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BURNISHING | S.C.A.M.I.® Roller Burnishing Systems

Roller Burnishing Overview

A

The Principle of Roller Burnishing Roller burnishing is a cold-working process that produces a fine surface finish. The planetary rotaƟon of the hardened rolls creates pressure over a metal surface. Unlike cold rolling, which produces large secƟonal changes, roller burnishing involves cold-working on the surface of the workpiece to improve the surface structure. All machined surfaces consist of a series of peaks and valleys, all having irregular height and spacing. The plasƟc deformaƟon created by roller burnishing is a displacement of the material in the peaks. When under pressure, the material in the peaks flows into the valleys. During the process, tool marks and irregulariƟes are rolled out, resulƟng in a mirror-like finish with a tough, work-hardened surface that is also wear and corrosion resistant.

DRILLING

B

Burnishing Roll

Burnishing Pressure

BORING

C

REAMING

BURNISHING SPECIALS • The stresses formed on the material during the compression decrease toward the center. These stresses reach approximately 1 mm below the surface. This increases the surface hardness. The Process • The first contact with the machined surface occurs in SecƟon A. • PlasƟc deformaƟon occurs in SecƟon B as the yield point of the surface is exceeded. • SecƟon D is the pressurized depth. • Once the material endures the maximum compressive strain (SecƟon C), it starts relieving elasƟcally (SecƟon E) through the finishing zone. • This leaves a smooth surface and a compressive residual stress of significant peak value. Advantages of Roller Burnishing: Metallurgical ProperƟes • Grain structure is condensed and refined. • The compacted surface is smoother, harder, and more wear resistant than ground or honed surfaces. • The process reduces surface porosity and also removes scratches that could hold reacƟve substances or contaminants. This increases the corrosion resistance . • Depending on the material, the surface hardness can be increased by as much as 10 points Rockwell C . This may eliminate the need for heat treatment. • The plasƟc deformaƟon induces residual compressive stresses in the surface of the part. This increases the strength properƟes and faƟgue life of the part because any forces on the part must overcome these residual stresses, as well as the tensile strength of the materials, before faƟgue condiƟons occur. THREADING

Advantages of Roller Burnishing: Surface Finish • Creates a high finish to any machinable metal.

• Surfaces that are bored, reamed, or turned to 125 microinches or more can be finished to 4 microinch CLA or less in one pass (at feed rates of 125 to 300 mm/min). • Roller burnishing replaces grinding, honing, lapping, and other expensive secondary operaƟons. • Tool marks are rolled out.

D

Machined Surface

Burnished Surface

E

D

E

A B C

X

Compressive Residual Stress

Tensile Residual Stress

D: 2

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