Precision Manufacturing Technology

Attach pivot cartridge to the actuator body with high radial and axial stiffness and with minimal impact to pivot friction.




Interference Bands

Interference bands, or tolerance rings, are used to mate components with cylindrical features. Interference bands create reliable connections between components without requiring tight tolerances on the mating component diameters.

Flexible protrusions or bumps patterned on the interference band are compressed between the mating components. Interference bands are designed for the application to provide predictable axial and torsional slip or breakaway between components, without detrimental impacts to other critical assembly performance parameters.

MMI develops interference bands to attach magnetic recording head actuator assemblies to the actuator pivot bearing in computer hard disk drives. This application has many critical requirements including cost, high unit volumes, actuator height, concentricity and parallelism, pivot friction, initial slip force between components, assembled stiffness, resonance performance and part cleanliness. For example, poorly designed interference bands can distort pivot bearing races which results in irregular pivot friction as the actuator rotates through its working range. Irregular pivot friction can result in unpredictable head position over the disk drive data tracks.

Interference band parameters such as bump geometry, material thickness, yield strength, and surface finish are optimized for performance in hard disk drive applications. Design performance is confirmed through finite element simulation and in-situ performance testing in the MMI Innovation Centers. Similar approaches are used in other interference band applications, including those in the automotive and rotary tool industries.