Schallbert / QR-codengrave

Simple CAM tool to create a QR-code from text and yield G-code for engraving.

QR-codengrave

This is a small python application that takes a string, converts it into a QR-code (with help of @nayuki's excellent QR-code generator) and then allows to create CNC toolpaths that enables efficient and quick engraving.

The project is written in Python. The program is not very fast or creates super elegant tool paths, but special care has to be taken to get the machining time low while maintaining a high readability of the QR-code.

The full documentation is available on my website.

Disclaimer

Releases of this software are provided to users as-is. Although I created this application with all due care, created unit tests, and tested its output code on my own machine, I cannot take any responsibility for how and for what this software is used.

WARNING

This application outputs G-code instructions for real machinery that does actually do things in the physical world. There might be code errors or bugs that could potentially lead to machine crashes or even worse. I do not take liability for work accidents, system failures, equipment breakdown, loss of production, flow disturbances, or other negative effects that may be caused by the code this application generates.

NOTE

It is the machine operator's responsibility to carefully review the output G-code of this application, and to make sure that it works as intended without causing any harm.

Usage

Installation

Download the latest release (button on the panel on the right). It provides a .zip file containing the application and all related files. Start the application by double-clicking QR-codengrave.exe.

Alternatively, clone the repository and run from within your favourite python interpreter. Of course you're free to fork this repository and modify the code under your own responsibility.

QR-Code

Once running, just enter the text for the QR-code you want to have engraved. Press Create Qr. For drawing I used the (slow) turtle provided with tkinter, so you can optionally skip this by pressing Stop Draw.

Tool selection

Then add or select the tool you want to use for engraving. The QR-code's workpiece size directly depends on tool tip diameter. The tool list is persisted so no data is lost on application restart.

Engrave parameters

Click the parameter values to change. You can adjust

• flyover height (moving to workpiece XY-0)
• hover height (in-job moves between bit pixels)
• engrave depth which will be reflected in the G-code.

Set XY-0

Click the parameter values to change. You can select between an edge/center of the QR-code as XY-0 or enter a custom value, e.g. relevant if the qr-code is to be placed somewhere on a larger workpiece

Generate G-Code

This will run a StringIO generator that creates a file object containing the instructions for a milling machine to engrave your QR-code. Currently, it is optimized for my machine type and uses no postprocessor (I'm not familiar with other machines and their control software, so you might have to adjust the generator for your machine.)

Have it manufactured on your machine

For testing purposes I created a QR-code to my website schallbert.de and had it engraved to a piece of coated pylwood. I used an 6mm endmill which resulted in a qr-code size of 144x144 mm.

Versions

• 1.0 Initial release. Basic inward-pointing spiral as path algorithm.
• 1.1 Algo upgrade release. Uses a faster, single-pixel avoiding algo. Includes several minor bugfixes.
• 1.2 Implement tapered tool angle and engrave depth to QR-code size calculation. Major bugfix (missing tool change macro call)

How to upgrade

1. Navigate into src/assets of your QR-codengrave folder.
2. copy Persistence.dat to a temporary folder or e.g. your Desktop.
3. Remove the current installation.
4. Download the latest release, move it where your previous release was deployed.
5. Move the Persistence.dat into src/assets of your new installation and start the application.

All tools you entered in your old version, your engrave settings, and zero offsets should be available to you.

Code modules

The application consists of three modules:

• vectorize_qr
• gui
• cam

vectorize_qr

Contains all classes and helper functions to create a QR-code and convert it into vectors of "black" and "white" fields. It also defines the machining strategy by selecting the toolpath. Current implementation only supports inwards-spiral paths.

gui

The interface of the application to the user. Offers fields to enter the string to convert to QR-code, manages tools for the CAM module, and displays toolpaths and QR parameters (size, dimensions, etc). Also enables the user to select engrave depth parameters and to set the workpiece's XY zero offset.

machinify_vector

Class that is able to generate G-code instructions for a Computerized Numerical Control milling machine from QR-code bitfield vectors from line_path with help of parameters entered through the gui module.

Testing

The application features unit tests for the developed algorithms. It spares out the gui though which has been tested manually only.

Credits

• to my wife who always has my back.
• @likosdev who gifted the lovely QRUWU logo.