Thermoplastic Material Selection for Performance, Cost, and Feel

Eric R. Larson, P.E.
Owner / Chief Engineer
Art of Mass Production
Selecting Thermoplastic Materials
for Performance, Cost, and Feel

Agenda
!  Overview of Thermoplastics
!  Material Selection Criteria
!  Performance
!  Cost
!  Feel
!  Bicycles - Key Requirements
!  Recommended Palette of Materials

© 2016 Eric R. Larson, all rights reserved

My Background
!  Born in Detroit
!  B.S.E. (Aerospace)
!  LearFan


Intro to Thermoplastics
! Commodity Plastics
!  PE, PP, EPS

! Engineering Plastics
!  ABS, acetal, nylon, PC


Intro to Thermoplastics
! Application Engineer
!  acetal, nylon, PBT


Consulting Engineer
! 20+ years


Plastics Primer
!  Polymer Chemistry
!  unique language
!  chemistry + physics
!  Polymer Molecules
!  carbon based (organic)
!  primarily synthetic (man-made)
!  NOT base elements
!  Categorization
!  Characterization

Polymer Chemistry
!  Polymerization
!  marriage of the monomers
!  divorce of the monomers
!  The Mer Family
!  polymers
!  homo-polymers
!  co-polymers
!  ter-polymers


Categorization
! Traditional Polymers
! Aromatic Polymers
!  Kevlar = an aramid
! Fluorinated Polymers
!  PE => PTFE

Characterization - Property Data
“The designer who has access to standard data sheet
values only must use them cautiously as a source of
design information. Many of the tests reported on the
sheets come under the jurisdiction of the American
Society for Testing and Materials (ASTM), and the
properties are intended to characterize a material, not
necessarily to provide design information.”

- Engineered Materials Handbook,
Volume 2, Engineering Plastics. ASM International
(formerly known as the American Society for Materials)

Material Selection Based on Performance
!  Mechanical Performance
!  Strength, Stiffness, Toughness
!  Electrical Performance
!  Environmental Effects
!  The Effects of Time
!  durability, reliability

!  Strength
the ability to withstand an applied force

!  Stiﬀness
the ability to withstand bending

!  Toughness
the ability to withstand sudden impact

Toughness

Performance Killers

!  Avoid Data Sheets

!  Find Good Data
!  Design Modules


Material Selection Based on Cost
Why Use
Plastic?
corrosion resistance!
molded-in color!
reduced weight!
molded-in features!
global availability!
design freedom!
net shape manufacturing !
energy efﬁcient!
accurate and repeatable !
environmentally benign!
part consolidation!
lower part costs!
end-use performance!
99% of the time - we make something out of plastic
because it is a cost eﬀective manufacturing method
ease of use and re-use !

part cost = material cost + processing cost
where
material costs = material mass x material cost
per part per part per unit mass
and
processing costs = molding cost + handling cost +
ﬁnishing cost + assembly cost + packaging cost, etc.

where
material costs = material mass x material cost
per part per part per unit mass
and
material mass = ƒ(design)
material cost = ƒ(resin pricing, supply chain, etc)

where
total processing cost = molding cost + handling cost +
ﬁnishing cost + assembly cost + packaging cost, etc.
and
processn cost = processn rate x cycle timen

Molding Cost = machine rate x cycle time
where
machine rate = ƒ(machine size, age, location, etc)
and
machine size = ƒ(part size, geometry, cavitation,
required shot size, tonnage)
cycle time = ƒ(part design, mold design, material
used, wall thickness)

Understanding Cost is Your Job

Material Selection Based on Feel
!  A Methodology

!  verb 
to have perception, especially by touch or by any nerves of sensation (other
than those of sight, hearing, taste, and smell)  
to be aware of something that aﬀects you (physically, psychologically,
emotionally)  
to be aware of by instinct or inference
!  noun 
a quality of an object that is perceived by feeling or touching: the soft feel of a
feather 
a sensation of something, or a vague mental impression or feeling: the feel of
winter; a feeling of sadness in the air 
intuitive knowledge or native ability or acquired sensitivity: a feel for the game

thermoplastic materials offer unique
opportunities to inﬂuence human response

Good Feel = ƒ ( design, material, application, wow factor)
where
WOW = overall utility x (huh)n 
product cost
and
huh = ∑ ( function, cool factor, funkiness . . .)
n = ƒ (what?)


Xtl < Xjr < Xtm
where
X = the “feel” factor we are trying to determine
and
Xtl = too little X 
Xtm = too much X 
Xjr = just right X

credit: Robert Southey
c. 1837

Management
Commitment
 
The Feel Team

Develop a Process
resources: people, equipment,
time
those with a knack for “feel” 
curious, inquisitive
comfortable with ambiguity  
people skills
goals, milestones, deadlines 
a Decision Maker

Key Requirements for Bicycles
!  Mechanical Performance
!  Safety
!  Durability
!  Moderate Chemical Resistance
!  Moderate Temperature Requirements
! Cost Cost Cost

Key Manufacturing Processes
!  Machining
!  Prototyping
!  Short Run Production
!  Injection Molding
!  Blow Molding
!  Thermoforming / Pressure Forming

Recommended Material Palette
!  Good
!  ABS
!  PP, PE
!  Better
!  acetal
!  nylon
! Best
!  glass reinforced nylon
!  semi-aromatic nylon
!  toughened nylon
!  Custom Compounds
!  tougheners, lubricants
!  structural reinforcement
!  Special Applications
!  PTFE, Aramid, PPA
!  TP elastomers
!  New Developments
!  long glass ﬁber (LGF)
!  TP composites
!  alloys / blends

Material Selection Methods
! Based on Data
! Based on Experience
! Based on Familiarity
! Based on Feel
! Based on Other

Resources
!  Professional Societies
!  SPE / ASME / SAMPE
!  IAPD
!  Trade Publications
!  Plastics Engineering
!  Plastics Today
!  Plastics Technology
!  Resin Suppliers / Distributors
!  Compounders

www.artofmassproduction.com
619-269-0184
info@artofmassproduction.com
Contact Info

Thermoplastic Material Selection for Performance, Cost, and Feel

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Thermoplastic Material Selection for Performance, Cost, and Feel