08: CNC Milling
Lab July 24th, 2019
This week we were introduced to CNC milling and the lab’s very own shopbot. We were lead through a live demo of how to use an stl file to create some 3D object using the shopbot. Then we were shown how to make a 3D mold using that item. Our assignment for this week was to design our own 3D shape and use it as a mold. We were divided into groups and sent on our way. I was in a group with Julia and Adwoa.
We each came to lab with our own 3D designs, but decided to use Adwoa’s heart shaped model. Using an USB drive we took the stl file to the shopbot and got to work. The first few steps were to upload our file to the shopbot and make sure everything read in correctly. We created the first few layers of the sketch. The very first one was the “rough” sketch that was aimed at simply cutting the basic shape. After that we added two “finishing” layers that would go in and smooth the design out while also creating the smaller details such as the crook of the heart.
Next we had to set up the shopbot. We had to change the finer tip that was placed in the shopbot to a larger less precise bit. Although this bit wouldn’t create as much as detail as a finer one it would work a lot quicker, and would quickly chip away at all the material on the block.
After changing the bit we placed our styrofoam material onto the sacrificial layer, and made sure it would stay still by hot gluing it to the surface. We then centered the bit over the bottom left corner of the styrofoam block. After that we were ready to cut.
Here’s a couple videos of the actual cutting process:
Here’s what the design looked like after being cut out:
The next thing we had to do was actually use it as a mold. To do this we had to first wrap the design in a layer of seran wrap.
Then we had to begin the process of layering canvas over the mold. We cut three pieces of canvas in the shape of the design and then mixed some apoxy together. For each layer we spread some apoxy on the canvas and then layed it over the mold, making sure to try and form it neatly to the mold. We repeated this for each layer of canvas. As you can see in the pictures below the apoxy sticks to everything.
Once all the layers had been added we added the “bleeding layer” which is a layer of seran wrap that has several little holes in so that any extra apoxy can seep through. On top of that we added some soft cotton/felt like layer to absorb the extra apoxy.
Lastly we used a commercial plastic bag compresser usually found in kitchens to seal an airtight bag over the design.
After that all we had to do was wait for the apoxy to dry over the next couple of hours.
During today’s lab I also created a small replica of the Miami beach sign that I plan to 3D print. You can download the file for it below:
