Grinding Point Research Articles

A New Coolant Supply Method Using a Coolant Flow Guided Flexible Sheet Attracted to a Wheel Surface

To improve the characteristic of the floating nozzle method, a new coolant supply method using a coolant flow guided flexible sheet was developed. In this method, all the coolant supplied from the nozzle outlet can surely be directed immediately to the grinding point, because the coolant flow guided flexible sheet made of a thin sheet material is attracted to the wheel surface automatically, and confines the coolant between the wheel surface and the sheet. Therefore, the coolant can be completely prevented from deviating away from the grinding point. In fact, when the coolant flow rate of 4 l/min was supplied from the upper part of the wheel by using this method, the amount of coolant that reached the grinding point was 18 times higher than the case of only the floating nozzle method. It was clarified that this method had the effect to improve the grinding performance. Furthermore, this new method has a possibility of the wide application such as in profile grinding and cam grinding.

2617 研削液確実供給のためのフレキシブル導液シート法の開発(S74-2 砥粒加工(2),S74 砥粒加工)

To improve the characteristic of the floating nozzle method, a new coolant supply method using a coolant flow guided flexible sheet was developed. In this method, all the coolant supplied from the nozzle outlet can surely be directed immediately to the grinding point, because the coolant flow guided flexible sheet made of a thin sheet material is attracted to the wheel surface automatically, and confines the coolant between the wheel surface and the sheet. Therefore, the coolant can be completely prevented from deviating away from the grinding point. In fact, when the coolant flow rate of 4l/min was supplied from the upper part of the wheel by using this method, the amount of coolant that reached the grinding point was 18 times higher than the case of only the floating nozzle method. It was clarified that this method had the effect to improve the grinding performance.

CNCクランクシャフトピン研削機構の解析(S58 研削加工と砥粒加工,S58 研削加工と砥粒加工)

In this study, the grinding mechanism of the crankshaft pin carried out by the CNC crankshaft pin grinder, is theoretically analyzed. By this grinder in the grinding process, the geometrical interference form varies continuously, because the substantial grinding speed at the grinding point changes due to the revolution of the pin. Therefore, the grinding mechanism in the CNC camshaft pin grinder is made clear, from the investigation of the various relation of the speed at the grinding point. Furthermore, the control methods of the constant grinding velocity ratio and of the constant residual stock are proposed in order to regulate the variations of the grinding results. In these methods, the journal rotation angle velocity is controlled to maintain the size of the geometrical chip shape constant, and the high performance pin grinding ability is verified.

マイクロ非球面研削に関する研究 : クロス方式の斜軸研削における研削点固定制御方式の提案とその精度評価(S58 研削加工と砥粒加工,S58 研削加工と砥粒加工)

This paper deals with a precision grinding of micro axis-symmetric aspherical surface by use of a resinoid bonded diamond wheel. Ultra-precision grinding system of axis-symmetric aspherical surface was developed. In this study, a grinding point fixation control method on 45 degrees diagonal axis grinding method was proposed and its form deviation was evaluated. In this system, a resinoid bonded diamond wheel was scanned on the workpiece surface 3-dimentionally controlled with Inm resolution by linear scale feedback system.

Investigation for Estimating Form Accuracy Ground by a Generating Mechanism (Guide Lines based on Simulation for Design and Grinding Condition)

A rotor housing is one of main parts that compose combustion chambers of Wankel engine. The inside of it is peri-trochoidal form is shape. It is ground with a grinding wheel at a fixed point on the locus of workpiece moved by a generating mechanism. Workpiece radius and speed at the grinding point vary considerably. Inertia force, torque and grinding force that are caused in the grinding process, elastically deform this mechanism and wheel axis system in proportion to the square of workpiece rotational speed. Therefore, the positional errors arise between a workpiece and a grinding wheel and those affect grinding form. To grind it efficiently and accurately, it is extremely important in the design process of grinding machine and in the processing of peri-trochoidal form to forecast quantitatively the ground form accuracy under such grinding condition. In this report, the form accuracy has been analyzed by grinding simulation system when the conditions variously change. Useful and effective guidelines are obtained for designing the machine and grinding the form.

