Grinding 6000 grit-size wheel

A mirror surface was achieved on silicon nitride materials when ELID grinding was performed using a 4000 grit-size wheel. The finish ELID technology will find wide application in the optical and semiconductor industries such as mirror finishing of silicon wafers, many kinds of ceramics, ferrite, and glass. 

SEM and AEM studies reveal that the work piece was predominantly groimd in the ductile mode when ELID grinding was performed with a 4000 grit-sized wheel or finer. 

ELID grinding provides the ability to produce spectacular finishes on brittle material surfaces, with surface roughness on the nanometer scale (4-6 nm). Coarse grit size wheels (JIS 325 and coarser) show only slight differences in the final roughness when ELID is applied as compared to conventional grinding. However, for finer wheels (JIS 4000 and finer). 

Grinding wheels are by far the most important bonded abrasive product both in production volume and utility. They are produced in grit sizes ranging from 4, for steel mill snagging wheels, to 1200, for polishing the surface of rotogravure rolls. 

Test Condition HPSN Batch Wheel Grit Size dk (p.m) Table Feed v (mm/sec) Depth of Cut e (mm) Grind Direction Grit Depth of Cut hmax ((inl)... 

Conventional grinding and ELID grinding were performed with CIFB-D grinding wheels of grit size 170 under different grinding conditions such... 

It was proved that a grinding wheel with a larger grit size presents a larger damage depth to the grounded piece (Zhang et al., 2000). As the... 

When silicon was ground together with tungsten carbide, the surface roughness improved when compared with grinding the silicon alone brittle-to-ductile transition was observed for JIS 4000 mesh size wheel. In a later study (Itoh et al., 1998), silicon and glass (BK7) were ELID lapped with metal resin diamond-bonded wheels of grit sizes of JIS 8000, JIS 120,000, and JIS 3,000,000. 

It is possible to achieve mirror-like surface with an appropriate coarse grinding wheel the roughness obtained after ELID HI grinding with 2000 grit size is almost the same with the roughness obtained after ELID with 4000 with cBN. 

Other studies (Qnchi et al., 1995) reported an R 30 nm roughness after grinding SAE52KX) with a porous cBN wheel, but with relatively low removal rates and very fine cBN wheels, or up to R 60 nm (Puthanangady et al., 1995) after superfinishing hardened steel pieces with 500 grit size fused alumina stones. 

ELID grinding is more stable than conventional grinding from the removal rate value viewpoint. Material removal rates of 250 mm /min up to 8000 mm /min were reported. The chip thickness is of an order of 1-10 nm. Stock removal rate increases with the increase in the number of passes, stiffness of machine tool, and larger grit sizes of the wheels. Cast-iron-bonded wheels have a larger stock removal rate yet a lower grinding force as compared to a vitrified bonded grinding wheel. 

Wheel grit size used during final grinding step. (P) means polished. 

Chip storage space may be increased by use of a coarser grit size and less bonding material. However, both of these lower the tensile strength of the wheel and thus offer only a very limited solution to the chip storage problem. In order that safety not be sacrificed in order to increase productivity, it is a Federal requirement that the maximum surface speed of a grinding wheel be limited to 2/3 the speed at which the wheel disintegrates due to brittle fracture. This provides a factor of safety based on fracture stress of (1.5) = 2.25. 

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