Week 14 - Molding and Casting

Face Scanning, Mold Design, 3D Printing and Casting Process

Home Group Assignment Safety Data Sheets Test Casts Printing vs Milling

Group Assignment

The group assignment focused on safety, material behavior, and process comparison for molding and casting. As a team we reviewed the available safety information for each material, made small test casts, and compared three mold-making technologies: CNC milling, TPU 3D printing, and resin 3D printing.

Group Assignment Requirements

Review the safety data sheets for each molding and casting material.
Make and compare test casts with each material.
Compare printing molds versus milling molds.

Group working with molding and casting safety equipment — Group work session with gloves, safety glasses, prepared molds, and separated material containers.

Molding and casting materials arranged for comparison — Materials arranged for testing: Mold Star silicone, local RTV silicone, plaster, resin, and milled molds.

Safety Data Sheet Review

Before mixing or casting, the team reviewed the information available on the containers, labels, technical data, and product safety notes. The review focused on contact risk, ventilation, dust, heat, curing time, chemical residues, and safe disposal. The safest workflow depends on both the material and the technology used to make the mold.

Material	Main Risks	Safety Conditions
TPU filament	Hot nozzle, hot bed, and fumes during printing.	Use the printer in a ventilated area, avoid touching hot parts, and wait before removing parts.
PLA filament	Hot surfaces and minor fumes during printing.	Use normal 3D printer safety procedures and keep the work area clear.
Photopolymer resin	Skin irritation, eye irritation, odor, uncured chemical residue, and UV exposure during curing.	Use nitrile gloves, eye protection, ventilation, covered resin handling, washing, UV post-curing, and no direct skin contact.
Candle wax / paraffin	Burns from melted material and fire risk if overheated.	Heat slowly, avoid open flame, use thermal gloves, and pour carefully.
Plaster	Dust inhalation during mixing and heat during curing.	Use a mask when mixing powder, avoid breathing dust, and clean spills immediately.
Silicone rubber	Skin contact with uncured silicone, catalyst exposure, contamination, and incomplete curing if mixed incorrectly.	Use gloves, safety glasses, clean cups, accurate ratios, ventilation, and respect pot life and curing time.
MDF for CNC milling	Fine dust, machine movement, cutting tools, and noise.	Use dust extraction, mask, eye protection, hearing protection, and keep hands away from the toolpath.

Material Safety Evidence

Water washable resin packaging — Water washable resin was reviewed as a chemical material, not as a normal plastic. Gloves, ventilation, controlled cleaning, and UV post-curing were required.

Water washable resin technical data — The resin technical data helped identify expected hardness, strength, exposure settings, and the need to avoid uncured residues.

Mold Star silicone part A — Mold Star Part A was reviewed before mixing. The product label indicates a 1A:1B mix ratio by volume or weight and requires both parts to be stirred thoroughly.

Mold Star silicone part B — Mold Star Part B completed the two-part silicone system. We kept the containers separated until the mold box and tools were ready.

RTV2 T25 silicone component A — The local RTV2 T25 silicone was also reviewed. This material required catalyst control and careful mixing to avoid soft or partially cured zones.

Local silicone rubber container — Local silicone rubber was compared with Mold Star to evaluate availability, handling, flexibility, and curing behavior.

Test Cast Comparison

Different casting materials were tested to compare handling, surface finish, demolding, detail reproduction, and safety requirements. The same face geometry helped compare how each material reacted with different mold fabrication technologies.

Test Cast	Behavior	Result
Wax / paraffin	Easy to melt and pour, but requires heat control.	Useful for quick tests and visual validation of the face shape.
Plaster	Easy to mix, captures details, and cures into a rigid piece.	Good low-cost option, but powder handling requires respiratory protection.
Silicone rubber	Flexible after curing, reusable, and useful for demolding complex shapes.	Best option for a reusable flexible negative mold from the CNC master, but sensitive to mixing ratio.
Resin printed mold	High detail and smooth surface, but needs chemical safety controls.	Best surface definition, with stricter PPE and post-curing requirements.

Molding and casting materials prepared for testing — Material test setup with silicone, plaster, CNC molds, and group safety equipment.

Resin tray and flexible printed mold during handling — Resin workflow test used to compare surface finish, handling, and cleaning requirements.

Silicone component poured into mixing container — Silicone test preparation: components were poured into a clean cup while using gloves.

Silicone rubber measured and mixed — The silicone mixture was stirred carefully to reduce unmixed zones and improve curing.

Video record of the silicone preparation and material handling during the group test.

Group preparing silicone for test casting — Group silicone preparation with PPE and the CNC mold bases ready for comparison.

Printing vs Milling Molds

Three mold fabrication technologies were compared: CNC milling, TPU 3D printing, and resin 3D printing. Each method produced a different type of mold and required different safety precautions.

1. CNC Milling Mold

CNC milling was used to create a rigid MDF master mold from the scanned face. This method produced a strong base and allowed the silicone rubber mold to be cast from a physical master. Its main safety concerns were machine operation, dust extraction, cutting tools, and eye protection.

2. TPU Printed Mold

TPU printing created flexible mold parts. Its advantage was easier demolding because the mold could deform slightly. The limitation was surface texture from FFF layer lines, which can transfer to the cast if the printed surface is not sealed or post-processed.

3. Resin Printed Mold

Resin printing provided the best surface definition and captured small details more clearly. However, it required stricter chemical safety: nitrile gloves, mask, ventilation, cleaning of uncured resin, and UV post-curing.

Technology	Strength	Limitation	Safety Emphasis
CNC milling	Rigid master mold and good structural stability.	Requires dust management and machine setup.	Dust extraction, eye protection, hearing protection, safe machine operation.
TPU printing	Flexible mold and easier demolding.	Visible layer lines and slower printing.	Hot nozzle/bed safety and ventilation.
Resin printing	High detail and smooth finish.	Requires cleaning, supports, and UV post-curing.	Nitrile gloves, mask, ventilation, no skin contact with uncured resin.

CNC milled molds and casting materials — CNC milling creates rigid base molds, but requires dust and machine safety controls.

TPU printing process — TPU printing creates flexible molds for easier demolding, but the layer texture must be considered.

Resin mold removed from build plate with gloves — Resin printing provides high detail, but every uncured surface was handled with gloves and tools.

Group preparing silicone with CNC base molds — Final comparison setup: rigid CNC base molds and flexible silicone preparation.

Resin vat filled on printer — Resin workflow required controlling the vat, avoiding spills, and cleaning liquid residues before curing.

Resin printed mold draining after printing — Resin molds had to drain and be cleaned before post-curing, especially when geometry trapped liquid resin.

Video evidence of resin mold handling and removal using gloves and tools.

Video evidence of the TPU printed mold process and flexible mold fabrication.

Group Assignment Conclusion

The comparison showed that no single molding method is best for every case. CNC milling is useful for producing a strong master mold, TPU printing is useful for flexible molds, and resin printing is the best option when surface detail is the priority. Safety conditions change significantly between processes: CNC requires machine and dust safety, TPU requires 3D printer heat safety, and resin requires chemical protection and post-curing.

The main lesson from the group test was that material choice and mold-making technology must be decided together. A high-detail resin mold is not automatically better if the available safety workflow is weak. A CNC master is more stable for silicone casting, while TPU can help with demolding when flexibility is more important than surface finish.