10. Mechanical Design, Machine Design

This week's assignment is a complete group assignment. SO we have documented it at just one of our pages i.e. Jesal's page and I have linked it here:

Machine Design Documentation

Just incase the above link isn't working in future, you shouldn't be going back without anything to gain. So I have put up some basic data here:

So for the machine design assignment, my friend Jesal was very enthusiastic and he already single-handedly started and tried to design and make a plotter. The link to that work is here

Post that, we decided to work on Spirograph drawing bot.

What is a Spirograph?

Spirograph is a geometric drawing device that produces mathematical roulette curves of the variety technically known as hypotrochoids and epitrochoids. In simple terms, it is a device that can draw complex patterns based on simple principles. You all must have played or atleast known the kid toy spirograph.



It is just the same but with code and electronic actuation this time, instead of gears and manual actuation.

Plan

So initially we had planned that Jesal will handle all the mechanical side, and I will take care of the electronics and the PCB. Coding we thought we will figure out together. But plans don't always work the way you decide. So since our SRM 20 PCB milling mahcine was under maintenance, we prototyped everything on breadboard. I am yet to mill the PCB and replace it in the final version of the Spirograph.

I had planned to design the Spirograph in Solidworks, add a proper casing, and basically once the functionality is sorted, add some aesthetic touch to its looks. Hopefully soon I will get around this and add the new better looking photos of our Spirograph drawing bot on the documentation portal.

Execution

Hardware:
So it has basically 3 servos for 2 translational DOFs for 2 arms and 1 rotational DOF for the end effector. The end effector holds a pen/pencil. These servos are controlled by ULN2003 motor drivers and are programmed using Arduino uno. The power supply we are using is a 12V Power supply We have also included 3 linear potentiometers to control the speed.

Software:
We are using Arduino IDE for programming. We used AccelServo library for the Servo Motors, and we have analog pin reading from the potentiometers, based on which digital pin commands to the servos through the motor drivers are planned.

Primarily, everything including both of our work is documented on the above mentioned link. (Since our fablab node page was running into some issues, we documented it in one of our own page) But, here's some youtube links and photos of the current status of the spirograph: Youtube video 1, Youtube video 2, Youtube video 3