Abstract: The contact stiffness is measured at interfaces of several materials that are often used for the machine tool support. Models of machine tool supports and contact stiffness are described. Then, a measurement method of the contact stiffness is proposed according to the model and demonstrated. The unit normal contact stiffness is 1-2×106 N/mm/mm2 for general steel and cast iron. The unit normal contact stiffness is pSuperscript textositively correlated with the longitudinal elastic modulus. The unit tangential contact stiffness is 1/10-1/5 of the unit normal contact stiffness and not correlated with the elastic shear modulus. The surface roughness of the specimen should be small to reduce the dispersion of the measured unit contact stiffness.
Abstract: In this study, a small, 6-DOF (degree of freedom) parallel mechanism worktable for machine tool was developed. There are a lot of factors that affect the positioning error and the accuracy of the machine tools. The uncertainty in position is mainly due to the rigidity of the structure, the geometric error of parts and assembly errors. It is very difficult to estimate the assembly errors and the link parameter of each part. In this paper, the uncertainty factor in positioning of the worktable was investigated and compensated based on measurement of movement error by using coordinate measuring machine (CMM).
Abstract: In production of safety critical components in aero engine manufacture, to date broaching is the most efficient process machining fir-tree slots in turbine discs. Machining highly thermal resistant Nickel-based alloys, manufacturers commonly use High Speed Steel (HSS) tools and work at low cutting speeds in order to stay at rather low tool wear rates and avoid part quality defects. The key variable affecting tool wear as well as part quality, as in most machining processes, is the temperature. Excessive temperatures in the cutting zone lead to enhanced tool wear on the one hand, and surface defects such as white layer formation and residual tensile stresses on the other hand. In this article, the temperature development is investigated for typical tool geometries and cutting parameters in broaching. Furthermore, the possibility of a temperature control using intermediate variables such as process forces is discussed, and potentials employing a control are explained.
Abstract: NAS 979 has been used for over 40 years as a performance evaluation standard for five-axis machining centers. This standard provides some finishing conditions of the cone-frustum under five-axis control, and prescribes the measuring methods and permissible tolerances of geometric deviations. However, this standard cannot be applied to the tilting rotary table type five-axis machining center but to the universal spindle head type one. When the standard is applied to the tilting rotary table type, it is not clear yet that the effects of the geometric and synchronous deviations which influence the measured results. Thus, there are no methods for evaluating the accuracy of linear interpolation movement under simultaneous five-axis control. This paper proposes a machining test method using a truncated square pyramid for checking the accuracy of the tilting rotary table type five-axis machining centers. In the simulation and experiment, the bottom of the truncated square pyramid with a half apex angle of 15° is mounted on a fixture with a slope of 10° or 20°, and feed velocity of each axis is analyzed by changing the center position.
Abstract: This study deals with automation of polishing process by using an industrial robot. In polishingprocess, full automation of polishing operation has not been achieved due to the difficulty invisual inspection. Judgment of whether polishing is sufficient or not has been performed by skilledworkers. In this study, the polishing after milling process is targeted. In the previous report, the generationof robot program for polishing operation based on CAD data was already proposed. Focusingon the periodicity of cutter mark patterns on milling surface, we proposed an automatic judgment ofpolished surface quality based on the image processing which uses Discrete Fourier Transformation.In order to capture images of polished surface, a CCD camera was mounted at 6-axis controlled robothand. However, the image processing method proposed in previous report could not judge the curvedcutter mark patterns because the periodicity of those patterns is not uniform. The objective of thisreport is the development of automatic judgment method for non-periodic cutter mark patterns. Wedeveloped judgment method which uses pattern recognition as a mean to judge existence or not of cuttermarks. As a result, the developed system allows the automatic polishing that includes the surfacequality judgment.
Abstract: Much progress has been made in the machine tool technologies, aimed at improving the performances of the machine tools from various viewpoints, such as accuracy, reliability, produc-tivity, and flexibility. The machining accuracy is one of the most important characteristics of the machine tools. From the viewpoints of the design and the manufacturing of the machine tools and their components, one of the important issues is to clarify the relationships between the kinematic motion deviations of the machine tools and the geometric tolerances of the components, such as the guide ways and the bearings. The objective of the present research is to establish mathematical models representing the kinematic motion deviations of the machine tools, on the basis of the geo-metric tolerances of the components, and to apply the models to analysis of the kinematic motion deviations.
Abstract: This study deals with the cutting performance of ceramic tools in turning of mild steel and BN free-machining steel based on it. The tool lives of ceramic tools in turning standard steel were less than 15 min at the cutting speed 250 m/min. On the other hand, the tool lives in turning of BN free-machining steel were obvious longer than that of standard steel. The tool life of TiC added alumina ceramic tool reached almost 10 hours in the case that the tool life criteria was set at VB=0.3mm. This tool life was twice as long as that of coated carbide tool.
Abstract: We have developed a new scaife polishing machine for the purpose of polishing the high precision diamond cutting tools. As a high precision cutting tool, the high sharpness and flawless cutting edge are required. By using this polishing machine, the sharpness of a diamond tool at the cutting edge can be controlled within the range of 20nm. This machine is equipped with a submicron-scale mirror finished hardened-steel polishing Scaife, a supporting table can reduce the face deflection to less than 1μm, and a plastic diamond tool holder for protecting the edge of the diamond tool from the unexpected shock, which is supported by three points consisting of the edge of diamond tip and two control screws, this structure can help to adjust the work surface to any angles by only adjusting the two control screws. To facilitate the advanced angle operations, the algorithm was created to calculate the overhang length variations of the two control screws for controlling the changes of roll- and pitch-angle of the diamond tools.
Abstract: The miniaturization of many machine parts for machine tools is desired for the purpose of effective utilization of space, energy saving, and realization of desktop factory. To develop a compact and miniaturized NC machine tool, new downsized small parts such as hydraulic parts, pneumatic parts, electric parts and mechanical parts must be developed. These parts are not always satisfied for the practical usage in the present industrial level. Therefore, in spite of many requirements toward the miniaturization of the machine tool from the market, the miniaturized NC machine tool has not been put to practical use. The old-style structure of machine tools is one of the reasons of obstacle to solve this problem. We have proposed a newly developed ultra small size CNC lathe by using the pipe frame structure. The heat transfer between pipe elements and connecting block is affected strongly to the axial displacement. Therefore, the heat transfer between pipes can be insulated by the heat control on the connecting block. The thermal displacement control is realized by using the Peltier devices set on the connecting block. The results on the thermal displacement control of this structure and the effects on the cutting results are reported.
Abstract: There have been few reports dealing with the drilling of printed wiring boards (PWBs) with micro-drills that are smaller than 0.2 mm in diameter, and super-high-speed spindles that are higher than 160,000 rpm. In these cases, preventing the micro-drill from breaking and keeping the position accuracy of the drilled hole has been difficult. We therefore focus on the high-speed step-drilling method and short stroke as a novel way of resolving these problems. On the other hand, determining the complicated combination of feed speed, rapid feed speed, and stroke length is difficult. Under these backgrounds, in this report we propose a fast-feed step cycle that use fast-feed command without the processing feed. Thus, we attempted to apply the response surface method to optimize these parameters. As a result, a proposed method was found to be effective to improve the drilled hole quality and drilling efficiency in such kinds of micro-drilling of the PWBs.