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

  1. The rubber injection molding process begins with preparation of materials.
  2. Placement of uncured rubber in the machinery with a screw feeder system. This process requires no preforming.
  3. 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.
  4. Moving rubber to the barrel, in which is it heated for pliability and pushed into the runner system.
  5. Material begins filling the mold cavities and begins the curing process.
  6. 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

  1. Operators discern the amount of material necessary for filling each cavity.
  2. Operators then preform the uncured rubber to these measurements.
  3. Placement of the rubber into the mold cavity.
  4. Closing the mold over the rubber materials.
  5. Applying heat and pressure to the material for a specific amount of time depending on the materials and components.
  6. Opening the mold and removing the fully cured component.
  7. 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

  1. Operators discern the amount of material necessary for component.
  2. Operators preform the rubber with these measurements.
  3. Placement of preform into part of the mold.
  4. Close mold and apply pressure.
  5. Pushing of rubber through small opening known as a sprue.
  6. Material fills the mold cavities.
  7. Further heating and application of pressure to mold while the rubber cures.
  8. Release of mold and removal of components.
  9. 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

  1. Designers and operators decide whether hot or cold extrusion is appropriate.
  2. Feed the unvulcanized rubber into the hopper. A hopper is a container within the conveyor.
  3. Gravity then helps send the rubber through the bottom of the hopper and onto the conveyor.
  4. Conveyor moves the rubber to the die while a screw creates heat and pressure.
  5. At the end of the conveyor, the softened rubber passes through the die’s opening.
  6. Inside the die, the rubber begins to take shape.
  7. The rubber then passes through the die as a completed component shape.
  8. 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.

  1. First, we degrease and clean off any contaminants
  2. We then spray a special, heat-activated adhesive onto the metal components.
  3. 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
  4. Then we close the mold and the rubber molding process begins.
  5. 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:

  • Steel
  • Brass
  • Aluminum
  • Alloys
  • Exotics
  • Engineered resins
  • Plastics
Factors Affecting Rubber Tolerances

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If you are wondering how an experienced, industrial rubber products supplier can help your business, contact Qualiform today to learn more.
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