Molding & Casting – Totoro GK

Table of contents

1. Molding & Casting – Totoro GK
   1. Group Assignment for Molding & Casting
   2. Design
   3. Molding
      1. Molding Result
   4. Casting
      1. Casting Results
         1. Photo Gallary of Totoro GK

Group Assignment for Molding & Casting

review the safety data sheets for each of your molding and casting materials, then make and compare test casts with each of them.
extra credit: try other molding and casting processes.

shown in Week 7 of EECS Group Assignments.

Design

I am a huge fan of My Neighbor Totoro (となりのトトロ) or 龙猫 in Chinese, so I decided to make a garage kit figure of Totoro. So I picked my favorite scene from the movie, where the Medium Totoro is sneakly moving out of the house with the Baby Totoro as shown below.

I then searched a while for the 3D model of the Totoro and found exactly what I want from Cults3D by Patrick Li. And the texture of the model looks amazing to me, so I am encouraged to keep as many fine textures as possible during molding and casting procedure.

One curious and essential question is can I keep the eyes of the Totoro?

Medium Totoro from Cults3D by Patrick Li under license [CC BY-NC-ND 4.0].

Unfortunately, the 3D model is originally made for 3D printing and in STL format only. As Anthony reminded us in gitlab issue, the STL format with more than 10k faces would be devistating for Fusion 360 and this model has 419k vertices and 838k faces. So I used MeshLab to simplify the geometry (Filters ➔ Remeshing, Simplification and Reconstruction ➔ Simplification: Quadric Edge Collapse Decimation; ) and got a model with 20k faces. Then I imported the model into Fusion 360 and convert it to a solid body, so I split it into two parts and get the mold for each. Then I made a simple box as the base for the mold and added the matching holes for alignment when casting, as shown below.

With the help from Anthony, I managed to machining the mold base with the CNC machine that we used for Week 5. It’s relatively time-consuming since there are still tones of fine details in the model and Pencil toolpath was not happy with the huge number of faces in STL moddel.

Eventually, it took me 1 hour to finish the machining and I got a nice mold base.

Now, I got a satisfying mold base to work with and many fine textures are kept amazingly well.

Molding

Then I used the Silicone mold making kit to make the mold. I followed the instruction and mixed the two components of the silicone rubber and poured it into the mold base.

At first, it was a failure as the molds are super soft after even 3 hours. Yural reminded me that I did not mix well enough both components before and after mixing together. So I redo the process and make sure to mix well in every step. Then I leave the silicone mold for a whole night and it turns out to be a success.

Molding Result

It’s super satisfying to see the perfect molds and they actually align well with the designed alignment holes.

Casting

Then I drill a cone-shape hole for casting on two models and use the drystone powder to case the molds. Since the two molds aligns really well, I can easily cast the two models together. One mistake I made is the ratio of the drystone powder and water is not correct. I used the inverse weight ratio, that is 24g drystone powder to 100g water, where the correct ratio should be the inverse, that is 100g drystone powder to 24g water. So the casting is just the bottom part of the model, that is the ears of the Totoro, which is actually cool. So I fixed the issue and redo the casting, with some suggestions of the ratio from Yural and Anthony.

Casting Results

Eventually, it’s a really nice casting and I’m super excited about the result. Echoing the essential question about the Totoro’s eyes, it’s a huge YES! You can clearly see them on the photo gallary below.

Photo Gallary of Totoro GK

Side Note: I am happy with the white appearance of the Totor. I would also love to paint it with blue and gray colors to make it more like the Medium Totoro, as in the GIF.

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