Diameter change of materials during processing for "Superoll" Roller Burnishing Tools
Amount of change in diameter in Superoll processing
The internal processing by the Superoll finishes the inner surface with burnishing by setting the tool diameter larger than the dimensions used for pre-processing and by revolving and feeding the tool (or processed parts). This difference between the dimensions of the tool diameter and dimensions for pre-processing is called the burnishing amount.
The figure on the right shows the relationship among burnishing amounts, surface roughness, and the amount of internal diameter expansion for each metal material.
In general, the roughness of the surface is improved as the burnishing amount increases. For S45 material, the optimal finished surface is achieved with a burnishing amount of 0.04 to 0.07 mm.When the burnishing amount exceeds that amount, the surface roughness deteriorates. This is because the processing pressure from the roller increases as the burnishing amount increases, and the processed parts peel off the surface.
The optimal burnishing amount differs by the quality of material and thickness of the surface, but the best finished surface can be achieved with a burnishing amount that is three to five times the normal pre-processing surface roughness.
The amount of internal diameter expansion differs by the materials used in the processed parts. Because the amount of internal diameter expansion for non-ferrous alloys, such as aluminum or bronze, almost linearly increases as the burnishing amount increases, the ability of sizing (obtaining the dimensions) is high and finishing of less than 0.01 mm can be achieved even for variations in the pre-processing internal diameter dimensions of 0.03 mm.
Because the internal diameter seldom changes for steel or cast iron with a burnishing amount of between 0.04 to 0.07 mm, it is possible to correct variations in dimensions up to 60 to 70% with respect to pre-processing, although it does not have as much of an effect on sizing as with aluminum or bronze.
The surface roughness improves as the burnishing amount increases, but the optimal burnishing amount and internal diameter expansion amount differ according to the materials, so refer to the figure on the right when setting the optimum conditions.
Burnishing amount = (Tool diameter) - (Internal diameter before Superoll processing)
Internal diameter expansion amount = (Internal diameter after Superoll processing) - (Internal diameter before Superoll processing)