Emily Pena & Megan Enriquez

Hello everyone this is our Cat Casting and Molding Project! I worked alongside Megan Enriquez to deliver 8 molded Cat Chess pieces.To begin we found our design in Thingyverse but made some modifications for molding purposes. 

We sliced off the cross as we thought it wouldn’t have translated well on our final piece. Once with our final desired piece, we went on MeshMixer and sliced the design in half. We sliced it behind the arms but in front of the tail for uniform molding purposes.

 

Next we used solidworks to put our sliced halves on a base for molding. We had to do a few reiterations as we decided to include an air hole for the crown, and accidentally flipped the pegs. But this was our final 3D printed piece with the corresponding CNC half. 

The process of using the CNC machine had a few setbacks due to difficulties with securing the wooden 2 x 4, not having enough time booked resulting in a shutoff, and the machine changing course due to an inconsistency with the wood. After about 4 attempts, we were able to successfully CNC the other half of our cat chess piece. 

Once we had our final pieces ready we were ready to mold! This was a relatively straightforward process. We made a cardboard border that was water tight due to several reinforced layers of hot glue. We measure 1 cm a over the max height of our piece, to use as the height for the volume of fluid we’d need for the mold. Thus, 121.5  ml ( the calculated total volume 250 cm^3 – the volume of half our piece 7 cm^3 )/2 is how much of part 1 silicone we needed. This ended up being about 4 oz. And Part 2 was the same volume. We let that sit for 5 hours and we’re ready to demold!

Now we were ready for the casting process. We used Liquid Plastic to cast our pieces. This is also a 2 part solution that has a 2.5 minute cure time so we had to work fast. We first began by measuring our volume for our total piece. We then created a set up of big cups, smaller mixing cups for color with our needed volume, and our two molds rubber banded together. The rubber bands were the best method as it allowed us to manipulate the mold without having a wooden block there complicating the process. To get the gradient color we just used one drop once in our first mold then used the color leftover in the cup for the next mold and repeated the process. We let the mold sit for 10 minutes then demolded.

After we demolded, we immediately started post processing. Our air hole left too much excess and so we used flesh cutters to cut off overlapped pieces. We then used a course then fine sandpaper to remove any rough edges and smooth out that harsh mold line that splits the piece. 

Some takeaways: 

Ensuring a really good symmetric mold is really important for the alignment. We often had to manipulate the mold to make the alignment look better since our initial alignment with the pegs seemed off.

The air hole we included didn’t really seem to help as we still had air bubbles in the crown but maybe since it was on the cnc piece it wasn’t as crisp defined lines as opposed to a 3D printed air hole.

Doing the harder CNC homework helped in understanding how to do a rough pass and smooth pass on the machine. 

 

Cost Analysis:

• PLA for 3D Printing: $29.99/kg (330 m) x 10 m = $0.90
• Wood $2.98/8 ft x 1 ft = $0.38
• Silicone Mix $59.97/ 70 oz x 8 oz = $6.86
• Liquid Plastic $150/ 15.2 lbs x 12 oz = $7.40
• Labor $10/hour x 20 hours = $200
• Total: $215.54