes first (given similar axis speeds). This matters because it may yield a dog-leg or hockey-stick motion, which the programmer needs to consider, depending on what obstacles are nearby, to avoid a crash. Some machines offer interpolated rapids as a feature for ease of programming (safe to assume a straight line).

 

G01

Linear interpolation

M

T

The most common workhorse code for feeding during a cut. The program specs the start and end points, and the control automatically calculates (interpolates) the intermediate points to pass through that yield a straight line (hence "linear"). The control then calculates the angular velocities at which to turn the axis leadscrews via their servomotors or stepper motors. The computer performs thousands of calculations per second, and the motors react quickly to each input. Thus the actual toolpath of the machining takes place with the given feedrate on a path that is accurately linear to within very small limits.

 

G02

Circular interpolation, clockwise

M

T

Very similar in concept to G01. Again, the control interpolates intermediate points and commands the servo- or stepper motors to rotate the amount needed for the leadscrew to translate the motion to the correct tool tip positioning. This process repeated thousands of times per minute generates the desired toolpath. In the case of G02, the interpolation generates a circle rather than a line. As with G01, the actual toolpath of the machining takes place with the given feedrate on a path that accurately matches the ideal (in G02's case, a circle) to within very small limits. In fact, the interpolation is so precise (when all conditions are correct) that milling an interpolated circle can obviate operations such as drilling, and often even fine boring. Addresses for radius or arc center: G02 and G03 take either an R address (for the radius desired on the part) or IJK addresses (for the component vectors that define the vector from the arc start point to the arc center point). Cutter comp: On most controls you cannot start G41 or G42 in G02 or G03 modes. You must already have compensated in an earlier G01 block. Often, a short linear lead-in movement is programmed, merely to allow cutter compensation before the main action, the circle-cutting, begins. Full circles: When the arc start point and the arc end point are identical, the tool cuts a 360° arc (a full circle). (Some older controls do not support this because arcs cannot cross between quadrants of the cartesian system. Instead, they require four quarter-circle arcs programmed back-to-back.)

 

G03

Circular interpolation, counterclockwise

M

T

Same corollary info as for G02.

G04

Dwell

M

T

Takes an address for dwell period (may be X, U, or P). The dwell period is specified by a control parameter, typically set to milliseconds. Some machines can accept either X1.0 (s) or P1000 (ms), which are equivalent. Choosing dwell duration: Often the dwell needs only to last one or two full spindle rotations. This is typically much less than one second. Be aware when choosing a duration value that a long dwell is a waste of cycle time. In some situations it won't matter, but for high-volume repetitive production (over thousands of cycles), it is worth calculating that perhaps you only need 100 ms, and you can call it 200 to be safe, but 1000 is just a waste (too long).

 

G05 P10000

High-precision contour control (HPCC)

M

 

Uses a deep look-ahead buffer and simulation processing to provide better axis movement acceleration and deceleration during contour milling

 

G05.1 Q1.

AI Advanced Preview Control

M

 

Uses a deep look-ahead buffer and simulation processing to provide better axis movement acceleration and deceleration during contour milling

 

G06.1

Non-uniform rational B-spline (NURBS) Machining

M

 

Activates Non-Uniform Rational B Spline for complex curve and waveform machining (this code is confirmed in Mazatrol 640M ISO Programming)

 

G07

Imaginary axis designation

M

 

 

G09

Exact stop check, non-modal

M

T

The modal version is G61.

G10

Programmable data input

M

T

Modifies the value of work coordinate and tool offsets[9][8]

G11

Data write cancel

M

T

 

G17

XY plane selection

M

 

 

G18

ZX plane selection

M

T

 

G19

YZ plane selection

M

 

 

G20

Programming in inches

M

T

Somewhat uncommon except in USA and (to lesser extent) Canada and UK. However, in the global marketplace, competence with both G20 and G21 always stands some chance of being necessary at any time. The usual minimum increment in G20 is one ten-thousandth of an inch (0.0001"), which is a larger distance than the usual minimum increment in G21 (one thousandth of a millimeter, .001 mm, that is, one micrometre). This physical difference sometimes favors G21 programming.

