Letter 290

Surface finish and Roller Burnishing

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I am a manufacturing engineer who would like to learn more about roller burnishing. I am currently developing a new product which will be manufactured from stainless steel. This new product will require a surface finish of 2-10 micron finish. I am attempting to turn a 16 micron finish on a lathe, and then try to burnish the surface to the final 2-10 micron finish. I have considered grinding and electropolishing.

I would be grateful for any input....

Thanks

BOB SHELTON, Mfg. Engineer

A 2-10 micron isn't that unusual; I've recently been looking at some mirror-polished stainless sheet that is 1.17 microinch.

As for electropolishing, whether it is advisable doesn't primarily depend on what surface finish is desired, but on how important cleanliness, elimination of microscopic slivers, and passivation is. An electropolished finish will be very smooth at a microscopic level, but it will be wavy if the substrate has not been well polished.

I'm not truly familiar with roller burnishing, and will leave that to the next reader :-)

Ted Mooney, P.E.  finishing.com Brick, New Jersey

Roller Burnishing is a Super-finishing process. It is a Cold Working process which produces a fine surface finish by the planetary rotation of hardened rollers over a bored or turned metal surface. Since all machined surfaces consist of a series of peaks and valleys of irregular height and spacing, the plastic deformation created by roller burnishing is a displacement of the material in the peaks which cold flows under pressure into the valleys. The result is a mirror-like finish with a tough, work hardened, wear and corrosion resistant surface. Lapping and Honing is eliminated.

ADVANTAGES OF ROLLER BURNISHING:

Mirror Finish in One Pass, Accurate Sizing, Close Tolerances, Eliminates Lapping & Honing

Improved Metallurgical Properties - Work Hardened Surface, Increase in fatigue strength,

No Additional Machine Investment - attachable to any Standard Machine Tool Already Present in the Shop

Long Tool Life No Operator Skill Required Low Torque & Power Requirements Maximum Parts Interchangeability

Yashwant Pawar
manufacturer of burnishing tools - Mumbai, Maharashtra, India

hi, I am Shankaremarose here. I wish to do project in burnishing . i would be grateful if somebody answers this. sir ,how to measure the burnishing force? i am using roller type burnishing tool which i have to fabricate. i am mounting the tool in a lathe for cylindrical jobs.. moreover i am using hard material as my work piece. could u suggest to me some tool material? thanks

Shankar
student - Chennai, Tamil Nadu, India

Basically you have to mount a pneumatic cylinder on the saddle in the place of the tool post on your lathe at right angles to the work piece. You need also a pressure regulator a flow control valve, a pressure gauge and a lever operated three way poppet valve.This set up will ensure a constant regulated supply of air at your pneumatic cylinder. The cylinder will actuate the roller holding shaft which is sliding in linear bearings so that there are no friction losses. Just behind the burnishing roller you will place on the shaft your force measuring strain gauges. The signal from the strain gauges is passed to an amplifier and then to a UV recorder. Deflection on the UV recorder show the measuring load at the tool.(You have to calibrate.)
Material for the roller is good at stainless steel . The roller could be radiused or flat. Loads from 400 N - 2.5 kN.

Mr. Symeon Krezias
- Athens ,Greece

Saw your request for burnishing information.

We found a website from a company called cogsdill and that's what they specialize in - they helped us no end with their technical knowledge.

Regards,

Lee Donaldson
- Nuneaton, Warwickshire, United Kingdom

You can measure the burnishing force with help of spring of known stiffness and dial gauge. keep the spring inside the tool. and place the dial gauge at the end of the tool shank. the deflection of dial gauge multiplied by stiffness of the spring gives the value of burnishing force.
u can use tungsten carbide or diamond as the tool .

Devendra Kumar
Student - Chennai, Tamil Nadu and India

This method is for to making the workpiece -- which has passed through the pre-machining -- smooth and hard. It is possible to process any kind of metallic material by using this method. The roller burnishing is done by contacting of the rollers on the surface of the workpiece by the help of a precision mechanism. When such a contact is obtained, the workpiece or the tool turns at a specified speed, then the rollers go forward on the workpiece's surface by rotation. In addition, a stress is applied on the surface of the workpiece with a certain force thus the process of roller burnishing is achieved.

Nalan CIFTCI
- Turkey

Here is a burnish roller with built in force meter. Comes in pretty handy.
www.metaltec.co.kr/product/ProductList.php

Verl Hayes
- Eupora MS