Fabrication And Grinding Performances Of A New Diamond Wheel

The random nature of the abrasives geometries and their distribution in conventional wheel results in high temperature and high specific energy. It can cause the abrasives to fall off the grinding wheel prematurely, leading to inefficient use of the abrasives. Moreover, grinding wheel wear and loading problems become more severe when grinding "sticky" materials, which requires more frequent wheel truing and dressing and thus reduces grinding efficiency. This paper is aimed at developing a new diamond wheel in order to overcome these shortages of conventional diamond wheels. The diamond cutting edges are fabricated by combining powder injection molding with vacuum brazing, which have a large aspect ratio and diamonds grits pullouts cannot happen due to the presence of the chemical bonding. These diamond cutting edges can be artificially ordered so as to have the desired arrange pattern and space among themselves, and then suppressed with resin bond materials to prepare a new diamond wheel. The appropriate pore inducer is chosen to improve the self-sharpening ability and increase the clearance for debries of wheel. The paper compares the machining performance of the new diamond wheel with that of conventional resin bond diamnd wheel in machining the Al2O3ceramic, the machining performance of the new diamond wheel with that of the engineered cutter in machining the WC/12Co coating, respectively, and further discusses the grinding mechanism.The fabrication of diamond cutting edges is a key step for the successful preparation of the new diamond wheel. The typical fabrication process of the diamond cutting edges are mixing, injection molding, debinding and vacuum brazing. Initially, a suitable formulation of binder is mixed with the coated diamonds and copper based alloy powders. The injection green parts are molded on a reciprocating screw injection molding machine. The binder must be removed from the molded parts, a two-step debinding process is selected. Brazing is the last stage of the process, it is essentially a removal of pores, accompanied by strong bonding strength between the diamonds and copper based alloy. The test indicated that the diamond cutting edges with no defects were prepared by vacuum brazing process (brazing temperature is920℃, holding time is10min, heating/cooling rate is5℃/min). The paper investigates the machining performance of the single diamond cutting edge in machining the WC/12Co coating. The test indicated that diamond cutting edge has good cutting properties, the diamonds mainly occurred micro-fracture and fracture, diamonds pull-out cannot easily happen during the grinding processing owe to the presence of strong adhesion between the diamond grits and brazing alloy, the diamond grits were used efficiently.Because the diamond cutting edges have high transverse-rupture strength and large aspect ratio, they can been artificially distributed in the matrix material in accordance with array parameters, and further fabricate the new diamond wheel through autoclave process. The production process flow of the new diamond wheel is as follow:Initially, produce diamond segment die and oval open in the cylindrical in accordance with array parameters. Secondly, put the diamond cutting edges into the hole and hold them immovably, Then embeds into resin bond materials and porosity inducer to fabricate diamond segments. Finally, prepare the new diamond wheel through autoclave process and further make the bond matrix higher strength through curing processAfter the preparation of the new diamond wheel, it discusses the grinding performances of the new diamond wheel and the conventional resin bond diamond wheel machining Al2O3ceramic at the same conditions. The test indicated that the grinding force and grinding temperature of the new diamond wheel are smaller than that of the conventional wheel, and the machining quality of the former is better than that of the latter. The changes of morphologies of diamond grits in grinding are observed, the worn states of diamond grits of the new diamond wheel are intact, micro-fractured, macro-fractures, and the diamond grits are difficult to be pulled out because of the strong bonding strength, in addition, the blockage of wheel is decreased through the controlled distributing of diamond cutting edges. In contrast, diamond grits falling off from conventional grinding wheel are observed, and the surface easy to block, which would result in grinding temperature rise even thermal damage. The machining performance of the new diamond wheel with the engineered cutter in machining the WC/12Co coating was compared, the test indicated that the machining quality of the former is better than that of the latter, And the wear test showed that the cutting edges of the engineered cutter appear tipping, they need to be sharpened again, but the sharpening technology is complex and time-consuming. In contrast, The primary wearing way of the diamond grits of the new diamond wheel are intact, micro-fractured and macro-fractured, and it was easy dressed.The new diamond wheel has more superiority than conventional diamond wheels on grinding performance. On the one hand, the new diamond wheel overcome the shortage of diamond grits easy to fall off the surface of the conventional grinding wheel, on the other hand, the lifetime of the new diamond wheel is longer than that of the brazed monolayer wheel. When the diamonds of the new diamond wheel lose the cutting ability, the diamonds under-layer can expose and continue to cut. The chip-pocket space and cooling ability are increased because of the optical orientation of diamond cutting edges, which also affects the wheel life and machining quality.