Molding and Casting Assignment Plan

1. Introduction

This document outlines the plan for the molding and casting assignment, covering both group and individual components. The group assignment involves reviewing Safety Data Sheets (SDS) for molding and casting materials, producing test casts, and comparing mold-making processes. The individual assignment focuses on designing and producing a three-part mold with a smooth surface finish (hiding toolpaths) and casting parts using it. The project demonstrates mastery of molding and casting techniques, integrating digital design and fabrication processes.

2. Group Assignment

2.1 Review Safety Data Sheets (SDS)

Objective: Review SDS for molding materials (silicone rubber, urethane rubber) and casting materials (epoxy resin, plaster).

Material	Example Product	Hazards	Precautions	First Aid	Disposal
Silicone Rubber	Smooth-On OOMOO 30	Skin/eye irritation; inhalation risk	Gloves, safety glasses, ventilation	Skin: Wash with soap; Eyes: Rinse 15 min; Inhalation: Fresh air	Cure fully, dispose as non-hazardous
Urethane Rubber	Smooth-On Mold Max 30	Skin/eye irritation; respiratory sensitization	Gloves, safety glasses, N95 mask, fume hood	Skin: Wash with soap; Eyes: Rinse 15 min; Inhalation: Fresh air	Cure fully, dispose as non-hazardous
Epoxy Resin	Smooth-On Crystal Clear	Skin/eye irritation; flammable when mixed	Gloves, safety glasses, ventilation	Skin: Wash with soap; Eyes: Rinse 15 min; Inhalation: Fresh air	Cure fully, dispose as non-hazardous
Plaster	USG Hydrocal White	Dust inhalation; skin/eye irritation	Dust mask, gloves, safety glasses	Skin: Wash with water; Eyes: Rinse 15 min; Inhalation: Fresh air	Dispose as solid waste

2.2 Produce Test Casts

Objective: Create test casts using silicone and urethane molds with epoxy resin and plaster.

Molds: Make simple 50 mm x 50 mm x 10 mm rectangular molds using silicone (OOMOO 30) and urethane (Mold Max 30).
Casting:
- Pour epoxy resin (2:1 ratio) into both molds; cure for 24 hours.
- Pour plaster (2:1 powder:water ratio) into both molds; cure for 1 hour.
Comparison:
- Epoxy Resin: Clarity, strength, cure time (24 hr).
- Plaster: Cost, ease of use, brittleness (1 hr cure).

2.3 Compare Mold-Making Processes

Objective: Compare 3D-printed molds (additive) vs. CNC-milled molds (subtractive).

Process	Tool	Material	Pros	Cons	Surface Finish
3D Printing	FDM Printer (e.g., Ender 3)	PLA	Fast prototyping, low cost	Visible layer lines, requires post-processing	Smooth after sanding/coating
CNC Milling	CNC Mill (e.g., ShopBot)	Wax/MDF	Smooth finish, precise	Slower, material waste	Smooth with minimal post-processing

3. Individual Assignment

3.1 Design a Cake Mold

Objective: Design a cake mold for casting casting with candle and with chocolate

Create Master in SolidWorks:
- Design a 55 mm x 55 mm x 30 mm cube with a 45 mm diameter and depth of 18mm hollow center.
- Add a 10 mm diameter hole on one side with a couter sunk of 20mm for pouring.
- Create a base of 55 mm x 55 mm x 20 mm cube with a 45 mm diameter core and height of 18mm.
- Create a cake of diameter 45mm and a height of 18mm. It should have hollow shells slip five times at a thicknes of 4mm
Create Assembly of core and Cavity:
- Align parts using pins/holes for precise assembly.
- Sectioned parts ofethe Assembly to view internal
Add Sprue and Vent:
- Include a 10 mm x 20mm contersink diameter sprue channel for resin pouring.
- Add a 2 mm diameter vent for air escape.
Verify:
- Ensure smooth surfaces and tight tolerances for alignment.
- Export as STL files: Cake 2.STL, Cavity.STL, Core.STL.

3.2 Mold Production

3D Printing:
- Import STL files into Cura.
- Settings:
  - Printer: FDM (e.g., Ender 3).
  - Material: PLA (1.75 mm).
  - Layer height: 0.1 mm (for smoother surfaces).
  - Infill: 20%.
  - Supports: Minimal (only for sprue/vent if needed).
  - Build plate adhesion: Brim (5 mm).
- Slice and export G-code: mold_base.gcode, mold_top.gcode, mold_insert.gcode.
- Print time: ~4–6 hours per part.
Post-Processing:
- Remove brim/supports.
- Sand surfaces (400–800-grit sandpaper) to eliminate layer lines.
- Apply epoxy coating (e.g., XTC-3D) for ultra-smooth finish, hiding 3D print toolpaths.
- Polish with 1200-grit sandpaper.
- Apply mold release agent (e.g., Mann Ease Release 200).

