Coarse-grained Diamond Grinding Wheel Research Articles

Research on the Grinding Performance of an Electroplated Coarse-Grained Diamond Grinding Wheel by Dressing

The coarse-grained electroplated diamond grinding wheels is increasingly favored in precision grinding of hard and brittle materials owing to its high material removal efficiency, high wear resistance and steady surface contour accuracy. However, how to determine whether the dressed grinding wheel surface topography can achieve the desired precision ground surface quality is still a huge challenge to this day. In this paper, a novel numerical simulation model, which was established basing on the statistical features of actual electroplated coarse-grained diamond grinding wheel and the kinetics of the grinding process, was proposed for theoretically and thoroughly studying the influence of the surface dressing depth of coarse-grained electroplated diamond grinding wheel on ground workpiece surface morphology. At first, the statistical features of actual electroplated coarse-grained diamond grinding wheel was acquired and a novel numerical grinding wheel surface model was established. Subsequently, a numerical ground workpiece surface simulation model was also developed. And then, the evolving mechanism of the grinding wheel surface topography with the dressed wheel surface abrasive grain protrusion height was theoretically studied by numerical simulation. Moreover, the influence of the wheel surface abrasive grain protrusion height on the ground surface roughness was thoroughly researched by means of theoretical model and experiments. The simulation and experiments results in this paper indicated that precision ground workpiece surface with nano-scale surface roughness can be acquired by grinding with a dressed grinding wheel with a certain abrasive grain protrusion height of 25% of the typical abrasive size. Comparing with the undressed grinding wheel (grinding wheel with original surface topography and not be dressed), the surface roughness Sa and Sq of the surface ground with a well-dressed wheel can achieving a significant decrease of 97.75–99.77% and 97.57–99.73%, respectively. Therefore, carefully dressing the electroplated coarse-grained diamond grinding wheel is of great significance for obtaining a precision ground workpiece surface quality.

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.

Precision grinding of a microstructured surface on hard and brittle materials by a microstructured coarse-grained diamond grinding wheel

Microstructured surfaces on hard and brittle materials are widely used in a series of scientific and industrial applications, such as micro-electro-mechanical systems, nano-electro-mechanical systems, electronic devices, and medical products. However, the efficient precision machining of microstructured surfaces on hard and brittle materials faces great challenges. In this study, a new machining technology for high-efficiency precision fabrication of microstructured surface on hard and brittle materials was developed by a microstructured coarse-grained diamond grinding wheel. Initially, the laser microstructuring of the conditioned coarse-grained diamond grinding wheel was introduced. The influence of the laser-machined microstructure geometry on the form accuracy of the final, ground microstructured surface was theoretically analysed. Subsequently, the ductile regime grinding of the microstructured surface was examined for WC cermet and BK7 optical glass. The ground surfaces mainly under the ductile regime material removal were successfully achieved, especially in the case of WC ceramic. Finally, different linear and square microstructured surfaces with high form accuracy, sharp microstructure edge, and nanoscale surface roughness were efficiently fabricated on WC and BK7 optical glass by the method developed in the study.

A study of the grinding performance of laser micro-structured coarse-grained diamond grinding wheels

