Spark Plug Insulator Injection Molding with Multi-Point Feeding
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Solution Overview
Problem
Existing methods for manufacturing insulators for spark plugs via injection molding often result in reduced dielectric strength properties due to insufficient material density at the front and rear ends, caused by inadequate material injection positions and long material movement distances, leading to pressure loss and burr formation.
Innovation Solution
The method involves injecting material into a mold cavity from multiple positions along the axial and circumferential directions, reducing the movement distance and pressure loss, and injecting from the inner circumferential surface to minimize burr formation and enhance density, thereby maintaining dielectric strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If material is injected from a single position at the front end of the insulator, then the injection process is simple, but the material movement distance is long causing insufficient density at the rear end and reduced dielectric strength
Solution Approach 1:
The injection system is segmented into multiple injection positions (front end injection position and rear end injection position) along the axial direction. This segmentation allows material to be injected from both ends simultaneously, reducing the movement distance to the center region and ensuring uniform density distribution throughout the insulator, thereby resolving the contradiction between simple injection system and density uniformity.
2Ease of manufacture
If material is injected from the front end position only, then the injection process is straightforward, but pressure loss occurs during long material movement causing insufficient density and reduced dielectric strength
Solution Approach 1:
The injection process is segmented into multiple injection positions including front end and rear end positions. By injecting material from both ends simultaneously, the movement distance for material is halved, reducing pressure loss and ensuring sufficient density and dielectric strength properties throughout the insulator, while maintaining ease of manufacture through a relatively simple dual-position injection system.
3Device complexity
If material is injected from a single position at the maximum diameter portion, then the injection setup is simple, but the long material movement distance causes insufficient density at front and rear ends reducing dielectric strength
Solution Approach 1:
The mold structure is segmented to include multiple injection positions: front end injection position, rear end injection position, and maximum diameter portion injection position. This segmentation enables material to be injected from multiple locations simultaneously, ensuring uniform density distribution throughout the insulator including the front and rear ends, while maintaining relatively simple mold structure.
Solution Approach 2:
The injection system transitions from single-point injection to multi-point injection along the axial dimension. By adding injection positions at both front and rear ends in addition to the maximum diameter portion, the system creates a three-dimensional injection network that ensures uniform material distribution and density throughout the insulator volume, resolving the density distribution issue.
4Ease of manufacture
If material is injected from positions far from the cavity walls, then the injection process is simple, but burrs form at the front end requiring removal processes that may cause cracks or breaking
Solution Approach 1:
The injection positions are strategically located at the front end and rear end positions where the cavity walls are accessible. By injecting material directly at these locations, the material fills the cavity uniformly without excessive pressure buildup at the front end, preventing burr formation while maintaining simple injection process.
Data Source
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Figure 3(A)~3(B)
AI summary
When an insulator is formed by means of injection molding, reduction in dielectric strength property of the insulator is reduced. A method for manufacturing an insulator for a spark plug includes a molding process of forming a cylindrical molded product having an axial hole that extends in a direction of an axial line, by means of injection molding using a mold that has a columnar cavity therein and a bar-shaped member disposed in the cavity and extending in the direction of the axial line. In this method, the molding process includes an injection step of injecting a material containing a ceramic. In the injection step, the material is injected into the cavity from a plurality of injection openings that are opened at an inner circumferential surface, of the mold, that forms the cavity. The plurality of injection openings include two or more injection openings located at different positions in the direction of the axial line, or two or more injection openings located at different positions in a circumferential direction.