Papers by Keyword: Machine Tool

Abstract: In recent years, electronic devices have become lighter, thinner, shorter, smaller, and more multifunctional, driving advancements in drilling technologies. To meet the demands of electronic applications, this study proposes a drilling machine tool with a counterbalanced vibration control mechanism. In this study, machining experiments were conducted using a machine tool equipped with a left-right ball screw counterbalance mechanism during the step operation. Observations were made with a high-speed camera and a thermal camera, followed by examinations of the drill and holes after machining. As a result, significant findings regarding the drill tip temperature and runout were obtained. It was also confirmed that drill wear and runout affect machining quality.

Abstract: The miniaturization of components and the functionalization via micro structures demands for flexible and economic manufacturing processes. Micro machining, i.e. micro milling and micro grinding can meet these requirements. In this paper, desktop-sized machine tools and their components that were developed at our institute are presented. With those machine tools, micro tools can be machined and used in one clamping, allowing for increased machining quality. Grooves milled with such machine tools achieve a bottom surface roughness below 10 nanometer.

Abstract: A polishing jig was designed and manufactured to enable polishing of metal surfaces on CNC machining centres, on which these surfaces are normally finish-machined first. The jig accommodates ring-type tools rotated by a high speed spindle, rendering the machining centre’s own spindle redundant. Passive control of the polishing force is materialized through the machining centre’s Z axis displacement acting on the jig’s springs. Jig design is explained laying special emphasis on calculations pertaining to the springs employed. Functionality of the jig was tested with trochoidal polishing paths and typical results are presented in terms of peak-to-valley surface roughness attained, verifying that a uniform ‘mirror range’ finish is achievable.

Abstract: Thermal deformations of machine tool are among the most significant error source of machining errors. Most of current thermal error modeling researches is about 3-axies machine tool, highly reliant on collected date, which could not predict thermal errors in design stage. In This paper, in order to estimate the thermal error of a 4-axise horizontal machining center. A thermal error prediction method in machine tool design stage is proposed. Thermal errors in workspace in different working condition are illustrated through numerical simulation and volumetric error model. Verification experiments shows the outcomes of this prediction method are basically correct.

Abstract: In this paper, the influence of friction on static, dynamic characteristics, the strength and lifetime of a 3-axes flexible CNC machine tool are taken into account. The machine tool is first modelled by using finite element method (FEM) to perform static structural analysis. After that, the dynamic effects caused by the inertia forces and the displacement of moving part of the machine on contact stress are considered in this study. Then, the stress and contact force distributions on solid-flexible contact are also obtained. Finally, the influence of dynamic structure, cutting conditions and material properties on strength and lifetime of CNC machine tool are discussed by using fatigue analysis. Consequently, the proposed method can be used for efficient simulation of structural dynamics, lifetime assessment as well as interactions of the real CNC machine with the machine tool structure in a virtual environment.

Abstract: In the field of machining industries it is always required to improve the accuracy of precise products, die and molds. The feed drive system for the machine tools consists of an AC servo motor, an amplifier and rolling elements etc. It is well known that the nonlinear behaviors of the rolling elements influence the motion accuracy of the feed drive system. However, in spite of the analysis of static behaviors have been done, the dynamic behaviors are not so examined. Our special interest is how to control the nonlinear behaviors of the rolling elements and to operate the feed drive system with high accuracy. In order to model the nonlinear behaviors of the feed drive system, we measure the transient response when the step inputs of microscopic displacement are input to the AC servo motor and the detail analysis will be done. Experimental results show that the step responses become slow as the input displacement becomes microscopic. It means that with the ball bearing built into the AC servo motor used to feed driving system have the nonlinear behavior in microscopic displacement range.

Abstract: It is frequently the case that the feed rate indicated in a numerical control (NC) program does not obtain in actual machining processes and the cutting tool does not path the points indicated in the NC. A reason underlying such problems is that control gains are not optimized, which causes issues with acceleration and deceleration in the control of machine tools. To address these problems, in this paper, we propose a method for the optimization of control gains using the MATLAB and Simulink software by considering the weight of the workpiece, the controlling distance, and the controlling speed. Simulations confirmed the effectiveness of our proposed optimization.

Abstract: Ball screws and nuts represent the inseparable part of machinetool building. The thread lead accuracy ranges in hundredths of millimetres per 1 m. In addition to the undesirable phenomena caused by heat (dilatability) and, e. g., torsional and transverse oscillations, the bending stress of the ball screw is considerably undesirable too. This stress and at the same time behaviour are transferred to the bending stress of the ball screw nut. This has a very harmful influence on setting of the ball screws, when the machine tool is assembled. Using the analysis by means of the FEM method, the paper conducts a survey of deformation issue of the arrangement "machine – ball screw – ball screw nut" during the assembly stage as well as a survey of compensation possibilities and other technical measures determined to limit the undesirable deformations and stress of the ball screw originating already in the manufacturing stage of the machine tool.

Abstract: The paper deals with the issue of geometric precision measuring at large parts (especially at castings having big dimensions) in their manufacturing stage. The large parts of machinetool frames are required to have their geometric tolerances in thousandths of millimetres. The production or cooperation abilities of the particular company must be adapted to these demands and it is also necessary to adapt the company metrological equipment and measuring procedures to them. The standard measuring equipment cannot be used in most cases, because the particular parts are too large. For this reason, it is necessary to search such methods and procedures which enable to perform measuring with the relevant result. It could be considered to use e. g. 3D scanners. Unfortunately, their measuring precision has not reached the required tolerances up to now. For example, the HandyPROBE 3D scanner measures with the precision of 0,022 mm [1].

Abstract: This paper deals with a new experimental approach to the analysis of radial, axial, and tilt error movements of machine tool spindles under load. The main focus is on the identification of error spindle movements under different machine operation conditions between 500 - 5000 rev / min and loads in the range of 50 - 500 N. Errors of the spindle movements are measured on the cylindrical workpiece using capacitance sensors for different loads. The analysis of measurements of radial, axial, and tilt error movements of machine tool spindle indicates a dependency of loads and measured errors. The integration of error measurements into novel multi-body dynamic models of machine tool spindles is very important for prediction of machine behaviour during a cutting process and for prediction of workpiece geometric accuracy.