Do Roller Burnishing Tools have self-feed design?

Yes they do.The rolls axes are set at a slight helix angle to the axis of the mandrel and workpiece. This angular relationship causes the rolls to move in a helical path around the workpiece surface, thus establishing a self feeding characteristic in the burnishing tool. Thus they have a self-feed design.

Improved Metallurgical Properties

Burnishing 'cold-works' the metal of a machined part. Tool marks are rolled out. Grain structure is condensed and refined, and compacted surface is smoother, harder and longer wearing than ground or honed surfaces.

Rolling action greatly reduces surface porosity, pits and scratches which could hold reactive surfaces or contaminates. As a result the corrosion resistance of burnished surface is higher than the open surfaces produced by grinding or honing. Depending on the type of material being burnished surface hardness can be increased by as much as 1O-Rc. This increase often eliminates the need for heat treating or surface treatment as a means of improving wear resistance.

Due to plastic deformation in the roller burnishing operation, residual compressive stresses are inducted in the surface of the part. This compressive stresses greatly increase the strength properties and fatigue life of the part, because any forces on the part must overcome these residual stresses, as well as the tensile strength of the material, before fatigue conditions occur.

Advantages of Roller Burnishing Tools

1. Cost Effective
   
   Roller burnishing is a cost effective method to achieve a good surface finish. Burnishing on a CNC lathe or mill can be less expensive than standard grinding.
   
   
2. High Surface Finish
   
   Roller burnishing can provide a surface finish between 0.05 Ra – 0.2 Ra on a turning or milling machine. This removes the need for secondary surface operations like grinding.
   
   
3. Surface Hardening
   
   The rolling method also has a work hardening effect for many material types, resulting in increased surface hardness. A harder surface will resist premature wear, improves corrosion resistance and increases the part service life.
   
   
4. Tolerance and consistently
   
   Size control is improved by burnishing. Use of a roller burnishing tool has the possibility of consistently attaining higher tolerance. In some situations an improvement in part roundness can also be obtained. This reduces the rework or rejections.
   
   
5. Simple to Use
   
   Burnishing tools can be used on non-CNC machines such as automatic lathes, semi automatic lathes and multispindle machines. The accuracy of the roller burnishing method is a function of the tool design, not the accuracy of the machine that is holding the tool.
   
   
6. Single Pass Operation
   
   Since roller burnishing is single pass operation very less cycle time is required to complete the job to required. A semi skilled operator can easily work.

The need to lubricate roller burnishing tools and the how to

A metal filter (maximum 50mm) in the lube system is recommended to prevent entering of chips and grit into the tool. The tool requires lubrication, but cooling only in case of long workplace as hydraulic cylinders.

Therefore, any light lubricating oil or a rich, soluble oil mixture is recommended. Lubricant should be fed to the tool in a steady ample volume to provide flushing and cleaning action.

Usage areas of burnishing tools

Roller Burnishing tools generally consists of a series of tapered and highly polished precision rollers made of High Speed Steel or Carbide material, positioned in slots with a retaining cage. The rollers rotate around on an inversely tapered mandrel. The tool or part can be rotated at optimum speed to develope pressure that exceeds the yield of softer work piece to get desired results.

Burnishing tools can be used for the following

• INNER DIA
  
• OUTER DIA
• TAPER INTERNAL
• TAPER EXTERNAL
  
• PROFILE
• CIRCULAR FLAT FACE.
  

Burnishing tools can be fitted with any rotating device like Lathe, Drilling, C.N.C. Machine and S.P.M's. Any unskilled labourer can do the burnishing operation.

Minimum Operator Skill required

Set-up of roller burnishing tool takes less than a minute, using the built-in micrometer adjustment.

Unskilled operators can produce close tolerance work with consistent part-to-part uniformity through an entire production run.

Speed Recommendations of Burnishing Tools

The burnishing tool is designed for conventional right hand rotation,and either the tool or the workplace can be rotated. Rotational speed is not critical, but higher than recommended speeds will reduce tool life. If long-length tools, or tools with extension drive are used, Speed should be reduced to prevent excessive whip.

Since the rotation speed of the tool is not critical to performance, high surface, speed will produce the same burnishing result as low speed; therefore rapid production cycles for the burnishing operation yield the most economical pieces part cost when compared with other types of finishing operation.

Applications of Burnishing tools

Burnishing tools are utilized in a wide range of tooling products, some of them are given below.

• Pneumatic Cylinders
• Hydraulic Cylinders
• Connecting Rod Small / Big End
• Rocker Arm
• Bearing Housing
• Pipes
• Drilled Holes etc.
  
• Master Cylinders
• Brake Cylinders
• Mixie Shaft
• Fan Rotor Shaft
• GM / Bronze Bushes
• Piston G.P. Holes
• Valve Rod
• Valve Guide
• Rotor Stamping I.D.
• Motor End Cover

What is Roller Burnishing?

Burnishing is a Cold rolling process without actual removal of metal. It is a new concept in finishing the Components. Whereever there is need for accurate size and surface finish, the Burnishing Tool is the one and only solution. Consistency can be acheivable by burnishing. This process eliminates Grinding and honing which are costlier processes.

The surface of metal parts worked thro' turning, reaming or boring operations is a sucession of "PROJECTIONS or PEAKS" and "INDENTATIONS or VALLEY" when microscopically examined. (See Fig.1). The Roller burnishing operation compresses the "Projections (Peaks) into the Indentation (Valleys) thus forming a smooth mirror finished surface (as in Fig.2). Any material not exceeding 40 Rockwell Hardness "C" can be roller burnished.

Surface before burnishing.

Surface After burnishing

Burnishing is the cheapest process and High productivity is assured. Rejections will be totally eliminated as you can achieve accurate size as well as super surface finish by doing the burnishing operations