Design of Tools for SUMIKAEXCEL PES

As SUMIKAEXCEL PES has high melt viscosity and low mold shrinkage, the following factors must be taken into account when designing tools.

Sprue

  • The length of the sprue should be designed as short as possible. It is preferable to have as large as possible a taper ( - 5°).
  • A sprue lock should be installed in order to provide better sprue removal, as shown in the accompanying figure.
スプルの説明図

Runners

  • Runners must be thick and short. The thickness and length should be determined with consideration for moldability.
  • Runners should have a circular or trapezoidal cross-sectional shape.
  • Runners should have a circular or trapezoidal cross-sectional shape.
image of Runners

Examples of Runner Cross-sectional Sizes (mm)

A B C D E
>4 >3 >3 >4 D/2

Gate System

Side Gates

  • For rectangular gates, it is most efficient to use deep lands with short lengths. The gate depth should be about 70% of parts wall thickness.The preferred land length is 1mm or less.
image of Side Gates

Pinpoint / Submarine Gates

  • The gate diameter should be between 0.8 - 1.2 mmΦ, with gate land lengths of 1 mm or less. If flow distances are long, it is preferable to have multiple points rather than enlarging the gate diameter.
image of Pinpoint / Submarine Gates

Film Gates

  • The preferred gate thickness used should be equivalent to the wall thickness of the molding × 0.5. The land length should be 1mm or less.
image of Film Gates

Extraction Taper

  • As PES has low mold shrinkage, it is recommended that an extraction taper with an angle of at least 1° (1/60) - 2° (1/30) be used, even for products molded with shallow molds. If the product uses a deep mold, the extraction taper should have a larger angle.
  • As thin-walled moldings tend to be susceptible to overcharging, a larger extraction taper angle than usual is recommended. As well, a larger extraction taper angle should also be utilized with glass fiber reinforced grades.
  • If an adequate extraction taper angle cannot be utilized due to the shape of the molding, then creative use must be made of slide cores and mold ejection methods.

Air Venting (Gas Drainage)

  • As SUMIKAEXCEL PES has high melt viscosity, flash does not easily occur, even if air venting of only 1/100 - 5/100 (mm) has been installed.
  • Air venting should be installed for the molding of thin-walled products.

Mold Material

  • Molds used for making prototypes and for small production lots can be composed of carbon alloy steel for machine structural use (S55C). However, these molds should be hardened by quenching if they are to incorporate sliding core parts.
  • When mass production and high dimensional precision are required, it is recommended that steels having greater rigidity be used, such as chrome molybdenum steels (SCM3 and 4) and alloy tool steels (SKD11 and 61).
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