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Week 14 Modeling and Casting

Group assignment

Week 14 Chaihuo group assignment.

The link to our group work:

https://fabacademy.org/2026/labs/chaihuo/docs/week14/chaihuo/week14_group_assignment

Individual assignment

I used modeling and casting to make an ancient-style coin, as shown below. I think it is a fun idea.

Step 1 — Onshape modeling

Step 1: Use Onshape to make a similar sample, as shown below.

Step 1.1

I used a circle and rectangle with extrude, as shown below. I set the thickness to 5 mm and the diameter to 50 mm.

Step 1.2

Add the text "FAB LAB" and extrude it by 2 mm.

I got the model below and exported the 3D file.

Design file: Week 14-3D printing.stl

Design file: Part Studio 1 - Part 1.stl

Design file: Fab.svg

Design file: Fab.dxf

Step 2 — 3D printing

Step 2: Print the model with a 3D printer.

Molding

I made a small box to hold the 3D-printed part. I used a waste packaging box and a hot glue gun to add one wall and reduce the space, saving material.

Materials

  • Silicone

  • Silicone curing agent

  • Scale to measure the weight of silicone and curing agent. The weight ratio is 100 (silicone) : 2 (curing agent).

  • Scale

  • Stir stick to mix the silicone and curing agent

  • Release agent

Step 1

Place the 3D-printed coin in the box and spray release agent twice, with a 2-minute gap between sprays. Wait for the release agent to dry.

Step 2

Mix the silicone and curing agent at a ratio of 100:2.

Step 3

Pour the silicone mixture into the box.

Step 4

Wait 24 hours for the silicone to solidify. The result is shown below.

Casting

Materials

  • Epoxy A and B, mixed by weight at a ratio of 3:1.

Step 1

Mix epoxy A and B at a ratio of 3:1.

Step 2

Stir with a stick for 15–20 seconds. The A/B liquid solidifies within 1.5–2 minutes after mixing, so work as quickly as possible.

Step 3

Pour the liquid into the mold.

Step 4

Check back the next day. The cast parts are shown below for comparison.

Reflection

Overall the result is good, but there are some small bubbles. Two steps may be related: 1) mixing and 2) pouring into the mold too quickly.