.Molding and casting.

For this week we compare we explore a new form of prototyping!!

Molding

Molding and casting are complementary manufacturing processes used to create identical objects by filling a hollow cavity (mold) with liquid material that solidifies.

A widely very commonly used molding process that we see all around us is Injection molding

Injection molding

Injection moulding is a high-volume manufacturing process that produces plastic parts by injecting molten material into a metal mold cavity under high pressure.

It is ideal for creating complex, consistent parts, such as bottles, toys, and automotive components.

For this week I decided to explore silicon molds and a 2 part mold

Silicone: The Chill Shape-Shifter

Silicone (not to be confused with silicon, the semiconductor cousin that runs your laptop) is a flexible, rubber-like material made from silicon, oxygen, carbon, and hydrogen. Think of it as the material equivalent of someone who can fit into any social group effortlessly — it adapts, behaves, and performs without drama.

In simple terms: Silicone is a liquid (or paste) that turns into flexible rubber when cured.

Why Silicone is Great for Molding

Flexibility: It bends and stretches, so you can remove complex shapes without breaking anything (including your patience).
Detail Capture: It picks up extremely fine details — textures, engravings, even fingerprints if you're not careful.
Non-Stick Nature: Most materials don’t bond to silicone, which means easy demolding and fewer regrets.
Durability: It survives multiple casts without degrading quickly — a reliable workhorse.
Heat Resistance: It can handle high temperatures, so it works with a wide range of casting materials.

Where It Shines

Silicone molds are used for everything from industrial prototyping to chocolate making. Whether you're casting resin parts, wax models, or experimental prototypes, silicone plays nice with almost everything.

https://www.galindberg.se/storage/937D3F2A7F56E7A035E5C00D8051BFB1B7E6CA9BBC32907C7A274FE189A17227/dc2dbac1b2b94ef2ba6ba488ad9045e5/pdf/media/a398324366cb4bceafc87d5faafb68bd/Silastic%20MS-1001.pdf

Above is the datasheet for 1:1 silcion mold by silastic

This is the silcon we bought for our usecase

first i made a very basic trial file in cad to just try out the the wax block milling operations

The basic idea behind this was that i wanted to make it seem like a squirtle is floating on a water body

SO i made ripple like texture and added a online model of squirtle

This is a one part mold

Checking for any undercuts using accesibility analysis feature on usion 360 software.

Once done export the stl file to bring over to srp player to make a Milling file.

SRP player

This is the basic landing page of the srp player software

Import you're exported stl file for milling prep

First tab, you can scale your object here.

Fix the orientation of the model.

The right tab of jobs is a linear checklist of all to be done.

Options based on type of finish

Cross check options if the roughing and soothing operations are using the correct end mill parts

Sometimes roughing has a ball tip(zub300) we manually change it to ZUB 150

You also have rto set a job area, around the desgn you are cutting

The (-vlaue) that you see are minimum dimensions of the job area

Hit create tool path

Hit Start

After setting origin usin vpanel on srm 20, we start cutting

Voila

You will have to change end mill after toughig operation without changing xy origin for the next operation

Flat and ball nose end mills

Cutting and milling operation

This was the final result

I did not keep scale of model in mind thus the grooves and model was toooooo thin to make anyhting out of

I decided to still just try out what happens and make a new planned model later.

using rice for volumetric calculation of mother mold

The rice coverng inside is 10 grams thus we need 10 grams of silicon liquid that will fill in this space

Since are compund is 1:1, we need 5 grams of part a and 5 grams of part b

Pouring proportionate liqui silicon

Remember to mix side to side and not swirl,

Swirling will cause air bubbles

Remember to clean your beakers after use, silicon will dry in the ealls of your beaker causing inaccurate readings the next time you use it

Taping to remove airbubbles

Final result

Learning

I modelled very inefficiently, causing leakage points and improper depth for forming, little measurents earlier could have had a better result

.Final model. pixel Sonic the hedgehog

For a more refined model i decided to create a pixel form from various materials like choclate, cement. Using a well planned 2 part silicon mold

Initial final pixel model

In fusion under Inspect you have an option of accesibility analysis, which shows you if you model has any undercuts

Undercuts

Undercuts are

Choose the body you want to analyse

choose the direction of opening by selecting an axis

Depending on type of opening choose the option

We have a tonne of undercuts here....

I manually fixed all extrusions that had undercuts to suffice a 2 part mold

Designing a 2 part mold

Now we need to make the mother mold to form the silicon in

Split the model into 2 halfs exactly at the desired split line

Extrude a simple box to act as the base

Extrude a thin wall around for the walls of silicon

Add a small draft angle of 1 to 2 degrees outward on this wall

connect the 4 corners with a construction line and create a circle on the points

Revolve the circle to cretate a indent on one side and an extrusion on the other

This step is done to align the two molds when kept together, without this there can be misalignement

Circular patten the indent feature and the extrudes feature on both sides for 4 alignment points

Indented feature in the other side of the mother mold

Checking accesibility analysis of the the mother mold as well

I couldnt add any draft angles to the model itself without it looking super odd, I did not want to risk a fresh wax mold and waste it if the silicon does not come out thus I decided to print a mother mold first

My model had many small extrusions which were very probable to snap from my print, increasing infill for th whiole block would increase time drastically

Thus i added modifiers to my models small parts