Centring Stem Alignment in Plastic Injection Moulding
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Solution Overview
Problem
Existing injection moulding apparatuses for plastic containers, such as single-dose bottles, face issues with misalignment of male and female elements leading to inconsistent wall thickness, increased production rejects, material waste, and aesthetic defects due to wear and metal inclusions, which are costly and affect product quality and consumer trust.
Innovation Solution
An apparatus with automatic centring stems having a locator surface with a decreasing cross-section that slides transversally within the matrix die, allowing precise alignment and reduced wear by minimizing sliding contact, and using anti-friction coatings to prevent metal scraps from entering the moulding space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If automatic centring stems are used to align male elements with female matrix die, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent introduces centring stems as intermediary elements that mediate between the male elements and the female matrix die. These stems slide within guide holes to provide automatic centring, ensuring precise alignment without requiring complex external positioning mechanisms. The stems act as a simple yet effective intermediary that resolves the alignment problem while adding minimal structural complexity.
2Manufacturing precision
If stems slide repeatedly in holes to provide centring, then manufacturing precision is improved, but reliability deteriorates due to material wear and metal scrap formation
Solution Approach 1:
The patent extracts the harmful sliding friction mechanism by introducing a lubrication system that separates the stem surfaces from direct metal-to-metal contact. The lubricant film is introduced into the guide holes to eliminate direct friction between the stems and hole walls, thereby preventing wear and metal scrap formation while preserving the centring function.
Solution Approach 2:
The patent changes the physical parameters of the stem surfaces by applying anti-friction coatings that reduce the coefficient of friction. This parameter change transforms the interaction between stems and guide holes from high-friction sliding to low-friction movement, significantly reducing wear and extending mould durability while maintaining centring precision.
3Manufacturing precision
If narrow tolerances are used for stem-hole coupling to ensure precise centring, then manufacturing precision is improved, but ease of manufacture deteriorates due to increased difficulty in assembly
Solution Approach 1:
The patent applies preliminary action by pre-coating the stem surfaces with anti-friction materials during manufacturing. This preliminary treatment reduces the coefficient of friction before assembly, allowing for easier insertion and adjustment of stems into guide holes even when narrow tolerances are specified. The lubricated surfaces facilitate smooth assembly while maintaining the required centring precision.
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 solution ensures consistent wall thickness within tight tolerance intervals, significantly reduces production rejects and costs, and maintains product quality by preventing metal inclusions, making the process more efficient and economically viable.
Implementation Method 1
anti-friction coatings to prevent metal scraps from entering the moulding space
Data Source
AI summary
The apparatus (1) for the injection molding of containers in plastic material comprises a mold (2) having a female matrix die (3) and a corresponding male element (4) that can be coupled to one another, between the female matrix die (3) and the male element (4) being defined a forming inter-space (5) of at least a container, and at least a centering stem (10) for centering the male element (4) with respect to the female matrix die (3), which comprises a first extremity (12) having a locator surface (12a) for the male element (4), is sliding along a sliding direction (D) substantially transversal with respect to the male element (4) inside a corresponding centering hole (11) obtained in the female matrix die (3), and is mobile with reciprocating motion between a backward configuration, in which the locator surface (12a) is substantially arranged in correspondence to the inner surface of the female matrix die (3), and a forward configuration, in which the locator surface (12a) is up fast on the male element (4), the first extremity (12) of the centering stem (10) having a cross section substantially decreasing towards the locator surface (12a).