Movable Core Injection Molding for Thick Cosmetic Jars
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Solution Overview
Problem
Existing methods for manufacturing cosmetic product jars with thick bottoms using plastic materials face issues such as visible furrows and the need for expensive multi-nozzle systems or overmolding, which result in unsightly marks and increased costs.
Innovation Solution
A process that enlarges the molding cavity during injection by moving a core away from the injection station using a gear mechanism with a toothed wheel, allowing a single injection nozzle to achieve the desired wall thickness without waves or traces, using a single layer of copolyester material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a standard injection nozzle with small opening diameter is used to minimize injection point visibility, then the injection point appearance is improved, but significant filling rippling occurs around the injection point in thick walls
Solution Approach 1:
The core is made movable instead of fixed, allowing it to dynamically adjust its position during the injection process. The core moves away from the injection nozzle as injection proceeds, progressively enlarging the molding cavity volume to accommodate thick wall formation without rippling, while maintaining a small nozzle opening for clean injection point appearance.
Solution Approach 2:
The core is positioned in advance at an initial location that defines a starting molding cavity volume suitable for the nozzle opening size. This preliminary positioning allows the injection process to begin with optimal cavity-n nozzle matching, preventing immediate rippling while the core subsequently moves to enable thick wall formation.
2Manufacturing precision
If the number of nozzles is increased or overmolding is performed to achieve thick walls, then the wall thickness is improved, but visible marks appear where materials meet and expensive equipment is required
Solution Approach 1:
The core is extracted from its traditional fixed role and transformed into a movable component driven by a gear mechanism. This extraction from the static mold structure enables dynamic cavity volume adjustment during injection, allowing single-nozzle thick wall formation without the surface marks inherent in multi-nozzle or overmolding processes.
Solution Approach 2:
The molding cavity volume parameter is changed dynamically during the injection process through core movement. The cavity volume increases progressively as the core moves away from the injection nozzle, enabling the same small-opening nozzle to successfully fill thick walls by adapting the cavity size to match the filling progression.
3Manufacturing precision
If successive injections or overmolding is used to create thick walls, then the desired thickness is achieved, but expensive equipment with multiple nozzles or overmolding capability is required
Solution Approach 1:
The movable core serves multiple functions: it defines the initial molding cavity volume, dynamically adjusts cavity volume during injection, and enables thick wall formation with a single nozzle. This multi-functionality eliminates the need for specialized multi-nozzle equipment or overmolding machinery, achieving thick walls with standard injection equipment augmented by a gear-driven core mechanism.
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
Enables the production of jars with uniform thickness without visible injection marks or furrows, using a standard-sized nozzle and reducing production costs by eliminating the need for multi-nozzle systems or overmolding.
Implementation Method 1
a gear mechanism with a toothed wheel (53) in helical connection with the core (40)
Implementation Method 2
said gear comprising a toothed wheel (53) in helical connection with the core (40)
Data Source
Figure 1~2
Figure 3a~3b
AI summary
A method for producing a receptacle, in particular a receptacle for a cosmetic product, includes injecting a material into a moulding cavity in an injection step. The moulding cavity is expanded during the injection step in such a way as to increase the thickness of a wall of the receptacle in a separation step. A receptacle is obtained using such a method and a device is used for implementing said method.