Antlr4-based parser and interpreter for the GCode dialect described in "The NIST RS274NGC Interpreter - Version 3" by Thomas Kramer Frederick, Thomas R. Kramer, Frederick M. Proctor, and Elena Messina, written in Python3.
https://www.nist.gov/publications/nist-rs274ngc-interpreter-version-3
DISCLAIMER: This was written as an exercise, to gain a better understanding of GCode. It is incomplete and almost certainly contains errors. Use at your own risk.
Antlr4 grammar and generated classes for Python3:
- GCode.g4
- GCodeLexer.py
- GCodeParser.py
- GCodeListener.py
- GCodeVisitor.py
The grammar doesn't contain any embedded actions, so it can be used as-is to target languages other than Python3.
Interpreter and support classes:
- GCodeInterpreter.py
- GCodeFormatter.py
- GCodeExprEvaluator.py
- GCodeParamMemory.py
The GCodeInterpreter visitor class executes program lines (blocks) in the parse tree using an idealized machine model capable of infinite acceleration/deceleration. Circular/helical movements are approximated with a series of linear movements. GCodeInterpreter calls onMove with each linear movement and tracks min/max travel, distance moved, and estimated runtime as it goes. Internal units are inches and minutes.
The GCodeFormatter visitor class reconstructs a string representation of the program in the parse tree.
The GCodeExprEvaluator visitor class evaluates value nodes in the parse tree, including any expressions and parameter values they contain. The GCodeParamMemory class stores parameter values.
See the sample programs for examples of GCodeFormatter and GCodeInterpreter usage.
Supported G Codes (from Table 5):
| Code | Support | Description |
|---|---|---|
| G0 | Y | rapid positioning |
| G1 | Y | linear interpolation |
| G2 | Y | circular/helical interpolation (clockwise) |
| G3 | Y | circular/helical interpolation (counterclockwise) |
| G4 | Y | dwell |
| G10 | Y | coordinate system origin setting |
| G17 | Y | XY-plane selection |
| G18 | Y | XZ-plane selection |
| G19 | Y | YZ-plane selection |
| G20 | Y | inch system selection |
| G21 | Y | millimeter system selection |
| G28 | Y | return to home |
| G30 | Y | return to secondary home |
| G38.2 | straight probe | |
| G40 | cancel cutter radius compensation | |
| G41 | start cutter radius compensation left | |
| G42 | start cutter radius compensation right | |
| G43 | tool length offset (plus) | |
| G49 | cancel tool length offset | |
| G53 | Y | motion in machine coordinate system |
| G54 | Y | use preset work coordinate system 1 |
| G55 | Y | use preset work coordinate system 2 |
| G56 | Y | use preset work coordinate system 3 |
| G57 | Y | use preset work coordinate system 4 |
| G58 | Y | use preset work coordinate system 5 |
| G59 | Y | use preset work coordinate system 6 |
| G59.1 | Y | use preset work coordinate system 7 |
| G59.2 | Y | use preset work coordinate system 8 |
| G59.3 | Y | use preset work coordinate system 9 |
| G61 | Y | set path control mode: exact path |
| G61.1 | Y | set path control mode: exact stop |
| G64 | Y | set path control mode: continuous |
| G80 | Y | cancel motion mode (including any canned cycle) |
| G81 | canned cycle: drilling | |
| G82 | canned cycle: drilling with dwell | |
| G83 | canned cycle: peck drilling | |
| G84 | canned cycle: right hand tapping | |
| G85 | canned cycle: boring, no dwell, feed out | |
| G86 | canned cycle: boring, spindle stop, rapid out | |
| G87 | canned cycle: back boring | |
| G88 | canned cycle: boring, spindle stop, manual out | |
| G89 | canned cycle: boring, dwell, feed out | |
| G90 | Y | absolute distance mode |
| G91 | Y | incremental distance mode |
| G92 | Y | offset coordinate systems and set parameters |
| G92.1 | Y | cancel offset coordinate systems and set parameters to zero |
| G92.2 | Y | cancel offset coordinate systems but do not reset parameters |
| G92.3 | Y | apply parameters to offset coordinate systems |
| G93 | inverse time feed rate mode | |
| G94 | Y | units per minute feed rate mode |
| G98 | initial level return in canned cycles | |
| G99 | R-point level return in canned cycles |
Supported M Codes (from Table 7):
| Code | Support | Description |
|---|---|---|
| M0 | Y | program stop |
| M1 | Y | optional program stop |
| M2 | Y | program end |
| M3 | Y | turn spindle clockwise |
| M4 | Y | turn spindle counterclockwise |
| M5 | Y | stop spindle turning |
| M6 | Y | tool change |
| M7 | Y | mist coolant on |
| M8 | Y | flood coolant on |
| M9 | Y | mist and flood coolant off |
| M30 | Y | program end, pallet shuttle, and reset |
| M48 | Y | enable speed and feed overrides |
| M49 | Y | disable speed and feed overrides |
| M60 | Y | pallet shuttle and program stop |
Parse the program.
