Stretching Rod Support for Stable Preform Blow Molding

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Solution Overview

Problem

Existing injection stretch blow molding machines face issues with preform deformation and uneven thickness due to shrinkage during the molding process, leading to increased molding cycles and potential ruptures in hollow molded articles.

Innovation Solution

A method involving a stretching rod with a distal end portion having a peripheral wall matching the inner preform shape, supporting the preform until suitable temperature is reached, and using blow air to separate the preform, combined with a preform separation step to maintain thickness uniformity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the preform is supported by the stretching rod from the beginning of the blow molding process, then preform deformation is suppressed and skin layer thickness is maintained, but the stretching rod cannot be extended to press down the preform for stretching

Engineering Contradiction:

Improvepreform deformation controlVSAvoidmolding cycle time

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The stretching rod is designed with extendable functionality, transitioning from a retracted state during the waiting period (where it supports the preform) to an extended state during the stretching operation. This dynamic adjustment allows the same component to fulfill both protective and functional roles at different stages of the process.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The stretching rod is positioned in advance to support the preform before the blow molding operation begins. This preliminary support action prevents deformation during the critical waiting period when the preform temperature is stabilizing, ensuring the skin layer thickness is maintained before stretching occurs.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If the preform is stretched immediately after injection molding, then the molding cycle is shortened, but preform deformation occurs due to shrinkage and skin layer thickness changes

Engineering Contradiction:

Improvemolding cycle timeVSAvoidpreform shape stability

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The stretching rod acts as an intermediary support element between the preform and the deformation forces. By providing continuous support from the initial position, it mediates the thermal shrinkage process, allowing the preform to stabilize without deforming the skin layer.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If the stretching rod is extended to press down the preform, then the preform is stretched properly to form the hollow molded article, but the contact between the preform and stretching rod causes uneven thickness

Engineering Contradiction:

Improvestretching operation effectivenessVSAvoidwall thickness uniformity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The support function is extracted from the stretching operation itself. The stretching rod provides support during the waiting period, then is retracted or adjusted during the stretching operation to avoid interfering with the uniform wall thickness formation. This separation of support and stretching functions eliminates the cause of uneven thickness.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The stretching rod is designed with extendable functionality, transitioning from a retracted state during the blowing operation to an extended state for the stretching operation. This dynamic adjustment allows the same component to fulfill both protective and functional roles at different stages of the process.

Inventive Principle:

Principle #15Dynamics

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach suppresses preform deformation and shortens the molding cycle by maintaining skin layer thickness, ensuring consistent article quality and reducing defects.

Implementation Method 1

a preform supporting step of inserting a distal end portion of a stretching rod into the preform and bringing the distal end portion into contact with the preform to support the preform

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

a preform separation step of supplying blow air into the preform to release the contact between the preform and the distal end portion

Methodology Applied

Scientific EffectGas pressure: Pressure Increase

Data Source

PatentEP4706938A1Method for molding hollow molded article, and stretching rod and injection stretch blow molding machine used in the method

Publication Date: 2026.03.11 A K TECH LAB INC

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AI summary

A method for molding a hollow molded article, which can suppress deformation of a preform and shorten a molding cycle of the hollow molded article, and a stretching rod and an injection stretch blow molding machine used in the method are provided. The method for molding a hollow molded article, includes: an injection molding process of injection molding a preform; and a blow molding process of obtaining a hollow molded article by stretch blow molding the preform in a blow molding section. The blow molding process includes a preform supporting step of inserting a distal end portion of a stretching rod into the preform and bringing the distal end portion into contact with the preform to support the preform, and a preform separation step of supplying blow air into the preform to release the contact between the preform and the distal end portion.