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14. Molding ＆Casting

Group Work photo

  • Group assignment:
  • Review the safety data sheets for each of your molding and casting materials
  • Make and compare test casts with each of them

  • Compare printing vs milling molds

  • 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.

Materials

We prepared following three materials for our Molding & Casting work.
Ecoflex
 Mold Star 16
* Smooth-Cast 300
Materials

Safety Data Sheets

Here under are the Safety Data Sheets of Mold Star 16 and Ecoflex.
Safety Data Sheet

Here under are the Safety Data Sheets of Smooth Cast 300.
SDS of smooth cast 300-1
SDS of smooth cast 300-2

Here under is the table summarize by Chat GPT regarding above three materials.

Item Ecoflex™ 00‑30 Mold Star™ 16 FAST Smooth‑Cast™ 300
Product page Smooth‑On Ecoflex 00‑30 product page 1 Smooth‑On Mold Star 16 FAST product page 2 Smooth‑On Smooth‑Cast 300 product page 3
Technical Bulletin (TB) Ecoflex Series TB (ECOFLEX_SERIES_TB.pdf) 4 Mold Star 15/16/30 TB (MOLD_STAR_15_16_30_TB.pdf) 5 Smooth‑Cast 300 series TB (Smooth‑Cast_300q,_300,_305___310.pdf) 6
Material type Platinum‑cure (addition‑cure) silicone rubber, super‑soft 14 Platinum‑cure (addition‑cure) silicone mold rubber 25 Polyurethane casting resin, bright white, ultra‑low viscosity 36
Mix ratio 1A:1B by weight or volume 14 1A:1B by volume 25 1A:1B by volume or 100A:90B by weight 36
Pot life (23°C) 45 min 41 6 min 25 3 min 63
Cure / demold time (23°C) 4 hr 41 30 min 25 10 min 63
Shore hardness Shore 00‑30 41 Shore A 16 25 Shore D 70 63
Key characteristics Very soft/strong/stretchy; certified skin safe (cured) 14 Low viscosity; vacuum degassing usually not required; tear‑resistant; low shrink; heat resistant to 232°C 25 Virtually bubble‑free; no vacuum degassing necessary; cured parts tough/machinable/paintable; moisture & mild‑solvent resistant 36
Process memo (handling) Cure inhibition possible; vinyl gloves recommended (latex inhibits cure) 14 Will not cure against sulfur surfaces; vinyl gloves recommended (latex inhibits cure) 25 Moisture sensitive; keep tools/containers dry; use release agent for most molds; ventilate & wear PPE 36
SDS (Part A) FG‑823A (Part A: Ecoflex series & many silicone elastomers) 7 FG‑823A (Part A: Mold Star series & many silicone elastomers) 7 FG‑4021A (Part A: Smooth‑Cast 300/300Q/305/310 etc.) 8
SDS (Part A) classification summary Not classified / not hazardous (CLP: mixture not hazardous) 7 Not classified / not hazardous (CLP: mixture not hazardous) 7 Classified as hazardous (OSHA HCS 2024): multiple hazard categories apply 8
Skin corrosion/irritation Not classified (mixture not hazardous) 7 Not classified (mixture not hazardous) 7 Category 2 8
Skin sensitization Not classified (mixture not hazardous) 7 Not classified (mixture not hazardous) 7 Category 1 8
Eye damage/irritation Not classified (mixture not hazardous) 7 Not classified (mixture not hazardous) 7 Serious eye damage/eye irritation Category 2A 8
Acute toxicity (inhalation) Not classified (mixture not hazardous) 7 Not classified (mixture not hazardous) 7 Category 4 8
Respiratory sensitization Not classified (mixture not hazardous) 7 Not classified (mixture not hazardous) 7 Category 1 8
Carcinogenicity Not classified (mixture not hazardous) 7 Not classified (mixture not hazardous) 7 Category 2 8
STOT (single exposure) Not classified (mixture not hazardous) 7 Not classified (mixture not hazardous) 7 Category 3 8
STOT (repeated exposure) Not classified (mixture not hazardous) 7 Not classified (mixture not hazardous) 7 Category 2 8

Notes (common reasons values may differ)

  • Pot life and cure/demold time become shorter as temperature increases. The values shown here are based on 23°C.
  • (For resins such as Smooth‑Cast 300) The material is moisture sensitive, and storage, measuring, and mixing conditions can affect bubbling and curing behavior.
  • (For addition‑cure / platinum‑cure silicones such as Ecoflex and Mold Star) Cure inhibition can cause failures (e.g., latex, sulfur‑containing clays, etc.).

Here under are the information pages of above mentioned materials;

Ecoflex 00-30 product page: https://www.smooth-on.com/products/ecoflex-00-30/ 1

Ecoflex Series Technical Bulletin (PDF): https://www.smooth-on.com/tb/files/ECOFLEX_SERIES_TB.pdf 4

Mold Star 16 FAST product page: https://www.smooth-on.com/products/mold-star-16-fast/ 2

Mold Star 15/16/30 Technical Bulletin (PDF): https://www.smooth-on.com/tb/files/MOLD_STAR_15_16_30_TB.pdf 5

Smooth-Cast 300 product page: https://www.smooth-on.com/products/smooth-cast-300/ 3

Smooth-Cast 300 series Technical Bulletin (PDF): https://www.smooth-on.com/tb/files/Smooth-Cast_300q,_300,_305___310.pdf 6

SDS FG-823A (Part A, silicone elastomers; EU CLP format PDF): https://www.smooth-on.com/sds/10003097-10003114.pdf 7

SDS FG-4021A (Part A, Smooth-Cast 300 etc.; OSHA HCS 2024 format PDF): https://www.smooth-on.com/sds/10003074-10003941.pdf 8

Preparation for the work

Cups, plastic bags, chopsticks, towels were prepared.
tools

Cover whole surface of the table to work on.
covering table

Prepare all the materials on the table.
preparation on the table

Cut the PET Bottle into two pieces.
cups for the testcups for the test

We tried following three materials
3 materials

Ecoflex

Pour 50g of Ecoflex A in a cup
Ecoflex A
Pour 50g of Ecoflex B in a cup
Ecoflex B

Smooth‑On Mold Star 16 FAST

Pour 50g of Mold Star 16 A in a cup
Mold Star 16 A
Pour 50g of Mold Star 16 B in a cup
Mold Star 16 B
Mold Star 16 B
mixing Mold Star 16

Smooth-Cast 300

Cas300
Since Smooth-Cast 300 has very low viscosity, it is better to use a stick to pour for gradually pouring into the cup.
poring Cas300
Pouring Cast300

10G of A
10G of B

After mixing all, place them on a flat table.
After mixing
Top view

Taking off the material by breaking the PET cup
taking off the material

Ecoflex Casted result
ecoflex

Used Mold Star 16 casted result
Mold Star 16 used one
Cross Section of casted Used Mold Star 16 seems OK
cross section

New Mold Star 16 casted result
Mold Star 16 new

Smooth-Cast 300 casted result
Smooth-Cast 300

This failed because a large amount of bubbles were generated during the reaction.

Upon rereading the SDS, I realized I had overlooked the instruction to shake the container well before use. So, on my second attempt, I first shook the container to mix the solution inside.

The two liquids were mixed and stirred briefly, then left for a while until the air bubbles escaped and the reaction began.

Smooth-Cast 300 retry

Successful Smooth-Cast 300

Smooth-Cast 300 retry　2

All cast materials All casting