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Material Selection


Material Selection Material Selection Getting the optimum balance of performance, quality and cost requires a careful combination of material and plastics part design ... – PowerPoint PPT presentation

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Title: Material Selection

Material Selection
Material Selection
  • Getting the optimum balance of performance,
    quality and cost requires a careful combination
    of material and plastics part design
  • Once end use requirements have been specified,
    the designer can begin searching for plastic
    materials that are suitable for the application

Material Selection
  • Material selection/screening process is
    accomplished by comparing material properties
    with a property profile derived from the end use
  • Best to select 3-6 materials during the initial
    process based on the property profile and costs

Material Selection
  • Material Selection should be based primarily on
    the functional requirements of the parts
  • Those items without which the part will not work
  • Then go to design considerations
  • Those items involving manufacturing factors
    without which the part cannot be made profitably

Material Selection
  • Functional requirements are physical properties
  • The ability to operate over a wide range of
  • Resistance to chemicals and environments
  • Any other condition that can be described by
    testable parameters
  • Some functional are more important than others
  • These should be given a top priority

Material Selection
  • Design considerations are the
  • Raw material costs
  • Processing cost
  • Tooling costs
  • Recyclability
  • Familiarity of material
  • Acceptance of material in the market place

Material Selection
  • Final choice of material almost always involves
    compromises between functional requirements and
    design considerations

Property Profile
Step 1
  • Develop property profile
  • The polymer required is classified and ranked
    according to the following representative
    grouping of functional requirements
  • The list can be expanded or filtered to fit
    particular needs

Step 1
  • Rigid
  • Flexible
  • Opaque
  • Translucent
  • Transparent
  • High strength to weight
  • Ordinary strength to weight
  • High Temperature resistance
  • Sterlizable
  • Ductile at low temperatures
  • Resistant to chemicals
  • Dielectric constant
  • Arc resistance
  • Nonflammable
  • Slow burning
  • Very low density
  • Ordinary density
  • Wear resistance
  • Friction coefficient
  • Acceptable for food
  • Post-consumer recyclable
  • Weather resistant

Step 2
  • It is now possible to refer material property
    data sheets and databases to arrive at a short
    list of candidates that match with the property
    profile developed in Step 1
  • If similar application exist, begin with the
    current materials

Step 3
  • Material properties are used to select likely
    candidates with corresponding property value or
    ranking listed
  • Best to begin with properties that cannot be
    enhance by design
  • Coefficient of thermal expansion
  • Transparency
  • Chemical resistance
  • Softening temperature

Step 3
  • Then go to mechanical properties, which can
    generally be enhanced by design
  • Wall thickness
  • Ribs
  • Reinforcements

Step 4
  • The next step in the elimination process is to
    consider items such as
  • Creep modulus
  • Dielectric strength
  • Mold shrinkage
  • Costs
  • The designer may want to consider statistically
    designed experiments to narrow the list of

Material Selection Example
  • There are a wide range of properties within
    polymer families and between families
  • The problem here is to select a injection
    moldable polymer based on mechanical properties
    as a first priority
  • The property profile is developed first

Material Selection Example
  • Property Profile

Material Selection Example
Material Selection Example
  • In the preceding table all the resins checked yes
    meet the preliminary specification
  • The next step is to consider secondary matters
    such as creep, dielectric strength, shrinkage and

Material Selection Example
Material Selection Example
  • From the data in the preceding table, the higher
    cost resins can be eliminated first
  • The filled resins can be eliminated next because
    they are more difficult to process
  • This leaves 6/6 nylon and PPO
  • The HDTUL of nylon is must lower than PPO
  • The shrinkage values for PPO are much less than
  • PPO is the best choice