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13. Moulding and Casting

This week I worked on getting to know how to make molds and casts.

Weekly Objectives

  • Group assignment:

  • Review the safety data sheets for each of your molding and casting materials

  • Make and compare test casts with each of them Compare printing vs milling molds

  • Individual assignment:

  • Design a mold around the process you’ll be using, produce it with a smooth surface finish that does not show the production process, and use it to cast parts.

Group Assignment

In this week group assignment, I testing different materials for casting and compared with each other. You can find our full group documentation here.

Failed Gear Belt

During the week, we were still working on the wire benting machine for the machine week. Our teacher Mr.Dubick suggested us to applymolding and casting into building the machine. So we decided to make a gear belt using the silicone.

First, I designed the belt using Fusion 260.

Then I 3D printed out as my cast.

Then I used Smooth-Sil 940 to make the mold.

First Kathryn and I mixed Part A and Part B with the 10:1 ratio.

Then we put te cast on the bottom of the cup and then poured the mixture in. Since it was our first time doing it, we made too much mixture which caused unnecessary waste.

We waited for 1 day to let the mold fully dry and it took us really long time to take out the mold because we forgot to spray an oil that can easily separate the mold and the container.

After we took out the cast, we got this:

Then we found out a problem: since the mold is soft and we want the belt to be soft as well, it is generally not allowed to pour soft material into soft mold. But since we lareadymade the mold, we still tried it. The result was that the cast was stuck in the mold which made us gave up on this version.

2nd Version of Gear Belt

Then we decided to use 3D printer to make a hard mold. I followed this tutorial made a one-part mold.

Then we printed out the design and make it as our mold. Then we used Sorta Clear 37 to make the cast.

Unfortunately, since it was hard mold, it was really hard to take the belt out. It turned out that the belt was broken and we could not use it anymore. So we decided to gave up on making belt using molding and casting and turned to electrical tape instead.

I learned that for this kind of mold, it would be better to use two-part mold to take thecastout intact.

Soap Dish

For my individual assignment I decided to make a soap dish since my mom requires me to make one.

I first designed it in Fusion360.

Then I printed out using smaller extruding filament so that the cast would not have the layers showing.

I used the 0.08mm extra fine to decrease the layer height.

Then, I used the same material which is Smooth-Sil 940 to make the mold. I brought my own container. However it was too big so molding materials would be wasted. So I found a container that can barely fit my cast.

Then I mixed the Part A and Part B and put my mold at the bottom of the container and poured the molding material in.

However, after 10 minutes, I saw my cast was floating up. So I had to stand there, using a chopstick to hold the cast down. Later, Mr. Dubick told me thatI can hot glue my cast down so it would not float.

The next day, I took out the mold from the container. It was really hard to take it out since there was little gap between the mold and the walls of the container. But with the help of Ms.Horstman and Stuart Christhilf， I manged to took the mold out and took out the cast from the mold.

Next, I decided to use Smoooth Cast 65d to make my cast. Once I mixed the Part A and Part B together, the mixture began to warm up. Right after I poured the mixture into my mold, it staretd to harden.

It took only 2 minutes max to get it harden.

Then I took my final product out carefully.

I did not do anything for solving the bubble issue and this material seemed to not have any issue like that so my soap dish turned out pretty well.

Then my soap dish is completed!

Reflection of the Week

This week was really fun. As the week after machine week, we regained some energy and started to work on our machine while working on this week. Itwas really messy since the molding material isusually sticky and when we poured the mixture in, it was inevitablle to pour some outside of the container. At first we did not put cardboard under our container which got Mr.Dubick really mad. So we had to get up early and came to school and clean the mess up. But generally it was pretty fun and enjoyable.

File Download

You can download my file here.

Last update: June 3, 2025