Foamed Thermoplastic Injection for Thick Plastic Walls
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Solution Overview
Problem
Current plastic molding processes face challenges in producing parts with great wall thicknesses, as they often result in high costs, prolonged production times, and inadequate mechanical characteristics, particularly when trying to achieve rigidity and resistance to strains, due to limitations in existing machinery and methods such as high-pressure injection and structural foam injection processes.
Innovation Solution
A hybrid process that combines conventional plastic molding techniques like injection, extrusion, or thermoforming with the injection of a foamed thermoplastic material within specific zones of the molded parts, using a low-pressure injection machine to achieve increased wall thicknesses without the need for costly specialized equipment, allowing for enhanced mechanical properties and reduced production cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-pressure injection process is used to mold parts with wall thickness up to 4.0/5.0 mm, then manufacturing precision is maintained, but mechanical strength and rigidity are insufficient for greater thicknesses
Solution Approach 1:
The patent uses a two-material system combining a thermoplastic matrix material with a foaming agent. The foamed thermoplastic creates a composite structure with air pockets distributed throughout the material, providing both structural integrity and enhanced insulation while achieving greater wall thicknesses without compromising molding precision.
Solution Approach 2:
The patent changes the physical and chemical parameters of the molding process by introducing a foaming agent that reacts to create gas bubbles within the thermoplastic material. This parameter change allows the material to expand in-situ, achieving greater thickness while maintaining dimensional control and molding precision through controlled foam expansion.
2Strength
If wall thickness is increased to improve mechanical characteristics, then strength and rigidity are improved, but manufacturing time and production costs increase
Solution Approach 1:
The patent utilizes the phase transition of the foaming agent, which transforms from a liquid or dissolved state into a gas phase upon reaction or heating. This phase transition creates expanding foam cells within the thermoplastic material, rapidly increasing volume and achieving greater wall thickness without proportionally increasing manufacturing time, as the foam expansion occurs quickly during or after injection.
3Strength
If wall thickness is increased beyond 5.0 mm to achieve greater strength, then mechanical characteristics improve, but sink marks and deformations occur
Solution Approach 1:
The patent creates a porous internal structure within the thermoplastic material through controlled foaming. The distributed air pockets throughout the material provide internal support and reduce density, allowing thick walls to be formed without the sinking and deformation issues that occur in solid materials of comparable thickness. The porous structure acts as internal reinforcement.
4Strength
If structural foam injection process is used to mold parts with wall thickness greater than 6.0 mm, then mechanical strength is improved, but production costs and device complexity increase
Solution Approach 1:
The patent employs a multi-functional approach where a single thermoplastic material serves both as the structural matrix and as the carrier for the foaming agent. This eliminates the need for separate foam injection systems or specialized equipment, as the foaming process is integrated into the existing thermoplastic molding operation. The same injection molding machine can produce both solid and foamed parts by simply changing the material formulation.
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 hybrid process enables the production of plastic parts with significantly improved mechanical characteristics, such as impact strength and bending strength, while reducing production costs and time, and eliminating the need for expensive machinery, allowing for thicker walls without extended cooling periods.
Implementation Method 1
injection of a foamed thermoplastic material, with a foaming or expanding agent added thereto
Implementation Method 2
a thermoplastic material which, with a foaming or expanding agent added thereto, is injected within zones
Data Source
Figure 1A~1C
Figure 1D~1F
Figure 1G~1H
AI summary
The present invention relates to a hybrid process for producing molded plastic articles by reinforcing the walls thereof through the injection of a foamed thermoplastic material, thus increasing the thickness of the wall in previously determined zones in order to improve the mechanical characteristics thereof. According to the invention, said hybrid process comprises to strengthen previously defined zones of the plastic articles formed by any of the already known processes, such as: injection, extrusion, extrusion-blowing, injection-blowing, thermoforming, roto-molding, or any combination thereof; and afterwards the injection of a foamable thermoplastic material to fill up said strengthening predesigned zones.