This was a complex toolchain, and required using a few different pieces of software and a few different pieces of hardware, as well as learning some new physical skills.

 

Our process was as follows:

First we 3d modeled Ferb in blender:

We started by modeling the shape of his head with a cylindrical shape that slopes outward slightly. Then we added Ferb’s shirt with a rectangular shape and then softened the corners. Ferb’s hair is a 6 pointed star extruded and sloped to get the correct shape. His nose is a cube pressed into the head cylinder and the corners of that also got softened. Ferb’s lip- our favorite part- was made by taking one of the cross sections of the cylinder and pulling it out and shaping it into the perfect lip shape. After many small edits, the model of Ferb was complete. 

This was the finished Ferb model, and we had some debate over adding eyes, but after putting it to an informal class vote, we settled on no eyes.

 

Then we sized up our model, and designed both plates in Blender

We designed it to the specifications in the instruction document. We decided to use Blender for this step because the Ferb model was already there and Benji was familiar with the software and was able to model the backing plates quickly. 

These were the finished plates, after this we sliced them and prepared them for 3d-printing/CNC’ing

After that we 3d printed and CNC’ed our positives:

 

To 3D print Ferb, we sliced the front half of Ferb in Bambu Slicer. We then printed off two options for our model. One had the default layer height of .16mm and the other had a custom layer height of 0.06mm. They both had no support and 15% infill. The Ferb with the smaller layer height was much smoother, but had some slight bubbling along the infill pattern visible on his fairly flat shirt. We ultimately decided it was not necessary to reprint and moved on to prepare this print for silicone.

For the CNC part of the project, Izzie had done a topography for the CNC project and was fairly comfortable with the CNC so this part of the project did not take long at all. We CNC cut Ferb over thanksgiving break so the CNC was all ours to use. Before cutting we realized our Ferb model was slightly too wide to fit on a standard 2×4 so we took some plywood from the woodshop and cut equal pieces that would fit Ferb. We then laminated the pieces of wood together with wood glue and put clamps to hold it overnight. Then we were ready to CNC. Something we learned from the CNC project was that pieces have to be very securely clamped down on the bed. Once we had double checked the wood would not shift at all during the cut we initialized the machine, zeroed it, and then cut it out. The first cut with a ¼” end mill took around 30 minutes. After that first cut was done we switched out the bit for an ⅛” ball nose bit and hit start on the finishing path. After that, the CNC part of this project was done!

Silicon pour

Silicone pouring was really fun, and we perfectly measured the volume needed and did not waste any silicone. Our thin stream and corner pouring method game the molds have a very clean finish.

We built the mold boxes around both the 3D print and the CNC part using strips of cardboard and hot glue. We made sure to go back over all the seams with hot glue to solidify them and ensure no leaks. We mixed a batch of tin cure silicone for the first mold, but that ran out by the time we did our second pour so we used the platinum cure. In both cases we mixed together a 1:1 ratio by weight and mixed for 7 minutes making sure to scrape down the edges to incorporate all parts of the silicone. The platinum cure silicone was nicer to work with in our opinion because the parts were different colors. With the 2 part clear tin cure silicone, it was hard to tell if we were fully mixing the parts of the silicone together. Even with all of that mixing, we had a small bit on the side of our bottom mold that didn’t fully cure, possibly because that part didn’t fully get mixed. It wasn’t a big deal however and we moved on to the liquid plastic step

Plastic pours

We poured our Ferbs over two sittings, two the first time and six the second. We did a variety of colorations, solid color, two color, swirl-two-color, swirl-three-color. Our workspace layout was as seen below.

We labeled our placemat so we would not mix up what went where. We had specific cups for part A and B as well as a cup to mix the color into part A so that we had time to get the perfect color and didn’t spill the different parts. Our final cup was designated for mixing the different parts together and cured along with each iteration of Ferb and we were able to simply peel out the leftover cured plastic before each new color. Each Ferb needed exactly 2 oz of liquid plastic. We calculated this by simply filling the Ferb mold with water and dumping it out into a measuring cup. However we found this calculation to be slightly too small of a number when doing our first pour so we rounded each part up to 1 oz to account for the liquid that gets left in each cup at each stage. After some trial and error we found 2 oz to be the perfect amount for our Ferbs. To hold the molds together straight, we clamped the two silicone sides making a sandwich with wood and then securing it with rubber bands. This keeps the silicone from warping under the stress of the rubber bands and keeps each side nice and flat. When pouring we started in sections first filling his hair part and swirling and tapping the sides of the mold to release air bubbles. We repeated these steps the whole way up Ferb taking care to make sure he had no bubbles stuck in his lip. It took a lot of trial and error, but by the end Ferb barely had any bubbles in his lip. We also had a mishap where we spent too long mixing the colors together and the liquid plastic actually started curing as we poured it in. This resulted in a strange looking Ferb with a squiggly torso. After ironing out the mishap, we had fun experimenting with different color combinations for our Ferbs. We enjoyed the two tone look and worked on getting a swirl of a different color. We achieved the swirl look by mixing everything like normal and then dropping a single drop of color into the mold before it set and giving it a quick swirl with the popsicle stick. We poured 8 different Ferbs and then the final project was complete!

Cost Of Creating the Ferbs

Cost

• Labor
  • 3d modeling
    • 1hr
  • sizing /slicing
    • 1hr
  • Designing plate
    • 30 minutes
  • 3d print
    • 30 minutes
  • CNCing
    • 2hrs
  • Silicon pours
    • 1hr total
      • (2 sides)
  • Plastic pours
    • 20min/pour for a total of 2 hours and 40 minutes

If we assume a standard wage for a mold creator and caster of $17/hour. These chess pieces cost $147.34 in labor.

• Material
  • 3d print
    • $3.54 in test prints
    • $2.53 for final print
  • Wood of CNC half
    • 128 square inches of ¾ inch plywood. From Lowes.com, a 2ftx4ft sheet is $39.98, so we used $4.44 of wood.
  • Silicone:
    • One half of our mold was made using tin cure silicone and we used 7 oz for $3.37
    • The other half was made with platinum cure silicone, and since our part was smaller we only needed 5 oz for this side which cost $6.40
  • Liquid plastic
    • We cast 8 ferb chess pieces, each one containing exactly 2 oz of liquid plastic for a total of $9.74
  • Dye
    • We used a negligible amount of dye for our chess pieces

Adding up the material costs we get a total of $30.12

Total cost: 147.34 + 30.12 = $170.46

What we would have done differently

If we were to do this again, we pour our plastic over more sittings, because it is difficult to keep a clean workstation while pouring more than a few.