08: CNC Milling

7/24/19 – Composites, Milling, and Switching to a Nano

Today, we made a CNC-milled foam mold and layered pieces of burlap with epoxy to make a bowl!

I was working with Tony, and after vetoing the idea to make a tapeworm, we decided on a hexagonal-shaped bowl. We modeled it in fusion by extruding a hexagon, filletting the top edges, and then filletting the sides. You can download our mold model here.

When we got to class, we imported our model into the V-carve software, and made a rough cut path and then two smoothing paths. Then, the mill started to cut the foam!

After the mold was cut, we first draped the burlap over our mold to figure out what shape we would use for our resin-coated pieces of burlap. We realized the shape should have 6 darts to account for the vertices, and we measured the distance of the vertices directly across from each other across the curved surface (21cm) to get the diameter of a circle, and measured the curve from the vertex to the top (5cm). I used these dimensions to make a circle with 6 radial slits in Fusion that we could cut. However, one problem I ran into was that Fusion restarted my computer when I tried to save the file to a .dxf. Here was the shape: Then, we lasercut 5 of the burlap circles, and the normal cardboard settings turned out well!

Next, we moved onto making our composite. First, we covered the hexagon in saran wrap to protect the epoxy from sticking. We also sprayed mold release onto the top layer of saran wrap to further prevent stickage.

Then, we mixed up the epoxy to put onto the burlap. For the epoxy, it’s a 2:1 ratio of part A to part B, so we put two squirts of A to one squirt of B into a paper cup and mixed with a popsicle stick.

After the epoxy was mixed, we used a squeegee to apply the epoxy and spread it evenly across the fabric, and then molded it onto the saran wrap and other layers. It made a pretty big mess!

Then, we used the medieval torture device (a roller with spikes) to cut holes in the saran wrap for the “bleeding” layer. The bleeding layer is supposed to allow extra epoxy to seep through the holes and not stay in the fabric. After we cut the bleeding layer, we put it on top of the burlap.

The next step was to cut batting (stuffing) and put our mold into a vacuum-sealed bag. These are all the layers we put into the vacuum bag: We struggled with Andrei to get the vacuum-sealing machine to work, but when it finally worked, our mold was safe! First, we cut sealed the bottom end of the bag, and then slid in our mold and batting. Afterwards, the machine removed the air and sealed the bag.

Here is our final mold, vacuum sealed and all! Now we wait and see how the composite will turn out tomorrow in class.

UPDATE 7/25/19

Our mold turned out even better than expected!! It released from the saran wrap and mold pretty easily, and after we got the mold out, I used the Japanese hand saw to get rid of the excess material that curved over.

back to documentation:

After Tony and I finished making our composite mold, I worked on my glove prototype from the other day. One of the problems I ran into on Tuesday was that the Arduino UNO is way too bulky to function well. So, I decided to switch to an Arduino Nano to make it easier to manage the wristband. Normally, we solder male pinheaders onto an Arduino Nano to plug it into a breadboard. I decided to solder female pinheaders onto my Arduino so similarly to the UNO, I could put it in a box to glue onto the webbing. It was pretty easy to solder. Again, I used the MakerCase website to make a box for the Nano after taking my measurements with a caliper, and then cut my box. You can download my box template here. Then, I glued the box down to my band and extended and soldered the wires where necessary. This newer version turned out very well! It’s a lot easier to wear and looks much nicer.