 

G21

Programming in millimeters (mm)

M

T

Prevalent worldwide. However, in the global marketplace, competence with both G20 and G21 always stands some chance of being necessary at any time.

 

G28

Return to home position (machine zero, aka machine reference point)

M

T

Takes X Y Z addresses which define the intermediate point that the tool tip will pass through on its way home to machine zero. They are in terms of part zero (aka program zero), NOT machine zero.

 

G30

Return to secondary home position (machine zero, aka machine reference point)

M

T

Takes a P address specifying which machine zero point to use if the machine has several secondary points (P1 to P4). Takes X Y Z addresses that define the intermediate point that the tool tip passes through on its way home to machine zero. These are expressed in terms of part zero (aka program zero), NOT machine zero.

 

G31

Feed until skip function

M

 

 Used for probes and tool length measurement systems.

 

G32

Single-point threading, longhand style (if not using a cycle, e.g., G76)

 

T

Similar to G01 linear interpolation, except with automatic spindle synchronization for single-point threading.

G33

Constant-pitch threading

M

 

 

G33

Single-point threading, longhand style (if not using a cycle, e.g., G76)

 

T

Some lathe controls assign this mode to G33 rather than G32.

G34

Variable-pitch threading

M

 

 

G40

Tool radius compensation off

M

T

Turn off cutter radius compensation (CRC). Cancels G41 or G42.

 

G41

Tool radius compensation left

M

T

Turn on cutter radius compensation (CRC), left, for climb milling.
Milling: Given righthand-helix cutter and M03 spindle direction, G41 corresponds to climb milling (down milling). Takes an address (D or H) that calls an offset register value for radius.
Turning: Often needs no D or H address on lathes, because whatever tool is active automatically calls its geometry offsets with it. (Each turret station is bound to its geometry offset register.)

G41 and G42 for milling has been partially automated and obviated (although not completely) since CAM programming has become more common. CAM systems let the user program as if using a zero-diameter cutter. The fundamental concept of cutter radius compensation is still in play (i.e., that the surface produced will be distance R away from the cutter center), but the programming mindset is different. The human does not choreograph the toolpath with conscious, painstaking attention to G41, G42, and G40, because the CAM software takes care of that. The software has various CRC mode selections, such as computer, control, wear, reverse wear, off, some of which do not use G41/G42 at all (good for roughing, or wide finish tolerances), and others that use it so that the wear offset can still be tweaked at the machine (better for tight finish tolerances).

 

G42

Tool radius compensation right

M

T

Turn on cutter radius compensation (CRC), right, for conventional milling. Similar corollary info as for G41. Given righthand-helix cutter and M03 spindle direction, G42 corresponds to conventional milling (up milling).

 

G43

Tool height offset compensation negative

M

 

Takes an address, usually H, to call the tool length offset register value. The value is negative because it will be added to the gauge line position. G43 is the commonly used version (vs G44).

 

G44

Tool height offset compensation positive

M

 

Takes an address, usually H, to call the tool length offset register value. The value is positive because it will be subtracted from the gauge line position. G44 is the seldom-used version (vs G43).

G45

Axis offset single increase

M

 

 

G46

Axis offset single decrease

M

 

 

G47

Axis offset double increase

M

 

 

G48

Axis offset double decrease

M

 

 

G49

Tool length offset compensation cancel

M

 

Cancels G43 or G44.

 

G50

Define the maximum spindle speed

 

T

Takes an S address integer, which is interpreted as rpm. Without this feature, G96 mode (CSS) would rev the spindle to "wide open throttle" when closely approaching the axis of rotation.

G50

Scaling function cancel

M

 

 

G50

Position register (programming of vector from part zero to tool tip)

 

T

Position register is one of the original methods to relate the part (program) coordinate system to the tool position, which indirectly relates it to the machine coordinate system, the only position the control really "knows". Not commonly programmed anymore because G54 to G59 (WCSs) are a better, newer method. Called via G50 for turning, G92 for milling. Those G addresses also have alternate meanings (which see). Position register can still be useful for datum shift programming. The "manual absolute" switch, which has very few useful applications in WCS contexts, was more useful in position register contexts, because it allowed the operator to move the tool to a certain distance from the part (for example, by touching off a 2.0000" gage) and then declare to the control what the distance-to-go shall be (2.0000).

