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Mold Design / Mold Material

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List of DURACON® POM grades This page's PDF(0.97MB)

8. Mold Design

8.7 Mold Material

The following must be taken into consideration for mold materials when molding DURACON® POM:

  • Corrosion by decomposition gas
  • Abrasion by glass fibers (when using glass fiber reinforced grades)

When mold corrosion is a problem, enlargement of gas vent or review of molding conditions is required. When these do not solve the problem, the mold material is changed. The following results were obtained in an experiment in which various steel materials were immersed in formic acid and the corrosion of their surfaces was examined:

2055 < P21 < D2 ≤ 440C < S17400

(Inferior) ← -------------------------------- → (Superior)

Hardening and nitriding are good measures against abrasion. For reference, Tables 8-1 and 8-2 show the properties of various mold materials.

Table 8-1 Thermal conductivity of mold materials

  Thermal conductivity (W/m·°C)
Copper (Pure) 386
Beryllium-copper 20C 121
Beryllium-copper 275C 109
Aluminum (Pure) 221
Aluminum 7075 151
Zinc alloy (ZAS) 109
Carbon steel 53
H13 34
D2 27
Stainless steel 410 26
Stainless steel 304 16

 

Table 8-2 Characteristics of mold materials

  AISI Hardness HRC Wear resistance Corrosion resistance Toughness Dimensional change in heat treatment
Prehardened steel 1055 13 D D A' -
4140, 4142 28 D' D' B' -
P20 33 C C A -
420 33 C A' A  
S17400 35 C' A' A  
H13 40 B B B -
P21 40 B C D' -
Hardened -tempered steel D2 60 A' B C' B
A2 57 A B C' B'
H13 50 A B B B
420 52 A A' B A'
440 57 A' A C A

 

  AISI Machinability Surface finish Etching, electrical discharge machining Weldability
Prehardened steel 1055 A" C B B'
4140, 4142 A B B' B'
P20 A' C' B A
420 D' A' A A
S17400 D' B' B' A
H13 B' C C' B
P21 A' A B B'
Hardened -tempered steel D2 B A' A D
A2 B' C' C C
H13 A B' B' B
420 B A" A' B
440 C' A' A D

Appraisal class: (Superior) A" > A' > A > B' > B > C' > C > D' > D (Inferior)

 


Runners  Gates  Draft  Undercut  Gas Vents  Mold Temp. Control  Mold Material

Contents Introduction Safety Molding Machines Molding Conditions Recycling
Molding Characteristics Product Design Mold Design Countermeasures for Defects