cncPathPreview

CNCpathpreview is a small command-line helper application written in Python that takes a G-code file, reads its Move-commands (G00, G01, G02, G03) and determines maximum and minimum values for its movements in X and Y direction.

These values are then written to an output file that can be run as a Jobfile by the CNC application to check whether the CNC paths are within dimensions of the workpiece.

Which problem does it solve?

• You are unsure where to position your workpiece
• You do not know if your milling paths fit on the workpiece

Features

Detects "extreme values" of any given move command including arcs that have multiple possible values. Supports G92 coordinate shift and takes them into account.

Arguments

CNCpathPreview has no mandatory argument.

Parameters

CNCpathPreview's parameters:

1. --file or -f: The source file to be analyzed. This parameter is required.
2. --zsafety or -s The safety height you want the machine to run to the XY extreme points.
3. --zprobe or -p The probe height the machine will go to at the extreme points to simplify manual adjustments of workpiece position. This Z parameters are optional.

The two optional parameters default to zsafety=40mm and zprobe=15mm if no or an erroneous value is given.

Dialog

The Beta version 0.9.4 requires a MSG command to inform the user about the next extreme value to pinpoint. Thus, the CNC interpreter needs to understand that command. I'm also using a pause command M00 to have the user press the Start button for each pinpoint.

How to create and run an executable

The application Python's supports setuptools. The following steps assume you have a virtual python environment that can run Python's package manager pip.

To deploy, type the following commands in a shell within the root folder of this project:

• python setup.py --quiet bdist_egg This will create an eggfile that can just be installed using pip.
• .\venv\Scripts\Activate.ps1 Activates the virtual environment in your venv folder
• pip install --editable . Installs the eggfile
• cncpathpreview -f "./test/arcg02ij.tap" -s 30 -p 10 runs the program with custom safety and probe height. just use your path.

Example

You can run the script from command line like this:

Alternatively, you can deploy an executable and enter the parameters later:

This is how the output file for a circle of r=5.66, Pcenter(0|0) will look like. The machine will start at XY0 and probe down to a given height. It will then pause using command M00. As soon as the user hits 'start', the machine will probe the job's extreme points starting with Y-. When complete, the machine will return to XY0 at safety height.

G90

MSG "Zmin of this job: -1.0"
G00 Z40
G00 X0 Y0
G01 Z15 F1200

MSG "PathPreview: Hit START to go to Ymin: ['0.0', '-5.66']"
M00
G00 Z40
G00 X0.0 Y-5.66
G01 Z15 F1200

MSG "PathPreview: Hit START to go to Xmin: ['-5.66', '0.0']"
M00
G00 Z40
G00 X-5.66 Y0.0
G01 Z15 F1200

MSG "PathPreview: Hit START to go to Ymax: ['0.0', '5.66']"
M00
G00 Z40
G00 X0.0 Y5.66
G01 Z15 F1200

MSG "PathPreview: Hit START to go to Xmax: ['5.66', '0.0']"
M00
G00 Z40
G00 X5.66 Y0.0
G01 Z15 F1200

MSG "PathPreview: Hit START to go to X0 Y0 Z40: ['0', '0']"
M00
G00 Z40
G00 X0 Y0
G01 Z40 F1200

M30