 

G52

Local coordinate system (LCS)

M

 

Temporarily shifts program zero to a new location. It is simply "an offset from an offset", that is, an additional offset added onto the WCS offset. This simplifies programming in some cases. The typical example is moving from part to part in a multipart setup. With G54 active, G52 X140.0 Y170.0 shifts program zero 140 mm over in X and 170 mm over in Y. When the part "over there" is done, G52 X0 Y0 returns program zero to normal G54 (by reducing G52 offset to nothing). The same result can also be achieved (1) using multiple WCS origins, G54/G55/G56/G57/G58/G59; (2) on newer controls, G54.1 P1/P2/P3/etc. (all the way up to P48); or (3) using G10 for programmable data input, in which the program can write new offset values to the offset registers.[8] The method to use depends on shop-specific application.

 

G53

Machine coordinate system

M

T

Takes absolute coordinates (X,Y,Z,A,B,C) with reference to machine zero rather than program zero. Can be helpful for tool changes. Nonmodal and absolute only. Subsequent blocks are interpreted as "back to G54" even if it is not explicitly programmed.

 

G54 to G59

Work coordinate systems (WCSs)

M

T

Have largely replaced position register (G50 and G92). Each tuple of axis offsets relates program zero directly to machine zero. Standard is 6 tuples (G54 to G59), with optional extensibility to 48 more via G54.1 P1 to P48.

 

G54.1 P1 to P48

Extended work coordinate systems

M

T

Up to 48 more WCSs besides the 6 provided as standard by G54 to G59. Note floating-point extension of G-code data type (formerly all integers). Other examples have also evolved (e.g., G84.2). Modern controls have the hardware to handle it.

 

G61

Exact stop check, modal

M

T

Can be canceled with G64. The non-modal version is G09.

G62

Automatic corner override

M

T

 

G64

Default cutting mode (cancel exact stop check mode)

M

T

Cancels G61.

 

G68

Rotate coordinate system

M

 

Rotates coordinate system in the current plane given with G17, G18, or G19. Center of rotation is given with two parameters, which vary with each vendor's implementation. Rotate with angle given with argument R. This can be used, for instance, to align the coordinate system with a misaligned part. It can also be used to repeat movement sequences around a center. Not all vendors support coordinate system rotation.

 

G69

Turn off coordinate system rotation

M

 

Cancels G68.

G70

Fixed cycle, multiple repetitive cycle, for finishing (including contours)

 

T

 

G71

Fixed cycle, multiple repetitive cycle, for roughing (Z-axis emphasis)

 

T

 

G72

Fixed cycle, multiple repetitive cycle, for roughing (X-axis emphasis)

 

T

 

G73

Fixed cycle, multiple repetitive cycle, for roughing, with pattern repetition

 

T

 

G73

Peck drilling cycle for milling – high-speed (NO full retraction from pecks)

M

 

Retracts only as far as a clearance increment (system parameter). For when chipbreaking is the main concern, but chip clogging of flutes is not. Compare G83.

G74

Peck drilling cycle for turning

 

T

 

G74

Tapping cycle for milling, lefthand thread, M04 spindle direction

M

 

See notes at G84.

G75

Peck grooving cycle for turning

 

T

 

G76

Fine boring cycle for milling

M

 

Includes OSS and shift (oriented spindle stop and shift tool off centerline for retraction)

G76

Threading cycle for turning, multiple repetitive cycle

 

T

 

G80

Cancel canned cycle

M

T

Milling: Cancels all cycles such as G73, G81, G83, etc. Z-axis returns either to Z-initial level or R level, as programmed (G98 or G99, respectively).
Turning: Usually not needed on lathes, because a new group-1 G address (G00 to G03) cancels whatever cycle was active.

 

G81

Simple drilling cycle

M

 

No dwell built in

G82

Drilling cycle with dwell

M

 

Dwells at hole bottom (Z-depth) for the number of milliseconds specified by the P address. Good for when hole bottom finish matters. Good for spot drilling because the divot is certain to clean up evenly. Consider the "choosing dwell duration" note at G04.

