Mold Core Cooling for Plastic Pipe Fitting Flow Resistance
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Solution Overview
Problem
Existing mold assemblies for injection molding of small-sized plastic pipe fittings with long channels and rounded inner corners face challenges in maintaining structural integrity and cycle time due to high pressure and temperature conditions, making it difficult to produce economically viable products with reduced flow resistance.
Innovation Solution
Incorporating a built-in cooling arrangement within the core members of the mold assembly, which includes elongated blind holes, high thermal conductivity heat conductor elements, and cooling fluid channels, allows for effective heat transfer and enables the production of small-sized pipe fittings with rounded inner corners within a reasonable cycle time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If collapsible core arrangement is used to create rounded inner corner face, then flow resistance is reduced, but manufacturing complexity and difficulty increase
Solution Approach 1:
The core arrangement is divided into multiple core members (first core member, second core member, third core member) that can move independently. Each core member has specific functions: the first defines the outer portion, the second defines the inner portion with rounded corners, and the third supports the second core member. This segmentation allows the complex rounded corner geometry to be achieved while maintaining manageable complexity through functional division.
Solution Approach 2:
The core members are designed with dynamic movement capabilities during the injection molding cycle. The second core member moves to advance and retract positions to create the rounded inner corner face, while the third core member provides dynamic support. This dynamic behavior enables the formation of rounded corners without requiring permanently complex core structures.
2Volume of moving object
If small-sized core members are used to produce small pipe fittings, then product size is reduced, but structural strength and reliability deteriorate
Solution Approach 1:
The core members are made from tool steel or beryllium copper alloy, which are high-strength materials capable of withstanding the severe injection molding conditions (1000 bar pressure, 400°C temperature). These materials provide the necessary strength-to-size ratio, allowing small core members to maintain structural integrity under high pressure and temperature while producing small pipe fittings.
Solution Approach 2:
The core members have optimized geometric designs with specific dimensional ratios. The inner diameter to rounding radius ratio (D/R) is maintained between 2-5, and the channel length to inner diameter ratio (L/D) is maintained between 3-8. These local geometric qualities ensure that the small core members have sufficient structural strength at critical locations while maintaining the required rounded corner geometry.
3Length of moving object
If long channel parts are used in small pipe fittings, then flow path length increases, but manufacturing precision and cycle time control become difficult
Solution Approach 1:
The second core member is designed with a predetermined rounded corner geometry that is formed during the injection molding process. The core member's shape is pre-configured to create the desired rounded inner corner face, ensuring manufacturing precision is achieved through the tooling design itself rather than requiring post-processing or complex adjustments during production.
4Use of energy by moving object
If high pressure and temperature conditions are used for injection molding, then material flow improves, but core member durability and cycle time efficiency worsen
Solution Approach 1:
The selection of tool steel or beryllium copper alloy for the core members provides high thermal conductivity and mechanical strength, enabling the cores to withstand repeated exposure to 1000 bar pressure and 400°C temperature conditions without degrading, thus extending service life while maintaining material flow capability.
Solution Approach 2:
The core members are designed with optimized geometric parameters including specific dimensional ratios (D/R = 2-5, L/D = 3-8) and surface finishes that facilitate material flow under high pressure and temperature conditions. These parameter optimizations reduce the severity of thermal and mechanical stresses on the core members, improving durability while maintaining effective material flow.
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
The cooling arrangement significantly reduces cycle time and improves the production of small-sized pipe fittings with reduced flow resistance by maintaining core member strength and efficiency under high pressure and temperature conditions.
Implementation Method 1
a built-in cooling arrangement for cooling of the core package, the cooling arrangement extending longitudinally inside said core member over a substantial length of said core member
Implementation Method 2
cooling fluid channels, allows for effective heat transfer
Data Source
AI summary
A mold assembly (1) for injection molding of a plastic pipe fitting (2, 3). The pipe fitting comprises an elbow-shaped or a tee-shaped internal flow channel (4). At least one of the first core member (14) and the second core member (15) of the core package (12, 13) comprises a built-in cooling arrangement (20) for cooling of the core package (12, 13), the cooling arrangement (20) extending longitudinally inside said core member over a substantial length of said core member. The pipe fitting (2, 3) comprises an elbow-shaped or tee-shaped internal flow channel (4) comprising at least two channel parts (5, 6, 7) arranged at a first angle (α) in relation to each other, the channel parts (5, 6, 7) each having a circular cross-section and a smoothly radiused inner corner face (8) between each two channel parts being at said first angle in relation to each other, the at least one of the channel parts having an inner diameter D, a length L from central corner point to the end of the channel part, the inner corner face having a rounding radius R. The ratio (D/R) of the inner diameter D and the rounding radius R is in the range 2 to 5, and the ratio (L/D) of the length L and inner diameter D is in the range 8 to 3.