Abrasive Lapping Research Articles

Machined Surface Characteristics and Removal Mechanism of Soft and Brittle Solids

Surface characteristics of CZT wafers machined using wire sawing, free abrasives lapping and polishing and ultra-precision grinding were investigated. Wire sawing resulted in the removal of material in both ductile and brittle regimes, but both polishing and grinding led to a ductile removal. The grinding produced very smooth surfaces free of embeddings and scratches, which is thus considered to have better machinability than the free abrasive machining. The nanoindentation and nanoscratch on MCT wafers at nanometric scales resulted in considerable plastic deformation, but no fracture features. The hardness of the MCT wafer was 500 to 550 MPa, and the coefficient of friction was particularly high, ranging from 0.45 to 0.55.

Mechanical Characterization of Lapping Plate Materials in Diamond Charging Process

In the lapping of magnetic heads and other electronic components composed of multiple materials, differences in the processing characteristics of the composite materials result in “residual steps” forming on the surface at composite interfaces. Residual step heights have been reduced to as little as a few nanometers. We investigated using fine abrasives in fixed abrasive lapping for this purpose, which requires highly secure, high-density embedding of the abrasives on the lapping plate. To this end, we modeled the abrasive embedding process and investigated the relationship between the mechanical properties of the lapping plate and the retention of the abrasive, to determine the direction of further research and development. The results of this investigation revealed a correlation between the work hardening in the plate and the resulting abrasive density and cutting edge height. The investigation also showed that it is possible to suppress the reduction in lapping rate that occurs during use by increasing the work hardening coefficient of the plate.

Fixed Abrasive Lapping and Polishing of Hard Brittle Materials

Fixed abrasive lapping and polishing (FALP) is a new machining technology and was adopted to manufacture hard brittle materials and obtain the high productivity because of fixed abrasive. The preparation process of fixed abrasive pad (FAP) was described. FALP of K9 glass, mobile panel glass and Si were investigated with fixed 5-10 µm diamond abrasives. The effect on material removal rate (MRR) and surface quality of different materials was studied. The results show that in the same FALP process conditions, Si is the highest MRR and reaches 4428 nm/min, mobile panel glass is inferior to and K9 glass is the lowest. And surface quality of mobile panel glass that surface roughness Sa is 2.10 nm and little and less damages is the best, Si is followed and K9 glass is the worst. So FALP can obtain the higher MRR and reaches several micrometers per minute and the better quality that surface roughness Sa can reach nanometer level for different materials.

Comparison of Processing Features between Semi Bonded Abrasive Lapping and Loose Abrasive Lapping

Semi bonded abrasive lapping is an effective ultra-precision lapping method. It can obtain good surface quality of workpiece in short time. This paper focused on the differences of processing features by comparing semi bonded abrasive lapping and loose abrasive lapping in several groups processing parameters. The results showed that the surface roughness of workpiece in semi bonded abrasive lapping was far superior to that of loose abrasive lapping in same processing parameters. And the MRR (material removal rate) of semi bonded abrasive lapping was slightly lower than that of loose abrasive lapping. For these features of semi bonded abrasive, a new processing flow would also be proposed in this paper.

Study on Parameters Optimization in Ultra-Precise Processing of Germanium Substrate

To improve efficiency in ultra-precision lapping germanium (Ge) substrate, a new ultra-precise process technology is introduced in this paper. Two steps ultra-precise process were semi bonded abrasive lapping in rough machining, and CMP process in finish machining. A good surface quality workpiece was obtained in semi bonded abrasive lapping process efficiently. Several machining parameters were compared and applied. After CMP process, the mirror-like surface of Ge substrate was obtained.

Study on Semi-Fixed Abrasive Lapping of Ultra-Thin Silver Electrode Layer

Silver electrode layer of piezoelectric ceramic transducer requires good surface quality and high efficiency. Efficiency of traditional lapping and polishing is very low. Ultra-precision grinding technology is also unsuitable for the thickness of workpiece is extremely thin. Semi bonded abrasive lapping is a new ultra-precision processing method. The new ultra-precise method can achieve good surface quality in short time, and removal stock of workpiece is small. In order to research the optimal technology of semi bonded abrasive lapping about silver electrode layer, this paper research several major processing parameters by experiments. The results show that appropriate processing load can obtain better surface roughness of silver electrode layer，and surface roughness of silver electrode layer has little change with different processing speed. By using ultra-fine semi bonded abrasive plate, 94.08KPa processing load and 40 rpm polishing speed, after 30 minutes, surface roughness of silver electrode layer is 11nm, and removal stock is 11.5μm.

