Rubber bearing sleeves may look like small and simple parts, but they play a critical role in ensuring stability, reducing vibration, and extending the service life of equipment. For engineers, knowing the manufacturing process helps in better design. For procurement managers, it reveals whether a supplier has stable production and quality control capabilities. And for end users, it ensures durability and lower maintenance costs. Let’s walk through the complete process step by step.
Step 1: Order and Requirement Confirmation
The process starts with clarifying customer requirements.
- Key factors include inner and outer diameter, wall thickness, length, and tolerance.
- Hardness usually ranges from 50 to 80 Shore A depending on load and application.
- Service conditions such as operating temperature, medium (oil, water, chemicals), and dynamic load must be confirmed.
This step ensures the final product matches both design and customer needs.
Step 2: Raw Material Inspection and Formula Confirmation
Material choice is the foundation of performance.
- Common materials: Natural Rubber (NR), Nitrile Rubber (NBR), EPDM, Neoprene, Silicone, and Fluoroelastomer (FKM).
- Incoming inspection covers Mooney viscosity, ash content, density, and batch traceability.
- Compounds include fillers, antioxidants, and curing systems (sulfur or peroxide).
Buyers usually request suppliers to provide raw material test reports to guarantee stability.
Step 3: Rubber Mixing (Compounding)
Mixing is a critical step that directly affects performance.
- Proper order of feeding, temperature control, and mixing time are key.
- Poor dispersion may cause weak spots, while overheating can lead to scorch and scrap.
For engineers, compound consistency is crucial to ensure reliable mechanical properties.
Step 4: Maturation of the Compound
The mixed rubber needs time to relax molecular stresses.
- Storage time: typically 8–24 hours.
- Conditions: cool and dry, away from sunlight.
This stage improves processability and reduces defects in later molding.
Step 5: Preforming and Preheating
Before molding, rubber is cut and shaped into blanks.
- Preforming ensures correct size and weight.
- Preheating (70–100°C for most rubbers) improves mold filling and reduces air traps.
Customers benefit from more consistent appearance and dimensions.
Step 6: Molding or Extrusion
Two main methods are used:
- Compression or injection molding: ideal for flanged or grooved sleeves with complex geometry.
- Extrusion: suitable for tubular sleeves, cut into required lengths.
Mold precision and design directly affect dimensional stability.
Step 7: Vulcanization
Vulcanization gives rubber its final strength and elasticity.
- Typical ranges: NBR/EPDM at 170–180°C for 10–15 minutes; Silicone and FKM require higher temperatures and longer post-curing.
- Risks: under-cure reduces strength, while over-cure makes rubber brittle.
Durability, one of the top concerns of end users, is largely determined here.
Step 8: Demolding and Trimming
After curing, parts are demolded and trimmed.
- Common methods: cryogenic deflashing or manual trimming.
- Inspection: surface quality (no cracks, burns, or bubbles) and dimensional accuracy.
This step ensures both appearance and usability.
Step 9: Post-Curing and Surface Treatment
Some materials (like FKM) require post-curing at 200–230°C for several hours to enhance chemical and heat resistance.
Surface treatments, such as plasma activation or applying a wear-resistant coating, may also be used depending on the application.
Step 10: Machining and Finishing
For precision parts, secondary machining is needed.
- Common operations: end-face grinding, ID/OD adjustment, and groove shaping.
- Typical tolerances: ±0.05–0.20 mm depending on size.
Procurement managers often request SPC (statistical process control) data to verify stability.
Step 11: Final Inspection and Testing
Comprehensive testing ensures performance and safety.
- Hardness (Shore A).
- Tensile strength and elongation (ASTM D412).
- Compression set (ASTM D395).
- Oil and chemical resistance tests.
Certificates of Analysis (COA) and inspection reports provide buyers with confidence in product reliability.
Step 12: Cleaning, Marking, and Packaging
Final preparation includes cleaning and protection.
- Cleaning: isopropyl alcohol or deionized water.
- Packaging: PE bags with desiccants, cartons to prevent deformation, protection from ozone and sunlight.
- Traceability: every sleeve is labeled with batch number and date.
Conclusion
The manufacturing of rubber bearing sleeves is a systematic process involving raw material selection, precise processing, and strict quality control.
- Engineers need to know how each step impacts performance.
- Buyers focus on consistency, traceability, and testing reports.
- End users benefit from products that last longer, reduce downtime, and provide reliable performance.
By understanding these steps, you can make informed decisions when designing, sourcing, or using rubber bearing sleeves.
