Wafios USA
WAFIOS Machinery Corporation  •  27 NE Industrial Road  •  Branford CT 06405 USA  •  Telephone (203) 481-5555  •  Fax (203) 481-9854

 


                                            
                                  Excerpted from:

Spring End Grinding
An Introduction to Machine and Process Technology


Grinding Wheel Composition:

Advantages of sintered, 
over fused, Aluminum Oxide


About CBN
-The solidity of sintered aluminum oxide as well as the high bonding strength, enable longer working cycles between grinding wheel dressing and shorter down-feed movements during dressing. 

- Due to its micro-crystalline structure and greater hardness, sintered aluminum oxide grains are constantly resharpening themselves. Thus less grinding pressure is necessary and less heat is produced in the process.

- Lower grinding pressure causes a longer service life: the abrasive grain crushes at a considerably lower grinding pressure. Thus the service life of the grinding wheel is increased.

- Good cooling enables higher grinding speeds: the maximum permissible circumferential speed of fused aluminum oxide is 35 m/s and 50 m/s for sintered aluminum oxide. Thus the amount of material removal can be increased.

- Longer working cycles due to more accurate grain dimension and shape; fewer dressing cycles with shorter down-feed movements.

- Due to better surface and fewer burrs, the springs have greater dimensional accuracy (Lf, es, ep).

Cubic boron nitride is an artificially produced super abrasive for processing ferrous materials, which cannot be ground with diamond tools. 

CBN wheels carry a single layer of cutting grains in an electroplated nickel bond on a steel disc mounting. These grinding wheels do not require dressing and over long operating times they do not require adjustment for wheel wear. They can be replated and reused at lower cost, when they are worn. 

CBN grinding is not an all-purpose process. Springs other than those for which the grinding wheel was specified should never be ground with CBN. Otherwise an irreversible failure of the grinding wheel can result. 

If, however, the machine and spring are both suitable for CBN grinding wheels, then excellent grinding results and very high efficiencies can be obtained. Long grinding wheel lives, high machine efficiencies and high outputs can be achieved by adjusting the CBN grinding wheel to the spring and to the machine parameters. 

Optimal cutting speed for CBN wheels is relatively high, at 120 m/sec. For a wheel with 400 mm diameter (15.75 inch, the common size for WAFIOS spring grinders that can use these wheels)  this gives a wheel speed of 6000 rpm.