5-axis Machining Center Research Articles

S132012 工作物測定結果に基づく5軸マシニングセンタの運動精度測定

The new evaluation method of geometrical accuracy for the 5-axis machining center (MC) based on the measured results of the machined workpiece has been developed. The strategy of our evaluation utilizes the coordinates measuring machine (CMM) as a master gauge because of its accuracy so that machine operator devotes to machine the workpiece and technologist of precise measurement dedicates to the measurement. In our study, the non-rotational machining is utilized to copy and trace the machine trajectory on the workpiece by minimizing the machining error. The profiles of machined workpiece are measured and evaluated by CMM and the geometric errors of the machining center are extracted. The measured results are enough accurate compared with those by the square master gauge calibrated by CMM previously. In this report, the machining setup including workpiece design, tool and cutting conditions is proposed and the evaluated results are shown with the experimental procedures.

A24 5軸マシニングセンタの円錐台試験法(OS1 最新工作機械(1))

ISO standards related to accuracy test of 5-axis machining center is currently undergoing the final stages. In this research, real cutting is performed by accuracy inspection about truncated cone cutting by the 5-axis simultaneous control under proposal, and cutting conditions and an evaluation method are examined. In addition, we also consider motion accuracy inspection by using ball bar interpolation accuracy of the proposed tests, simulating the cutting of the above mentioned truncated cone.

Evaluation of Geometric Deviations Inherent to 5 Axis Machining Center Based on Checkered Pattern of Machined Surface Using Ball End Milling

Evaluation of Geometric Deviations Inherent to 5 Axis Machining Center Based on Checkered Pattern of Machined Surface Using Ball End Milling

Dynamical Modeling of Spindle with Active Magnetic Bearing for Milling Process

A dynamical modeling of spindle with Active Magnetic Bearing (AMB) is presented. All the required parameters are included in the model for stability analysis. The original map of stability is generated by Time Domain Simulation. The major importance of forced vibrations is highlighted for a spindle with AMB. Milling test are used to quickly evaluate the stability. Finally, the simulation results are then validated by cutting tests on a 5 axis machining center with AMB.

Dynamic Characteristic Analysis and Structural Modification of a 5-Axis Horizontal Machining Center Considering Joint Surface

In order to make a 5-axis linkage horizontal machining center have better dynamic characteristics, considering the influence of joint surface, dynamic characteristic analysis is conducted to the machining tool. Based on finite element modal analysis results, the weak link is found and optimized. Through the finite element calculation and analysis, the structure rigidity obviously raises after optimization. This offers a new idea on how to improve the rigidity of complete machine of machining tool for later research.

Chatter milling modeling of active magnetic bearing spindle in high-speed domain

A new dynamical modeling of Active Magnetic Bearing Spindle (AMBS) to identify machining stability of High Speed Milling (HSM) is presented. This original modeling includes all the minimum required parameters for stability analysis of AMBS machining. The stability diagram generated with this new model is compared to classical stability lobes theory. Thus, behavior's specificities are highlighted, especially the major importance of forced vibrations for AMBS. Then a sensitivity study shows impacts of several parameters of the controller. For example, gain adjustment shows improvements on stability. Side milling ramp test is used to quickly evaluate the stability. Finally, the simulation results are then validated by HSM cutting tests on a 5 axis machining center with AMBS.

Singular Problem and Improved Plane Interpolation Algorithm

In the 5-axis machining, when the tool orientation approaches the one of the rotation axis, the sharp changing of the rotation angles obtained by the transforming of tool orientations causes a large over cutting or under cutting for the limit of the machine’s dynamic characteristic, which is called singular problem. After analyzing the causing of the singular problem, the position of singular point, the singular value and the nonlinear error, etc, an improved plane interpolation algorithm based on plane interpolation of tool orientation algorithm is given out in the paper following with the simulation and test of the circumference milling of the tilt plane (tilt angle: 1°) separately with the plane interpolation and improved plane interpolation based on a 5-axis machining center with two swiveling heads (rotation axes: C/A). The results prove that the new interpolation is valid and correct.

