Rubber Compression Moulding is a highly effective method for producing a wide range of rubber products and parts. It is known for its ability to make precise rubber parts with consistent quality. This technique is widely used across various industries. In this guide, Crowns Machinery will take you through the detailed process, types, benefits, and applications of rubber compression molding.
Table of Contents
compression moulding process Flow
Material Preparation: The process starts with picking rubber materials. These are usually raw rubber or rubber compounds. These compounds may have additives. These include accelerators, curing agents, and reinforcing agents. They improve the final product’s properties.
Mold Preparation: In compression molding, a two-part mouldmold is commonly used, usually made of metal. The mold is preheated before the process begins. It is heated to a specific temperature to help curing.
Loading the Mould: Next, the rubber material is placed into the open mold cavity.
Closing the Mould: Once the mold cavity is filled with the rubber, the two mold halves are closed. They squash the rubber between them.
Vulcanization: Heat and pressure are then applied to the mold. This activates the vulcanization process, shaping the rubber and causing it to harden.
Cooling: Vulcanization is done. Then, the mold is opened, and the new rubber product is removed. The product is allowed to cool and solidify, ensuring its final shape and properties.
Trimming and Inspection: Finally, any extra material is trimmed off. The quality of the parts is inspected to ensure they meet the desired specs.
Rubber Compression Moulding types
Flat Plate Mold: The flat plate mold consists of two parallel metal templates, each containing mold cavities. This is a common and effective molding process. It involves closing the templates to push the rubber into the mold. There, it fills the entire cavity. The gap size between the templates determines the thickness of the final product. This method is frequently used to produce basic rubber items like gaskets and seals. It is simple and cheap. This makes it great for small to medium-sized production runs.
Extrusion Type Mold: Extrusion-type molds typically comprise two or more metal parts that align to match the final product’s shape. Unlike closed chamber molds, the opening of an extrusion mold produces a continuous shape, such as rubber strips or tubes. This method is great for making rubber products with even shapes. It is good for shapes that do not change. It makes production efficient and uniform.
Rotational Molds: Rotational molds are a special type of mold. They combine parts of compression molding and rotational molding. Equipped with a rotating mechanism, these molds allow the product to rotate during the molding process. This technique is great for making rubber items with unique shapes. It’s especially good for items with holes, ridges, or complex shapes. Common examples include seals, tire treads, and various rubber kits. The mold rotates. This spreads the material evenly. It improves the strength and detail of the final product.
Advantages & Disadvantages
Advantages of the process
Suitable for Complex Shapes: Compression-molded rubber can make many rubber products. These include ones with intricate designs. This flexibility makes it ideal for creating complex components.
Low Cost: Rubber compression molding is usually cheaper than injection molding. This is true, especially for small to medium production runs. This cost efficiency makes it attractive to manufacturers.
Adaptable to Small Batch Production: It is great for small batches because the equipment is cheap. So, it is good for limited runs.
No Need for Special Rubber Formulations: Rubber compression molding is different from some other molding methods. It does not need special rubber formulations. This makes it more versatile and easy to use.
Suitable for Large Products: This method is good for making big rubber products, like large seals. It does not need expensive machinery.
Simple Operation and Maintenance: The equipment used in rubber compression molding is easy to use. It is also easy to maintain. This reduces labor and maintenance costs.
Wide Applicability to Rubber Materials: Rubber compression molding can handle many types of rubber. These include NBR, silicone, and EPDM.
High Precision: The process can produce highly precise molded parts. It ensures consistency and accuracy in the final products.
Durable Products: Products made through rubber compression molding are durable. They are also known for their consistent quality, making them useful for various applications.
Disadvantages of the process
Relatively Slow Production Speed: Rubber compression moulding molding is slower than other methods like injection or extrusion molding. This makes it less suitable for large-scale production.
Manual Operations: The process can involve extra manual steps. This may reduce productivity and limit the automation possible.
Limited to Simple Shapes: It is effective for simple products. But, it is less suitable for complex or detailed items. For those, rubber injection molding might be a better option.
Waste of Raw Materials: Compression can create waste. It happens due to gaps or excess material in the molds. This waste raises costs and hurts sustainability.
Longer Molding Cycle: The full molding cycle has compression, vulcanization, and cooling. It is relatively long. This may lead to longer waits between batches.
Limited Product Consistency: In mass production, keeping consistent products is hard. This is because some steps are manual and there is little automation.
