Resin Pipe Annular Groove Step Elimination
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Solution Overview
Problem
Resin pipes manufactured using gas assist molding methods often exhibit a step in the annular groove on the outer circumferential surface due to the parting line of the mold, which compromises the sealing properties of the sealant.
Innovation Solution
A method involving a two-part type mold with a holding portion of larger diameter than the cavity, where an insert member with a cylindrical shape and an annular groove is fitted and integrated with the resin during the injection molding process, eliminating the need for a post-process bond and ensuring no step is formed in the annular groove.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a two-part type mold is used for resin injection molding, then the manufacturing process is simple and efficient, but a step is formed on the outer circumferential surface at the parting line location
Solution Approach 1:
A filler material is introduced as an intermediary substance into the cavity at the parting line location during injection molding. This filler material fills the gap created by the parting line, preventing the formation of a step on the outer circumferential surface. The filler material is injected through the parting line region and integrates with the resin to eliminate surface irregularities while maintaining the simplicity of the two-part mold system.
2Reliability
If an annular groove is formed in the resin pipe for sealant fitting, then sealing function is provided, but a step is generated in the annular groove due to the parting line, reducing sealing properties
Solution Approach 1:
The filler material acts as a mediator that specifically targets the parting line region within the annular groove. By injecting the filler material into the cavity at the parting line location, the groove surface is restored to flatness, ensuring proper sealing contact for the sealant while maintaining the groove's functional geometry for sealant retention.
3Manufacturing precision
If a cylindrical molding mold is used to avoid steps in the annular groove, then sealing properties are improved, but additional equipment and post-molding fitting steps are required
Solution Approach 1:
The filler material injection capability is extracted and integrated into the existing two-part mold system. Rather than requiring a completely different cylindrical molding mold, the solution extracts the essential function of step prevention by introducing a filler material through the parting line region, thereby maintaining the original mold structure while achieving the desired surface flatness.
Solution Approach 2:
The filler material injection process is merged with the existing injection molding cycle. The filler material is injected during the molding process itself, combining the step-prevention function with the primary resin injection operation, thereby eliminating the need for separate post-molding fitting steps and additional equipment.
4Manufacturing precision
If a filler material is injected into the cavity at the parting line location, then steps in the annular groove are eliminated, but the injection process becomes more complex
Solution Approach 1:
The filler material is injected preliminarily during the injection molding process itself, before the resin fully solidifies. By performing the filler material injection as a preliminary action within the existing molding cycle, the process avoids the need for separate post-processing steps, and the complexity is managed through integrated timing rather than additional equipment.
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 approach allows for the simple manufacturing of resin pipes with annular grooves on the outer surface without steps, enhancing sealing properties and eliminating the need for additional bonding processes, thus improving the manufacturing efficiency and quality of the resin pipes.
Implementation Method 1
injecting resin that is molten into a cavity formed in a mold of a two-part type and by subsequently injecting an assist material into the cavity and curing the resin that is injected
Implementation Method 2
injecting an assist material into the cavity... Instead of high-pressure gas, water, metal beads, or resin beads may be injected as an assist material into the mold at high pressure
Data Source
Figure 1(A)~1(B)
Figure 2
Figure 3
AI summary
Provided is a manufacturing method that can more simply manufacture a resin pipe having no step, the step due to a parting line of a mold, in an annular groove on an outer circumferential surface, by using a gas assist molding method or the like. A holding portion (3a) having a diameter larger than that of a cavity (3) is formed in communication with the cavity (3), in an area of a two-part type mold (2a, 2b), the area including a portion corresponding to an annular groove (8a). Subsequently, an insert member (8) formed in a cylindrical shape and provided with, on an outer circumferential surface, the annular groove (8a) having no step in a groove surface is fitted to the holding portion (3a), and then the mold (2a, 2b) is closed. On an inner circumferential surface of the insert member (8), a surface treatment layer (9) having a surface roughness rougher than those of other portions of the insert member (8) is formed. Molten resin (4) is injected into the cavity (3); thereafter, an assist material (5) is injected into the cavity (3) to mold the resin (4) into a desired pipe body (7). Then, the insert member (8) and the pipe body (7) are integrated along with curing of the resin (4).