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Valve Compression Mould, also be known as Umbrella Valve Mold, One-way Check Valve Molding, Membrane Moulding, Duckbill Valve Mold and Mushroom Valve Moulding, mainly produce silicone valve that be used as sealing elements in backflow prevention devices. The valves include umbrella valve, duckbill valve, membrane and cross slit valve. They are often used to block the return of gas or liquid, creating a one-way access.
Valve Compression Mould's advantage is that compare to transfer mlding and injection molding, it is one of the lowest cost molding methods; In addition, it wastes relatively little material, which gives it an advantage when dealing with expensive compounds.
Valve Compression Mould's Structures
Valve compression mold includes Three-layer Plate Structure, Transfer Structure, Top-bottom Structure and Keel Structure.
The umbrella valve mould is generally a three-layer plate structure, which is consist of a top plate, a bottom plate and a middle plate.
The raw material is placed on the middle plate, and the valve is formed after hot pressing. Its parting line is located on the curved side of the umbrella head.
Due to the tightness of the umbrella valve, some types of umbrella valves have undercuts. If its undercut is small, then it can be demold directly; If its undercut is large, direct demold will cause deformation or fracture of the product, then the valve needs to be demold from the bottom after the middle plate is inverted.
The duckbill valve mould can use either the keel structure or the three-layer plate structure. In general, the keel structure is suitable for large duckbill valves, and the parting line formed is located on both sides of the duckbill valve. For smaller duckbill valve, a three-layer plate structure mold is recommended, and the parting line is located at the bottom arc of the duckbill vlave. The parting line formed by the three-layer plate structure is generally invisible than the parting line formed by the keel structure, so the shaped duckbill valve surface is more perfect.
The membrane as shown in the figure adopts the transfer structure, which is composed of an ordinary three-layer plate structure and a transfer groove.
The metal sheet is placed on the middle plate and the raw material is placed in the transfer groove. Due to the undercut of the membrane, the formed membrane needs to be extruded from the hole above the middle plate to the bottom during the demold to avoid the deformation of the membrane caused by direct demold from the top.
The cross slit valve usually use the three-layer plate construction and top-bottom structure. Cross slit valve without undercut generally uses the top-bottom construction, so that the mold cost is less and the production efficiency is fast.
The cross slit valve with undercut usually needs to use three-layer construction, put the raw material on the bottom plate, and then put on the middle plate and formed on the middle plate. In order to prevent the valve from deformation or damage during demoulding, it is generally demoulded from below the middle plate.
Compression Mold Valve Materials
EPDM Valve | Hardness:30~90 Shore A |
Service temperature: -45℃~100℃ | |
Advantaged: Excellent heat resistance, weather resistance and ozone resistance. Good water resistance, electrical insulation, low temperature. | |
Disadvantages: Poor air tightness, self-viscosity and mutual viscosity, not resistant to non-polar solutions. |
Neoprene Valve | Hardness: 40~95 Shore A |
Service temperature:-45℃~135℃ | |
Advantages: Great resistance to exposure to the ozone, sunlight, oxidation, weather, oils, solvents, and several other materials. It is also tear resistant, is durable, and easily adheres to metals and fabrics. | |
Disadvantages: Poor resistance to strong oxidising acids, esters, ketone and certain hydrocarbons. |
FVMQ Valve | Hardness: 45~80 Shore A |
Service temperature: -60℃~180℃ | |
Advantages: Heat resistance, cold resistance, high voltage resistance, weather resistance, oil resistance, acid and alkali resistance, hydrocarbon solvent resistance. | |
Disadvantages: Poor wear and abrasion resistance. Not recommended for dynamic sealing. |
NBR Valve | Hardness: 50~90 Shore A |
Normal service temperature:-35℃~100℃ Low temperature resistance type: -55℃~100℃ High temperature resistance type: -30℃~125℃( in the air); -30℃~150℃( in the oil) | |
Advantages: Excellent resistance to oil and non-polar solvents, excellent bonding properties, good mechanical properties and air tightness. | |
Disadvantages: Weather resistance and ozone resistance is not strong. |
Compression Mould Surface Treatment
Sand blasting adopts compressed air as the power to form a high-speed jet beam to spray the material (copper ore, quartz sand, emery, iron sand) to the surface of the mold to be treated at high speed, remove the residual burrs and rust, and make the surface of the mold smoother. The surface requirements of the different products are different, and sand of different thickness is used. At the same time, the mechanical properties of the workpiece surface are improved, the fatigue resistance of the workpiece is improved, the adhesion between it and the coating is increased, the durability of the coating is extended, and the flow and decoration of the coating are also beneficial.
The sand blasting method is simple, so the cost is low. However, if the mold surface is sandblasted twice or multiple times, the tool edge of the mold will be damaged, resulting in more rough edges and thicker parting lines.
In the process of using chemical liquid to corrode the mesh, the liquid soaks the mold for a fixed time chemical reaction, which is not affected by the surrounding environment.
However, when the liquid corrodes the mesh, it needs to cover the non-texture area, which is difficult to operate. Moreover, the mesh life in the corrosion area of the liquid is relatively short, which can easily lead to the rapid scrapping of the mold core.
For the small mesh area that needs to be treated, there will be a dividing line between the mesh in different areas, so that the surface pattern of the products is inconsistent. In this case, chemical corrosion is suitable for products that need to form a large area of mesh.
EDM treatment is easy to operate, short time, high precision, suitable for small area of mesh processing. And the electrical spark hit out of the mesh is harder. Usually 5 Axis Machine is used for processing, so the cost of EDM is the highest.
