Determination of the First Digit for Injection Molded and Die Cast Parts

(Used under permission of Dixon and Poli,
Engineering Design and Design for Manufacturing)


Injection Molded Parts

The following chart should be used in determining the first digit for all injection molded parts:

Figure 11.1 Classification System for Basic Tool Complexity
Basic Complexity First Digit
Parts without internal undercuts(1) Parts whose peripheral height(2) from a planar dividing surface(3) is constant Part in one half(4) 0
Part not in one half(4) 1
Parts whose peripheral height(2) from a planar dividing surface(3) is not constant - or - parts with a non-planar dividing surface 2
Parts with internal undercuts(1) On only one face of the part Parts whose ONLY dividing surface is planar, or parts whose peripheral height(2) from a planar dividing surface(3) is constant 3
Parts whose peripheral height(2) from a planar dividing surface(3) is not constant - or - parts with a non-planar dividing surface 4
On more than one face of the part Parts whose ONLY dividing surface is planar, or parts whose peripheral height(2) from a planar dividing surface(3) is constant 5
Parts whose peripheral height(2) from a planar dividing surface(3) is not constant - or - parts with a non-planar dividing surface 6


Die Cast Parts

The following chart should be used in determining the first digit for all die cast parts:

Figure 11.1 Classification System for Basic Tool Complexity
Basic Complexity First Digit
Parts without internal undercuts(1) Parts whose peripheral height(2) from a planar dividing surface(3) is constant Part in one half(4) 0
Part not in one half(4) 1
Parts whose peripheral height(2) from a planar dividing surface(3) is not constant - or - parts with a non-planar dividing surface 2
Parts with internal undercuts(1) Internal undercuts cannot be generally die cast


Definitions:

  1. Internal undercuts are recesses or projections on the inner surface of a part which would prevent the mold cores from being withdrawn in the line of closure. The following figure shows an example of an internal undercut:

  2. The peripheral height from a planar dividing surface is considered constant if the height does not vary by more than 3 times the wall thickness.
  3. A part is said to be molded in one half the mold when the entire part is on one side of a planar dividing surface:

  4. If the dividing surface of the mold is in one plane then it is termed to have a planar dividing surface. The following figure shows examples of planar and non-planar dividing surfaces: