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Arduino based CNC foam cutter with display and SD-Card. Ruby Script for SketchUp Make 2017 to generate gcode. Swift base post processing

My goal was to build a foam based semi scale glider. So a lot of segments and very accurate working would have been necessary. This brought me to the idea to design the glider in SketchUp and build a 4 axis foam cutter.

The base idea ist very simple. Four independent linear axis with NEMA 17 stepper and belts. This simple system is satisfying, because the accuracy of the belt and stepper is better than the impact of the hot wire, it’s temperature and feed speed and almost no force is required to cut the foam. The only mechanical topic is to keep the hot wire stretched. Therefore I found a very good idea here on GitHub with retractable reels.

For controlling the four axis I found a solutions based on grbl 8c2 in combination with some Windows bases UIs and gcode sender. For generating the wing profiles I found some windows solutions or professional tools, but not free of charge, neither running on mac. For the fuselage I found only a professional tool. As I don’t want a computer in my workshop, the gcode should be executed from a SD card, similar as my 3D printer does. So I came to my project list:

- 4 independent axis
- local display, SD card reader and control buttons
- Arduino based gcode handling, based on grbl 8c2 version adapted for foam cutting.
- fixed frame based on 2020 profiles, v-slot based linear actors (it is my first cnc machine, so there are much easier and better mechanical constructions, have a lock on
- only one power supply
- wing design with third party tools:
- WingHelper (I have a licence), export of gcode is possible but post process is required, I use my own post processor in MacOS, see below.
-, Java based wing designer, including post processor. Exported dat file needs to be renamed to gcode-file extension. hotwire needs to be switched on manually.
-, Online wing designer, including post processor and hotwire controller. Exported file extensio needs to be changed to .gcode
- fuselage design with SketchUp, therefore I wrote a small tool to generate gcode, see below
- post processing to adapt gcode to machine geometry for MacOS and combine multible jobs, see below”

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