13. Molding and casting

Assignments for week 13:

1. Group Assignment

• review the safety data sheets for each of your molding and casting materials, then make and compare test casts with each of them

• compare mold making processes

2. 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 toolpath, and use it to cast parts extra credit: use more then two mold parts

1. Group Assignment.

Our group Assignment link is here

Learnings outcomes from the group assignment:

The safety precautions and safety equipment usage is most important for the users as some molding materails like polyurethane are toxic and need ventilated working area.User must follow the proper instructions and datasheets of each molding materials before using.The correct mixing of the mold materials with their mixing ratio ensures the quality of mold.

Always use negative mold obtained from parent mold for the final production of mold.The user should follow the setting and curing time to obtain quality molds.

The molds produced from Hydrostone and water is hard compared to the molds of liquid silicone rubber and liquid polyurethene rubber and therefore, it can be casted on silicone mold parts.

2. Individual Assignment.

For this assignment, I designed Molding frame for Bhutanese flag head using Fusion 360 and used Liquid Silicone Rubber LSR-225 and its Catalyst LSR-2 series as the mold making materials.The detailed working processes are below.

1. Design and 3D printing the mold frame.
2. setting and mixing the materials.
3. Silicone pouring.
4. Extraction of mold and finishing.

1. Design and 3D printing the mold frame.

I choosed top plane and and drawn circles and was extruded.

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Then, i selected to split bodies.

Then i have drawn the center rectangle and gave dimensions for outer frame and was extruded.

I sketch another circle at base to pour silicone solution.

I minimized the size and copied the part.

I make projection to join the parts, by extruding for a part and detruding for other part.

I sliced the STL file and 3d printed using Bambu Lab.

2.Mixing the materials.

I had used Liquid Silicone Rubber LSR-225 and Calalyst LSR-2 series as the materials for making my mold.It is the versatile product for making all kinds of molds and it is fast curing.

I had referred about those materials from this source

Specification for Liquid Silicone Rubber LSR-225 with Catalyst LSR-2 series

- Brand: SILOCZEST
- Manufacturer: CHEMZEST ENTERPRISES
- Origin: India
- Type: Two-part liquid silicone rubber (base + - curing agent)
- Color: White
- Hardness (Shore A): 25°A (medium-soft)
- Density: 1.09 g/cm³
- Viscosity (@25°C): 20,000 ± 2,000 cps (low viscosity, easy pouring)
- Fast curing (adjustable with catalyst %)
- Excellent detail reproduction
- High flexibility & tear resistance
- Cost-effective for beginners/professionals
- Can be thickened with THIX additive for brush-on applications.

Before starting, i made sure my working area surface is ventilated with flat and level for evenly distribution of silicone.

I used disposable hand gloves, face mask, disposable plastic apron, disposable plastic cup, stir stick, quick bar clamps, cellotape and weighing machine.

Then, i had clamp the molding frames with help of quick bar clamps.

I had poured 75.5g of Liquid Silicone Rubber LSR-225 in the disposable plastic cup.

For this i added 4 g of Catalyst LSR-2 series to the Liquid Silicone rubber with mixing ratio 100:5 or 5%.

Mixing ratio was 75.5*0.05= 3.775g of Catalyst.

I stir the mixture about 3 minutes.

3. Pouring the silicone mixture.

Without much delay, i had poured the silicone mixture into the mold frame, avoiding to form bubbles.I had to tap it for even distribution to the mold frame. Then, i left it to set for about 12 hours at the safe labelled area.

4. Extraction of the mold and finishing.

I had removed the clamps and tapes and checked if its was set.Then, extracted the mold and cleaned wherever necessary, followed by cleaning my working area.

Bhutanese flag pole mold

My Learning outcomes from this individual assignment.

The mold product obtained from liquid silicone rubber and its catalyst is soft and can be obtained from 3D printed and wax molds.The correct mixing ratio of liquid silicone rubber with its catalyst is 3-5%, i.e 100:5 of mixing ratio.The working area should clean and well labelled for even distribution of the mixture.The curing time should be followed as per their instructions and use of proper personal protectice equipment.

Design files

My mold designed using Fusion 360 is here