|Budget Amount *help
¥2,300,000 (Direct Cost : ¥2,300,000)
Fiscal Year 1996 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1995 : ¥1,800,000 (Direct Cost : ¥1,800,000)
A novel grinding method for ceramic balls has been proposed. In the method diamond grinding wheels are used instead of loose abrasive grits as in the conventional lapping method, and magnetic fluid support is adopted. The magnetic fluid support has a good combination of stiffness and damping, which enables the grinding wheel to rotate at a speed as high as 5000rpm. The magnetic fluid is sealed in a small container. Only a small amount of magnetic fluid is needed, and the magnetic fluid can be used almost permanently. Experiments on the effects of grinding wheel speed, grinding load, grinding wheel grit size and grinding fluid type on material removal rate, sphericity of ground balls, surface roughness were conducted. The effects of material type of guide ring and rotation of the thrust taper on grinding behavior were also investigated by using a cast iron and a diamond wheel guide ring, and fixing or freeing the rotation of thrust taper, respectively. Mechano-chemical polishing test wa
s also carried out by using a Cr_2O_3 grinding wheel. The main experimental results are as follows.
(1) The material removal rate is proportional to the grinding wheel speed and the grit size, and increases linearly as grinding load increases. Grinding fluid type also has great effect on the material removal rate and JC-707 gives the highest material removal rate among the four types of grinding fluid JC-707, water, SMS and half-dry grinding.
(2) An ultra-high material removal rate of over 30mum/min was obtained when an SD200 diamond grinding wheel was used under a grinding wheel speed of 4000rpm.
(3) The available sphericity is proportional to the grinding wheel grit size, and decreases linearly as the grinding wheel speed decreases. The effect of the grinding load on the available sphericity is dependent on the wheel speed. When the wheel speed is higher than 2000rpm, the available sphericity decreases as the grinding load increases, while in the range of the wheel speed less than 2000rpm the available sphericity decreases as the grinding load decreases. Grinding fluid types also affect the available sphericity greatly, and half-dry grinding gives the best sphericity.
(4) Surface roughness is almost proportional to the wheel grit size. The wheel speed, grinding load and grinding fluid type have only a minor effect on the surface roughness.
(5) Cast iron guid ring and diamond wheel guide ring give not much difference in both material removal rate and sphericity, and fixing or freeing of the rotation of the thrust taper does not change grinding performance.
(6) Mechano-chemical polishing improves the surface roughness greatly but not much the sphericity.
(7) The sphericity was improved from 43mum to 6mum in a short grinding time of 6min..
(8) High precision ceramic balls of 0.121mum sphericity and Rmax0.092mum were obtained by using the proposed method.