Direct Interpolation of Tool Orientation in 5-Axis Milling

By circumference milling with 5-axis machine or machining center has quite the machining efficiency and the surface quality of the products been improved. But when inclined inside surface of cavity is circumference milled with the default linear interpolation of rotation angle algorithm, it results in a serious non-linear error, which takes on over cutting or under cutting, e.g. the inclined plane will be over milled by the machine with dual swivel-head machining center. In order to resolve this problem, the direct interpolation algorithm of tool orientation is developed after analyzing the algorithm of linear interpolation of rotation angles and its non-linear error is. The algorithm is reported and tested with the object of a machine with AB-axis swivel head. The testing results proved that it can resolve the problem of non-linear error.

ボールエンドミル加工での切削抵抗および工具挙動に及ぼす工具姿勢の影響（第１報）―工具を１および２軸で傾斜させた切削過程の幾何学量と切削抵抗―

In milling with a ball end mill using a 5-axis machining center, the attitude of tool or workpiece is controlled by tilting two axes, therefore allowing milling to be performed by a cutting edge of an outer portion, which has a large cutting speed. However, the effects of the tool tilting angle on the cutting forces, tool deflection and machining error have not been clearly identified. In this 1st report, geometric quantities such as the tool-workpiece contact region, undeformed chip thickness along the cutting edge and the area of cutting cross-section, and the cutting speed in slot milling with tool tilted by one or two axes are analyzed, and variations of these quantities with the tool tilting angle are discussed. A cutting model proposed in previous papers, in which a cutting edge of both a spherical portion and a cylindrical portion engage with the workpiece, is applied to the above milling process. Cutting forces in various tool tilting angles are predicted, and compared with experimental results. Predicted results are in good agreement with experimental results. It is found that when a large positive angle is specified for each of the tool tilting angles, the variation of cutting forces in milling decreases, and it also becomes possible to obtain a large cutting speed.

微細溝切削による５軸制御マシニングセンタの幾何誤差推定方法の開発

Recently, a new method of quickly evaluating the machining accuracy of 5-axis machining centers has been proposed, and named this method ‘groove-matrix machining’. This method requires machining each sets of grooves arrayed in a matrix on a test piece mounted on a tilting rotary table, with its tilt or rotation angle changed. Under these conditions, machining accuracy can be evaluated from the test results. In our previous paper, however, the capability of estimating geometric errors inherent to 5-axis machines was not discussed when using groove-matrix machining. This paper proposes the use of ‘groove-matrix machining’ as a method to estimate the geometric errors from the machined workpiece, and confirms its effectiveness.

High-Speed Milling Toolpath Planning for Aviation Engines Impeller Using POWERMILL Software

In this paper, the machining process of integrated impeller is customized basing on the geometry feature, function characteristics and the processing difficulties. Considering the working performance and machining rigidity, the rough machining and finish machining toolpath of the hub are generated in surface projection manner and the finish milling toolpath of blade is created in driver surface manner providing by the POWERMILL software. After simulating the machining toolpath, an integrated impeller is machined by 5-axis machining center of HSM 600U.

G0400-3-5 彫金技法を応用した鋼板への新NC加工法の開発([G0400-3]機械材料・材料加工部門一般(3):成形性と強度)

It is difficult to mechanize the chasing technique as a traditional craft, and also to maintain the skill of the chasing technique. On the other hand, the patterns in the surface by chasing have the peculiar characteristic not obtained by the conventional NC processing. Therefore, in this research, a new processing method looking like the chasing technique was developed using the latest NC processing technology, and the reproduction of the pattern was tried. Minute patterns by chasing were sculptured to the sheet copper by attaching the non-rotational pneumatic tool to the spindle axis in the 5-axis machining center, and making 6-axis control which added the rotation control axis around the spindle axis. In this paper, out of the chasing technique, the reproduction results by the technique of the typical "KERIBORI" and "KEBORI" were reported.

