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Molding and Casting

Goals

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.

Prior Knowledge

None, besides printing the molds.

Projected Timeline

Molding and casting in the span of two days. Since this overlapped with finishing machine week, I needed to work efficiently.

Actual Timeline

  • Monday
    • Print mold
  • Tuesday
    • Cast

Group Assignment

I was in a group with Angel Fang, Noah Smith, and Kathryn Wu. I was assigned the multimeter and oscilloscope.

You can see our documentation on our group site.

Individual Assignment

Datasheet

I used Part A and B silicon for this mold. I checked the information in the data sheet to ensure that I was properly pouring and maintaining the mold while it cured.
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I looked at the shelf life, pot life, and cure time of a cast. Shelf life is the duration that the product works once opened, before expiring. Pot life is how much time one has to modify the cast when being used. Cure time describes the amount of time before the cast fully sets. One uses a cast before its shelf life ends, works with the material during its pot life, and waits until the cure time ends to remove the cast.

  • Shelf life: 6 months to 2 years
  • Pot life: 2-5 minutes
  • Cure time: 10-15 minutes

Designing the Mold

I decided on creating a star. Although somewhat basic-looking, I’ve never tried making a star in Fusion 360, and I knew using the points on the side would be physically challenging to work with.
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After creating a star, I sketched a surrounding square. I extruded both 1/10 of an inche and extruded the surrounding material half an inch. Albeit small, this would be fairly easy to handle, with less room for error.
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Printing the Mold

This was a straightforward process with no main issues. I simply exported and printed the design.
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Casting

I poured the Part A and Part B liquid rubber into the 3D printing. 24 hours later, I observed that the cast cured and turned into a somewhat flexible shape.
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I dealt with the issue of having to use the point of a scissors to pry it out, however, it became much easier once I extricated the first side from the mold. Since I used a rigid mold, the cast needed to be fairly soft.
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Post-Processing

As the layer lines of the 3D print were still showing, I needed to post-process the mold using XLA and re-cast with the smoother surface.

Re-Molding Plan

I decided that, since I understood the procedure here and knew my issue was just the resin I used, I would switch over to my final project. I talked to Mrs. Morrow, and she confirmed that I can 3D print and post-process the molds for the lake and bunkers.

Design

I took measurements for each hole using a ruler. Since the molds use tension, I would round up and add half an inch to each measurement. The lake is much too large for one print, so I will be attaching them with a joint.

Bunkers: - 5.54.25 - 3.252.5 - 4*5

Lake: - 20*9.5

Reflection

While molding and casting is a generally tedious process, it produces a quick and smooth result. I also found no major issues in either molding or casting. Since I intend to mold containers for the lakes and projects in my final project once I establish the proper dimensions, this introduced me to the specific process. I learned that I would need to 3D print a box around the container, with the container itself being empty. I will need to experiment and research a bit more to find logistics and previously used methods.

Group Work

Positives

I have never tried curing the resin from a 3D design, and the products are quite versatile. The main perk of this week was having another tool to work with.

Negatives

The logistics, datasheets, and wait time in order to find the products. Preventing layer lines requires often difficult measures.

Takeaways

Lessons

  • A soft cast belongs in a hard mold and vice versa.
  • There are multiple ways to make a mold, mainly printing and milling.
  • Pour the resin into a tray or other established space for molding. Do not do so in a random storage basket (you know who you are).

Last update: June 2, 2025