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Tag Archives: CNC

Heres a home CNC/drawing project with a twist. The drawing machine uses the time it takes for ink to bleed in to blotting paper to create a grayscale image. More information can be found  here along with some other awesome projects like a street art quadracopter and gesture driven drawing machine.

I learnt so much in the home brew CNC workshop and I am very aware that if I don’t do something with my new found knowledge soon then I will forget most of it. I am a collector of broken junk and in my collection I have an A3 scanner and an A4 scanner. I have decided to turn these deserted and tired old pieces of equipment into a homebrew plotter / engraver (if all goes well.) The first step was to take the Grbl ready Arduino from a previous post and make it control a stepper motor. I have been leant 3 stepper motor drivers to experiment with, the documentation for the drivers can be found here. The A4983 stepper motor driver is a very compact driver perfect for smaller CNC projects. The documentation for the A4983 is very good so it was very easy to connect it up to the Arduino and the stepper motor. The pictures below evidence my setup with the driver running full steps. I have not experimented with micro steps yet but the results are very promising.

The wiring:

mac to arduino - arduino to a stepper motor

Just a few photos and a video from the 3 days of training I took part in which started on Monday the 11th of July. In the 3 days we put together 2 machines; one that was a gantry based plotter and the other was a turn table based scanner. The interesting part was tooling the plotter to pour slip over clay. The pictures below are just a few photo I took over the 3 days. Mat, another from the CNC workshop documented the whole process better than I did, you can find his photos here

Recently I attended a 3 day training session on building home-brew CNC machines which was run by Dave Turtle from the RCA. It was an amazing 3 days and I will post the photos and videos of the results as soon as possible. One of the hurdles that came crashing in on day two was the limitation of running the kit from the parallel port. There really aren’t that many computers these days that still roll out with a parallel port as standard, not to mention my nice shiny mac does not come equipped with a parallel port. I was 100% sure the solution to this problem was the trusty Arduino. There have been many projects where the Arduino has already been used as the heart of a CNC machine, the first that comes to mind is the REPRAP. There is also another CNC project called Contraptor which utilises the Arduino at its heart. The home site for the Contraptor project has a lot of useful information, it was there I came across Grbl.

I tried the RepRap g code interpreter, fiveD but I could not get it to compile for the Arduino (Any tips would be gratefully recieved). I also tried a few other interpreters with varying success: teapot, rsteppercontrol and arduino-gcode-interpreter-new. I really struggled, probably partly due to my lack of understanding when it comes to g-code. I had no success over the three days of training but I did find Grbl though I didn’t have the kit to test it. Grbl seemed like a very simple solution but the main hurdle when it comes to implementing it is that you need to use avrdude to flash it to the Arduino you can’t just send it via usb direct to the Arduino. I have never done this before so I let the Arduino rest for the the remainder of the training with a mind to try it as soon as possible.

Today I started messing around with Flashing Grbl to the Arduino and was caught out by several issues which slowed my progress. There are already several sites with information on how to do this but I found I needed bits from all my sources to get the job done. I thought I would document my process in case anyone else finds it useful.

First off the sites that proved to be most useful:

http://www.sparkfun.com/tutorials/247

http://www.arduino.cc/en/Hacking/Bootloader

http://dank.bengler.no/-/page/show/5471_gettinggrbl

I started by downloading the prebuilt hex files for Grbl here

I then downloaded Crosspack-AVR from here which installs a version of AVRDUDE (used to handle flashing the data to the Arduino)

The Arduino that is going to act as a programmer needs to have the programming firmware uploaded to it. This is a very simple task as it is all built into the Arduino IDE. Open up the Arduino IDE then go to File -> examples -> Arduino ISP then upload the sketch to the Arduino. The Arduino is now fully setup to Flash another Arduino.

The next step was to wire one Arduino to another to use as a programmer. I found the wiring diagram from Sparkfun here and the picture below is my version of the wiring. One thing that sparkfun didn’t explain is that you must disable  auto reset on serial connection. I found out how to do this here. I could not find a cable to suit so unfortunately I had to solder directly to the ISCP headers (not pretty).

Wiring for flashing the arduino

Now all the setup is done it is time to put AVRDUDE to work, on a Mac this is done via terminal.

I found the terminal commands for AVRDUDE on sparkfun here about half way down the page.

command one (make sure the Arduino is ready for grbl):

avrdude -P /dev/tty.usbserial-A9007VP6 -b 19200 -c avrisp -p m328p -v -e -U efuse:w:0x05:m -U hfuse:w:0xD6:m -U lfuse:w:0xFF:m

change the red text for the name of the serial port that your Arduino is plugged into

command two (load Grbl):

avrdude -P /dev/tty.usbserial-A9007VP6 -b 19200 -c avrisp -p m328p -v -e -U flash:w:grbl.hex -U lock:w:0x0F:m

blue text is for the location of the grbl hex file on the computer

Hopefully thats it, Grbl is now installed!

If you want to test that Grbl is working properly the you can download CoolTerm which is a GUI for mac for sending and receiving information on serial ports.

Recently i have been pondering over how the hell CNC milling machines get such precision based vector lines. I was hoping to find some tutorials for arduino that would explain the theory behind this technology. All i found out so far is that the whole thing is fairly confusing. Despite my confusion i am very happy to have found this CNC controlled etch a sketch. Its not a toy its a precision engineers dream.

A couple of people have acheived etch a scetch prefection:

http://axis.unpy.net/etchcnc

http://instruct1.cit.cornell.edu/courses/ee476/FinalProjects/s2004/jml66/EAS_final.htm

and last but not least (check out the retro main image):

http://neil.fraser.name/hardware/etch/

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