# 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undercuts are recesses or projections on the inner surface of a part which would prevent the mold cores from being withdrawn in the line of closure.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: