- [Narrator] Based on what we learned so far,
you can probably guess that not all products
can be molded in one easy piece.
Many products involve multiple parts coming together
in your assembly.
For the function of your project,
you need to think about
where you're going to split it up.
This is where the parting line comes into play.
To review, the parting line is the line along the
surface of your part where where your mold halves meet,
leaving a seam.
The parting surface can be plainer
for really simple parts like this stool,
but it often requires a more complex split.
For symmetrical products, like a lot of power tools,
it makes sense for the line to split
the product exactly in half,
which makes it easy to work out where
all the internal components are going to go.
For asymmetrical, complex or undulated parts
the parting line will get more complicated.
When the two main mold halves come together,
they leave a perceptible parting line on the
surface of your part.
When your mold isn't flush or properly ventilated,
this is where flash will appear.
Flash is an overflowing edge of your mold material.
Usually a thin squeeze out with a ragged edge.
For obvious reasons you'll want to
minimize flash where you can
and trim it off later if you have to.
For both cosmetic and functional reasons,
parting lines are often hidden along edges like this.
When you've got your mold to meet along an edge
that already exists in your design,
you've got a bit more wiggle room when it comes to
any slight misalignment of the machine.
Your tolerances are a bit higher.
Another reason for placing the parting line on any edge
that if any deburring is required,
it'll be easier to do.
Hiding a line along a texture or a material change
can also disguise the line.
The parting line is also a big deal when
it comes to designing the correct amount of draft.
On this first simplified stool,
the parting line is plainer,
so determining the draft direction is relatively simple.
Cosmetically, masking the parting line can
increase perceived valuation.
Perceived value is what the user or customer thinks
that the product is worth.
If your price point doesn't match, you've got a problem.
Many designs make it difficult to find the line
because having incongruous placement
can make it look or feel cheap.
A lot of product design is all about increasing
the perceived value of the product.
Visible lines and any unintentional texture,
including parting lines,
are undesirable for goods that are
handled regularly or have high cost.
It looks cheap when you can see the injection site
and/or parting line clearly on a part.
Well integrated marks of manufacture
give the opposite effect.
Hand feel is important too,
especially on product handles.
A sharp edge on an otherwise smooth face won't feel good.
Texture is a great way to improve grip, add style,
and break up your design,
all while using the same material.
Texture will also, if your head isn't spinning already,
affect the draft you can put on your part.
This is due to how plastic flows and cools
because texture can stick and needs more draft.
A major developer of textures for injection molding:
"There's nothing less forgiving than a
perfectly smooth face on a plastic part.
Every tool mark, flow mark, and flaw will show.
In order to hedge your bets,
having at least some of your part with a matte surfacing
will give you a little bit more tolerance,
which is something we can all use."