Coarse-grained Wheels Research Articles

Bone grinding using coarse-grained diamond wheels to suppress thermal damage

Bones, which are hard tissues in the human body, are frequently removed during spine, joint, and brain surgeries. Diamond grinding wheels are widely used for the careful removal of bones during surgeries such as an endoscopic surgery. However, the wheels generate a considerable amount of heat, causing thermal damage, such as thermal bone necrosis and thermal injury to adjacent tissues. Considerable research has been conducted to suppress this heat generation using #120–#200 (grit size) wheels; notably, #30–#120 wheels are often used in actual surgeries to reduce the operating time. In this study, the bone grinding characteristics associated with a temperature increase were studied when using a coarse-grained wheel, i.e., a #30 wheel. Results showed that the temperature increased owing to the large grain size of the wheel. Furthermore, a decrease in the rotation speed of the wheel effectively suppressed the temperature increase. Consequently, an increase in the grain depth of cut and a decrease in the generated frictional heat between bone and grains effectively suppressed the temperature increase.

High Efficiency Precision Grinding of Micro-structured SiC Surface Using Laser Micro-structured Coarse-Grain Diamond Grinding Wheel

Accompanying with the extensive applications of micro-structured surfaces on hard and brittle material in MEMS and NEMS sensors, optical elements, electronic devices and medical products, efficiently fabricating of these surface has gradually become the focus of manufacturing community. Basing on precision grinding with conditioned and laser micro-structured coarse-grained diamond grinding wheel, a novel high efficiency technique for micro-structured surfaces on hard and brittle material, such as silicon carbide, was developed in this paper. Firstly, the maximum undeformed chip thickness for conditioned coarse-grained wheel and the ductile grinding of silicon carbide was theoretically and experimentally studied. Silicon carbide surface formed mainly in ductile regime was successfully achieved. And then, the strategy for micro-structuring the conditioned wheel with designed micro-structure geometry, sharp edge and small inclination angle side-wall was investigated. Finally, the linear and square micro-structured surfaces with high form accuracy and ultra-precision surface roughness were successfully and efficiently fabricated on silicon carbide by the technique developed in this paper.

Laser micro-structuring of a coarse-grained diamond grinding wheel

To address the significant subsurface damage of a workpiece after grinding by a coarse-grained wheel, the research on nanosecond ultraviolet laser micro-structuring of a coarse-grained diamond-grinding wheel was carried out, and the influence of process parameters on the depth and width of the groove, the micro-structuring efficiency, and the qualification rate of micro-structured grains were explored. The results show that the single-pass laser circular cutting method cannot achieve the desired groove size even with an arbitrarily large number of scanning cycles. The multi-pass laser circular cutting method can effectively improve the micro-structuring efficiency, and the width and depth of the groove increased and decreased respectively with the increase of the pass spacing. The qualification rate of micro-structured grains was related to the groove spacing, the distribution of the grains on the surface of the grinding wheel, the grain diameter, and the groove width. Under the assumption that the grains were evenly distributed on the surface of the grinding wheel, the qualification rate first increased and then decreased with the increase of the groove spacing.

Grinding damage of BK7 using copper-resin bond coarse-grained diamond wheel

Coarse-grained wheels can realize high efficient grinding of optical glass. However, the serious surface and subsurface damage will be inevitably introduced by the coarse-grained wheels. In this paper, the grinding damage of a copper-resin bond coarse-grained diamond wheel with grain size of 150μm was investigated on optical glass BK7. The wheel was first properly trued with a metal bond diamond wheel, then pre-dressing for the wheel and grinding experiments are carried out on a precision grinder assisted with electrolytic in process dressing (ELID) method. The surface roughness (Ra) of ground surface was measured using an atomic force microscope (AFM) and the surface topography were imaged by a white light interferometer (WLI) and the AFM. The subsurface damage level of ground surface was evaluated by means of both MRF spot method and taper polishing-etching method, in term of the biggest depth of subsurface damage, distribution of micro defects beneath the ground surface, the cluster depth of subsurface damage, relationship between subsurface damage (SSD) and PV surface roughness (SR), propagating distance and pattern of cracks beneath the ground surface. Experimental results indicate that a well conditioned copper-resin bond coarse-grained diamond wheel on a precision grinder can generate good surface quality of Ra less than 50nm and good subsurface integrity with SSD depth less than 3.5e for optical glass BK7.

Experimental assessment of residual stresses in plane ground thin plates

Surface and subsurface residual grinding stresses in plane dry ground steel plates were evaluated by using a layer-removal technique and the Stäblein equations. The maximum residual stresses do not occur at wheel-workpiece contact surfaces. These stresses increase for harder workpieces. As infeeds and longitudinal feeds rise, the maximum stresses increase up to certain limits and then decrease. The hardness of the grinding wheel, i.e. its grain-holding ability, also affects the residual stresses. Hard coarse-grained wheels produce shallower subsurface layers with higher maximum residual grinding stresses.