Considering the relatively poor surface and subsurface quality of workpieces that are ground by coarse-grained grinding wheels, the nanosecond ultraviolet laser micro-structuring of coarse-grained diamond grinding wheels and the grinding performance of micro-structured grinding wheels were investigated in this study. In addition, the effect of two processing sequences on the topographical characteristics of the grooves and the effect of the groove angle (α) on the surface roughness (R a ) of the ground workpiece were explored. Furthermore, the surface quality of workpieces that were ground by micro-structured (V-shaped and W-shaped patterns) and non-structured diamond grinding wheels and the grinding ratio (G) of the grinding wheels were comparatively analyzed. The results demonstrate the following: Compared with the grinding wheel that was subjected to micro-structuring followed by sharpening, the surface of the grinding wheel that was subjected to sharpening followed by micro-structuring had a more integral groove structure. Neither an overly large α nor an overly small α was favorable for improving the surface quality of the workpiece that was ground by a micro-structured grinding wheel. When α = 60°, the minimum R a of the workpiece was attained. The R a of the workpieces that were ground by the grinding wheel with a V-shaped pattern (grinding wheel A) was 17–31% less than the R a of the workpieces that were ground by the non-structured grinding wheel (grinding wheel C). The R a of the workpieces that were ground by the grinding wheel with a W-shaped pattern (grinding wheel B) was 32–41% less than the R a of the workpieces that were ground by grinding wheel C. The grinding performance of the micro-structured grinding wheels was related not only to the geometric parameters of the grooves but also to the micro-structure pattern. The W-shaped pattern was superior to the V-shaped pattern in terms of cooling and chip removal. Grinding wheel A and grinding wheel B had similar abrasion resistance, which were 26% less and 23% less than the abrasion resistance of grinding wheel C, respectively.

Application potential of coarse-grained diamond grinding wheels for precision grinding of optical materials

Fine-grained resin bonded diamond tools are often used for ultra-precision machining of brittle materials to achieve optical surfaces. A well-known drawback is the high tool wear. Therefore, grinding processes need to be developed exhibiting less wear and higher profitability. Consequently, the presented work focuses on conditioning a mono-layered, coarse-grained diamond grinding wheel with a spherical profile and an average grain size of 301 µm by combining a thermo-chemical and a mechanical-abrasive dressing technique. This processing leads to a run-out error of the grinding wheel in a low-micrometer range. Additionally, the thermo-chemical dressing leads to flattened grains, which supports the generation of hydrostatic pressure in the cutting zone and enables ductile-mode grinding of hard and brittle materials. After dressing, the application characteristics of coarse-grained diamond grinding wheels were examined by grinding optical glasses, fused silica and glass–ceramics in two different kinematics, plunge-cut surface grinding and cross grinding. For plunge-cut surface grinding, a critical depth of cut and surface roughness were determined and for cross-grinding experiments the subsurface damage was analyzed additionally. Finally, the identified parameters for ductile-machining with coarse-grained diamond grinding wheels were used for grinding a surface of 2000 mm2 in glass–ceramics.

Ultra-precision grinding of optical glasses using mono-layer nickel electroplated coarse-grained diamond wheels. Part 1: ELID assisted precision conditioning of grinding wheels

In order to realize ultra-precision grinding of optical glasses with mono-layer nickel electroplated coarse-grained diamond grinding wheels, a novel conditioning technique was developed using copper bonded diamond grinding wheels with grain sizes of 15μm (D15) and 91μm (D91), respectively, as conditioners for truing of diamond wheels with grain sizes of 46μm (D46), 91μm (D91) and 151μm (D151), respectively. During the conditioning process, the conditioners were continuously dressed by means of electrolytic in-process dressing (ELID). A force transducer was used to monitor the conditioning force while a coaxial optical distance measurement system was used to monitor the wheel run-out. In addition, a white-light interferometer (WLI) and a scanning electron microscope (SEM) were used to characterize the successively modified diamond grain morphologies of the conditioned wheels both directly and by a replication technique. The experimental results show that with optimized conditioning parameters, the developed conditioning technique can be applied for truing of coarse-grained diamond wheels within the abrasive layer achieving a constant wheel peripheral envelop surface exhibiting flattened diamond grains with a run-out <2.5μm, which is a prerequisite for introducing coarse-grained diamond wheels into ultra-precision machining of brittle and hard-to-machine materials.

