I needed a way to generate Gcode to tell my Makerbot to move in circles, so I wrote a Matlab script to do so. The script has various parameters that control the code that is generated.

The result of the script is Gcode telling the machine to move in circles (or elipses) of increasing speed.

The code's messy, and single use, but I thought I'd post it in case someone else wanted to make Gcode draw circles :-)

circles.gcode is the file generated when all settings are set to their defaults.

1. Run the script in Matlab.
2. A file dialog will open, choose a name and location for your Gcode.
3. The "Main Settings" dialog will open, in it are 4 settings: a) Feed cap mode: 0 sets the machine to move at a constant net speed, 1 uses the slowest axis cap to set the faster axis speed (confusing, but the code makes a bit more sense) b) Ramp Control Mode: 0 sets the script to ramp the speed up between loops (one speed per loop, each loop faster than the last), 1 sets the script to ramp up smoothly (each move slightly faster than the last), and 2 sets it to just use the max speed the whole time (disables ramping)
4. Next you will see the "Machine settings" Dialog, where you can set machine specific parameters: a) Total X size (the X dimension of the elipse to be generated) b) Total Y size (the y dim ---) c) Low X Feedrate: the starting feedrate of the ramp for the X axis (if ramp is enabled) d) Low Y Feedrate: -------- Y axis ---- e) Max X Feedrate: top of X axis speed ramp (or max X axis control speed if set to no-ramp) f) Max Y Feedrate: -- Y ----- Y -------- g) Initial Feedrate: Doesnt work right, leave it at 1000 if your printer can move at least 1000 mm/min in all axes
5. When you hit OK, three things will happen: a) The Gcode will be generated and saved b) Mode and feed information will be printed to the command window c) a set of three graphs will appear detailing: i) an XY plot of the extruder movement ii) a plot of axis speed vs position (with the y graph rotated 90 degrees, and both plots scaled to fill the graph) iii) a plot of the speeds of both axes with respect to time
6. run the Gcode on your machine and see how it handles circles!
7. ???
8. Don't profit (sorry, non-commercial)