grandopenauto / gcode_machine

A simple CNC state machine implemented in Python that can be used for simulation and processing of G-code

GcodeMachine

Python3 module containing a class that emulates a simple CNC state machine that can be used for simulation and processing of G-code.

After setting initial machine conditions (position, feed, etc.) you can send Gcode lines to it. Sent Gcode lines change the state of the machine, most importantly:

• machine position
• coordinate system position
• feed rate
• travel distances
• spindle speed
• motion mode
• distance mode
• plane mode
• etc.

In addition, by calling corresponding methods, the machine also can transform the Gcode, e.g. for

• variable substitution
• feed override
• cleanup (comments, spaces, whitelisted commands)
• fractionizing of lines and arcs down into small linear fragments

Typical use:

from gcode_machine import GcodeMachine

# initial conditions
initial_machine_position = impos = (0,0,0)
initial_coordinate_system = ics = "G54"
coordinate_system_offsets = cs_offsets = {"G54":(0,0,0)}

# make a new machine
gcm = GcodeMachine(impos, ics, cs_offsets)

input = ["G0 Z-10", "G1 X10 Y10"]
output = []

for line in input:
    gcm.set_line(line)       # feed the line into the machine
    gcm.strip()              # clean up whitespace
    gcm.tidy()               # filter commands by a whitelist
    gcm.find_vars()          # parse variable usages
    gcm.substitute_vars()    # substitute variables
    gcm.parse_state()        # parse positions etc. and update the machine state
    gcm.override_feed()      # substitute F values
    gcm.transform_comments() # transform parentheses to semicolon comments
    output.append(gcm.line)  # read the processed line back from the machine
    gcm.done()               # update the machine position

For each interation of the loop, you should feed the command line into the machine with the method set_line. Then, call processing methods as needed for your application (see source code for all methods).

Also, you can inspect the machine state as needed. When done with one line, call done -- this will update the virtual tool position.

Processing can happen as fast as possible, or asynchronously in a realtime manner.

This machine is experimental and subject to further extensions. It works well for simple cases though.

I believe the class is well documented. Also, code is documentation.

Examples

Linear fractionization of arcs:

gcm.position_m = (0,0,0)
gcm.set_line("G2 X10 Y10 I5 J5")
gcm.parse_state()
print('\n'.join(gcm.fractionize()))

Result:

;_gcm.arc_begin[G2 X10 Y10 I5 J5]
;_gcm.color_begin[0.35,0.50,0.40]
G1X-0.33Y0.353Z0
X-0.634Y0.727
X-0.913Y1.122
{ snip }
X8.037Y11.386
X8.466Y11.164
X8.878Y10.913
X9.273Y10.634
X9.647Y10.33
X10Y10
;_gcm.color_end
;_gcm.arc_end

Comment transform:

gcm.set_line("G0 X0 (bob) Y0 (alice)")
gcm.transform_comments()
print(gcm.line)

Result:

G0 X0  Y0 ;alice

Strip unsupported commands (whitelist based):

gcm.set_line("T2")
gcm.tidy()
print(gcm.line)

Result:

;T02 ;_gcm.unsupported

Split commands (some Gcode generators do this stupid thing):

gcm.set_line("G55 M3 T2")
gcm.split_lines()

Result:

['G55 ', 'M3 ', 'T2']

License

gcode_machine - Copyright (c) 2016 Michael Franzl

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.