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diff --git a/files/baby-yoda.png b/files/baby-yoda.png Binary files differnew file mode 100644 index 0000000..b84e2a9 --- /dev/null +++ b/files/baby-yoda.png @@ -1,2 +1,3 @@ adieu-quake.md:Adieu, Quake! +opening-black-boxes.md:Opening Black Boxes index.md:Quite Frankly diff --git a/posts/index.md b/posts/index.md index 1f2f142..46fcfc9 100644 --- a/posts/index.md +++ b/posts/index.md @@ -2,6 +2,7 @@ This is my humble blog. Welcome. +- [On Opening Black Boxes or: How I Learned to Stop Worrying and Love G-Code](opening-black-boxes.html) (28 Nov 2019) - [Adieu, Quake!](adieu-quake.html) (27 Aug 2019) Contact: <me@fwei.tk> diff --git a/posts/opening-black-boxes.md b/posts/opening-black-boxes.md new file mode 100644 index 0000000..1857ed6 --- /dev/null +++ b/posts/opening-black-boxes.md @@ -0,0 +1,85 @@ +# On Opening Black Boxes or: How I Learned to Stop Worrying and Love G-Code + + + +**TL;DR** PhotoVCarve should not cost $149. I made [my own](https://github.com/built1n/rastercarve). + +Recently I've gotten my hands on a 3-axis [ShopBot milling +machine](https://www.shopbottools.com/products/max). For the +uninitiated, a CNC mill is essentially a robotic carving machine -- +think "*robot drill*": you put in a piece of wood/foam/aluminum, +program the machine, and out comes a finished piece with the right +patterns cut into it. I had the idea of +[engraving](https://en.wikipedia.org/wiki/Engraving) a raster image +using the machine, and there happens to be a nice piece of software +out there that claims to do just that: Vectric's +[PhotoVCarve](https://www.vectric.com/products/photovcarve). + +There's just one problem: PhotoVCarve costs $149. Now, I have no +qualms paying for software when it makes sense to do so, but in this +case, $149 is simply excessive -- especially for a hobbyist. And +besides, just see for yourself in the video below: all PhotoVCarve +does is take an image and draw a bunch of grooves over it -- *nothing +that couldn't be done in a couple lines of Python,* I thought. + +[](https://www.youtube.com/watch?v=krFyBxYwWW8) + +## G-Code + +The first step in the process was figuring out *how* to control a CNC +machine. Some Googling told me that virtually all machines read +"G-code", a sequence of alphanumeric instructions that command the +movement of the tool in 3 dimensions. It looks something like this: + +``` +G00 X0 Y0 Z0.2 +G01 Z-0.2 F10 +G01 X1.0 Y0 +``` + +These three commands tell the machine to: + +1. Go to (0, 0, 0.2), rapidly (`G00` is "rapid traverse"). +2. Go to (0, 0, -0.2), slowly (`G01` commands a slower move than `G00`). +3. Go to (1, 0, 0), slowly. + +My program just had to output the right sequence of G-code commands, +which I could then feed into the ShopBot control software. (This was +far simpler than I had originally imagined.) + +At this point, one of my flow states kicked in. I sat down, and got to +coding. + +## The Program + +The development process was surprisingly straightforward -- I put in +perhaps a total of 4 hours from my initial proof-of-concept to the +current viable prototype. There were no major hiccups this time +around, and even though I'm still in the process of learning it, +Python made things *so* much easier than C (or God forbid -- [ARM +assembly](adieu-quake.html)). + +The heart of my program is a function, +[`engraveLine`](http://fwei.tk/git/rastercarve/tree/src/rastercarve.py?id=c2de4a3258c3e37d4b49a41d786eef936262f137#n118), +which outputs the G-code to engrave one "groove" across the image. It +takes in a initial position vector on the border of the image, and a +direction vector telling it which way to cut. + +After this was written, it was a simple exercise to write a driver +function to call `engraveLine` with the right vectors in the right +sequence -- and that was all it took! (I really wonder how Vectric +manages to charge $149 for this...) + +I fired up the program on a test image and fed its output into +ShopBot's excellent G-code previewer. Success (see above)! I added a +couple of tweaks (getting the lines to cut at an angle was fun) and I +christened the program +[*RasterCarve*](https://github.com/built1n/rastercarve). + +## Conclusion + +This was a fun little project that falls into the theme of "gradually +opening up black boxes." G-code, I learned, isn't nearly as hard as it +might seem. It's all too easy to abstract away the details of a +technical process, but sometimes the best way to really understand +something is by opening up the hood and tinkering with it. |