Reliance on Vulcanization: Vulcanization is critical. It ensures the elasticity and performance of rubber products. But, it needs a lot of time and energy. This adds to the production cost and complexity.
rubber compression VS rubber injection
operation principle
- Rubber compression moulding: We put rubber in the open mould. Then we close the mould, and the rubber comes out to form the product shape. Next, we heat the mould, and the rubber finally cures.
- Rubber injection moulding: Rubber is heated, injected into a closed mould, and fills every corner. Then, the rubber is cured.
production efficiency
- Rubber compression moulding: The production speed is slow, which is good for making small and medium-sized batches. It requires more manual work and has low automation.
- Rubber injection moulding: The production speed is faster, making it good for mass production. It also has more automation, so less manual work is needed.
utilisation rates of raw materials
- Rubber compression moulding: the gap between the moulds and the flash edge may lead to a certain waste of raw materials.
- Rubber injection moulding: The rubber is injected into the mould with precision, resulting in high use of raw material.
mould and equipment costs
- Rubber Compression Moulding: Relatively low mould and equipment costs, suitable for small scale production.
- Rubber injection moulding: mould and equipment costs are relatively high, suitable for large-scale production.
product consistency and precision
- Rubber Compression Moulding: A relatively low level of automation may affect product consistency.
- Rubber Injection Moulding: A highly automated process helps to improve product consistency and accuracy.
rubber compression vs rubber extrusion
Rubber compression molding and rubber extrusion molding are two common ways to shape rubber. They differ in how they work, what they can be used for, and how efficiently they produce goods.
operation principle
- Rubber compression moulding:The rubber is put in a mold. The mold is closed and the rubber is pushed into the shape. The mold is heated to harden the rubber.
- Rubber Extrusion Moulding:The rubber mixture is heated and passed through the die of the extruder. It is then extruded into a continuous rubber strip shape. Finally, it is cut or cooled to form the desired shape.
application
Rubber compression moulding: This material is good for making rubber products in different shapes, especially simple shapes and small-scale production.
- Rubber extrusion moulding: This machine is good for making products with a consistent shape, like seals, pipes, and rubber strips. It’s often used for making a lot of things at once.
production efficiency
Rubber compression moulding:The production speed is slow, which is good for small and medium-sized mass production. It requires more manual operation and has a lower degree of automation.
Rubber extrusion moulding: The production speed is fast, making it good for mass production. It has a high degree of automation and needs less human intervention.
utilisation rates of raw materials
Rubber compression moulding: the gap between the moulds and the flash edge may lead to a certain waste of raw materials.
Rubber extrusion moulding: The extruder carefully controls the filling of rubber into the mold, resulting in high raw material utilization.
product shapes
- Rubber compression moulding: suitable for various shapes, but especially for flat and relatively simple shapes.
- Rubber extrusion moulding: suitable for products with continuous cross-section, such as tubes, strips and other shapes.
Applicable materials
The process of rubber compression moulding works well for many types of rubber, especially elastic rubber. Rubber materials are squeezed and treated with heat and pressure to make different shaped rubber products. The material chosen depends on how it will be used and how well it performs. The types are listed below:
Nitrile Rubber (NBR): Nitrile rubber is a man-made material that resists oil and wear. It works well for making seals, gaskets, and other rubber items.
Acrylic rubber (ACM): It can resist high temperatures and oil, so it is often used in car engine seals and heat-resistant rubber products.
Silicone rubber:This material has great resistance to high temperatures, oxidation, and electrical conductivity. It is used to make things like high-temperature seals and heat-insulating gaskets.
Natural rubber: Natural rubber comes from the rubber tree and is great for making springs and gaskets. It’s elastic and tear-resistant.
Styrene-Butadiene Rubber (BR): This material is resistant to wear and cold. It is often used to make rubber tires, gaskets, and other items.
Chloroprene rubber (CR): This material is resistant to oil and abrasion, making it ideal for making oil-resistant seals and rubber kits.
Butyl rubber (BIIR \ CIIR): It has good resistance to ozone and abrasion, making it suitable for making rubber capsules, gaskets, and other products.
