2DOF Axidraw Pen Plotter Clone Kit Lessons Learned

Just finished putting together an Axidraw H-bot configuration pen plotter with no instructions – just using info picked up in various Youtube videos and blogs. It was an educational experience. The kit only cost about $50 dollars where I live. The kit includes Arduino Uno, CNC Shield V3.0, two Nema 17 stepper motors and a 12volt power supply. The frame includes all components and the hardest ones are already assembled (eg. bearings into their holders, pen mechanism).

This is not a how-to assemble the kit as I'm not sure it is even available in the US in this wooden framed configuration. It is more a lesson learned. I spent 3 days finding all the information necessary to put this kit together and to get it working with Grbl on the Arduino Uno.

This printer is an H-bot or CoreXY configuration with a single belt used by both steppers so if you use Grbl to communicate with it you must turn on the CoreXY option in the grbl program you load into your Arduino. The one I listed below works great and includes the code to control the pen up/down mechanism.

Warnings:

• do not power the shield and motor controllers on until the stepper motors are connected to the shield/motor controllers or you will burn them out.
• Put some additional weight on the pen drop mechanism so that it will not get stuck in the up position
• .If the G1 X10 goes in the wrong direction you can flip the stepper cable header over on the shield to change direction.
• Also, you may have to set the $3 variable to other than 0 to get the steppers to move in the correct directions.If G1 X10 moves diagonally, that means the CoreXY option in the Arduino Grbl is not on. It is automatically set correctly in the version listed below. In an H-bot configuration, both motors must run simultaneously to move in the X or Y axis only. To move diagonally only one motor moves or both motors move simultaneously at different speeds.

The plotter works great and the only problem I have run across is that the pen mechanism is a little loose and so the plots could be a touch tighter. I will work on my own mechanism later but with the style printing I do, scribble art, it doesn’t hurt it.

Update: the last photo shows my homebuilt pen lift mechanism - much better than the one that came with the kit as the kit version had at least a mm of pen movement. Mine has much less movement - almost none at all but easily is lifted and dropped to the paper. I mounted the pen in a tube, epoxied to a lever mounted on an old hard disk drive motor that is itself mounted to another wooden mounting plate. The servo pulls a string to lift and lower the pen. Gravity is perfect for dropping and holding the pen on smooth paper. I have a small weight that sits on the top of the pen for a little more downward force.

SOFTWARE:
I use this grbl version 9i, modified to use a servo to control the pen drop here: https://github.com/misan/grbl-servo

Then I use DrawingBotV3 to modify a picture into a scribble style gcode. In this software you can set the commands M3 S200 to drop the pen and M4 to raise it, and have them inserted into the code file for you. Save the gcode file.Code for DrawingBotV3 here: https://github.com/SonarSonic/DrawingBotV3

Finally I use Grbl Controller to connect to the Arduino grbl and send the gcode file I want to print. Code for Grbl Controller here: https://grbl-controller.software.informer.com/3.6/