- [Instructor] Let's talk about different mold types.
The first difference is between destructive
and multi-use, but before we get started,
I wanted to call out this display pane.
I use this quite a lot when working with assemblies,
so that I can easily hide, show,
and make parts transparent, so I can see what I'm doing.
You can find the display pane by clicking
this little arrow, and you'll have toggle buttons
for all of the parts in your assembly.
In this first example, I've created a sculptural object
that has a lot of cut-throughs, so it'd be difficult
to separate into reusable mold parts.
This calls for destructive molding.
Destructive molding is just what it sounds like.
You have to crumble, break, or destroy the mold
in order to get the cast out.
One of the most common types of destructive molding
is sand casting, where specialized sand
is packed around patterns of the master shape
that you're going to be molding.
The master shape is melted out,
and then the void is filled with molten metal.
Once the metal is cooled, the sand is broken up
and recycled back into the process
and can be reused many times.
Foundries are specialized factories that do sand casting.
Sand-cast parts can range dramatically in size,
from tiny cast iron skillets
to massive industrial parts, weighing literal tons.
Destructive molding is well-suited
for the creation of complex, single-piece metal parts.
Lost-wax casting can be a great solution
for projects like this one,
that would be otherwise difficult to mold.
Now, let's look at some examples of multi-use molding.
One of the first types we've already talked about
is a one-sided mold, like the ice cube tray.
One-sided molds are generally solid,
have a primary detail face, supporting faces,
and an open back like this.
One-sided molds are useful for creating relief sculptures
and architectural facade blocks,
because they don't require detailed backs.
Additionally, open-faced molds can make sense
for any kind of expanding or foam material,
so that irregular muffin tops
can be easily shaved off to exact measurements.
But let's say all of the sides have important geometry.
Bivalve molds, also called two-part molds,
are one of the most common types of molds.
Bivalve molds are created in two separate pours.
The first pour requires you
to affix your master part in place
with clay, pins or glue,
to firmly stabilize your part into position.
When you use clay, you're able
to put the parting line exactly where you want it to be.
The parting line is the line
thaT defines your two mold halves, and where they meet up.
When you're using soft molds, your parting line
can follow a relatively curvy path, if needed.
If you're using clay, you can combine this technique
with the creation of registration marks.
These are shapes
placed to register your mold pieces together,
so they can line up as exactly as possible.
Ideally, they should work like 3-D puzzle pieces
that can only fit together in one way.
In this example, my registration blocks
are different sizes at the corners,
so as you can see, that one
and that one meet up.
When your design is too complex
for a two-part mold like this,
you'll have to get creative to figure out
where that third or fourth or fifth mold split needs to go.
Multi-part molds are exactly what they sound like.
If you can't break your master part up
into easily moldable chunks and assemble them later,
you may need to do separate pours.
Prototype molds are often made of flexible silicone.
The advantage of having a softer mold
is that it's more flexible,
and it's easier to get your part out,
but the softer the mold, the faster it deteriorates.
When you need to cast a high volume of parts,
the mold will need to be metal, usually hardened steel.
With metal molds, you won't have the same flexibility
in removing your cast parts.