Valve Compression Mould, also be known as Umbrella Valve Mold, One-way Check Valve Molding, Membrane Moulding, Duckbill Valve Mold and Mushroom Valve Moulding, mainly produce silicone valve that be used as sealing elements in backflow prevention devices. The valves include umbrella valve, duckbill valve, membrane and cross slit valve. They are often used to block the return of gas or liquid, creating a one-way access.
Valve Compression Mould's advantage is that compare to transfer mlding and injection molding, it is one of the lowest cost molding methods; In addition, it wastes relatively little material, which gives it an advantage when dealing with expensive compounds.
Valve Compression Mould's Structures
Valve compression mold includes Three-layer Plate Structure, Transfer Structure, Top-bottom Structure and Keel Structure.
The umbrella valve mould is generally a three-layer plate structure, which is consist of a top plate, a bottom plate and a middle plate.
The raw material is placed on the middle plate, and the valve is formed after hot pressing. Its parting line is located on the curved side of the umbrella head.
Due to the tightness of the umbrella valve, some types of umbrella valves have undercuts. If its undercut is small, then it can be demold directly; If its undercut is large, direct demold will cause deformation or fracture of the product, then the valve needs to be demold from the bottom after the middle plate is inverted.
The duckbill valve mould can use either the keel structure or the three-layer plate structure. In general, the keel structure is suitable for large duckbill valves, and the parting line formed is located on both sides of the duckbill valve. For smaller duckbill valve, a three-layer plate structure mold is recommended, and the parting line is located at the bottom arc of the duckbill vlave. The parting line formed by the three-layer plate structure is generally invisible than the parting line formed by the keel structure, so the shaped duckbill valve surface is more perfect.
The membrane as shown in the figure adopts the transfer structure, which is composed of an ordinary three-layer plate structure and a transfer groove.
The metal sheet is placed on the middle plate and the raw material is placed in the transfer groove. Due to the undercut of the membrane, the formed membrane needs to be extruded from the hole above the middle plate to the bottom during the demold to avoid the deformation of the membrane caused by direct demold from the top.
The cross slit valve usually use the three-layer plate construction and top-bottom structure. Cross slit valve without undercut generally uses the top-bottom construction, so that the mold cost is less and the production efficiency is fast.
The cross slit valve with undercut usually needs to use three-layer construction, put the raw material on the bottom plate, and then put on the middle plate and formed on the middle plate. In order to prevent the valve from deformation or damage during demoulding, it is generally demoulded from below the middle plate.
Compression Mold Valve Materials
EPDM Valve | Hardness:30~90 Shore A |
Service temperature: -45℃~100℃ | |
Advantaged: Excellent heat resistance, weather resistance and ozone resistance. Good water resistance, electrical insulation, low temperature. | |
Disadvantages: Poor air tightness, self-viscosity and mutual viscosity, not resistant to non-polar solutions. |
Neoprene Valve | Hardness: 40~95 Shore A |
Service temperature:-45℃~135℃ | |
Advantages: Great resistance to exposure to the ozone, sunlight, oxidation, weather, oils, solvents, and several other materials. It is also tear resistant, is durable, and easily adheres to metals and fabrics. | |
Disadvantages: Poor resistance to strong oxidising acids, esters, ketone and certain hydrocarbons. |
FVMQ Valve | Hardness: 45~80 Shore A |
Service temperature: -60℃~180℃ | |
Advantages: Heat resistance, cold resistance, high voltage resistance, weather resistance, oil resistance, acid and alkali resistance, hydrocarbon solvent resistance. | |
Disadvantages: Poor wear and abrasion resistance. Not recommended for dynamic sealing. |
NBR Valve | Hardness: 50~90 Shore A |
Normal service temperature:-35℃~100℃ Low temperature resistance type: -55℃~100℃ High temperature resistance type: -30℃~125℃( in the air); -30℃~150℃( in the oil) | |
Advantages: Excellent resistance to oil and non-polar solvents, excellent bonding properties, good mechanical properties and air tightness. | |
Disadvantages: Weather resistance and ozone resistance is not strong. |
Compression Mould Surface Treatment
Sand blasting adopts compressed air as the power to form a high-speed jet beam to spray the material (copper ore, quartz sand, emery, iron sand) to the surface of the mold to be treated at high speed, remove the residual burrs and rust, and make the surface of the mold smoother. The surface requirements of the different products are different, and sand of different thickness is used. At the same time, the mechanical properties of the workpiece surface are improved, the fatigue resistance of the workpiece is improved, the adhesion between it and the coating is increased, the durability of the coating is extended, and the flow and decoration of the coating are also beneficial.
The sand blasting method is simple, so the cost is low. However, if the mold surface is sandblasted twice or multiple times, the tool edge of the mold will be damaged, resulting in more rough edges and thicker parting lines.
In the process of using chemical liquid to corrode the mesh, the liquid soaks the mold for a fixed time chemical reaction, which is not affected by the surrounding environment.
However, when the liquid corrodes the mesh, it needs to cover the non-texture area, which is difficult to operate. Moreover, the mesh life in the corrosion area of the liquid is relatively short, which can easily lead to the rapid scrapping of the mold core.
For the small mesh area that needs to be treated, there will be a dividing line between the mesh in different areas, so that the surface pattern of the products is inconsistent. In this case, chemical corrosion is suitable for products that need to form a large area of mesh.
EDM treatment is easy to operate, short time, high precision, suitable for small area of mesh processing. And the electrical spark hit out of the mesh is harder. Usually 5 Axis Machine is used for processing, so the cost of EDM is the highest.
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