ELID Assisted Precision Conditioning of Coarse-Grained Diamond Grinding Wheel

In order to realize ductile machining of optical glasses using mono-layer nickel electroplated coarse-grained diamond grinding wheel, a novel conditioning technique features using a copper bonded diamond grinding wheels of 15m grain size dressed by ELID (electrolytic inprocess dressing) to condition the 46m grain sized diamond wheel has been developed. During the conditioning process, a force transducer was used to monitor the conditioning force, a coaxial optical distance measurement system was used to in-situ monitor the modified wheel surface status. White-light interferometry (WLI), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize the conditioned wheel surface status as well as the ground optical glass surface topography correspondingly. The experimental result indicates that a minimized wheel radial run-out error of less than 2μm as well as the top-flattened diamond grains of constant wheel peripheral envelop profile were generated on a 5-axis ultra-precision machine tool. The grinding experiment proved that the well conditioned 46μm coarse-grained diamond wheel can be used in realizing the ductile grinding of optical glass BK7, which indicates that the newly developed conditioning technique is feasible and applicable to introduce the coarse-grained diamond wheels into precision machining of brittle and hard-to-machine materials.

Precision Machining of Silicon Carbide with Diamond Micro Tool Array (DMTA)

An advanced conditioning technique was developed to precisely and effectively condition the nickel electroplated mono-layer coarse-grained diamond grinding wheel of 46m and 91m grain size with an aim to fabricate Diamond Micro Tool Arrays (DMTA), to meet the high demands of form accuracy, surface quality and low subsurface damage in ductile machining of silicon carbide (SiC). The precision machining experiments on SiC were carried out on a precision grinder to determine the applicability of these fabricated diamond micro tool array (DMTA). The experimental result indicates that the newly developed DMTA is applicable and feasible to realize ductile machining on SiC with high efficiency and low diamond tool wear rate, which shows a good prospect to apply this new concept diamond tool type in precision machining of SiC, as well as the other brittle and hard-to-machine materials.

Surface and Sub-Surface Integrity of Ultra- Machined BK7 Using Fine and Coarse Grained Diamond Wheels

This paper aims to evaluate the surface and sub-surface integrity of optical glasses which were correspondingly machined by coarse and fine-grained diamond grinding wheels on Tetraform ‘C’ and Nanotech 500FG. The experimental results show that coarse-grained diamond grinding wheels are capable of ductile grinding of optical glasses with high surface and sub-surface integrity. The surface roughness values are all in nanometer scale and the sub-surface damages are around several micros in depth, which is comparative to those machined by fine-grained diamond wheels.

Ultra-precision ductile grinding of BK7 using super abrasive diamond wheel

In this paper, a novel conditioning technique using copper bonded diamond grinding wheels of 91 μm grain size and electrolytic in-process dressing (ELID) is first developed to precisely and effectively condition a nickel-electroplated monolayer coarse-grained diamond grinding wheel of 151 μm grain size. Under optimised conditioning parameters, the super abrasive diamond wheel was well conditioned in terms of a minimized run-out error and flattened diamond grain surfaces of constant peripheral envelope. The conditioning force was monitored by a force transducer, while the modified wheel surface status was in-situ monitored by a coaxial optical distance measurement system. Finally, the grinding experiment on BK7 was conducted using the well-conditioned wheel with the corresponding surface morphology and subsurface damage measured by atomic force microscope (AFM) and scanning electric microscope (SEM), respectively. The experimental result shows that the newly developed conditioning technique is applicable and feasible to ductile grinding optical glass featuring nano scale surface roughness, indicating the potential of super abrasive diamond wheels in ductile machining brittle materials.

Fabrication of Diamond Micro Tool Array (DMTA) for Ultra-Precision Machining of Brittle Materials

A novel conditioning technique to precisely and effectively condition the nickel electroplated mono-layer coarse-grained diamond grinding wheel of 91m grain size was developed to fabricate a Diamond Micro Tool Array (DMTA) in ductile machining of brittle materials. During the fabricating process, a copper bonded diamond grinding wheels (91m grain size) dressed by ELID (electrolytic in-process dressing) was applied as a conditioner, a force transducer was used to monitor the conditioning force, and a coaxial optical distance measurement system was used to insitu monitor the modified wheel surface status. The experimental result indicates that the newly developed conditioning technique is applicable and feasible to generate required wheel topography of less than 2μm run-out error and grain geometries. The taper cutting test on BK7 proves the fabricated DMTA is capable of realizing ductile machining of brittle materials.