Investigation for Estimating Grinding Accuracy and Power Machined by Generating Mechanism

A rotor housing of a Wankel engine has a peri-trochoidal form that is machined by internal grinder, which is operated upon generating mechanism. This mechanism is elastically deformed by inertia force, torque and grinding force that are caused in grinding process. Therefore, some gaps arise in positional relation between a workpiece and a grinding wheel. Besides, grinding parameters, such as radius of curvature, work speed, the contact length and interference anele at the grinding point, vary considerably while the workpiece rotates in a revolution. In this case, it is necessary to estimate the accuracy of ground form and grinding power to design and to manufacture a form generating mechanism or to grind the trochoidal form. The authors show how to estimate the accuracy of ground form and grinding power by the grinding process simulation. Some results are presented in graphs and tables. Good agreement is found between analytical results and measured values.

217 CNC カム研削機構のシミュレーション

This paper describes about the accurate camshaft grinding methods verified by the simulation analysis for the cam grinding mechanism based on both the curvature radius change of the cam shape and the peripheral velocity change at the grinding point. In the case of the grinding under constant rotation of the camshaft, the great fluctuations, it is necessary to optimize the rotation velocity of the camshaft and the horizontal travel speed of the wheel head. Then the effectiveness of three grinding technique are made clear, such as the controlled normal force grinding method, the controlled surface roughness grinding method and the constant velocity ratio grinding method.

Hybrid High Speed Machining (HSM): System Design and Experimental Results for Grinding/HSM and EDM/HSM

Point grinding and electrical discharge machining (EDM) are detailed on high speed machining centres. A Taguchi design was employed to evaluate operating parameters when point grinding (plunge) nickel-based superalloys with 15 mm diameter electroplated diamond and cubic boron nitride (CBN) wheels using speeds up to 60,000 rpm provided by an ancillary spindle. Material removal of up to 120 cm 3 and roughness values down to 1.2 μm Ra were obtained when machining Inconel 718. A retrofit EDM servo head unit was designed for die sinking and workpiece surface texturing. When texturing 2D and 3D workpieces, surfaces were produced with an Ra of 1-10 μm, depending on operating parameters.

ガス通気研削加工法の開発

Grinding has drawbacks where the attrition wear of grain deteriorates the accuracy and the quality of workpiece under the condition of high speed and high pressure. So far it has been made clear that a chemical reaction in manufacturing is the cause of the attrition wear of grain. In other words, the chemical reaction control should make possible to manufacture with the sharp grain. This study pays attention to the chemical reaction caused by grinding into steel materials with aluminum oxide grain. The purpose of this study is to reduce a chemical reaction by removing oxygen that is caused by it in the grinding point and to propose a new grinding method that maintains sharp grain on wheel surface for long time. The method used is a kind of processing method where argon gas passes through a grinding wheel. According to this method, the chemical reaction should be caused between workpiece and grain controlled, and the workpiece surface should be manufactured as good one with the sharp grain. As a result obtained it was clear that the manufacture efficiency of the new processing method was improved better in comparison with a conventional method of it. This paper shows the valuation of grinding phenomena and effect of the new processing method.

233 非球面研削における研削条件の影響 : 超精密研削面のナノトポグラフィーに関する研究(OS5 電子部品・光学部品の超精密加工)

In aspherical grinding using spherical wheel, whether the rotational direction of the workpiece and the cutting direction of the wheel are perpendicular or parallel at the grinding point have direct effects upon a generation of surface roughness. In the case of axisymmetric surface grinding, it is revealed that the parallel grinding generates finer surface than the cross grinding. This report deals with statistical approach in theoretical calculations of maximum height roughness of ground surfaces. The grinding results in parallel and cross grinding methods are compared and investigated theoretically and experimentally.