Experimental Study on New Bonding Materials for Developing Nano-Grinding Plates

This paper describes a method for experimental development of a novel fixed abrasive nano-grinding plate (FAG-plate) which is proposed for lapping some rigid brittle materials, such as quartz crystal and silicon. The FAG plate is developed with ultraviolet-cured resin by rapid prototyping technology. The analysis shows that such FAG-plate can keep its grinding ability constant and continuous and it can make the roughness of machined surface reach to nanometer level. Based on experimental comparisons with conventional free abrasive slurry lapping plates, the lapping process using FAG-plate has several distinct advantages. One is that the machining efficiency is significantly improved. The second is that it improves the surface roughness of machined work-pieces, although it decreases the flatness tolerance of materials. Furthermore, the fixed abrasive nano-grinding plate is made by the new bonding materials- ultraviolet curing resin and thus the fabrication of FAG-plate is convenient and economical.

Research on the properties of ultraviolet-curing resin lapping plate

This paper reports a new method using ultraviolet-curing resin as a bonding agent to develop a new fixed-abrasive lapping plate. The results of lapping experiments have shown that it increases the machining efficiency compared with the conventional loose abrasive lapping plate and makes the machined surface roughness to reach nanometre level. Moreover, this technique of the lapping plate makes it not only easier to manufacture but also more convenient to dress with low cost, high speed and clean technology.

Study on Anodic Smoothening Velocity in Electrochemical Abrasive Lapping

By analysing the change of the anodic surface topography in Electrochemical Abrasive Lapping (ECAL), the influence of the lapping action and the electrochemical action on the anodic smoothening velocity is studied. In electrochemical finishing, the micro-peaks on the anodic surface could be smoothened quickly by electrochemical action and the surface topography presents the profile wave, but in ECAL, the profile wave after electrochemical action could be divided into micro-peaks renewedly by lapping action and the alternation of electrochemical action and lapping action makes the surface topography before electrochemical action present profile micro-peaks, which will increase the anodic smoothening velocity. The influence of machining parameters, such as abrasive grain sizes, tool’s pressure, abrasive content, frictional velocity and current density etc, on the anodic smoothening velocity is discussed in detailed.

Basic study on fixed abrasive lapping characteristics of diamond pellets

Basic study on fixed abrasive lapping characteristics of diamond pellets

Study on Fixed Abrasive Lapping Technology for Ceramic Balls

To improve low lapping efficiency of silicon nitride balls in conventional lapping process, fixed abrasive lapping technology for ceramic balls is investigated in this paper. Diamond abrasives and photosensitive resin are used to fabricate the fixed abrasive plate. The lapped ball surface is observed with microscopy to identify the dominant wear mechanism. The results show that the material removal rate of the fixed abrasive lapping is about 20 times of that of conventional free abrasive lapping process, and the roughness is close to the conventional one. The experimental results indicate that the fixed abrasive lapping technology is a promising process to instead of conventional free abrasive lapping process for ceramic balls in rough and semi-finishing process.

A Basic Study on Precision in Electrochemical Abrasive Lapping of Plate

Taking plate as the example, this paper studies the effect of tool’s shape and movement on the electrochemical as well as mechanical lapping characteristics in Electrochemical Abrasive Lapping (ECAL). It is assumed that the removal size of electrochemical action at a random point is in direct proportion to the electrical amperage through this point and the removal size of the lapping action is in direct proportion to the relative frictional distance. Based on the assumption above, electrochemical and mechanical lapping characteristics with different tools shape are studied theoretically. The results show that the diameter of the tool should be larger than the width of the workpiece when a discal tool is used and the inner diameter of the tool should be larger than the width of the workpiece when a ringed tool is used, on the other hand the ratio of the revolving radius of the tool to the diameter of the tool as larger as possible avails to improve the precision and so does the ratio of the angular velocity of the workpiece to the rotating angular velocity of the tool.

Deterministic Microgrinding, Lapping, and Polishing of Glass-Ceramics

We report a series of microgrinding and polishing experiments on glass–ceramics. Microgrinding includes deterministic microgrinding (two-body abrasion at fixed infeed rate) and loose abrasive lapping (three-body abrasion at fixed pressure). We correlate material mechanical properties (Young's modulus, hardness, fracture toughness) and chemical properties (chemical susceptibility or mass loss under chemical attack) with the quality of the resulting surface (surface microroughness and surface grinding-induced residual stresses). We compare deterministic microgrinding (at fixed infeed) and loose abrasive microgrinding (at fixed pressure) in terms of material removal rates and resulting surface quality.

