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.

Milled Mold vs 3D Printed Mold

The group compared two mold-making approaches used during the casting workflow: a mold produced by CNC milling and molds produced with 3D printing. The comparison focused on surface finish, fabrication time, demolding, material limitations, and the type of geometry each method can reproduce.

Mold Type	Pros	Cons	Best Use Case
CNC milled mold	Strong and dimensionally stable mold; good for flat bases and rigid master molds; surface can be improved with toolpath settings, sanding, and sealing.	Generates dust and requires extraction; needs machine setup and safe tool handling; internal corners are limited by tool diameter; machining time can increase with fine details.	Best when the group needs a rigid mold, a reusable master, or a controlled surface made from MDF, wax, foam, or machinable board.
3D printed mold	Faster to iterate from a digital model; can create complex shapes without CNC tool access; flexible materials can help demolding; useful for quick tests and custom geometries.	Layer lines can transfer to the cast; material may deform with heat or pressure; resin printing requires chemical safety; FDM prints may need sealing to prevent leaks.	Best for quick prototypes, organic shapes, flexible molds, or geometries that are hard to machine.
Result comparison	CNC produced a cleaner rigid reference for the cat-face mold, while 3D printing allowed a direct comparison of printed texture and demolding behavior.	Neither method is automatically better: CNC requires machine safety and setup, while 3D printing requires post-processing and attention to surface texture.	Choose the method according to the casting material, desired detail, mold flexibility, and available equipment.

CNC milling a cat face mold — CNC milling process: the rigid mold is cut from a block material, producing dust and requiring machine safety controls.

CNC milled cat mold compared with a 3D printed mold — Side-by-side comparison: the milled mold and the printed mold show different surface qualities and different preparation requirements.

3D printed mold with cast result on the side — 3D printed mold example: printed walls and layers are visible, which can affect the final cast surface.

3D printed face mold and casting result — Printed face mold and cast result: useful for quick testing, but the printed texture and demolding strategy must be considered.