| Summary: | 碩士 === 華梵大學 === 機電工程學系博碩專班 === 97 === The purpose of this paper is to investigate the performance of wet grinding alumina for the specific designed tools containing a controlled diamond protrusion and arrangement with three types of metal bonds of 50vol.%85Cu/15Sn/ 50vol.%Fe, 50vol.%85Cu/15Sn/50vol.%Co, and 100vol.%85Cu/15Sn. Changing the depth of cut and feed rate under a fixed spindle speed during the grinding alumina was used to evaluate the grinding forces, workpiece roughness and diamond wear.
The experiment results showed that the grinding forces with the increase of feed rate during the wet grinding alumina slowly increased. However, the grinding forces with the increase of depth of cut showed a relatively larger rise. When the depth of cut reached to 0.09 mm (that is about one fourth of diamond size), the axial grinding force obtained above about 20 N caused some weaker or higher protrusive diamonds to produce a relatively larger fracture or pull-out. Furthermore, under a larger depth of cut and a larger feed rate the workpiece roughness obtained was the poorer. Tool with a bronze bond displayed the better results than that of tool with iron/bronze or cobalt/bronze bond. The reason for this may be due to the results of the difference of active contact faces or points and protrusive height of diamond particles.
When bronze bonded diamond tool was employed under a longer grinding test, 110 hrs, of the spindle speed, 600 rpm, the depth of cut, 0.03 mm, and feed rate of 40 mm/min, the resulting axial grinding force only slowly increased and diamonds displayed an attritious wear. In addition, the alumina workpiece roughness obtained showed about Ra 1.2-2.2 μm. Furthermore, a larger feed rate of 100 mm/min and the depth of cut of 0.05 mm were used to grind alumina for 10 hrs. Diamond wear showed an attritious condition as well and the workpiece roughness showed about Ra 1.86-2.04 μm. Thereafter, a larger depth of cut of 0.07 mm was employed to grind more 10 hrs. Diamond mainly showed an attritious wear, but some diamonds started to produce micro fracture. The workpiece roughness rose to about Ra 2.34-2.56 μm. This implies that metal bonded diamond tools designed can be used to grind alumina for a long time under the circumstances that the axial grinding force does not cause the diamond to produce the macro fracture or pull-out.
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