-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.
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