 

G83

Peck drilling cycle (full retraction from pecks)

M

 

Returns to R-level after each peck. Good for clearing flutes of chips. Compare G73.

 

G84

Tapping cycle, righthand thread, M03 spindle direction

M

 

G74 and G84 are the righthand and lefthand "pair" for old-school tapping with a non-rigid toolholder ("tapping head" style). Compare the rigid tapping "pair", G84.2 and G84.3.

 

G84.2

Tapping cycle, righthand thread, M03 spindle direction, rigid toolholder

M

 

See notes at G84. Rigid tapping synchronizes speed and feed according to the desired thread helix. That is, it synchronizes degrees of spindle rotation with microns of axial travel. Therefore, it can use a rigid toolholder to hold the tap. This feature is not available on old machines or newer low-end machines, which must use "tapping head" motion (G74/G84).

 

G84.3

Tapping cycle, lefthand thread, M04 spindle direction, rigid toolholder

M

 

See notes at G84 and G84.2.

G85

boring cycle, feed in/feed out

M

 

·       Good cycle for a reamer.

·       In some cases good for single-point boring tool, although in other cases the lack of depth of cut on the way back out is bad for surface finish, in which case, G76 (OSS/shift) can be used instead.

·       If need dwell at hole bottom, see G89.

 

G86

boring cycle, feed in/spindle stop/rapid out

M

 

Boring tool leaves a slight score mark on the way back out. Appropriate cycle for some applications; for others, G76 (OSS/shift) can be used instead.

 

G87

boring cycle, backboring

M

 

For backboring. Returns to initial level only (G98); this cycle cannot use G99 because its R level is on the far side of the part, away from the spindle headstock.

 

G88

boring cycle, feed in/spindle stop/manual operation

M

 

 

G89

boring cycle, feed in/dwell/feed out

M

 

G89 is like G85 but with dwell added at bottom of hole.

 

G90

Absolute programming

M

T (B)

Positioning defined with reference to part zero.
Milling: Always as above.
Turning: Sometimes as above (Fanuc group type B and similarly designed), but on most lathes (Fanuc group type A and similarly designed), G90/G91 are not used for absolute/incremental modes. Instead, U and W are the incremental addresses and X and Z are the absolute addresses. On these lathes, G90 is instead a fixed cycle address for roughing.

 

G90

Fixed cycle, simple cycle, for roughing (Z-axis emphasis)

 

T (A)

When not serving for absolute programming (above)

 

G91

Incremental programming

M

T (B)

Positioning defined with reference to previous position.
Milling: Always as above.
Turning: Sometimes as above (Fanuc group type B and similarly designed), but on most lathes (Fanuc group type A and similarly designed), G90/G91 are not used for absolute/incremental modes. Instead, U and W are the incremental addresses and X and Z are the absolute addresses. On these lathes, G90 is a fixed cycle address for roughing.

 

G92

Position register (programming of vector from part zero to tool tip)

M

T (B)

Same corollary info as at G50 position register.
Milling: Always as above.
Turning: Sometimes as above (Fanuc group type B and similarly designed), but on most lathes (Fanuc group type A and similarly designed), position register is G50.

G92

Threading cycle, simple cycle

 

T (A)

 

G94

Feedrate per minute

M

T (B)

On group type A lathes, feedrate per minute is G98.

 

G94

Fixed cycle, simple cycle, for roughing (X-axis emphasis)

 

T (A)

When not serving for feedrate per minute (above)

 

G95

Feedrate per revolution

M

T (B)

On group type A lathes, feedrate per revolution is G99.

 

G96

Constant surface speed (CSS)

 

T

Varies spindle speed automatically to achieve a constant surface speed. See speeds and feeds. Takes an S address integer, which is interpreted as sfm in G20 mode or as m/min in G21 mode.

 

G97

Constant spindle speed

M

T

Takes an S address integer, which is interpreted as rev/min (rpm). The default speed mode per system parameter if no mode is programmed.

G98

Return to initial Z level in canned cycle

M

 

 

G98

Feedrate per minute (group type A)

 

T (A)

Feedrate per minute is G94 on group type B.

