Grinding wheel for roll grinding application and method of roll grinding thereof
View Patent ↗Iron and steel rolls are ground to production quality requirements with a grinding wheel that requires minimal wheel wear compensation, profile error compensation or taper error compensation during the grinding process. The grinding wheel consists essentially of a superabrasive material selected from the group of natural diamond, synthetic diamond, cubic boron nitride, and mixtures thereof, in a bond system, for a grinding wheel with extended wheel life, and which removes minimum amount of stock off the roll to achieve desired roll geometry.
1. A method of grinding a ferrous roll having a rotating roll surface with a rotating grinding wheel, the ferrous roll having a hardness greater than 65 SHC and a minimum diameter of at least 10 inches and a length of at least 2 feet, the method comprising:
a) mounting a grinding wheel on a machine spindle and setting an angle between the grinding wheel rotational axis and roll rotational axis less than about 25 degrees;
b) bringing the rotating wheel into contact with the rotating roll surface and traversing the wheel across an axial roll length of the roll, while maintaining a ratio of axial taper tolerance (TT) to radial wheel wear compensation (WWC) of greater than 10; and
c) grinding the roll surface to a surface roughness R a of less than 5 micrometer while leaving the roll surface substantially free of feed marks, chatter marks, and surface irregularities.
2. The method of claim 1 , wherein the roll is ground to a surface roughness R a of less than 3 micrometer.
3. The method of claim 1 , wherein the ferrous roll surface is substantially free of thermal degradation.
4. The method of claim 1 , wherein the ratio of TT to WWC is greater than 25.
5. The method of claim 1 , wherein said grinding wheel includes a layer comprising of a superabrasive material having a Knoop hardness greater than 3000 KHN, selected from the group of natural diamond, synthetic diamond, cubic boron nitride, and mixtures thereof, with or without a secondary abrasive with Knoop hardness less than 3000 KHN, in a bond system.
6. The method of claim 5 , wherein the superabrasive material comprises cubic boron nitride, and the amount of cubic boron nitride in said grinding wheel bond system is in the range of 10 to 60 volume %.
7. The method of claim 5 , wherein the bond system is one of: a) a vitrified bond comprising at least one of clay, feldspar, lime, borax, soda, glass frit, fritted materials and combinations thereof; and b) a resin bond system comprising at least one of a phenolic resin, epoxy resin, polyimide resin, and mixtures thereof.
8. The method of claim 1 , wherein the grinding wheel is rotated from 3600 to 12000 fpm.
9. The method of claim 1 , wherein said method further comprises the step of removing stock off the ferrous roll in one pass or multiple passes.
10. The method of claim 1 , wherein the grinding is carried out at a G ratio of at least 20.
11. The method of claim 1 , wherein the grinding wheel has an axis of rotation that is substantially parallel to the rotational axis of the roll.
12. The method of claim 1 , wherein said ferrous roll is a solid revolution having a surface geometry selected from one of: a convex crown, a concave crown, a continuous numerical profile, and a polynomial shape along the axis of the roll, ground to a form profile tolerance of less than 0.05 mm.
13. The method of claim 1 , wherein said grinding wheel has a traverse rate of at least 50 mm/min.
14. The method of claim 1 , wherein said grinding wheel removes a stock grind amount of less than about 0.2 mm from the minimum worn roll diameter.
15. A method of grinding a ferrous roll having a rotating roll surface with a rotating grinding wheel, the method comprising:
a) mounting the grinding wheel on a machine spindle;
b) bringing the rotating wheel into contact with the rotating roll surface and traversing the wheel across an axial roll length of the roll; and
c) grinding the roll surface while at least one or both of said grinding wheel rotational speed and said mill roll rotational speed is varied in an amount of +/−1 to 40% in amplitude, with a period of 1 to 30 seconds;
wherein a ratio of TT to WWC is greater than 25.
16. The method of claim 15 , wherein the bond system is one of: a) a vitrified bond comprising at least one of clay, feldspar, lime, borax, soda, glass frit, fritted materials and combinations thereof; and b) a resin bond system comprising at least one of a phenolic resin, epoxy resin, polyimide resin, and mixtures thereof.