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					Chapter 2 Introduction
 Why would a   product designer choose a die
  casting over a component manufactured by
  another competing process?
 What are the capabilities of a product made
  with a die casting?



                                                2-1
Chapter 2 Objectives
 List the advantages of  using die castings
 Identify die casting applications
 List the characteristics of the optimum die
  casting configuration
 Identify the components of the die casting
  shot


                                                2-2
New Terms
 Die casting “shot”
 EMI
 Overflows
 Runner
 Sprue




                       2-3
Die Casting Advantage
 Produces components     at high speed
 Uses a range of durable metal alloys
 Faithfully captures the most intricate design
  details
 So, it’s   the choice for:
   • High volume
     production components
   • Lower-volume
     production as well                           2-4
Die Casting Applications
 Agricultural machinery    Instrumentation
 Automotive vehicles       Lawn and garden
 Building hardware          equipment
 Electrical and            Office furniture
  electronic equipment      Office machines
 Hand tools                Portable power tools
 Home appliances           Recreational
 Industrial products        equipment
                                                    2-5
Optimum Configuration
 Fill completely with metal
 Solidify quickly without defects
 Eject readily from   the die




                                     2-6
Principle 1
 Wall thickness should be     as consistent as
  possible
  •   No hard and fast rules
  •   Wall section possesses a dense fine-grained skin
  •   Defects likely in material in between walls
  •   Wall sections should be as uniform as possible.
  •   Thinner walls contribute a lesser heat load than
      heavier walls and will have a longer die life
                                                    2-7
Principle 2
 Intersections ofwalls, ribs and gussets
  should blend with transitions and generous
  radii
  • Generous radii and transitions promote metal
    flow and
    internal integrity
  • Radii and fillets enhance structural integrity
  • Fillets reduce heat concentration in both the die
    and castings                                      2-8
Principle 3
 Specify standard draft
  • Draft is highly desirable on surfaces parallel to
    the direction of die draw
  • Recommended draft is determined by:
     – The alloy
     – The length of the dimension parallel to the die draw
     – If the dimension is an inside or outside wall


                                                              2-9
Principles 4 and 5
 Eliminate or   minimize sharp corners
  • Accommodate them at parting lines and at the
    junctions of die components
  • Break them with radii or chamfers
 Avoid undercuts
  • May require machining operations or additional
    die components, such as retractable core slides

                                                   2-10
Principle 6
 Dimensions with critical tolerances should
  relate to only one die member
  • Precision is greatest when related features are in
    same piece of cavity steel
  • Precision is reduced for relationships across the
    parting line or to moving components
  • Judicious use of ribbing can aid die filling and
    strengthen the component
                                                    2-11
The Shot
 The result of injecting metal into the die,
  i.e., making a shot (verb), is also called
  a shot (noun)
 Shot elements:
   •   Runner
   •   Biscuit
   •   Overflows (not pictured)
   •   Casting
                                                2-12
Overflow
 A reservoir   for the first metal to flow through
  the cavity
 Vents inside provide a path for air to get out
  of the die
  • A strategically placed overflow can be used to
    add heat in a cold area of the die
 May help eject the   casting from the die

                                                     2-13
Summary
 Many reasons to choose die casting over   a
  competing process
 Many product lines made from die castings
 6 principles must be followed to ensure
  optimum design



                                                2-14

				
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posted:10/27/2011
language:English
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