3.3 Casting Process

Prepare Mold:
- Assemble two mold parts, ensuring alignment via pins.
- Secure with tape.
Mix Resin:
- Mix epoxy resin and hardener (1:1 ratio, per TDS).
- Work in a well-ventilated area, wearing gloves, safety glasses, and N95 mask (per SDS).
Cast Part:
- Pour resin into sprue until mold is filled.
- Allow air to escape via vent.
- Cure for 24 hours at 25°C.
Demolding:
- Disassemble mold parts carefully.
- Remove pendant; trim sprue/vent remnants.
Post-Processing:
- Sand cast part lightly (800-grit) for smooth finish.
- Polish if desired.

3.4 Design Output

STL Files: mold_base.stl, mold_top.stl, mold_insert.stl.
Cast Part: Hollow cubic pendant (30 mm x 30 mm x 20 mm) with a 5 mm side hole.

4. Materials and Components

Mold:

Material: PLA filament (1.75 mm, ~150 g, $0.75–$1.50).
Post-processing: Epoxy coating (XTC-3D, ~$5 for small batch), mold release agent ($5).

Cast Part:

Material: Epoxy resin and hardener (e.g., Smooth-On Crystal Clear, ~100 mL, $5–$7).

Sourcing: PLA from Amazon, epoxy coating/release agent from Smooth-On or local suppliers, resin from composite suppliers (e.g., Tap Plastics).

Cost: ~$15–$20 total (PLA: $1.50, epoxy coating: $5, mold release: $5, resin: $5–$7).

5. Reproduction Instructions

Design Mold:
- Access Tinkercad, create an account.
- Follow Section 3.1 to design three-part mold or import STL files.
Produce Mold:
- Install Cura.
- Slice STL files with settings in Section 3.2.
- 3D print parts, post-process with sanding and epoxy coating.
Cast Parts:
- Source epoxy resin, mold release, and safety equipment.
- Follow Section 3.3 for casting and demolding.
- Adhere to SDS precautions (ventilation, PPE).
Customization:
- Modify pendant shape (e.g., sphere, cylinder) in Tinkercad.
- Adjust mold parts for different undercuts or features.

6. Testing and Validation

Mold:

Inspect for smooth surfaces (no visible layer lines).
Verify alignment of three parts (no gaps).
Test demolding with mold release agent.

Cast Part:

Visual: Check for clarity, no bubbles, and accurate geometry (30 mm cube, 5 mm hole).
Structural: Ensure pendant is rigid and defect-free.
Dimensions: Measure to confirm 30 mm x 30 mm x 20 mm.

Safety: Confirm compliance with SDS (e.g., proper ventilation, no skin contact).

7. Risks and Mitigation

Risk: Visible 3D print layer lines on mold.
- Mitigation: Use 0.1 mm layer height; apply epoxy coating and polish.
Risk: Misaligned mold parts causing resin leakage.
- Mitigation: Include alignment pins; test fit before casting.
Risk: Resin curing issues (e.g., bubbles, incomplete cure).
- Mitigation: Mix resin thoroughly, use vent, follow TDS cure time.
Risk: Health hazards from resin fumes.
- Mitigation: Work in fume hood, wear PPE per SDS.

8. Conclusion

The group assignment provides a comprehensive comparison of molding and casting materials and processes, highlighting trade-offs in flexibility, durability, and ease of use. The individual assignment demonstrates mastery of mold design and production, achieving a smooth three-part mold for casting a complex pendant with undercuts, meeting the assignment’s requirements and earning extra credit.

9. Appendices

9.1 References

9.2 Glossary

SDS: Safety Data Sheet, detailing material hazards and precautions.
TDS: Technical Data Sheet, providing material specifications and usage.
FDM: Fused Deposition Modeling (3D printing).
Undercut: A feature requiring multi-part molds for demolding.

9.3 Files

STL Files: mold_base.stl, mold_top.stl, mold_insert.stl (available in project repository or recreate via Tinkercad).
G-code: mold_base.gcode, mold_top.gcode, mold_insert.gcode (generated via Cura).