My DrawBot, with a small changes in some pieces, and its controlled by Arduino UNO with a modified GBRL Software.
can you share your grbl please?
The source code is in the next video, I know its not the DrawBot but in the description of the video you can see the link of the source code:
The calibration is a little bit dificult, if your drawings are like a diamond, maybe its the rotation of the base, or maybe the initial angle, i mean when the arms going to home, thats the inital angle.
If you want to do a straigth line, you must do it in small increments, see the TXT file inside the Zip File, I explain everything in there.