Remixed MTvplot with optional LPWAN
Couldnt find a few of the parts from the original so remixed it to suit, namely the bearings in the original which ive replaced with a printed barrel that is attached to the servo holder.
In the version i built i connected it to a catm1 network via serial output (TX RX to RX TX) then simulating serial communication between the 2 boards with commands coming from a server as opposed to a USB connection. more to come on that
- 5m roller blind cord 4.5 sphere /12mm gap or 4.5 sphere /6mm gap
- 2x stepper motor - NEMA-17 200 steps/rev, 12V 350mA
- 1x Arduino UNO
- 1x Motor Drive Shield L293D For Arduino, i used a Adafruit v2 motor shield
- 8x set screws M4 (10mm), i only had 15mm screws
- some M2/M3/M4 screws to secure the motor holders, servo and gears
- 10 meters of 4 wire electrical cable, this is to extend the cables from the motors and servo to the arduino.
- Whiteboard marker, i used Expo dry erase markers
- 12v power supply with at least 2 amps, this will depend what stepper motors are being used. The NEMA 17 motors have a very low amp requirement so for my build i used a 12v 1amp supply going straight to the uno stack.
Most of the below i printed at 0.2 layer height with 20% infill using rafts for just about everything (depending on printer specs).
This is easier before you start assembling everything, depending what shield you use will depend if that needs soldering. With the Adafruit v2 motorshield the header pins needed to be soldered into place. I used 3 meters of cabling on each of the steppers and on the servo (although the motors themselves need the most cable room) then covered all cable solder with heat shrink (to keep things tidy).
On the wiring side be careful not mix up the wires from the steppers, if you are using steppers with 5 wires there will also need to be a ground wire running into the motor shield.
Each motor hooks up to the M1/M2 and M3/M4 headers respectfully with the server running into the server input on the motor shield.
In my Arduino stack i also have 2 wires running into the TX/RX pins to transmit data from a iot network connected device. In this case i used the Arduino MKR NB1500 which means i dont need to run a USB cable or memory card for the plotter to run.
These need to be attached to the barrel which is glued together inside the arms circle so that the arms are free moving. Ive modified the ones in this print to include a hole for the blind cord to feed into and a screw to hold it in place.
Feed the blind cord into each arm so that the spheres pass past the screw hole, then secure them in place by using a M4 screw.
Servo/Barrel & Barrel Top
Super glue together between the plotter arms so that it forms a moveable arm mechanism. Take extra care to not glue the barrel to the inner circle of the arms (arms need to be free moving).
Screw the servo into the mount so that the arm is on the inner side of the mount (with the wire facing on the outside).
Upper Pen lock
This i glued to the top of the upper barrel to hold the top of the marker in place using screws.
Servo body Weight
Glued to the bottom of the Servo/Barrel then filled with weight, i used spare screws in mine.
Stepper Motor Mounts
Screw the stepper motors into the motor mounts using M4 10mm screws, in my pictures i only had 15mm screws so put some circular housings to keep things tidy. Ive included both mounts in this but only print the one you need.
My demo version is mounted on a window so the Stepper Mounts sit directly on the board that it writes on. Its important to keep in mind that if you mount on a whiteboard bracket it will potentially lift the mounts away from the board (and ideally the gear needs to sit flush with the board).
Mounting the Stepper motors i used 3m sticky hook backings (which had more than enough load) but could just as easily be screwed into the board.
Screw onto the end of the stepper motor, this needs to sit as close to the board/glass as possible to make sure the gondola sits close to the board. Ive included the original which uses blind cord that is 4,5mm and a distance (mid-sphere to mid-sphere) of 12mm. I used 4.5mm spheres at a distance of 6mm mid-sphere (this one prints a bit easier in 2 parts).
Blind cord weights
For this i repurposed one of my favourite prints Capsules. The idea for these is to counter weigh the gondola by clipping the capsule around the blind cord so that it feeds through the middle of the capsule, fit the cord itself (between the spheres) between the teeth of the capsule half then line the other side up with the gaps in the print.
Inside the capsule i loaded some spare screws to weigh it down but just about anything can be used providing it adds enough counter weight and is easy to clip everything together.
Tried a few different sketches and apps but by far the best is Polargraph by Sandy Noble, namely https://github.com/euphy/polargraph_server_a1.
In my version i connected the plotter to a catm1 LPWAN network via the Arduino MKR NB1500 by linking serial outputs between that and the Arduino uno + adafruit v2 motorshield stack. Then streaming gcode from a server (more on that to come) but works fine with direct USB or SDCard output too.
Eraser on the back of the servo arm