Takanori Yazawa

In-process measurement and workpiece-referred form accuracy control system (WORFAC): application to cylindrical turning using an ordinary lathe

Abstract High levels of accuracy can be achieved in precision machining through the use of highly accurate machine tool elements and under good machining and environmental conditions. To improve the accuracy and stiffness of the machine tool, we proposed a new method using in-process measurement and confirmed its effectiveness. In this work, this method is applied to cylindrical turning. The following were determined: the effectiveness of simulation for estimating the form accuracy, a new function of the corrective servo by changing the feedback gain, and the effectiveness of the new function for correcting the error. These were confirmed by both simulation and experiment.

Radial shearing interferometer for in-process measurement of diamond turning

A stable interferometer using two zone plates to measure concave mirror figure is developed. The principle of the measurement is based on the radial shearing interference in which the measuring wavefront from the entire mirror surface under test is referred to that of the central part. On-machine experiments showed that the interferometer would be applicable to the in-process measurement for a diamond turning in about 0.06 micrometers p-p accuracy.

Concept and basic study of improvement system of surface roughness, waviness and figure accuracy by WORFAC

Abstract In ultraprecision machining technology, manufacture of more precise and large elements is expected. The author proposed a new system, named workpiece-referred form accuracy control system (WORFAC), and confirmed an effectiveness of this manufacturing method on a waviness improvement. In this report, we propose a new system with WORFAC, which has three control systems; a waviness control system, a figure control system, and a surface roughness control system. So far, basic studies on the figure and surface roughness control systems are carried out. And the possibility of this new system is confirmed.

Tool Wear Characteristics for Near-Dry Cutting of Inconel 718

In recent years, high-combustion-efficiency jet engines are required in the aircraft industry. Inconel 718, which has excellent mechanical and chemical characteristics. However, Inconel 718 is difficult to cut material because of its low-thermal conductivity. Consequently, Wet cutting is ordinarily adopted to reduce the heat on cutting heat edge in Inconel 718 cutting. Wet cutting which uses large amount of cutting fluid requires much cost and energy on maintenance or disposal of cutting fluid, and this method is environmentally-unfriendly. From the view point of reducing cost and environmental load, we examined the method of Near-Dry cutting which uses very small amount of cutting fluid for the cylindrical cutting of Inconel 718. However, this method has some problems, such as tool wear and cutting stock removal rate. In this report, we experimentally examined the relationship between cutting speed, tool materials, and tool fracture of near-dry cutting of Inconel 718. We compared these results with those of wet cutting, a method which is more expensive, requires significantly greater amounts of energy, and is less environment-friendly. The results indicate that when cutting speed is 100 m/min, tool fracture occurs at a cutting distance of 200 m. When cutting speed is 50 m/min, tool fracture does not occur and near-dry cutting distances can continue beyond 600 m. Moreover, tool wear could be reduced when S05 tool material, which has high bending strength, was used.

Accuracy of triangulation method sensor with optical skid

To measure a profile on a machine accurately, it is necessary to remove influences caused by various disturbances such as vibration. Vibration between a workpiece and a sensor causes measurement error on machine measurements. Therefore, the authors proposed a sensor using triangulation with an optical skid to remove vibration error. It showed effectiveness against vibration. When the skid probe diameter is not much larger than the wavelength of the profile, the amplitude of the measured profile is smaller than the actual amplitude. This report presents reconstruction method for use with the profile surface of a workpiece with the optical skid sensor and describes effects obtained by simulations and experiments using reconstruction method.

ACCURACY IMPROVEMENT OF MACHINE TOOL BY WORKPIECE-REFERRED CONTROL; - Simulation of sensor position for plain turning -

Simulation of WORFAC (Workpiece-Referred Form Accuracy control) is an effective method for estimating the formed accuracy made by controlling system. In this study, the simulation is applied to plain turning and the positioning of sensor is investigated.

Influence of Scratch Marks on Undeformed Chip Thickness in Ultra-Precision Cutting of Al-Mg Alloys

Recently, high efficiency and performance have become necessary attributes of information equipment such as laser printers. Thus, demand has increased for optical scanning parts that reduce optical aberration, scatter, and diffraction are required in laser printers. Polygon mirrors are manufactured by polishing a plating or glassy material to a mirror finish. In this study, we shortened the manufacturing process to improve the productivity and ultra-precision cutting technology of polygon mirrors made of aluminum. Thus, we had to reduce the geometric surface roughness achieved by mirror-cutting Al-Mg alloy and remove tear-out and scratch marks that occur during the cutting process. We investigated the cutting edge shape by using a straight diamond tool to decrease the surface defects produced during the ultra-precision cutting of Al-Mg alloy. We examined the mechanism for the occurrence of scratch marks and a method to reduce them. First, we measured the shape of the scratch marks and the cross-section with a scanning electron microscope. We found the tool collides with crystallization to produce small pieces, which then cause scratch marks. We developed a triple-facet tool with a double-facet at the end cutting edge to remove scratch marks and investigated the influence of surface defects. We clarified that using the triple-facet for a tool setting angle of 0° to 0.04° could achieve a good-quality machined surface without tear-out and scratch marks. In addition, the undeformed chip thickness was less than 80 nm

