This is a in-depth living hinge design guidelines. This guide is intended to be the one and only ultimate source for designing living hinges. The guide will show the what, where, why of living hinges and then goes in to specific living hinge design examples. We will discuss the four main types of living hinges flat hinges, double hinges, butterfly hinges and bi-stable hinges. Suitable material for living hinges like Polypropylene PP and Polyethylene PE will be discussed.

1. Living Hinge
Design
The Ultimate Guide

2. What is a living hinge?
A living hinge is a thin section of plastic
that connects two plastic bodies together.
The use of a living hinge allow you to keep
the two bodies connected while allowing
rotational movement

3. Living hinge example?
A common example of a living hinge is a ketchup cap.
The two sides are connected by a thin hinge. The cap
can rotate out of the way while still being connected.
Living hinge

4. What are living hinges
used for?
• Makeup compacts
• Candy container caps (Tic Tac mints)
• Condiments
• Shampoo and liquid soap
• Fishing tackle boxes

5. What are the benefits?
• Eliminate assembly- Conventional hinges
need to be assembled. Living hinges do not
• Lower Cost- Lower cost though eliminating
assembly steps and eliminate hardware
• Durability- properly design living hinges can
last indefinitely

6. Conventional Hinges

7. Reason not to use a
living hinge?
• Limited material selection- Living hinges
require the use of Polypropylene PP or
Polyethylene PE
• Limited load bearing- Living hinges can not
handle much load parallel to the hinge.
• Added development time- Living hinges take
effort and time to design.

8. Living hinge design
considerations

9. Typical living hinge
designs

10. Typical living hinge
designs
• Flat hinge – the strait hinge is common and It
consist of a landing in both sides and a thin hinge
section.
• Double Hinge – A double hinge has two strait
hinges separated by a narrow landing section.
• Butterfly hinge – A butterfly hinge is commonly
used on dispensing caps.
• Bi-stable Hinge – this is very similar to the
butterfly hinge only instead of one uniform living
hinge there are three separate hinge sections.

11. Living hinge geometry

12. Living hinge geometry
• Web thickness- Should range between 0.007” –
0.015” thick.
• No sharp corners – Every corner should have a
radius in your design.
• Gate placement – RevPart will help you with this.
The gate placement is very critical.

13. Hinge Material
• Polypropylene aka PP- is the best resin by far for
living hinges. Use Homopolymer PP when
possible.
• Polyethylene – Every corner should have a
radius in your design.
• Gate placement – RevPart will help you with this.
The gate placement is very critical.

14. Fillers
Fillers are commonly added to plastic to
meet physical or aesthetic requirements.
Most fillers are not recommended for living
hinges.

15. Molecular Orientation
The key to a quality living hinge is getting
all the resin molecules to line oriented in
the same direction. This direction is in
parallel to the flow though the living hinge.

16. Environmental Factors
• UV exposure- UV light is brutal to all plastics in
varying degrees. Living hinges will not last very
long with degraded plastic and fissures. UV
additive is recommended in all outdoor
applications.
• Chemical Exposure- It is important to take into
account what chemicals the living hinge will come
in contact with and see if the selected resin is
applicable.

17. Prototyping a living
hinge
• CNC Machining- RevPart has the expertise to
CNC machine your living hinges out of
Polypropylene.
• Prototype injection molding- RevPart can
produce inexpensive prototype mold that let you
test the real deal living hinge. This allow you to
make revisions and ensure your design works
before going to full scale production.

18. Click the Link
www.revpart.com
We have tons of guidelines, tutorials and
helpful information on our site.
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