Thermo101 Reality

A TECHNICAL ARTICLE 2005 VOLUME 24, #2

Comparing Concept to Reality1

We began our discussion of part
design by reviewing why we
might not want to quote on a job.
If we are serious about fabricating
the customer’s concept, we need
to understand the methodology in
reducing a concept to reality.

Naiveté v. Experience

Before we consider developing a
hard cost for a given project, we need
to ascertain the technical level the
customer brings to the design. Most
of us have dealt with customers of at
least one of the following levels:

• Expert Customer. Fully cognizant
of the advantages and
limitations of thermoforming
in general, conversant of the
plastics characteristics, and
having a complete understanding
in the myriad ways
of fabricating his design, in
particular.

• Experienced Customer. Has
designed certain parts in thermoforming
in the past but
is not up-to-date, vis-a vis2,
newer processing techniques,
mold materials, polymers, and
so on.

• A Non-Thermoforming Technical
Customer. Has extensive
experience in blow molding,
rotational molding, or injection
molding, but has no
knowledge of the differences
between these techniques and
thermoforming.

• A Technically Naïve Customer.
Knows little about plastics and
nothing about thermoforming.
Has always purchased his
plastic products to either mate
with or package his non-plastic
products.

• The Totally Naïve Customer.
Has a great idea worked out
on the back of a Burger King
napkin, has no funding, no
customer, and no idea how to
reduce his idea to reality.

We all agree that it is very difficult
to treat each of these in the same
fashion. In other words, a checklist of
things necessary to reconcile prior to
quotation might be too technical for
the naïve customer and an insult to
the experienced one. Nevertheless,
we should all keep in mind before
every take-off and landing, the pilot
and copilot are required to complete
an extensive checklist, regardless
of their years of experience and the
number of times they had flown the
specific airplane. So let’s take a look
at a typical design checklist.

General Advantages
and Limitations of
Thermoforming

We all know the advantages and
limitations of our skills. But the
customer may not. So tell him/her.
Some advantages:

• Lower tooling costs

• Quicker design-to-prototype
time

• Quicker prototype-to-production
time

• Relatively wide selection of
polymers, grades

• Large surface area per unit
thickness

• Economic production of a few
pieces (heavy gauge) or many,
many pieces (thin gauge)

Some limitations:

• Non-uniform wall thickness

• Single-surface molds

• Hollow parts difficult

• Sheet cost

• Extensive trimming, recycling
needed

• Mostly neat plastics (few
reinforced and highly filled
plastics)

• Wide forming windows desired
(needed)

The Material Issue

We, along with the astute customer,
need to discuss material choices in
some detail. It is not enough for the
customer to specify “general purpose
polystyrene.” He/she needs to work
with us to develop a list of property
requirements. In other words, what
are the elements of the environment
in which the product must perform?
Some examples are:

• Environmental temperatures
(high and low)

• Corrosive/erosive conditions

• Static/dynamic loading conditions

• Impact conditions

• Surface quality

• Product lifetime

• Assembly restrictions (if any)

And we must all be aware that
some of these conditions are compound.
For example, the product
may need to withstand dynamic
loading at high temperature in a
corrosive environment. And the
customer must understand that
not all grades of plastics that meet
the desired criteria are available in
sheet form.

Before we can discuss design concepts
with our customer, we need to
review them ourselves. We’ll continue
this litany after our review. ¦

Keywords: advantages,
limitations, material choice,
experienced customer, naïve
customer

THERMOFORMING

101

1 This is the second in a series that
focuses on part design

2 vis-à-vis, French for face-to-face, with the
usual meaning being “as compared with”
or “in relation to.”

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