The methods of manufacturing rubber are similar for all producers World-Wide. Variances, however, may occur regarding specific compounds, each manufacturer&#;s production methods and levels of sophistication.
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Formulation and Mixing of Rubber Compounds:
VIP-Polymers process a variety of rubber materials, both natural and synthetic, into compounds suitable to face the most challenging performance and environmental criteria.
Natural rubbers are supplied from traditional countries in the Far East such as Malaysia and Indonesia. Synthetic rubber is primarily manufactured at chemical plants in Industrial Europe and the U.S.A.
On its own, basic rubber is of little use and must be formulated to make it suitable for manufacture and to ensure desired properties in finished products.
Following laboratory development, precise formulations are used in production mixing operations to blend compounds into strip or slab form suitable for later processing. This is accomplished as follows:
- Blend using a roll milling process.
- Under computer control, each &#;Batch&#; is processed through a series of heavy-duty mixing systems to add more ingredients and finally discharge batches at a designated time and/or temperature.
- Weigh designated formulation ingredients into specified batches using computer control to ensure accuracy.
- Finally, the material is formed into strips or slabs and then automatically cooled.
The processed material compound is now suitable for moulding or extrusion. Test coupons are also sent from each &#;Batch&#; to Quality Control and subjected to a testing programme before releasing to production.
How rubber products are manufactured:
Industrial Rubber components are usually manufactured by one of the following methods:
- Injection Moulding &#; Using strip compound produced as previously described.
- Compression Moulding &#; Requires secondary operations to process material into suitable forms of the correct weight and/or shape to suit particular products.
- Extrusion &#; Using strip compound produced as previously described.
Injection and Compression moulding require highly accurate single or multi-cavity moulds, typically made in high-grade steel and designed and made using CAD/CAM programmes.
Injection Moulding:
Injection moulding has a number of elements operating automatically on timed sequences with moulding temperatures usually between 165°C and 200°C.
Moulding cycle:
- Mould closes.
- A plasticising screw rotates to force the injection of an accurate volume of pre-plasticised rubber compound into the mould.
- Material is directed into the mould via a system of runners to each individual cavity, each having small injection ports.
- Material is cured for a pre-determined time during which the plasticising screw retracts and plasticises sufficient rubber for the next injection.
- The mould opens and parts are removed manually or automatically by robotic or other systems.
- The cycle is repeated.
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During each machine cycle an operator may perform a variety of operations including: Trimming excess rubber (flash), inspection, packaging or assembly. Alternatively, the part may be forwarded for trimming by other methods.
Compression Moulding:
This simpler process is slower in operation than injection moulding in that special uncured preformed and weighed blanks are used. The process employs hydraulic presses with pre-heated platens at (150-170°C) that in turn heat up the mould.
Moulding cycle:
- Open mould and remove the product from the previous cycle.
- Load required blanks into each cavity.
- Close mould and move into a hydraulic press.
- Activate hydraulic press. The closing action causes displacement of rubber to fill each mould cavity. To overcome certain conditions, pressure is sometimes released and the mould &#;bumped&#; to allow air escape.
- Cure &#; Time is determined as a function of material and cross-section of the part being moulded.
- Remove part(s) manually or automatically after pulling mould from the press.
- Repeat cycle.
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Again the operator may have tasks to perform as described for injection moulding. Compression moulding is generally more suited to low volume production or where tooling costs are to be kept to a minimum. Compression moulding is also not suitable for moulding complex shapes.
Extrusion:
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Extrusion is used for either of two functions:
- Manufacture of long lengths of cured sections for fabrication of items too large for injection or compression moulding.
- The production of blanks for compression moulding.
Continuous Vulcanisation:
VIP-Polymers utilise a manufacturing process known as Continuous Vulcanisation for production of cured extrusion for conversion into certain finished products as follows.
Two items of machinery are required for this process:
- An extruder with a barrel and screw, and a die of the correct cross-section at the outlet end.
- A heating source to cure the rubber which may be one of the following:
- A hot air oven.
- A microwave unit/hot air oven combination.
- A specialised bath containing molten salt.
The &#;Continuous Vulcanisation&#; process is as follows:
- Strip rubber is fed into the extruder. It is then plasticised by the screw and extruded through the die orifice. The extruder operates under controlled conditions of temperature and screw speed.
- The continuous extrudate is passed down the heating medium which causes it to cure. Again, speed and temperature are accurately controlled.
- The emerging cured profile is cooled and cut to length automatically or rolled onto drums for subsequent secondary operations.
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This process invariably involves a line length of as much as l00 feet, and optional operations may utilise a U-format to economise on space.
Rubber Parts Manufacturing Process
Qualiform is a leader in the custom manufacturing of rubber products. We create high-performance rubber components with a precision rubber parts manufacturing process. With our experience in the rubber molding industry, we have developed comprehensive knowledge surrounding all areas of rubber molding materials, techniques, and components. As a result, Qualiform is equipped to assist all customs with the design and manufacturing of any component. Furthermore, our rubber parts manufacturing process will meet and exceed performance standards for your application.
Qualiform offers the following rubber manufacturing processes:
- Injection Molding
- Compression Molding
- Transfer Molding
- Rubber Extrusion
- Rubber to Metal Bonding
Injection Molding
The rubber injection molding rubber parts manufacturing process is a modified version of the plastics process. This process heats the rubber and places it under much more pressure in the molding. This contrasts from plastic injection molding in which materials are cooled and subjected to significantly less pressure.
The injection molding process has also gone through many improvements over the years. As a result, injection molding is now one of the most efficient rubber parts manufacturing processes for a large variety of components, applications and industries.
