Manufacturing Insights with FMC: Friction Plate Polishing

In our last edition, we explored the critical role of heat treatment in the FMC manufacturing process. Today, we turn our attention to the next stage of our factory workflow: the careful preparation of the steel mating plate surface. 

Since surface preparation plays such a pivotal role in the manufacturing process, it remains one of our highest priorities. To make sure all mating surfaces work in perfect harmony with our friction plates, we use several advanced friction plate polishing techniques. 

Linishing

Linishing uses continuously lubricated abrasive belts to produce a controlled surface finish while maintaining temperature and dimensional stability, as well as removing any other imperfections such as burrs or pitting.

In our industry, the aim isn’t a mirror finish, but instead a controlled cross-hatched or linear finish which will help oil distribution and friction performance. Failure to do this properly has a direct impact on the performance of the clutch or brake.

Tumbling 

Typically used for smaller diameter parts, components are placed in a vibrating rotary trough and polished with stone abrasives. At FMC, we work to maintain strict controls on timings and media lifetime to achieve the perfect surface finish, every time.

Rotary Grinding

Finally, we use rotary grinding when necessary. Here, brushes and grinding stones rotate over a conveyor in a circular motion. The decision on which process we use is based on over 35 years of manufacturing experience, balancing the technical and commercial requirements of our customers.

Every plate is then inspected to verify the surface finish (typically measured in Rz or Ra) via rigorous in-process inspections. Below, you will find a before-and-after of the friction plate polishing process.

At FMC, we understand that manufacturing is about how components work together under stress. By investing in precision friction plate surface finishing, we ensure our customers receive parts that provide reliability and longevity.

Ready to choose the ideal friction plate polishing process for your next friction application? Contact the FMC team today to ensure peak performance and durability for all of your components.

FAQs

Q: Why is a mirror finish bad for friction plates?

A: A mirror finish is often counterproductive because it lacks the necessary surface texture (like a cross-hatch) required to manage oil distribution. Without a controlled surface topography, the friction material cannot function optimally, potentially leading to performance degradation in clutches and brakes.

Q: How does surface finish affect clutch and brake performance?

A: The surface finish dictates how well the friction plate interacts with the mating plate. A proper finish ensures adequate oil retention and a consistent friction coefficient. If the surface is too smooth, oil cannot distribute correctly; if it is too rough, it may cause premature wear or erratic engagement.

Q: How do I choose between linishing, tumbling, and rotary grinding?

A: The choice depends on the specific geometry of the part and the required finish specifications. Linishing is excellent for maintaining dimensional stability on larger parts, tumbling is ideal for smaller parts requiring uniform polishing, and rotary grinding is selected based on production volume and specific technical requirements.

Q: Why does oil distribution require cross-hatched steel surfaces?

A: A cross-hatched finish creates a network of microscopic grooves that trap oil. This ensures that even under high pressure, a thin film of lubricant is maintained between the plates, which prevents overheating, reduces wear, and ensures smooth engagement.

Q: Measuring Rz vs Ra in friction plate manufacturing: what’s the difference?

A: Ra (Average Roughness) measures the average deviation of the profile from the mean line, while Rz (Mean Roughness Depth) measures the average distance between the highest peaks and deepest valleys. Both are vital for verifying that the surface texture is consistent and suitable for the application.

Q: Precision metal finishing vs polishing for friction plates: what is the difference?

A: Polishing often focuses on achieving a certain aesthetic or smoothness. In contrast, precision metal finishing in our factory is about functional engineering – ensuring the surface has the specific texture and geometry required to optimise friction, heat dissipation, and oil flow for the life of the component.