Offset Mold Twinning for Variable Wall Thickness
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Solution Overview
Problem
Existing thermoforming and blow molding processes are limited in creating plastic parts with selectively increased wall thickness, as they require uniform material thickness, leading to increased costs when thicker materials are needed in specific areas, such as hinge regions or structural components, which can result in material failure or higher production costs.
Innovation Solution
A method involving offset molds that allow for the simultaneous molding of two parts with increased thickness areas adjacent to reduced thickness areas, using a combination of single sheet and twin sheet thermoforming or blow molding, where the mold portions are arranged face to face with offset sections to create a composite part that can be separated, enabling cost-effective production of parts with varying thicknesses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If uniform thick material is used throughout the part, then structural strength and durability are improved, but material cost and weight increase
Solution Approach 1:
The patent applies local quality by creating parts with non-uniform wall thickness, where specific areas (such as hinge regions, connection points, and high-stress zones) have increased thickness while other areas maintain standard thickness. This is achieved through the offset mold technique that selectively deposits additional material in predetermined locations, providing structural strength exactly where needed without unnecessarily increasing material quantity throughout the entire part.
2Quantity of substance
If offset mold technique is used to create selective thickness areas, then material efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the mold into offset portions that correspond to different thickness zones of the final part. The mold is structured with first and second offset portions that are laterally displaced relative to each other, allowing selective formation of thick and thin areas. This segmented approach to mold design enables precise control over material distribution while maintaining relatively simple mold construction.
3Reliability
If thicker material is used in critical areas, then reliability and durability are improved, but production cost increases
Solution Approach 1:
The patent applies parameter changes by varying the wall thickness parameter selectively throughout the part geometry. The offset mold technique enables continuous or discrete changes in material thickness based on local structural requirements. Critical areas such as hinges, connection points, and high-stress zones are formed with increased thickness parameters, while non-critical areas use standard thickness, thereby optimizing durability without proportionally increasing production cost.
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 method allows for the cost-effective production of plastic parts with selectively increased wall thickness, reducing material waste and tooling costs while maintaining structural integrity, particularly in areas prone to stress or wear, like hinges and base connections.
Implementation Method 1
providing a heated piece of thermoplastic material
Implementation Method 2
molded utilizing vacuum or pressure or both to draw the material into a one sided mold
Data Source
AI summary
Thermoplastic parts are made of predominantly single unit thickness but with marginal areas of increased thickness by molding two parts in a common mold having overlapping mold portions. Two thicknesses of thermoplastic material are molded together in the areas of increased thickness at opposite ends of the common mold and the parts are separated from one another by trimming such that each part has an area of increased solid wall thickness and an area of reduced thickness.