総形研削に対応した研削液注水方法の開発 フローティングノズルの試作と性能評価

The coolant reduces the grinding temperature and prevents the grinding wheel wear. The wear of grinding wheel, especially in the formed grinding to the difficult grinding materials, is disliked for the preservation of the exact size of the workpieces. So the new coolant nozzle which is named floating nozzle has been developed to decrease the grinding temperature and the wear of superabrasive grinding wheel. The new nozzle consist of the graphite and is pushed to the grinding wheel by the weak rigidity of spring. When the surface shape of the top of nozzle becomes the same as the circumference configuration of grinding wheel, it will have floated and separated from the grinding wheel owing to the pressure of grinding fluid. Therefore the narrow gap between the grinding wheel and the nozzle is made and the grinding fluid adheres to the wheel. Then the new nozzle cuts off the airflow around the grinding wheel and the adhered coolant is always supplied just to the grinding point. In the result of experiment on grinding SiC and Si3N4 with the new nozzle, it showed the high performance of grinding ability on the dressing interval, the specific grinding energy and the surface roughness.

平面研削加工面の圧力分布

In high speed surface grinding, the grinding fluid is excluded from the front of the grinding wheel by bubbles. These bubbles are made as a result of the air of boundary layer on the grinding wheel surface being mixed in the grinding fluid. To make clear this phenomena between the fluid and the bubbles, the pressure distributions of the ground surface are measured. Composition of WA wheel used in the experiment is as follows:bonding materials are Vitrified and Resinoid ; mesh is #120 and #1000, and the fluid is water. Conclusions are as follows: 1) In high permeability of the wheel, the generated pressure at the front of the grinding point causes the grinding fluid to flow into the porous wheel, therefore the pressure is not high. 2) In high permeability and high surface roughness of the wheel, the grinding fluid is found insufficient even in a low rotational speed.

Temperature Effect on Vapor Phase Etching of Ground Silicon Substrate and Surface Morphology

AbstractWe have been using the low-cost method of fabrication of epitaxial wafer for discrete devices for many years. This low-cost operation is done by eliminating the conventional but costly polishing procedure, instead of using grinding, cleaning and etching processes prior to epitaxy growth. The etching step is needed to remove any residual grinding scratches and possible remaining contamination. In this study, etching is accomplished with HCl gas at a temperature range from 1120 to 1150 °C, at atmospheric pressure. The surface analysis and inspection techniques were used to test residual grinding scratch removal and point defect density. It is found that the temperature effect on the etch rate is small, but the surface morphology with ground pattern is very sensitive to the etching temperature. The study revealed the presence of regions of temperature which the silicon surface has a minimum of grinding scratches and little etch pits. The etching temperature has strong effect on the substrate surface thereby strongly impacting subsequent epitaxial layer morphology. The different morphologies and their temperature dependence can be explained on the basis of the thermodynamics of the surface and role of surface diffusion and evaporation.

Mechanical-Chemical Finishing Using a Lapping Stone Including Microcapsules.

This paper proposes the lapping stone which enables mirror finish for sticky soft metals, such as aluminum and copper. Then we examined the application of tribochemical reaction of perfluoropolyether oil to the finishing. The oil as a lapping fluid has, however, too high lubricity to generate the removal motion of the stone. Then the oil was introduced into the lapping stone in a capsulated form to supply the oil just to the grinding point. From the lapping results, the fluorine compound having good machinability was generated under high pressure and high temperature during the process and was observed on the ground surface of aluminum. This demonstrated the tribochemical reaction between the oil and the surface; the result was a significant improvement of the finishing efficiency and the surface quality of aluminum workpieces, as well as silicon wafers.

The basic study about the effect of single point grinding on the bending strength of brittle material

Single point grinding was investigated by using a sliding indentation apparatus. Sharp indenter sliding against brittle solid produces a scratch with a median crack. The size of the crack depends on the applied indenter load and the sliding speed. The effect of the crack size and its orientation on bending strength of glass is investigated experimentally. It is shown that the tested glass has high bending strength when the indenter load is low, bending direction is parallel to the scratch, and sliding speed is low. The results of bending test are predictable by fracture mechanics analysis including residual stress effect. This study makes it possible to understand the influence of grinding conditions on the bending strength of ground ceramics.

