Saturday, March 3, 2012

First test of CNC plotter

Pretty exciting today, since I was able to get the system functioning for the first time.  Since I haven't decided what kind of cutting head I want to use, and I haven't finished all of the alignment steps, I wanted to start with a simple 2d plotter test.  I mocked up a simple pen holder, and put a handy whiteboard grid I had on the bed to use as a worksurface.

I decided to use Inkscape, and to treat the plotter head as an engraver.  Inkscape has a nice extension called Gcodetools that will allow you to export paths to G-code.  I used the text function to type a few simple words in, broke them down into paths, and exported the file.  I used the serial terminal I had on my Ubuntu test system to send the file to the TinyG board.  After a couple of issues tweaking the feed rates, homing the pen, and inverting the X axis, I was able to get a pretty nice first result!

 I still have several small tweaks to do to the system, including tramming, getting the bed support attached to the bed, routing the hold down channels, and bolting/screwing the base to the sides.  Right now I'm just using a couple of pipe clamps to hold everything in alignment as I tweaked various things.  I'm pretty surprised about the amount of parallelism I have even without tramming - the pen didn't really drift much.

I also don't seem to have any issues with backlash or overheating, at least for now.  I rewired all of the steppers to be in parallel mode, which theoretically draws 2.8A, over the 2.5A the tinyG drivers can support.  I should be able to manage that using the current pots on the board however, and even in my current configuration I see the benefit.  I'm looking to get another power supply from Jameco, which I think will also allow me to run at higher seek rates - right now I'm running about 225 mm/min max.

Before I move on, I'm going to play with this setup for a bit.  I believe I can take a photo, run some edge detection, then have Inkscpae build me a vector path to plot the image.

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