Diaphragm Valve Diaphragm Molding for Stress-Free Clean Surfaces
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Solution Overview
Problem
The production of diaphragms for diaphragm valves, particularly those made from PTFE, is complex and involves challenges such as internal stresses and contamination risks due to the use of injection molding, which is not suitable for thin-walled components with long flow paths.
Innovation Solution
A method involving injection compression molding with a feed channel design that allows the plastics melt to flow radially into a mold cavity, avoiding internal stresses and sprue-related issues, and using a fluoropolymer like PFA to produce thin-walled diaphragms suitable for high-purity applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If injection molding is used to produce PTFE diaphragms, then production efficiency is improved, but internal stresses and contamination risks occur due to long flow paths in thin-walled components
Solution Approach 1:
The patent changes the material parameter from PTFE (which cannot be injection molded) to PFA (perfluoroalkoxy polymer), which can be successfully injection molded. This parameter change enables the use of injection molding for producing thin-walled diaphragms while avoiding the long flow path problems associated with PTFE, thus resolving the contradiction between production efficiency and manufacturing precision
Solution Approach 2:
The patent transitions from the conventional multi-step process (pressing powder, sintering, hot forming) to a direct injection molding process. This dimensional change in the production methodology eliminates the need for long flow paths and multiple processing steps, thereby reducing internal stresses and contamination risks while maintaining high productivity
2Device complexity
If conventional injection molding is used for thin-walled components, then production is simplified, but long flow paths cause internal stresses and material degradation
Solution Approach 1:
By changing the material parameter from PTFE to PFA, the patent enables direct injection molding of thin-walled diaphragms without requiring complex multi-step processes. This material parameter change allows for short flow paths that prevent internal stresses while simplifying the overall production process
Solution Approach 2:
The patent incorporates the sprue directly into the diaphragm structure as a predetermined feature, eliminating the need for separate sprue removal operations. This preliminary action simplifies the production process while avoiding the internal stresses associated with conventional sprue removal methods
3Loss of substance
If sprue is present on the wet side of the diaphragm, then material utilization is improved, but cleanability and purity are reduced due to sprue residues and surface tensions
Solution Approach 1:
The patent applies asymmetric design by placing the feed channel opening and resulting sprue exclusively on the dry side of the diaphragm, away from the wet side that contacts the process medium. This asymmetric arrangement maintains material utilization efficiency while eliminating sprue residues from the critical wet side, thereby preserving cleanability and purity
Solution Approach 2:
The patent applies local quality by differentiating the treatment of the two sides of the diaphragm: the dry side accepts the sprue and associated material flow, while the wet side maintains a clean, sprue-free surface. This localized differentiation ensures that the area requiring high purity and cleanability is protected from sprue-related contamination
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 method simplifies the production of diaphragms, reduces material usage, and ensures high-purity environments by preventing material entry into the process medium, enhancing cleanability and expanding applications to highly sterile conditions.
Implementation Method 1
The plastics melt thus flows radially evenly into the mold cavity in all directions and thus prevents internal stresses in the diaphragm produced in this way
Implementation Method 2
In the liquid state, the plastics melt thus covers a short flow path to the outside. This is particularly advantageous for shear-sensitive PFA
Implementation Method 3
The connecting pin is advantageously surrounded by the plastics melt on both sides as a result of the aforementioned spacing and is thus fixed to the diaphragm so as to be secured against pulling out
Data Source
AI summary
The invention relates to a method for producing a diaphragm for a diaphragm valve. The method includes the steps of conveying a plastics melt through at least one feed channel into a mold cavity which is delimited by a first mold and a second mold; moving the first and second molds toward one another; removing the at least one diaphragm from the mold cavity; and cutting off a sprue from the at least one diaphragm removed from the mold cavity.