Influence of Micro End Mill Tool Run-Out on Machining Accuracy

Micro-channel chips used in micro total analysis systems have been attracting attention in the medical field. Photolithography, which is a technology used in semiconductor manufacturing, is used to manufacture micro-channel chip dies. This technology requires many processes, such as making photomasks, applying photoresist to a substrate, and the availability of expensive clean-room facilities. Micro-channel chips have ‘micro-channels,’ which are micro-grooves having a width of 30–100 μm. These fine grooves require high accuracy in manufacture; for example, the surface roughness on the bottom face is 1.0 μmRz. A previous study showed how tool run-out on the order of several μm incurred during micro-groove milling, reduced machining accuracy, and tool life. To bridge that gap, this study investigated how to form a fine groove by using micro endmilling. Specifically, a method was experimentally examined for reducing the influence of tool run-out on machining accuracy by using two types of endmill—two-tooth square and ball—by modifying the tool setting angle. Modifying the tool setting angle improved the surface roughness of one side of the groove, and reduced change of cutting force in two-tooth square-endmilling. In addition, it was able to reduce the influence of groove width on tool run-out by up to 1/10. A modification of tool setting angle in ball endmilling reduced the influence of tool run-out on machining accuracy.

Influence of Tool Wear on Cutting Characteristics in Ultra-Precision Cutting

Recently, increasingly high efficiency and high performance have become to be required of information equipment. As a result, optical scanning parts that reduce optical aberrations, scatter, and diffraction are required in laser printers. It is therefore necessary to improve the geometric surface roughness achieved in mirror cutting of Al alloys and eliminate tear-out marks and scratch marks that can be created during the cutting process. In this study, we investigated the effect of tool wear on the occurrence of surface discontinuities in ultra-precision cutting of Al alloys. In our previous studies, a crystal orientation of {110} plane was adopted in cutting an Al-Si alloy (AHS material, 11wt% Si) and Al-Mg alloy (A5186 material, 4.5wt% Mg) using a straight diamond tool. The cutting edge recession that occurs when cutting AHS material has been reported to be approximately 5 times greater than that which occurs when cutting A5186 material. Therefore, we cut the AHS material for accelerated wear and investigated the cutting edge recession, the surface roughness and the cutting force. We found that the cutting edge recession decreases as the tool wear angle γ increase. For example, at a tool wear angle γ = 40°, the cutting edge recession is approximately 7 times greater than that which occurs at a tool wear angle γ = 12°. As the tool wear angle increases, the cutting distance increase, which produces a mirror like surface. In addition, we were able to obtain a good machined surface using a positive tool setting angle because side cutting edge produces residual stock of removal 0.1 μm when the cutting edge recession is 0.3 μm or more and when it is cut by following end cutting edge.

Tool Wear Characteristics in Near-Dry Cutting of Ni-Based Superalloy

Recently, high-combustion-efficiency jet engines have become required in the aircraft industry. High burning temperatures are necessary to maximize the combustion efficiency of jet engines. Inconel 718, which has excellent mechanical and chemical properties, has been selected for use in many jet engine parts. However, Inconel 718 is a difficult material to cut because of its low thermal conductivity. Consequently, wet cutting is typically used to reduce the heat generated in cutting Inconel 718. Wet cutting, which uses a large amount of cutting fluid, is costly and requires considerable energy for maintenance and disposal of the cutting fluid, making this cutting method environmentally unfriendly. To reduce the associated cost and environmental load, the near-dry cutting method, which uses a very small amount of cutting fluid, may be preferable for cylindrical cutting of Inconel 718. However, this method has some drawbacks, such as the cutting stock removal rate and the wear on cemented carbide tools. For example, the cutting stock removal rate is lower than with wet cutting because cutting edge fracture occurs easily in near-dry cutting. In this study, we conducted experiments to examine the relationships between the tool materials, cutting speed and tool fracture in near-dry cutting and wet cutting, and we compared the results obtained using the two cutting methods. We found that an S05-type cemented carbide coating can reduce tool wear. We also found that in the early stages of cutting, between cutting speeds of V = 50 and 90 m/min, the tool wear can be comparatively reduced.