Elongated Hollow Article Molding With Core Positioning Control
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Solution Overview
Problem
Conventional injection molding techniques face challenges in producing elongated hollow articles, such as urinary catheters, with consistent diameters and flex patterns, particularly due to core displacement and material degradation issues, limiting the production of long tubular parts with adequate tolerances and reproducibility.
Innovation Solution
A method and apparatus that balance material flow rate, end mold speed, and fluid flow rate, incorporating cooling mold blocks and controlled temperature settings to stabilize and shape the molding process, allowing for single-step production of elongated hollow articles with varying diameters and geometries, including a proximal tip and distal funnel-shaped connector end.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional injection molding is used to produce elongated hollow articles, then the manufacturing process is simple, but core displacement occurs and manufacturing precision deteriorates
Solution Approach 1:
The core pin is pre-positioned in a substantially centered, straight-line configuration relative to the central axis of the mold cavity before injection. This preliminary positioning prevents displacement during the molding process, directly resolving the contradiction between simple manufacturing and high precision by establishing the correct geometry before the harmful injection pressure is applied.
2Productivity
If injection pressure is increased to fill the cavity, then productivity improves, but core displacement increases and manufacturing precision worsens
Solution Approach 1:
The core pin is designed with features that preemptively counteract the harmful effects of injection pressure. The pre-centered positioning and straight-line configuration create a stable geometric framework that resists displacement even under high injection pressures, allowing fast cavity filling without sacrificing the straightness of the central hole.
3Speed
If plastic material temperature is raised to prevent solidification during slow injection, then material flow improves, but material degradation occurs
Solution Approach 1:
The invention changes the geometric parameters of the mold cavity and core pin arrangement to optimize material flow characteristics. By designing the cavity and core positioning to promote balanced flow distribution, the process achieves adequate material flow at lower temperatures, preventing both solidification issues and thermal degradation of the plastic material.
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 elongated hollow articles with precise inner and outer diameters, reduced manufacturing costs, and improved flex pattern consistency, overcoming core displacement and material degradation issues.
Implementation Method 1
As the cavity is filled, an end mold starts moving. Molding material is injected into the cavity including the end cavity
Implementation Method 2
The outer mold and the mold core are heated to a temperature above the melting temperature of the molding material
Implementation Method 3
The end mold is cooled, i.e., well below the melting temperature of the polymer molding material
Data Source
Figure 1
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AI summary
A molding apparatus includes a mold comprising a stationary outer mold with a substantially tubular mold cavity, a moveable end mold with an end mold cavity alignable with the tubular mold cavity, and a stationary elongated mold core with a fluid channel therethrough, the mold core extending through the tubular cavity into the end mold cavity. A method of using the apparatus includes injecting a molding material at a material flow rate into the mold, moving the end mold at a speed in a linear direction from a first position to a second position, supplying a fluid at a fluid flow rate to the fluid channel, and varying at least one of the material flow rate, the end mold speed and the fluid flow rate as the end mold moves from the first position to the second position.