For this week, the goal was to make a 3D design of an object, and then make the object using composites. First, we started with mold making in the N51 shop, using foam. I started by modeling the object in Rhino. I wanted to make a nice bowl for this week. One of the design considerations included not having a draft angle along the edgees that would be lesser than 2-3 degrees. If this happens, the tool will not be able to bend inwards, and so, it won't work.
Once I was done modeling in Rhino, I started to work with Mastercam to set up the file for the Onsrud CNC, and generate the gcode! By this time, I have worked with Mastercam enough to remember the steps to set up a file. We first click on File --> Merge and then choose the rhino file. then, we choose the machine that we will be machining with. Next, we set up the stock size - in this case it was 12" x 12" x 2". Then, we start setting up the tools. I picked a 0.5" spherical end mill for the entire surface, and a 0.5" flat end mill for the edges, so that I dont have curved edges. Thanks to Calvin for helping with this! Then, with Chris' help, I was able to get the CNC milling set up and done. And, this is what my mold looks like !!
Here's a short video of the Mastercam simulation through which I verified all the operations..
And, then, it was time to cut using the Onsrud CNC machine in the N51 shop..
Next, I sanded the surface gently and applied the white gesso. I let it dry in the fume hood overnight. Then, I came back in the morning and sanded it thoroughly. Then, I applied white gesso again, and repeated the sanding procedure. Same thing 3 more times over the day..
Next, I applied a thin coating of the wax, and let it dry.. I had to repeat this 3 times..
Then, I picked out the fabric and all the packaging material required for the resin curing process..
First weigh the fabric.
Then measure out the resin (100:43 ratio of part A to B), total of about 5 times the weight of the fabric is what I used..
Then I put the fabric layer by layer and applied the resin such that the fabric sat snugly around the mold without creases. Then, I put all the packaging material, and into a vacuum bag, ready to cure !!
There you see the pump pulling all the air out..
I let it cure for 4 hours..
Then, I came back and demolded the bowl.. It came out quite easily once I had the sides removed..
I was happy with the result!!!