- [Instructor] So far we've talked about molding
individual parts, or in pairs.
Lots of smaller parts are made into family molds
where the same part is repeated.
Another common use of family molds is when many different
parts of a whole are made of the same material.
There are several different configurations one can use
for this, and there is a more extensive use of runners.
In this example, I have a simple bottle cap.
It wouldn't make sense to have such a small part
in an individual mold.
I've demonstrated both the use of a radial family mold,
and a grid.
In the radial mold, the initial sprue river of plastic
splits into eight individual runner streams
into the center of mass for each cap.
In the grid example, the main sprue could be
at almost any point of this grid,
though likely closer to the center, before separating out
into individual runners.
An example of family molds you may be familiar with
is with small plastic model toy sets
that you have to remove from a grid.
They ship the parts with all of the sprues still attached.
There are also injection molders that can produce products
with more than one material at the same time.
These parts are sometimes produced in something called
a two-shot machine.
In a two-shot machine, the first and smaller volume goes
through a process cycle while the second mold remains empty.
The interior parts are then transferred robotically
to the second die.
Both of the molds open and close with the same mechanism
at the same time.
You can save time by using a two-shot machine
if you design calls for it.
But calculate the time per unit with using separate
machines and make sure it's worth the extra cost
of a more complicated machine.