G99

Return to R level in canned cycle

M

 

 

G99

Feedrate per revolution (group type A)

 

T (A)

Feedrate per revolution is G95 on group type B.

G100

Tool length measurement

M

 

 

 

There are some further description from FUSION360:

G0 – Rapid Move

This code tells a machine to move as fast as possible to a specified coordinate position. G0 will move the machine axis by axis, meaning that it will first move along both axes and finish the move on whichever axis is not in positions. You can see an example of this motion in the image below:

 

G1 – Linear Move

This code tells a machine to move in a straight line to a coordinate position with a defined feed rate. For example, G1 X1 Y1 F32 will move the machine to coordinates X1, Y1, at a feed rate of 32.

 

G2, G3 – Clockwise Arc, Counter-clockwise Arc

These codes tell the machine to move in an arc to a coordinate destination. Two additional coordinates, I and J, define the arc’s center location as shown below:

 

G17, G18, G19 – Plane Designations

These codes define what plane an arc will be machined on. By default your CNC machine will use G17, which is the XY plane. The other two planes are shown in the image below:

 

G40, G41, G42 – Cutter Diameter Compensation

These codes define the cutter diameter compensation, or CDC, which allows a CNC machine to position its tool to the left or right of a defined path. A D-register stores the offset for each tool.

 

G43 – Tool Length Compensation

This code defines the length of individual tools using a Z-axis height. This allows the CNC machine to understand where the tip of a tool is in relation to the piece it is working on. A register defines the tool length compensations, where H is the tool length offset and Z is the length of the tool.

 

G54 – Work Offset

This code is used to define a fixture offset which determines the distance from a machine’s internal coordinates to the datum on a workpiece. In the table below only G54 has an offset definition. However, you can program multiple offsets if a job requires machining multiple parts at once.

 

Canned Cycles

 

The last aspect of G-code to touch on is canned cycles. These are similar to methods or functions in computer programming. They allow you to perform a complicated action in only a few lines of code without having to type out all of the details.

 

Take for example the canned cycle below. Here we are telling the CNC tool to create a hole with a peck drill in only two lines of code on the left. This same action takes over 20 lines of regular G-code.

 

Some common drill cycles includes:

 

G81 – Simple Drill Cycle

This cycle will make a hole by plunging to a specific Z-axis coordinate and then retracting. Programming this cycle requires a depth, feed rate, XY coordinates, and plane to drill on.

 

G83 – Peck Drill

This cycle is used for quickly drilling deep holes. A tool will first drill a defined distance and then retract, which clears any material out of the hole and allows coolant to flush away chips. The simplest implementation of this cycle requires an initial height, feed plane, peck increment, and depth.

 

G98 – Return to Initial Rapid Height

This cycle will retract a tool to a clearance plane between holes which helps to avoid clamps. Programming this cycle requires an initial height and feed plane to drill on.

 

G-code stands for “geometric code,” and follows some variation of the alpha numeric pattern: N## G## X## Y## Z## F## S## T## M##

N: Line number
G: Motion
X: Horizontal position
Y: Vertical position
Z: Depth
F: Feed rate
S: Spindle speed
T: Tool selection
M: Miscellaneous functions
I and J: Incremental center of an arc
R: Radius of an arc

 

 

G-Code Tips to Note

  • Some machines and controllers ignore spaces. G01 X1 Y1 Z1 might mean the same thing as G01 X1Y1Z1.
  • The Z-axis is positive in the up direction. Z1 will bring the tool up, while Z-1 will bring the tool down.
  • Your machine’s g-code dialect will specify if a leading zero is necessary (as in G01, as opposed to G1).
  • The dialect will also determine if decimal points are always necessary (ex. G01 X1. Y1. Z0.5)
  • It’s a good idea to run the sample programs that come in your machine manual before you try to run a big program. Oftentimes, the sample programs do not work and you will need to note the issues and set your own benchmarks.

 

 

https://en.wikipedia.org/wiki/G-code

https://slideplayer.com/slide/3470550/

https://www.autodesk.com/products/fusion-360/blog/cnc-programming-fundamentals-g-code/

https://www.autodesk.com/industry/manufacturing/resources/manufacturing-engineer/g-code

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