The Injection Molding Rubber Parts Manufacturing Process
- The rubber injection molding process begins with preparation of materials.
- Placement of uncured rubber in the machinery with a screw feeder system. This process requires no preforming.
- Machinery uses the screw feeder to bring in as much material as necessary for the mold. This eliminates any uncertainties and, in turn, the production of material waste.
- Moving rubber to the barrel, in which is it heated for pliability and pushed into the runner system.
- Material begins filling the mold cavities and begins the curing process.
- Upon completing the curing process, the components can be removed to make room for the incoming materials.
Advantages of Injection Molding
- A mid-to-high volume, efficient process
- Full automation is available
- Provides high-tolerance, precision rubber molded products
- The best rubber process for consistency and repeatability
- Allows for molding of complex geometry
- Ideal for rubber to metal bonding, insert molding and over-molding
- Color molded rubber
- Lower unit cost
- Eliminates preforms and preform labor cost
- Flashless molding / flashless tooling / eliminating secondary trimming
- Rapid cavity filling
- Reduced cycle time
- Minimal material waste
Injection Molding Disadvantages
- Higher start-up/shutdown costs
- Suited for high volume applications
- Not all elastomers are suitable due to fast cure times
Compression Molding
The process of compression molding involves creating preforms roughly shaped like the desired product with a rubber compound or mixed raw materials. These preforms require an abundance of material to ensure a complete fill of the cavity.
This process is ideal for medium hardness compounds, productions of lower volume or applications with expensive material requirements. Compression molding also helps reduce overflow created during the molding process, so you can minimize
The Compression Molding Rubber Parts Manufacturing Process
- Operators discern the amount of material necessary for filling each cavity.
- Operators then preform the uncured rubber to these measurements.
- Placement of the rubber into the mold cavity.
- Closing the mold over the rubber materials.
- Applying heat and pressure to the material for a specific amount of time depending on the materials and components.
- Opening the mold and removing the fully cured component.
- Overflow material or flash can be trimmed by hand or by a deflasher.
Advantages of Compression Molding
- Lower cost molds
- Tooling savings
- Short setup time (saves on short production runs)
- The capacity to process stiff, high durometer materials
- Ideal for large parts that require a long cure time
- Maximized cavity count
- Ideal for low volume part requirements
- Ability to process most elastomers and cure systems
Disadvantages of Compression Molding
- Longer cycle times
- Mid-range precision and consistency
- Labor intensive
Transfer Molding
In similarity to compression molding, transfer molding also requires the use of secondary raw materials for the preparation of preforms. However, its main difference is the placement of materials into a pot between the top plate and plunger.
The Transfer Molding Rubber Parts Manufacturing Process
- Operators discern the amount of material necessary for component.
- Operators preform the rubber with these measurements.
- Placement of preform into part of the mold.
- Close mold and apply pressure.
- Pushing of rubber through small opening known as a sprue.
- Material fills the mold cavities.
- Further heating and application of pressure to mold while the rubber cures.
- Release of mold and removal of components.
- Overflow material or flash is removed.
Advantages of Transfer Molding
- Low cost molds
- Ideal for molding complex components
- Able to maintain high tolerances
- Reduced material waste
- Cost-efficient tooling and part repeatability
- Higher cavity count to simplify and minimize preforms
- Capable of creating overmolded parts
- Ideal for the production of high precision components
The central disadvantage of the transfer molding process is the production of excess material waste from the rubber left behind after curing the materials.
Rubber Extrusion
Rubber extrusion varies greatly depending on which components are involved. The process involves forcing the parts through the die of the cross section, which is under pressure from an extruder. It also involves soft, unvulcanized rubber compounds. As a result, the extrusion creates a soft, pliable rubber. These materials require post-processing such as vulcanization or hardening to become applicable components.
Extrusion Process
- Designers and operators decide whether hot or cold extrusion is appropriate.
- Feed the unvulcanized rubber into the hopper. A hopper is a container within the conveyor.
- Gravity then helps send the rubber through the bottom of the hopper and onto the conveyor.
- Conveyor moves the rubber to the die while a screw creates heat and pressure.
- At the end of the conveyor, the softened rubber passes through the die&#;s opening.
- Inside the die, the rubber begins to take shape.
- The rubber then passes through the die as a completed component shape.
- Operators decide which post-processing methods are best for the component. These processes include: vulcanization, drilling, coiling, dusting and more. Vulcanization is a necessity in rubber extrusion post-processing.
Rubber to Metal Bonding | Rubber Parts Manufacturing Process
Using injection and transfer molding to encapsulate and bond rubber to metal is the most effective way to adhere rubber to metal or plastic parts. The rubber to metal molding process also provides a superior mechanical bond of rubber to metal parts, inserts or plastic parts.
The Rubber to Metal Bonding Process
The process requires a two-step preparation of the metal or plastic part prior to molding the rubber.
- First, we degrease and clean off any contaminants
- We then spray a special, heat-activated adhesive onto the metal components.
- Once the part is prepared for rubber overmolding, we insert the parts into the mold cavity. When molding a specific area, special magnets hold the part in place. During complete encapsulation, chaplet pins hold the part
- Then we close the mold and the rubber molding process begins.
- High molding temperature cures the rubber and also activates the adhesive, which forms a mechanical bond of rubber to metal or bonds rubber to plastic.
Rubber to metal bonded parts range in size from smaller inserts to larger components. Overmolded components are also applicable in a wide variety of applications and industries.
Materials capable of being insert molded, overmolded or bonded of a specific area include:
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- Steel
- Brass
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- Exotics
- Engineered resins
- Plastics