Week13. Moulding and Casting

Group assignment:

1. Review the safety data sheets for each of your molding and casting materials 2. Make and compare test casts with each of them 3. Compare printing vs milling molds

  Individual assignment:

   Design a mold around the process you’ll be using, produce it with a smooth surface finish, and use it to cast parts.

Group Assigment My Part

Part1. Safety DataSheet Review

Our assignment this time is mainly to use silicone to make molds and then use AB glue for molding to produce the final product.

The first important thing is to review the safety data sheet as follows:

• Safety Data Sheet of Silicone
• Safety Data Sheet of A&B Glue

Safety Precautions Summary：

When handling silicone molds and AB glue, the following safety precautions should be kept in mind:
1. Work in a well-ventilated area to avoid inhaling harmful vapors.
2. Wear appropriate protective equipment such as gloves and safety goggles to prevent skin contact and eye irritation.
3. Do not mix or use the products beyond their recommended usage and expiry dates.
4. Keep the products away from heat sources and open flames as they may be flammable.
5. In case of skin contact, wash the affected area immediately with plenty of water and seek medical advice if irritation persists.
6. If ingested accidentally, seek medical attention immediately and show the Safety Data Sheet to the medical personnel.

Part2. Making and comparing test casts with silicon and AB glue:

- Observing the hardness, I have found that the silicon cast is more flexible and resilient, while the AB glue cast is harder and more brittle. - The curing time has varied significantly. Maybe silicon took several hours to fully cure, while AB glue set within minutes. - Special features have included the transparency of the silicon or the adhesion strength of the AB glue.

Part3. Comparing printing vs milling molds for silicon and AB glue:

- In the case of printing molds, I have discovered that the advantage could be the ability to create complex geometries with high precision. For example, I have seen that one can print a mold with intricate internal channels for a silicon part. - Milling molds have shown me that they might offer better surface finish for certain applications or be more suitable for larger-scale production. Overall, through these experiences, I have gained valuable insights into the properties, handling, and mold-making options for silicon and AB glue, which will greatly assist me in future projects involving these materials.

Individual Assigment

Step1. Design the moulding module

I used fusion360 to design a moulding module to cast a cut rabbit

1. Set up parameters

2. Create the sketch for box bottom

3. Extrude the box bottom

4. Rotate the origin to the back and project the new side of the box

5. Create sketch on the projected face

6. Extrude the back side

7. Repeat step4- 6, project all the other side of the box and create sketch and exturde.

8. Finally, the box is ready!

9. For the bunny, I used a svg image of a bunny and converted to sketch

10. Extrude the Bunny

11. Final view of the mould box

12. 3D print it

13. The mould box！

Step2. Make the silicone mould

1. Prepare to make the mould

2. Weight the mould box

3. Weight the mould box with water

4. Calculate the weight of water and convert to the weight of silicone needed

- Weight of water is : 379.94 - 158.37 = 221.47 - The density ratio of silicone gel to water is 1.1-1.3 - I go with 1.2 and calculated the silicone I needed 265.884g with extra for waste in the box The ratio of the curing agent to the silicone gel is 1:200. So I calculated the weight of the curing agent as 1.32g

5. Weight the silicon and curing agent

6. Mix and stur them for 5 minuts, then pour the silicon into the box

7. Waited 8 hours and get the mould out, it is perfect!

Step3. Use the mould to cast

1. Weight the mould

2. Weight the mould with water

3. Calculate the weight of water and convert to the weight of AB glue needed

- Weight of water is : 322.86 - 268.94 = 53.92 - The AB glue I used are the Epoxy resin AB glue： The A glue is a colorless and transparent viscous liquid with a density of approximately 1.1 - 1.2 g/cm³ The B glue is a transparent or slightly yellowish viscous liquid with a density of approximately 1.0 - 1.1 g/cm³. And the A and B glue needs to be mixed 1:1, so the weight of A or B glue needed is 53.92/2*1.1 = 29.565g

3. Pour in the A glue and B glue and mix them for 1 minuts.

4. Pour mix of AB glue into the mould.

5. The AB glue I used needs to wait for 12 hours, so I put it outside for casting.

6. Finally, I got my cute Rabbit!

Source Files

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