Molding and casting
Hero Shot
Summary
This assignment gave me full exposure to the end-to-end workflow of designing, molding, casting, and finishing a complex part. I learned the technical and safety aspects of each step, along with troubleshooting (e.g., stuck wax walls). The final result was a high-quality two-part molded plastic donut shape, showcasing precise geometry and surface smoothness
The group assignment Page :
Work Process Detail
1. Group Work: Material Exploration and Safety
- Gathered and tested 8 types of silicones and liquid plastics available in the lab.
- Created a comparison table summarizing material specifications and best-use recommendations.
- Recorded differences in properties: mix ratio, pot life, cure time, color, and typical use cases.
| Material Name | Type | Mix Ratio | Pot Life | Cure Time | Color | Special Properties |
|---|---|---|---|---|---|---|
| Smooth-Cast 305 ✅ | Liquid Plastic | 1A:1B by Volume | 7 min | 30 min | White | Fast setting, good for detail casting |
| Smooth-Cast 326 ✅ | Liquid Plastic | 1A:1B by Volume | 7 min | 60 min | Off-White | Color-match, slower set for large casts |
| Dragon Skin 10 Medium ✅ | Silicone Rubber | 1A:1B by Volume or Weight | 20 min | 5 hours | Translucent/Purple | Very flexible, highly tear-resistant |
| Sorta-Clear 18✅ | Silicone Rubber | 100A:10B by Weight | 60 min | 24 hours | Clear | Skin-safe, translucent, needs vacuum degassing |
| Mold Max 60 ✅ | Silicone Rubber | 100A:3B by Weight | 40 min | 24 hours | Pink | High heat resistance (up to 560°F/294°C) |
| UNITED SAT Silicon Rubber✅ | Silicone Rubber | Not specified | Not specified | Not specified | Likely White/Clear | Likely basic molding silicone, general use, no detailed spec available |
| Ecoflex 00-30 ✅ | Platinum Silicone Rubber | 1A:1B by Weight | 45 min | 4 hours | Translucent | Extremely soft, stretchy, skin-safe |
| OOMOO 25 ✅ | Tin Silicone Rubber | 1A:1B by Volume | 15 min | 75 min | Blue | Easy to use, flexible, no degassing needed |
| Hydro-Stone Super X ✅ | Gypsum Cement | Water mix (depends on use) | N/A | 17–20 min | White | Very strong gypsum cement, durable |
| Ultimate Drystone ✅ | Casting Media (Gypsum) | Water mix (specific ratio) | N/A | 17–20 min | White | Ultra-hard, lightweight gypsum |
Safety and Technical Datasheets
https://fabacademy.org/2020/labs/techworks/students/aziz-wadi/assignments/week16/
Each material used is accompanied by a technical and safety datasheet. The technical datasheet provides important information such as material specifications, recommended processing methods, and operational guidelines. The safety datasheet outlines potential hazards, safety precautions, and risk levels associated with handling the material.
For example, the following risks are listed in the safety datasheet of Smooth-Cast® 305.
And also, the following first aid measures are listed in the safety datasheet for the same material.
In the technical datasheet information about working on the material could be found. For example, for OOMOO™ 25 the following guidelines are listed (in addition to safety ticket!).
- Learned how to safely operate the vacuum pump and compressor, including checking PSI levels and oil levels before use.
https://www.smooth-on.com/products/vacuum-chamber/
2. Material Preparation and Curing
- Divided materials between team members for individual trials (I tested 4 materials).
- Poured, vacuumed, and cured samples over 24 hours.
- Results were shared and analyzed to understand surface quality, curing behavior, and ease of demolding.
3. Individual Assignment: Design and Manufacture of a Two-Part Mold
3.1. Design Phase
- Designed a two-part mold with a donut cavity using Fusion 360.
- Prepared CAM setup in Fusion, selecting proper tool paths and tool types.
3.2. CNC Machining Phase
- Used ShopBot CNC to cut the mold from wax:
- Roughing pass with 6 mm flat-end mill.
- Finishing pass with tapered ball mill for detailed surfaces.
- Adaptive cleaning, flat finishing, and scallop finishing were applied for a smooth surface.
- Problem: After machining, manually cleaned up small stuck pieces with a sharp blade.
3.3. Silicone Mold Making
- Applied Vaseline as mold release agent.
- Measured and poured 103 ml of silicone into the mold.
- Used vacuum chamber to degas bubbles before final curing.
- Achieved a high-quality, smooth silicone mold.
4. Casting the Final Part
- Prepared Smooth-Cast 305 liquid plastic:
- Carefully measured and mixed parts A and B.
- Poured into the closed silicone mold, secured with rubber bands.
- Allowed 1 hour curing time.
- Opened the mold and removed the finished part, which had a smooth, round surface with excellent detail.
Learning Outcome
This week gave me a deep understanding of the molding and casting process, covering both group and individual work. I learned the safety considerations of working with silicones and resins, the properties of different molding materials, and the practical techniques of vacuum degassing and CNC mold creation. I also developed hands-on experience in designing, fabricating, and casting a two-part mold using a combination of digital design, CNC machining, and molding techniques. I understood the critical importance of material properties, mix ratios, pot life, cure times, and surface finishing techniques to achieve professional-quality results.