Polargraph Drawbot

Well, if you have decided to build yourself a polargraph, this is your instructable! A polargraph is a computer controlled drawing machine. Motors are fastened on the two upper corners of the drawing surface. They are equipped with gear pulleys. These pulleys run two lengths of cogged belts. These belts are attached in the center to a gondola. The gondola carries the drawing instrument, a pen or a marker. Also on the gondola is a little servo that lifts and drops the pen on demand.

The software converts images to files written in G code. Then the Drawbot uses this code to plot start and stop lines on a canvas of your size.

BOM

Gondola - (another one of my Instructables)

2'x4' MDF - Home Depot
Arduino Mega 2560
Ramps 1.4 shield
LCD/SD card module
2 x stepper drivers
2 x Nema 17 motors
2 x stepper mounting plates
2 x 16 tooth pulleys
10' GT2 6mm toothed belting
3G mini servo with 10mm arm
3/4" nuts for weights
12V power supply
Paper
Pen
Marker

Brains of the Operation

I read a lot on the subject of polargraph. There are a few software and firmware programs that you will need to make the polargraph work. The system I'm running is a Windows x64 system. All the files that are linked are for a similar system. You may have to do your homework for x32 and IOS systems. I also used all specific firmware and software options for Makelangelo 3.

In the end, this is the route I chose.

The arduino board of choice that is compatible with Ramps is the Mega 2560 (photo 1). You will need Arduino programming software to upload firmware.

Arduino IDE

The board is a Mega 2560, with a Ramps 1.4 shield. The Mega is powered by the USB cable connection. First, we must load the Makelangelo firmware to the board.

Polargraph Firmware

The Ramps shield can now be installed, then the two stepper drivers (photo 2) are inserted in their positions (X and Y). These ones have heat sinks installed. If you are using a LCD/SD card setup, you can connect this also. Finally, the steppers are connected.

Now, your computer needs some software to be able to talk to your printer. I chose Makelangelo.

Polargraph Software

After all the software is loaded, you can now connect the 12V power supply to the Ramps shield. Important note here, if you ever have to disconnect the servo or stepper plugs, be sure to disconnect power supply as the surge can kill a driver.

The servo for the gondola gets plugged in position 1 on the servo cluster on Ramps (photo 3). Note, a jumper must be installed to power up the servo pins. Another note here, the connections were reversed on my connectors I purchased. The positive and negative were backwards. Make sure you change the red and black wires in the plug if yours is too. Otherwise, every time the servo is activated, it will reset the board.

You can test the system now to make sure everything is working. There will be some settings to change in the firmware such as steps per mm, pulley sizes, Ramps or Rumba boards and LCD/SD card options. These are explained in their respective downloads.

Drawing Board Build

First, we start with a 2' x 4' MDF board from your local building supply store. You can later build it as large as you want, but I decided on this one for testing. To suspend the motors, you will need two motor mounts. You can purchase these or, in my case, I designed a set on Tinkercad and printed them on my 3D printer (the file is attached and has provisions for fans for stepper motor cooling). You can then attach them to upper corners and install motors and pulleys.

Then comes the gondola. There are many designs available on Thingiverse, or you can build one with very little tools and resources. Check out my other Instructables that show you how. The belts are now attached to the gondola then strung over the pulleys.

The ends of the belts must be weighted down to keep them from slipping on the cogged pulleys (Here, you can use anything on hand. I have used nuts, but water bottles have also been used.). Also, to keep the pen on drawing surface, it might have to be weighed down as well. this is a trial and error test. If you build my Inscrutable gondola, I have two bearings in center that act as weight. I also needed to add two nuts at bottom to keep in against the paper. On the ends of the belts, more nuts were added (I used shaft collars on mine, but it will be easier to find nuts). I found the rule of thumb, weigh your gondola and divide this number but two. this should give you the approximate weight to start with on the belts. You might have to up it a bit after testing.

This is all for the mechanical end of things.