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The Basic Principles of roller burnishing

Roller burnishing is a process for microfinishing metallic surfaces which belongs to the forming processes When roller burnishing, a rolling body, usually a roller or ball is pressed onto the surface and rolled over it. By this means a high compressive stress is created in the surface finish peaks which induces the material to flow. In doing so a forming of the boundary layers in micron range is induced.

The material flows from the areas of high compressive stress (peaks) to zones with less stresses and in doing so fills the valleys up from below. this process is illustrated in picture 1. The supposition that the peaks are bent over by roller burnishing can be refuted with the help of picture 1. In reality contact conditions between the work piece and burnishing roller or ball occur which do not allow bending of the peaks. The unequal scaling between measuring path and peak to valley height in measurement plots as illustrated in picture 2 is misleading.

In addition picture 2 illustrates what improvement in surface finish is possible in many cases. For unhardened ductile materials an improvement of 95% is achievable (e.g. Rz=20µm pre-machining to Rz=1µm after roller burnishing). As a rule, Rz values below 1 micron are achievable. For this reason the process is particularly interesting for replacing manual polishing. Consistent quality is ensured thereby and personnel costs can be reduced.

With cutting-edge ECOROLL tooling technology even hardened work pieces of up to 65 HRC are capable of being roller burnished. In doing so the roughness can be reduced by up to 60%. This application is particularly interesting in combination with hard turning, which is good pre-machining for roller burnishing.

Roller burnished surfaces excel with their:
  • Low peak-to-valley height
  • High percentage contact area
  • Plateau formation with slight depressions (suitable as lubrication pockets)
  • Absence of protruding peaks
  • Increased hardness
The roller burnishing process provides the following benefits:
  • Short primary machining time
  • For use on conventional or CNC lathes
  • Complete machining with one chucking
  • No removal of material
  • Easy reproduction
  • Low consumption of lubricants
  • low noise emissions
  • Long tool life Lange
  • No varying dimensions through tool wear
They are suitable as sliding surfaces, seal surfaces and joint surfaces. 		  
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Summary

Roller burnishing is a process for precision machining of metal surfaces. The process of burnishing leads to a low surface roughness, a high material support proportion, and hardness increase. The advantages of this method are including in low main times, the applicability of all conventional or CNC machines and the easy reproducibility. With the latest tool technology hardened work pieces with up to 65 HRC can be roller burnished.

In this case the roughness can be reduced by up to 60%. Roller burnished surfaces are also suitable as lubricants, sealants and mating surfaces.