Tatsuhiro Kojima

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 of Three-Dimensional Shape Measurement Using a Triangulation Method Sensor with Optical Skid

On-machine measurement is used in ultra-processing machining, but it is seldom used in precision machining. For on-machine measurement, it is necessary that the sensor not be easily affected by the moving error or environment vibration in the field of precision machining. A triangulation method sensor with the optical skid method made using a new design concept is proposed to remove the moving error and vibration. The optical skid method used two laser spots with different sizes: the small spot diameter is the stylus and the large spot diameter is the skid [1]. The difference between these two signals reflects the surface shape. The developed sensor comprises an optical source and two optical receiving systems. Each optical receiving system has an imaging lens and a detector. Instead of two laser spots of different sizes, two detectors with different sizes of receiving area serve as the optical skid. Results confirmed the possibility of reducing the influence of the vibration using the developed sensor. In on-machine measurements, measurement of the surface profile with long wavelength is often necessary. If the spot diameter of the skid is not much larger than the surface profile wavelength, then the smoothing effect of the skid is reduced. Therefore, the amplitude of the measured profile by the skid sensor is smaller than actual amplitude of the workpiece. This paper presents a method of reconstructing the surface profile from the measurement results and the obtained effects of the reconstruction method from simulations and experiments.

Effect of spindle speed control of air turbine spindle on milling for difficult-to-cut materials

In precision machining, machining efficiency is improved by high-feed, high-rotation milling using small-diameter ball end milling. Additionally, static air bearings having excellent properties including low friction, low vibration, high accuracy, and rapid response have been used widely to maintain cutting speed. However, insufficient investigations have been conducted of the stabilization of rotational speed during processing with an air turbine spindle used to drive the main shaft. We have been unable to conduct a systematic evaluation of the effects of changes of the rotational speed during processing on a machined surface with periodic cutting force. Therefore, this study controlled the rotational speed of the air turbine spindle using a high-precision, quick-response (HPQR) pneumatic pressure regulator to examine its effects on the material surface roughness. 1) Rotation-controlled milling was conducted with aluminum alloy and steel alloy, which has good machinability. Then its surface roughness was investigated. Aggravation of the surface roughness was prevented by maintaining the rotation speed: the cutting speed. 2) Rough milling for difficult-to-cut materials by the air turbine spindle without control was impossible. In the worst case, the rotation stopped because the spindle torque was insufficient. However, the rotation speed control of air turbine spindle resolved the torque shortage. An appropriate cutting speed was maintained throughout the milling process. These results demonstrated that the surface roughness was improved compared with non-controlled surface roughness.

Study on high-speed contactless 3D measurement for tooth plaster model

Now, in the dentistry domain, the tooth plaster model is genellary used to evaluate of medical treatment on a dentistry reform patient and to educate of a dental technicians skill. It is measured by the optical cutting system. However, it is difficult to use quantitative evaluation of a dental technicians skill because of total measurement time about 2 hours. If this time can be shortened till about 10 minutes, the number of times of total measurement / evaluation can be increased sharply, and improvement in the quality of medical treatment or skill education can be expected. In this paper, the cause of taking measurement time is analyzed and examined first. Next, the measurement system within 10 minutes is proposed using a 3-lines optical cutting and scanning method with measurement accuracy maintained. This system is developed and evaluated by a fundamental experiment.

Study on high efficiency milling of steam turbine blade

In response to global environmental issues, higher efficiency and improved operational reliability are increasingly being requested for steam turbines, essential equipment for thermal power generation. Its material is stainless steel, which is difficult to cut because of high work-hardening trend and high resistance to heat. As its complex shape and high accuracy requirement, conventional methods such as using a ball end mill have obstacles of achieve a high accuracy coexist with high efficiency. The main objectives of this study are to propose a new method called Linear Interpolation Milling(LIM) using a taper end mill and verify its validity both in theory and practice.

Development of Optical Sensor for Detecting Micro Crack on Contact Surface

This paper discuses the development of the optical sensor due to detect the micro crack and measure the surface property of the contact surface in the equipment. To measure the surface property is an index for detecting no uniformity contact and / or micro crack on the contact surface. So, there is demand of the development of the sensor to measure the surface property in using equipment. This sensor has two optical systems, called stylus and skid, to reduce the influence of vibrations on the measurement result. The stylus measures the surface property with the vibration, and the skid measures only the displacement between the sensor and the objective surface at the same place as the stylus, i.e. the vibration. Therefore, the stylus signal minus skid signal shows the surface property. In this research, the proposal of the principle of this system, the methods of the development and the evaluation of the stylus system of the sensor and the development of prototype sensor is described.