ＥＬＩＤ研削と放電加工の複合化に関する基礎的研究

A new machining method combining ELID, electrolytic in-process dressing, -grinding and EDM, electric discharge machining, is proposed in order to improve the productivity of precision curved-surfaces such as aspherical mirror. Since the wheel circumference under the ELID-grinding is covered with insulation materials, the electrodes made of graphite or Ag-W compound are inserted around the wheel periphery for EDM. During ELID-grinding, direct current is applied through the electrodes and a workpiece. When Ag-W plates are utilized for the electrodes, active but stable electric discharge have been observed at the grinding point, and grinding forces were successfully diminished in comparison with the conventional ELID-grinding. The roughness of the finished surface, however, deteriorates due to EDM. In order to obtain both machining efficiency and good surface finish, higher table speed is recommended and the down feed must be set slightly larger than the removal rate by EDM.

Nonaxisymmetric Aspheric Ceramic Mirror Machining Using Arc Envelope Grinding Method.

We report a grinding technique called the "arc envelope grinding method (AEGM)" and its grinding tests. In conventional form-generation grinding, loading and dulling of a diamond wheel can easily occur, which decrease both the machining accuracy and the wheel life, since the same part of the wheel is always used. In AEGM, a diamond wheel with a round profile is used and the workpiece profile is an envelope of a family of arcs. Since the grinding point is changed along the wheel profile with every grinding pass, the entire wheel width can be used and the wheel life is prolonged. In this study, arc truing accuracy, wheel design, surface roughness and form accuracy of the ground workpiece are investigated. Using the AEGM, nonaxisymmetric aspheric mirrors of silicon carbide were successfully ground. The form error after the first grinding (without any compensation) was less than ±0.8μm, and the roughness was Rmax=0.2μm.

Helical Micro-Drill Point Design and Grinding

A new drill point geometry, termed the helical drill point, specifically intended for micro-drills, is developed in order to alleviate the disadvantages of existing planar micro-drill points. A mathematical model for this new drill point has been established. It is shown that this model is more general than existing drill point models. The commonly used conical, cylindrical and planar drill point models are only special cases of the helical model. For uniquely determining the grinding parameters of the new drill point as well as guiding the grinder design, the characteristics, the controllability and the sensitivity of the grinding parameters have been analyzed. Finally the geometric characteristics of this new drill point are investigated.

Relationship between Grinding Mechanism and Residual Cracks in Single Point Grinding Test of Alumina Ceramics with Different Grain Sizes

In order to discuss the effect of grain size on material removal mechanism and crack type beneath the groove, the single point grinding tests of alumina ceramics with three kinds of grain sizes were carried out by use of conical diamond. The specimens of dense alumina ceramics were prepared by hot isostatic pressing (HIP) after presintering at various temperatures. The state of grooves were observed by SEM, and grinding force were measured by dynamometer. Main conclusions are obtained as follows: (1) Material removal mechanism changed from pseudo-plastic flow type to brittle fracture type with increase in depth of cut. The depth of cut, which varied from pseudo-plastic flow type to brittle fracture type, was increased with decrease in grain size. (2) The crack type varied from lateral and median type to microcrack with increase in grain size. (3) The normal grinding force was influenced by material removal mechanism of alumina ceramics.

グラインディングセンタ用研削焼付き防止カップ砥石の開発

Grinding center has been developed to built up an automatic grinding system. The grinding center can grind various kinds of surfaces simply by changing the grinding wheel accordingly. However there are some problems when using a cup wheel for face grinding. Specifically there is the problem of grinding seizure, which must be rectified immediately as this sometimes causes wheel fracture and grinding burn. This paper discusses the newly developed grinding wheel base, and the results of truing the bottom surface of the cup wheel at a small angle for use in face grinding. The function of this base is to draw coolant in and supply to the grinding point in order to prevent the seizure. It becomes clear that this newly developed wheel base and the slant truing on cup wheel surface are very effective for face grinding. As a result prospects are bright for the fabrication of automatic grinding systems by the grinding center.