Parallel Arm 2D Plotter Using Servos, Ver-I

In this instructable i will be sharing an odd type of 2d plotter (parallel arm plotter). I have used cheap SG90 servos to drive the arms. It would be my first verson which kind of works.

The idea came to mind when i was broowsing pinterest, the internet is full of those linear x-y plotters, there is nothing much on other type of plotters. Searching vigorously over net i found some more diff typ of cnc like the delta one, and to be honest i don't know that the parallel arm plotter is the right name for what i have made, i am hoping it should be correct( if not please leave a comment with the right name), i also can't find some good explaination on this type of plotter that i could link here. But in short the simultaneous movent of both the arms decides the effective position of the end.

Thats enough theory for the day, lets take a look at my contraption:)...

• Arduino
• Metal or Plastic pieces for Arm
• A pen
• Servos
• Some cardboard
  

Its the main part of our plotte, for the arms i have used the metal piece that i have salvaged from the back of my pc case. Add holes to the both ends of each strips and then make a hinge with each pair, imp is that the more precise you are with this step the better will be the accuracy of the plotter.

i made the one end hole little bigger so can fit pen reffile through it and using a plastic piece from above i have files it in place.

At the other ends hot glue the servo arms to fit those with servo motor. Here, the arm iscompleted.

The two servos are hot glues together with a acrylic part in middle to give more room for the arms to move.

Attach these servo to a carboard piece which have the a cutout from them like a kind of hinge mechanism. see the pic above for better understanding.

The third servo is placed under the arms servos which moves the whole contraption up and down to lift the pen from paper. This way i have low hanging mass on the ends, hopefully for better precision.

Its simple and effective.

And finally put every piece together and this should look something like above mentioned pic (by the way i love how it looks).

In the video you willl notice that the base is smaller, as i have trimmed the side of the base as they are of no purpose.

The circiut is simple, just connect left servo to arduino uno/nano pin 3 and right servo to pin 9 and the lift servo to pin 6 (for ref hold the base with front side and the servos up), and all the ground wire to GND and positve wires of servos to 5V pin of arduino.

For the code head to my github at https://github.com/tapish101/parallel-arm-plotter-ver-I

Upload the .ino file to your arduino and generate the gcode file using inkscape and unicorn-master gcode generator extension and send it to your arduino using processing ide using the script cnctool.pde

This step is same as for a simple 2d plotter, you can search on net for find better guides on this step.

The attached pic above is important if you want to create the project yourself, you can change the variable in code according to your plotter using this pic and the comments on my code.

Finally i think the only think it most needs in second ver is some precison, which i think should be easy, as i have learned so much while working on this project, for better precision , i have to change all the hinge mech as they are not very precise.

And judging from the third image (please watch the video first the attched drawing aren't as worse there:) ) that i tried to dray a circle, my inverse kinemetics model also needs some finishing up.

The main issue i recently have is driving the servo motors slowly, they just want to snap to desired angle asap which makes the plotter less precise.

Hopefully next ver would me more compatible with traditional plotters.