With the -v flag, prints the antlr4 parse tree.
% ./gcodeParse -h
Usage: gcodeParse.py [options] file.ngc ...
Options:
-h, --help show this help message and exit
-v verbose output
% ./gcodeParse.py references/c1.ngc
references/c1.ngc
Print the parsed program.
% ./gcodePrint -h
Usage: gcodePrint.py [options] file.ngc ...
Options:
-h, --help show this help message and exit
-v verbose output
% ./gcodePrint.py references/c1.ngc
references/c1.ngc
(this program mills "Hello world" between X=0 and X=81 millimeters)
n0010 g 21 g 0 x 0 y 0 z 50 (top of part should be on XY plane)
n0020 t 1 m 6 m 3 f 20 s 4000 (use an engraver or small ball-nose endmill)
n0030 g 0 x 0 y 0 z 2
n0040 g 1 z -0.5 (start H)
n0050 y 10
n0060 g 0 z 2
...
n0560 g 1 z -0.5 (start d)
n0570 y 0
n0580 x 79.5
n0590 g 2 j 2.5 y 5
n0600 g 1 x 81
n0610 g 0 z 50
Interpret the program and print min/max travel, distance moved, estimated runtime.
With the -v flag, prints each line of the program as it is executed.
% ./gcodeRun.py -h
Usage: gcodeRun.py [options] file.ngc ...
Options:
-h, --help show this help message and exit
-v verbose output
% ./gcodeRun.py references/c1.ngc
references/c1.ngc
min [0.0000 0.0000 -0.0197]
max [3.1890 0.3937 1.9685]
size [3.1890 0.3937 1.9882]
dist 17.1378 in
time 9.21 sec
% ./gcodeRun.py -v references/c2.ngc
references/c2.ngc
n0010 g 21 g 1 x 3 f 20 (expression test)
g 21.0000
g 1.0000
x 3.0000
f 20.0000
n0020 x [1 + 2] (x should be 3)
x 3.0000
n0030 x [1 - 2] (x should be -1)
x -1.0000
...
n0410 x [2 ** 3.0] #1=2.0 (x should be 8.0)
x 8.0000
n0420 ##1=0.375 (#1 is 2, so parameter 2 is set to 0.375)
n0430 x #2 (x should be 0.375) #3=7.0
x 0.3750
n0440 #3=5.0 x #3 (parameters set in parallel, so x should be 7, not 5)
x 7.0000
n0450 x #3 #3=1.1 (parameters set in parallel, so x should be 5, not 1.1)
x 5.0000
n0460 x [2 + asin[1 / 2.1 + -0.345] / [atan[fix[4.4] * 2.1 * sqrt[16.8]]/[-18]] ** 2]
x 2.0005
n0470 x sqrt[3 ** 2 + 4 ** 2] (x should be 5.0)
x 5.0000
...
Interpret the program and plot the tool path.
% ./gcodePlot -h
Usage: gcodePlot.py [options] file.ngc ...
Options:
-h, --help show this help message and exit
-v verbose output
% ./gcodePlot.py references/c1.ngc
Interpret the program and generate an OpenSCAD script to subtract a tool shape from a block of stock while moving along the tool path.
% ./gcodeScad.py -h
Usage: gcodeScad.py [options] file.ngc ...
Options:
-h, --help show this help message and exit
-v verbose output
--tool_type=value tool type (0 = square, 1 = ball, 2 = engraving)
--tool_diam=value tool diameter (inches)
--tool_doc=value tool depth of cut (inches)
--stock_size=X,Y,Z stock size (inches)
--stock_pos=X,Y,Z stock position (inches)
--fn=value $fn override
% ./gcodeScad.py --tool_type 1 --tool_diam 0.0625 --tool_doc 0.25 references/c1.ngc
- Python3 (https://www.python.org)
- Antlr4 (https://www.antlr.org)
On MacOS:
% brew install python3
% brew install antlr
% pip3 install antlr4-python3-runtime