Loose abrasive truing and dressing of resin bond diamond cup wheels for grinding fibre optic connectors

A loose abrasive lapping technology was developed for truing and dressing ultrafine diamond cup wheels for grinding spherical end faces of fibre optic connectors. The relative densities of exposed grits and grit pull-outs measured from wheel surfaces prepared using the loose abrasive lapping and the bonded abrasive dressing were compared. It was found that the lapping method with loose abrasives produced wheel surfaces with more exposed grits and less grit pull-outs, especially for finer grit size wheels. For dressing ultrafine grit size wheels, the particle size of the lapping paste should be smaller than the wheel grit size to achieve a better result. It is also found that the wheels dressed using the lapping method demonstrate an excellent grinding performance.

우주망원경용 비구면 반사경 표면조도 향상을 위한 진화형 수치제어 연삭공정 모델

우주망원경용 비구면 반사경 가공 공정은 고정입자 연삭, 자유입자 래핑, 연마의 순서를 따른다. 숙련공에 의한 경험적 공정조절에 의해 목표 비구면을 가공하는 전통적 연삭 공정에서는 수 <TEX>${mu}m$</TEX> 높이의 표면 밑 손상을 남기며 뒤이은 자유입자 래핑 및 연마 공정에서 이를 제거하며 가공한다. 본 연구는 컴퓨터 수치 제어 연삭 공정진화 모델을 개발하여, 연삭가공을 통해 반사경 표면조도 최소 40nm이하, 가공 예측정확도 20nm급을 이루었다. 구체적인 방법론으로 초정밀가공기의 연삭모듈을 이용하여 연삭 휠 입자의 크기, 이송속도, 공작물 회전선속도 등 연삭 변수를 변화시키며 직경 20, 100mm Zerodur 소재를 초기 연삭하였다. 초기 연삭 변수와 측정된 표면조도와의 관계를 경험적 해석과 다 변수 회귀분석 해석 방법을 통하여 공정조절용 수치 연삭 모델을 구성하였다. 정량적 공정제어는 입력된 연삭변수들로부터 가공 후 표면조도를 예측하고, 측정된 표면조도를 이용하여 수치연삭 모델을 개량한 후 다음 가공에서 측정될 표면조도를 예측하는 순으로 만복 진행되었다. 본 연구에서는 CNC 연삭공정조절로부터 최소 평균 표면조도 36nm, 예측정확도 <TEX>${pm}20nm$</TEX>를 얻었다. 이 연구결과는 정량적 연삭공정제어 모델을 사용하여 자유입자 래핑 공정을 수행할 필요 없이 연삭에서 직접 연마 공정으로 진행할 수 있는 획기적인 공정 효율 향상을 의미한다. Optics fabrication process for precision space optical parts includes bound abrasive grinding, loose abrasive lapping and polishing. The traditional bound abrasive grinding with bronze bond cupped diamond wheel leaves the machine marks of about <TEX>$20{mu}m$</TEX> rms in height and the subsurface damage of about 1 <TEX>${mu}m$</TEX> rms in height to be removed by subsequent loose abrasive lapping. We explored an efficient quantitative control of precision CNC grinding. The machining parameters such as grain size, work-piece rotation speed and feed rate were altered while grinding the work-piece surfaces of 20-100 mm in diameter. The input grinding variables and the resulting surface quality data were used to build grinding prediction models using empirical and multi-variable regression analysis. The effectiveness of such grinding prediction models was then examined by running a series of precision CNC grinding operation with a set of controlled input variables and predicted output surface quality indicators. The experiment achieved the predictability down to <TEX>${pm}20$</TEX> nm in height and the surface roughness down to 36 nm in height. This study contributed to improvement of the process efficiency reaching directly the polishing and figuring process without the need for the loose abrasive lapping stage.

アレーベア光ファイバーの一括端面加工

A precise process for machining arrayed optical fiber ends to have tapered corners and slightly convex planes for use as the bare optical fiber connectors have been developed. The taper shapes are determined by the length L of the fiber from holder to the fiber ends, the height h of the holder, and number of revolutions. The underlying principle is that the machining amount is proportional to the product of the load and the work traveling length. The curvature radius (8 to 18 mm) of the slightly convex fiber end plane can be controlled by adjusting the polishing load. The polished plane with the silica abrasive lapping film has high optical return loss (55 to 60 dB).