Rubber Compression Moulding Equipment
Rubber compression molding equipment is crucial. It shapes rubber with heat and pressure. This equipment is widely used in making many rubber products. These include seals, gaskets, and vibration buffers. Below are the main components and workflow of rubber compression molding equipment:
Rubber Refiner: The rubber refiner marks the initiation of the rubber molding process. This equipment mixes raw rubber with additives. The additives give specific properties to the rubber. These properties include hardness, elasticity, and durability. These additives also enhance the processability of the rubber.
Rubber Compressor: The rubber compressor serves as the core equipment for rubber compression molding. This process involves utilizing two molds—one positioned on top and the other on the bottom. The rubber material is heated and shaped between these molds through compression.
Mold: The mold is a pivotal component of rubber molding as it dictates the shape and size of the final product. It is usually made of strong materials like metal. The mold has the needed shapes and surfaces for molding.
Heating System: The heating system is critical in rubber molding. It makes the rubber soft and malleable. This softness helps compression molding. It ensures that the rubber reaches the appropriate temperature for molding.
Cooling System: After molding, the rubber product cools and cures. This keeps its shape. The choice between air or water cooling depends on the molding process and the characteristics of the final product.
Control System: The rubber molding process is made better with a control system. It monitors and adjusts many factors. These include temperature, pressure, and other critical things. This ensures precise and consistent molding results.
Application Areas
The rubber compression molding process has many uses. It is used in many industries. It helps make many types of products. Some of the key application areas include:
Automotive Industry: Automakers use rubber compression molding a lot. It makes many car parts. These parts encompass automotive seals and rubber components utilized in suspension systems.
Electrical and Electronic Industry: Rubber compression molding is common in the electrical and electronic industries. It is used to make products like insulating mats and cable seals.
Industrial Seals: Rubber compression molding is crucial for making industrial seals. These include O-rings and flange gaskets. They are vital for sealing pipelines and equipment.
Medical Devices: In medicine, rubber compression molding is used to make many medical devices. It’s used to make rubber parts for medical equipment.
Construction and Building Materials: In the construction industry, rubber compression molding is key. It is used to make waterproof and soundproof mats, among other materials.
Sports and Leisure Goods: Rubber compression molding is used to make sports shoes and rubber parts for sports equipment. It serves the needs of sports and leisure fans.
Quality Control
To make sure the final product is good, quality control is important in rubber compression moulding. Common quality control measures are as follows:
Quality control of raw materials: Make sure the rubber materials and additives meet the requirements for composition, hardness, viscosity, and other characteristics. Also, check the formulation and quality of the additives.
Control of mixing process: Monitor the mixing process to ensure that the rubber and additives are evenly mixed. To make sure the rubber is easy to work with, control the temperature and time when mixing it.
Design and manufacture of moulds:Make sure the moulds are designed to meet the product requirements. They should also have the right cooling systems. Inspect and maintain the moulds often to keep them smooth and last longer.
Heating and pressure control: In compression moulding, the heating system must be controlled carefully to process rubber at the right temperature. We adjust and check the pressure to make sure the rubber fills every corner of the mould and keeps the shape we want.
Product Size and Appearance Inspection: We inspect the size and appearance of rubber products to make sure they meet the requirements.
Vulcanisation control: To make sure the product is good, check how long it takes to harden and the temperature used.
Conclusion
Rubber compression molding is a key process widely used in several industries. The raw materials are pre-treated, heated, and pressurized for molding. Then, they are vulcanized and cooled. This process creates highly accurate and durable rubber products. The process is the best way to make many types of rubber parts. It is preferred because it is cheap, easy to use, and works with many materials. But, it has drawbacks. These include slower production and manual handling limits. But, its benefits in small batch production and complex shape-making are still clear.
If you have questions or needs about rubber compression molding equipment and processes, please ask Crowns Machinery for advice. We offer high-quality equipment. It will help you achieve top efficiency in your production process.
FAQ
Rubber compression molding is a process of molding rubber by heating and pressurizing a mold. The process is used to make various rubber products such as seals, gaskets, and vibration dampers.
It is suitable for complex shapes and low cost. It can handle small-batch production. It does not need special rubber types. It is good for large products. It is simple to use and maintain. It works with many materials. It is very precise and durable.
Production speeds are slow. Handling is manual. It’s suitable for simple shapes. There’s more waste of raw materials. Molding cycles are longer. Product consistency is limited. It depends on vulcanization.
It includes the car and electronics industries. It also includes industrial seals, medical devices, construction materials, sports goods, and more.
Rubber mixer, rubber compressor, mold, heating system, cooling system, and control system.
