Making the GradRat

My idea for this week's assignement is to make a big Gradrat (MIT graduate class ring). I work with the committee in charge of it & it seemed a good idea to have a big one which I will paint in gold and have it for the events.

In retrospect, this might have been a bit ambitious. As you will see, this is a guide of learning from one mistake after the other.

Design (& frustration)

I started by acquiring an existing ring and took some measurements to try to rescale it while keeping the correct aspect ratio. I then used Solidworks to CAD it. This was very useful & frustrating but I am much much better at CAD now. Here is a CAD of the main body, the cavities are there for when I do the details but I will come to that later

ring solidworks

Given that the dimensions are of the order of 3 feet and the thickness of about  1 foot, I needed the biggest and thickest material available. This happened to be pink insulation foam (8ft X 4ft X2").


I then made the sheets in solidworks and used the combine (boolean) function to make the appropriate cuts.


I realized that I will be needing alot of foam to make this happen so I made the ring smaller for that. After grabbing 3 pieces of foam from John & Tom (Thanks a lot for your help), I still needed more so I went to Home depot and got 6 more panels. Of course, with my luck, they only had 1.5" thick foam so I had to go back and redo the cuts.

    Cuts to be added
Machining- ShopBot

Alot of those cuts contain some 3D features which require surfacing. When I tried to surface all of them, we realized with James that each would take about 5 hours and all because of a very small 3D feature. So we decided that I would redesign the cuts and make as much profiles as possible and make a big job with all the 3D pieces.

    Cuts to be added


I used the ShopBot to make my profiles. The speed I used was 9500 rpm and the foam was cut very nicely and quickly.



I learned alot during this process and I would like to share some of it :
Important things to keep in mind :