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.




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)




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



!  verbto 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

!  nouna quality of an object that is perceived by feeling or touching: the soft feel of a feathera sensation of something, or a vague mental impression or feeling: the feel of winter; a feeling of sadness in the airintuitive 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 XXjr = just right X


credit: Robert Southeyc. 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, deadlinesa 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

Long Fiber Thermoplastics

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 . art of mass production . com

619-269-0184

info @ art of mass production . com

Contact Info

Thermoplastic Material Selection for Performance, Cost, and Feel

Engineering

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