Loose abrasive lapping hardness of optical glasses and its interpretation

We present an interpretation of the lapping hardness of commercially available optical glasses in terms of a micromechanics model of material removal by subsurface lateral cracking. We analyze data on loose abrasive microgrinding, or lapping at fixed nominal pressure, for many commercially available optical glasses in terms of this model. The Schott and Hoya data on lapping hardness are correlated with the results of such a model. Lapping hardness is a function of the mechanical properties of the glass: The volume removal rate increases approximately linearly with Young's modulus, and it decreases with fracture toughness and (approximately) the square of the Knoop hardness. The microroughness induced by lapping depends on the plastic and elastic properties of the glass, depending on abrasive shape. This is in contrast to deterministic microgrinding (fixed infeed rate), where it is determined from the plastic and fracture properties of the glass. We also show that Preston's coefficient has a similar dependence as lapping hardness on glass mechanical properties, as well as a linear dependence on abrasive size for the case of brittle material removal. These observations lead to the definition of an augmented Preston coefficient during brittle material removal. The augmented Preston coefficient does not depend on glass material properties or abrasive size and thus describes the interaction of the glass surface with the coolant-immersed abrasive grain and the backing plate. Numerical simulations of indentation are used to locate the origin of subsurface cracks and the distribution of residual surface and subsurface stresses, known to cause surface (radial) and subsurface (median, lateral) cracks.

固定砥粒によるＳｉウエハの超精密加工に関する研究 遊離砥粒法に代わる新開発砥石

This paper deals with some experimental results of the application of a newly developed PVA grinding stone to the lapping process of silicon wafer. The characteristics of the developed grinding stone are, about 30 vol% abrasive content, about 25 vol% resin content and about 45 vol% porosity, and by changing the flow rate of lapping fluid, experimental results are largely changed. Lower flow rate gives higher removal rate and coarser surface roughness similar to the free abrasive lapping process, and the higher flow rate gives lower removal rate and finer surface roughness. The depth of distorted layer is thinner and the surface of lapped wafer is cleaner than that of by free abrasive lapping process.

Computer Mechanics. Accelerated Wear Testing on Mn-Zn Ferrite Using the Grit Size Effect.

This paper describes a technique for wear prediction. It has been empirically established that the wear rate of an abraded workpiece is directly related to the grit size of the abrasive. Using this relationship, the wear rate of material subjected to very mild abrasion can be predicted from the measured wear rates of the same material under more severe conditions. This technique has been successfully applied to estimate the wear of magnetic recording head materials in a video tape system. Our results demonstrate that the wear rate of the head can be accelerated by as much as four orders of magnitude using abrasive lapping tapes of large grit size. The results also indicate that the wear rate of the recording head material decreases significantly with the magnetic or abrasive tape wear which typically occurs during the first five to ten tape passes. Microscopic examination using scanning electron microscopy indicates that this reduction in wear rate is not due to clogging of the abrasive tape but rather to changes in abrasive particle shape. This means a recording head subjected to continuous sliding with fresh tape will wear considerably faster than a head which slides repeatedly against a loop of tape. Accordingly in reporting the wear rates of head materials, it is important to describe the corresponding tape condition or usage history explicitly.

Accelerated wear testing using the grit size effect

This paper describes a technique for wear prediction. It has been empirically established that the wear rate of an abraded workpiece is directly related to the grit size of the abrasive. Using this relationship, the wear rate of material subjected to very mild abrasion can be predicted from the measured wear rates of the same material under more severe conditions. This technique has been successfully applied to estimate the wear of magnetic recording head materials in a video tape system. Our results demonstrate that the wear rate of the head can be accelerated by as much as four orders of magnitude using abrasive lapping tapes of large grit size. The results also indicate that the wear rate of the recording head material decreases significantly with the magnetic or abrasive tape wear, which typically occurs during the first five to ten tape passes. Microscopic examination using scanning electron microscopy indicates that this reduction in wear rate is not due to clogging of the abrasive tape but rather to changes in abrasive particle shape. This means a recording head subjected to continuous sliding with fresh tape will wear considerably faster than a head which slides repeatedly against a loop of tape. Accordingly, in reporting the wear rates of head materials, it is important to describe the corresponding tape condition or usage history explicitly.