• By Admin
  • 2025/4/8 15:58:00

PET preform mold manufacturing process

The manufacturing process of PET preform molds involves several precise steps to ensure high-quality molds capable of producing uniform and defect-free preforms for blow molding bottles. Below is a detailed breakdown of the process:

1. Design & Engineering

  • 3D Modeling: The mold design is created using CAD software (e.g., SolidWorks, AutoCAD) based on preform specifications (weight, neck finish, wall thickness, etc.).

  • Simulation Analysis: Software like Moldflow simulates injection molding to predict flow, cooling, and potential defects.

  • Core & Cavity Design: The mold consists of:

    • Cavity (Female Part): Forms the outer shape of the preform.

    • Core (Male Part): Shapes the inner wall and neck finish.

    • Neck Ring: Ensures precise threading and sealing surface.

2. Material Selection

  • Mold Base: Typically made from hardened steel (e.g., P20, H13, S136) for durability.

  • Cavity & Core: High-grade stainless steel or tool steel (e.g., 420SS, NAK80) for corrosion resistance and polishability.

  • Cooling Channels: Copper or beryllium alloys for efficient heat transfer.

3. CNC Machining

  • Rough Machining: Blocks of steel are milled to approximate shapes.

  • Precision Machining: CNC milling, EDM (Electrical Discharge Machining), or wire cutting refines critical surfaces (neck finish, inner walls).

  • High-Speed Machining: For fine details like thread profiles.

4. Heat Treatment & Hardening

  • Hardening: Steel components are heat-treated (e.g., vacuum hardening) to achieve HRC 48–52 for wear resistance.

  • Tempering: Reduces brittleness post-hardening.

5. Surface Finishing

  • Polishing: Mirror-like finish (Ra < 0.05 µm) to prevent preform sticking and ensure smooth ejection.

  • Texture Application: For special finishes (e.g., matte or glossy preforms).

6. Assembly & Fitting

  • Cooling System: Channels are drilled for water circulation to control mold temperature.

  • Ejection System: Pins and sleeves are installed for preform ejection.

  • Alignment: Guide pins and bushings ensure precise core-cavity alignment.

7. Testing & Validation

  • Trial Molding: Test runs with PET material to check:

    • Dimensional accuracy (neck inner diameter, wall thickness).

    • Cooling efficiency (to prevent crystallinity or warping).

    • Ejection reliability.

  • Adjustments: Fine-tuning cooling rates, gate size, or venting if defects (e.g., splay, sink marks) occur.

8. Production & Maintenance

  • Mass Production: Mold is mounted in an injection molding machine for high-volume preform manufacturing.

  • Maintenance: Regular cleaning, lubrication, and inspection to prevent wear or corrosion.

Key Quality Considerations

  • Precision Tolerance: ±0.005 mm for critical areas (neck finish).

  • Cooling Uniformity: Avoids uneven shrinkage or stress in preforms.

  • Venting: Prevents air traps that cause burns or incomplete fills.

Advanced Techniques

  • Conformal Cooling: 3D-printed cooling channels for faster cycle times.

  • Multi-Cavity Molds: 48–144 cavities for high-output production.

This process ensures PET preform molds meet stringent requirements for clarity, strength, and consistency in bottle manufacturing. Let me know if you'd like details on a specific step!