Assembly
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Inserts
Did you know?
Inserts are a good choice when an application requires disassembly/assembly.
There are a number of designs, styles and lengths to choose
from (see figure 2).
How does it work?
Inserts can be installed by the following methods:
Press
fit – inserts are pressed into a smaller diameter
hole. Quick and easy this offers the least strength and creates
a lot of hoop stress.
Expansion
type – inserts are pressed into a slightly
larger diameter hole. Also quick and easy, the insert gets
locked into place once the screw is fully engaged. Again,
this is a mechanical lock that creates a lot of hoop stress.
Ultrasonic
welding – one of the most common methods of
insertion, high frequency sound waves are applied to the insert
which is positioned over a smaller diameter hole. The plastic
melts and locks the insert into place. Make sure to add a
well at the top of the hole to allow room for the additional
melt flow. It’s quick, strong and causes the least amount
of stress in the plastic.
Heat
insertion – Cheaper than ultrasonic welding,
heat insertion is just that, heat is applied to the insert
while being pressed into a slightly smaller hole. A well is
required in the design of the hole for melt flow. While slower
than ultrasonics, it is cheaper, produces a strong bond and
leaves little stress in the plastic.
Molded-in – the inserts are hand loaded onto a core directly in
the injection mold. The plastic then melts around the insert
and provides a fairly strong bond if the parameters are correct.
The disadvantages are:
