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11. Molding and Casting

This week :

group assignment: review the safety data sheets for each of your molding and casting materials, then make and compare test casts with each of them

individual assignment: design a mold around the stock and tooling that you’ll be using, mill it (rough cut + (at least) three-axis finish cut), and use it to cast parts

Files to download:

Ramadan Mold STL

materials available in our lab:

Material Category Series Supplier
OOMOO™ 30 Silicone Rubber-Tin Cure OOMOO™ Smooth-on
OOMOO™ 25 Silicone Rubber-Tin Cure OOMOO™ Smooth-on
Mold Max™ 60 Silicone Rubber-Tin Cure Mold Max™ Smooth-on
SORTA-Clear™ 18 Silicone Rubber-Platinum Cure SORTA-Clear™ Smooth-on
Smooth-Cast® 305 Urethane Resins Smooth-Cast® Smooth-on

In our lab we just have [Sorta-Clear] because Oomoo 30/25 is expired

Below I will put more details about Sorta-Clear. Which, I will use it in this week:

Technical datasheet
Safety datasheet
Food safety technical datasheet


Before you begin, pre-mix Part B thoroughly.

After dispensing the required amounts of Parts A and B into mixing container, mix thoroughly for 3 minutes making sure that you scrape the sides and bottom of the mixing container several times.

After mixing parts A and B, vacuum degassing is recommended to eliminate any entrapped air.

Vacuum material for 2-3 minutes (29 inches of mercury), making sure that you leave enough room in container for product volume expansion.


For best results, pour your mixture in a single spot at the lowest point of the containment field.

Let the rubber seek its level up and over the model.

A uniform flow will help minimize entrapped air.

The liquid rubber should level off at least 1/2” (1.3 cm) over the highest point of the model surface.


Allow the material to cure fully at room temperature (73°F / 23°C) before demolding.

SORTA-Clear™ 18 cures in 24 hours.

Do not cure rubber where temperature is less than 65°F / 18°C.

Time to demold can be reduced with mild heat.

important : Rubber will darken considerably when exposed to heat.

Note : Allow mold to cool to room temperature before handling.

Smooth-On’s Plat Cat™ platinum silicone accelerator can also be used to accelerate Sorta-Clear


This week I have designed and mold a “dates” and “Ramadan Stamp”. I made them especially because we, as muslims, we have a month in which we fast, and one of our foods is dates.

Machinable Wax:

In the lab we have 3 sizes of machinable wax (dimensions in cm). This will be used to mill the positive mold of the final product.

For me I have choose 15x15x7.6(cm)

CAD Design with SolidWorks:

I designed two models (Ramadan text, date) and put them inside the wax box then export them as stl

Working with Vcarve:

Firstly, I uploaded the STL file that I have designed it in Solidowks Note: In Vcarce you have to go to Importthen upload the stl .You can’t with open files

Machine jobs:

Type Tool
1-Rhough (for cut the shape) 1/8” lat mill up cut
2-Finish 1 (post processing) 1/16” flat mill up cut
3- Finish 2 (post processing) 1/16” pull nose


Mold Frame:

for fixing the box I have cut 4 pieces of wood and drilling it with 35 degrees on the board.



The image aboce shown me while cleaning the box.

Problems and solutions

when I finish cutting I figured out the stamp is need more cut in depth around 5mm. I made pocket job in Vcarve to do it.

Hero shoot!!

material preparing:

1:10 ratio of A & B sorta-Clear:

274.2 of A

27.4 of B

Hero Shoot!!

While molding:

Hero shoot!!


After finishing the positve wax I started make the negative mold with glue in the dark molding

note: I added some blue color of solid ink with the glue in the dark mold

Hero Shoot

In addition I made a chocolate molding for the date and Ramadan text. I have purred the hot chocolate on the mold then I put in the freezer.

Hero Shoot!

Comparison between SORTA-Clear™ 18 /chocolate & Glue in the dark:


  • it can be ready to eat as a solid part after 1h in the freezer
  • easy to cast
  • no bubbles when Casting
  • can be eaten

SORTA-Clear™ 18::

  • 1-2 days to be ready for removing in warm weather
  • maybe you will see some bubbles
  • more solid than chocolate
  • some heating you will see when casting

Glue in the dark:

  • 1-2 days to be ready for removing in warm weather
  • maybe you will see some bubbles
  • some heating you will see when casting
  • can be a visible in the dark

Last update: July 2, 2021