The design:-

This is the first week of the two week make a machine project!!
In this week we were expected to design and develop a machine that we would be able to run manually.

Hence sooner we began with debuging of the ideas....

Project Ideas discussed:

It was observed that, for the past years all the fab academy students at Vigyan Ashram only worked on various iterations of XY plotters.

Wanting to standout, we decided to go with Robotic arm!

The following project was born out of curiosity about how the machine functions and as a word to break the trend of attempting X-Y plotters.
This time we wanted to try and push ourselves beyond the cartesian co-ordinates and try controls beyond that.

Hence we had decided to make an arm.

Initial Workout:


The initial workout was to start with the calculations for the making of the structure of the arm, there were plenty of things to be taken into considerations, including the materials involved, the strengths that the materials could handle, torques on each motors, and many more, which we had attempted calculating before.



It was found that, we were doing the same calculations over and over again.
If we increased the length of arm by 100mm we had to do all the calculations again. This is counter productive.
We decided to write a program which will calculate the values. This proved to be tough as there are many inputs and many outputs. Also to see whats wrong, sometimes we need to check the problem at each and every step. Hence we created a spreadsheet, loaded formulas, This would enable us to play with the parameters as we preferred.



Giving instant solutions!

Choosing the end effector:


The next requirement for a machine to define an actuator.
There are a few different types of arms available: The type of mechanism will depend upon the end effector.
We just wanted to study the making and the motions of the arm
Hence we initially had taken up a concept to try an arm that could weld, at least a straight run, the process expected was MIG welding, and we had planned to arm the bot with the MIG welding gun that we had in our workshop.

But as we went through with the calculations, we faced a lot of issues. We could not determine accurately the minimum reach and maximum reach of the arm.
We decided to make an arm of at least 1m in length.
It looked okayish and achievable.
Later the case was when we had calculated the torques of respective motors for a sustainable reach of the arm, we had found that the motors that we needed were all above the torque of 100Kg-cm.
This is not acceptable... also way over budget for our project.
We had another brainstorm station, wherein we came up with a few lighter/scaled down. We decided to go with laser module and pick and place.
But to make the end effector such that, in future we can add different features.

The calculation sheet was approximately the same that we had made for the welding bot, just we altered it a bit to make it little more sophisticated, and easy to work with.

Hence later we began to work with the things we had to put our way through..

Prototyping:


There were a few things that needed to be prototyped before manufacturing the complete arm.
  1. Calculating reach for given length of arm.
  2. Deciding on the length of each individual segments
  3. Testing mechanisms for the arm
  4. End effector mountings
    5. Add something below as done for above
  5. Testing if the motors work
    6. Add something below as done for above
These were solved as follows: