Method for grinding precision components

• US 6,019,668 A
• Filed: 03/27/1998
• Issued: 02/01/2000
• Est. Priority Date: 03/27/1998
• Status: Expired due to Term

• Current Assignee: Norton Company (Compagnie De Saint-Gobain)
• Original Assignee: Norton Company (Compagnie De Saint-Gobain)
• Inventors: Williston, William H., Kuo, Shih Yee, Buljan, Sergej-Tomislav, Ramanath, Srinivasan
• Primary Examiner(s): Hail, III, Joseph J.
• Assistant Examiner(s): Cooke, Dermott J.
• Application Number:
  US09/049,628
• Time in Patent Office: 676 Days
• Field of Search: 451/56, 451/540, 451/541, 451/542, 451/41, 451/48, 451/49, 451/50, 451/51, 525/480, 428/457
• US Class Current: 451/41
• CPC Class Codes: B22F 2005/001 Cutting tools, earth boring or grinding tool other than table ware
• CPC Class Codes: B22F 2998/00 Supplementary information concerning processes or compositions relating to powder metallurgy
• CPC Class Codes: B22F 7/06 of composite workpieces or articles from parts, e.g. to form tipped tools B22F7/002 takes precedence
• CPC Class Codes: B24B 1/00 Processes of grinding or polishing; Use of auxiliary equipment in connection with such processes
• CPC Class Codes: B24D 3/08 for close-grained structure, e.g. using metal with low melting point
• CPC Class Codes: B24D 5/06 with inserted abrasive blocks, e.g. segmental
• CPC Class Codes: C22C 26/00 Alloys containing diamond or cubic or wurtzitic boron nitride, fullerenes or carbon nanotubes

Abstract

A method for precision cylindrical grinding of hard brittle materials, such as ceramics or glass and composites comprising ceramics or glass, provides material removal rates as high as 19-380 cm³ /min/cm. The abrasive tools used in the method comprise a strong, light weight wheel core bonded to a continuous rim of abrasive segments containing superabrasive grain in a dense metal bond matrix.

Claims

1. A method of finishing brittle precision components comprising the steps:

a) mounting a cylindrical workpiece on a fixture;

b) mounting an abrasive wheel on a grinding machine, the abrasive wheel comprising a core and a continuous abrasive rim, the core having a minimum specific strength of 2.4 MPa-cm³ /g, and a circular perimeter adhesively bonded with a thermally stable bond to at least one abrasive segment in the abrasive rim, the abrasive segment consisting essentially of abrasive grain and a metal bond matrix having a fracture toughness of 1.0 to 6.0 MPa M^1/2 and a maximum porosity of 5 volume %;

c) rotating the abrasive wheel at a speed of 25 to 160 meters/second;

d) contacting the abrasive wheel to an exterior surface of a rotating workpiece; and

e) grinding the workpiece at a MRR of up to 380 cm³ /min/cm to finish the exterior surface of the ceramic component;

whereby after finishing, the ceramic component is substantially free of cracking and subsurface damage from grinding.

2. The method of claim 1, wherein the core of the abrasive wheel has a density of 0.5 to 8.0 g/cm³.

3. The method of claim 2, wherein the core is a metallic material selected from the group consisting of aluminum, steel, titanium and bronze, composites and alloys thereof, and combinations thereof.

4. The method of claim 1, wherein the abrasive segments consist essentially of 45 to 90 volume % metal bond and 10 to 50 volume % abrasive grain.

5. The method of claim 1, wherein the abrasive grain is selected from the group consisting of diamond and cubic boron nitride and combinations thereof.

6. The method of claim 1, wherein the metal bond matrix has a Knoop hardness of 0.1 to 3 GPa.

7. The method of claim 1, wherein the metal bond matrix comprises 35 to 84 wt % copper and 16 to 65 wt % tin.

8. The method of claim 7, wherein the metal bond matrix further comprises 0.2 to 1.0 wt % phosphorus.

9. The method of claim 1, wherein the abrasive segments have an elongated, arcurate shape and an inner curvature selected to mate with the circular perimeter of the core, and each abrasive segment has two ends designed to mate with adjacent abrasive segments such that the abrasive rim is continuous and substantially free of any gaps between abrasive segments when the abrasive segments are bonded to the core.

10. The method of claim 1, wherein the abrasive wheel is a type 1A1 wheel.

11. The method of claim 1, wherein the core is adhesively bonded to the rim with a two-part epoxy adhesive.

12. The method of claim 1, wherein the abrasive wheel is self-dressing.

13. The method of claim 1, wherein the step of grinding a silicon nitride workpiece with the abrasive wheel draws less than 30% more power as the speed of the abrasive wheel is increased from 32 to 80 meters/second at a constant MRR.

14. The method of claim 13, wherein the step of grinding the silicon nitride workpiece with the abrasive wheel draws less than 5% more power as the speed of the abrasive wheel is increased from 56 to 80 meters/second at a constant MRR.

15. The method of claim 1, wherein the abrasive wheel is substantially free of measurable wear over a ranges of MRRs from 9.0 to 47.1 mm³ /s/mm at an abrasive wheel speed of 80 meters/second after having removed from a silicon nitride workpiece at least 271 cm³ per cm of abrasive wheel.

16. The method of claim 1, wherein the workpieces consist of material selected from the group consisting essentially of silicon;

mono- and polycrystalline oxides carbides, nitrides, borides and silicides;

polycrystalline diamond;

glass; and

composites of ceramic in a non-ceramic matrix; and

combinations thereof.

17. The method of claim 16, wherein the workpiece is selected from the group consisting of silicon nitride, silicon carbide, silicon oxide, silicon dioxide, aluminum nitride, aluminum oxide-titanium carbide, tungsten carbide, boron carbide, boron nitride, titanium carbide, vanadium carbide, hafnium carbide, aluminum oxide, zirconium oxide, tungsten boride, and titanium boride, and combinations thereof.

18. The method of claim 1, wherein the precision components comprise ceramic engine valves and rods, pump seals, ball bearings and fittings, cutting tool inserts, wear parts, drawing dies for metal forming, refractory components, visual display windows, flat glass for windshields, doors and windows, insulators and electrical parts, silicon wafers, magnetic heads and electronic substrates.