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CNC Electronics : Arduino Uno + GRBL
After some considerable delay since I first started with the idea of building myself a cnc router, I am now working on the electronics in earnest.
Having decided to get an arduino to make my electronics easier, I then found out how much easier when I discovered Grbl, a gcode interpreter written for the atmega chip that is, among other things, used as the heart of an arduino.
So, I followed the instructions here to flash the latest stable grbl version to my arduino, then followed the information here to wire up my stepper driver boards to the arduino.
That just left me needing to try sending some signals through. There is a very simply python script that is provided in the grbl source that can take a gcode file and stream it bit by bit over the usb/serial interface. Once setup the magic begins!
The next step on this adventure is to attempt to couple the motors to the various axis of my homemade cnc rig. I suspect this is where the real trouble will begin. its one thing to spin a motor with tape attached to it, and quite another to do so with an actual threaded rod and the weight of a cnc machine to move around.
One key component here is the pieces that actually couple the motor shaft to the threaded rod. Fortunately I have a friend with a 3d printer, and some ready made designs on thingiverse to use, so I have a coupler printed up and ready to try. However the shaft dimensions are not quite right, a combination of a slightly uncalibrated printer, and the fact that the model was designed for 8mm threaded rod, but I used 10mm. So I made a few adjustments on the pillar drill to make the holes the correct sizes. This worked well because it was a pretty solid print (obviously the part needs to be strong) so having adjusted the hole size I used some bathroom sealant to provide the silicone layer between the two halves of the coupler. This has set pretty hard so there is actually a little less flex than I expected. Hopefully I’ll be able to get a reasonable alignment and it won’t matter.
You can see it in the video above, at the moment it is not gripping the stepper shaft, for that I require some m3 bolts/machine screws to tighten up the coupling.
This are starting to look pretty real now, I have a few adjustments to make to my physical rig, and I’m still a little concerned about the sloppiness in the x-axis, I need to make sure I eliminate the side to side without making the friction bad. I have a few ideas about how to achieve that, we shall see how it goes. its quite exciting to finally be coming towards the stage of actually connecting motors and trying it all out for the first time.
I’m anticipating a considerable amount of fettling, and part of me suspects i may need to build a whole new rig with better materials, but I’m going to give it a damn good try.