C5 Development of Groove-Matrix Machining Method for Evaluating 5-Axis Machining Centers(Multi-axis control machining)

This paper proposes a new method of evaluating the accuracies of 5-axis machining centers from workpiece machining tests. An array of grooves is machined on the workpiece while changing the rotation angle of the tilting table. From the created groove-matrix, the influences of the geometric deviations inherent to 5-axis machining centers, of the geometrical profile of the cutting edge of a ball end mill and of the tool length compensation errors on the machined surfaces are visible. The effectiveness of this proposed test has been experimentally verified.

Automatic polishing process of plastic injection molds on a 5-axis milling center

The plastic injection mold manufacturing process includes polishing operations when surface roughness is critical or mirror effect is required to produce transparent parts. This polishing operation is mainly carried out manually by skilled workers of subcontractor companies. In this paper, we propose an automatic polishing technique on a 5-axis milling center in order to use the same means of production from machining to polishing and reduce the costs. We develop special algorithms to compute 5-axis cutter locations on free-form cavities in order to imitate the skills of the workers. These are based on both filling curves and trochoidal curves. The polishing force is ensured by the compliance of the passive tool itself and set-up by calibration between displacement and force based on a force sensor. The compliance of the tool helps to avoid kinematical error effects on the part during 5-axis tool movements. The effectiveness of the method in terms of the surface roughness quality and the simplicity of implementation is shown through experiments on a 5-axis machining center with a rotary and tilt table.

Systematic evaluation of calibration methods

Today for geometrically testing and calibrating machine tools, many different measuring devices are used. Generally it is only based on the experience of single employees which methods for calibration are applied. There is no quantifiable understanding of the correlation between measurement method, measurement uncertainty, machine tool build-up (axes arrangement) and quality and the resulting obtainable workpiece accuracy. In this paper a kinematic model of machine tools is used with which resulting deviations of workpieces can be simulated, thus giving a realistic impression of the geometric performance of a machine tool by considering all relevant influence factors. For a 5-axis machining center as an example it is quantified how improved calibration methods can reduce the resulting workpiece deviations significantly. With this knowledge, optimal calibration methods can be chosen and weak points in the machine tool design can be identified systematically.

High Performance Motion Control of Rotary Axis for Simultaneous Multi-axis Controlled Motions

This paper describes the motion control techniques of rotary tables for 5-axis machining centers. Especially, in the machining of complex shapes such as impellers, three translational axes and two rotary ones are simultaneously controlled. A tilting rotary table powered by the worm gear is generally applied as the rotary axes for the 5-axis machining centers, and various causes of inaccuracy exist in the rotary axes. In this study, the causes of inaccuracy are investigated by the experiments and simulations. As the result, it is clarified that the main causes of inaccuracy : servo response, fluctuation of rotational velocity, backlash and the signal delay of rotary encoder. Motor torque saturation of the rotary axis also yields a problem. Based upon the investigated results, some compensators for the problems were proposed. In order to confirm the effectiveness of the proposed compensators, the compensators were applied to an experimental set-up including a rotary axis. As the results, it is clarified that the proposed compensators can much improve the synchronous accuracy.

Multi-functional machine tool

The functions of metal cutting machine tools have been increasing to meet the demands of high productivity and high accuracy in machining complicated and difficult parts on one machine. This paper presents a comprehensive survey of multi-functional machine tools used for metal cutting, and their kinematic configurations, control and programming technologies. Design principles and assessment of multi-functional machine tools are discussed mainly taking examples of 5-axis machining centers. The paper also presents examples of latest multi-functional machine tools as well as current status of related supporting technologies.

Tilted Tool Axis Machining on 5-Axis Machine Tools

High-efficiency machining and high-quality cutting are required in mold and die machining. To produce high-quality molds and dies, we require high rigidity for cutting tools and machining with effective cutting edges. We propose tilted tool axis machining, which involves indexing using 2-axis rotary motion and machining using 3-axis feed motion on a 5-axis machining center. To conduct tilted tool axis machining by ball end mill, we must know the tool attitude to ensure stable cutting and how to control the tool attitude to stable cutting conditions. Our main objective was to clarify the tool attitude ensuring stable cutting conditions and to develop automatic determination of the indexing angle for mold and die machining. We start by discussing machining experiments using a dynamic force dynamometer on a 5-axis machining center to analyze machining features using a tilted tool axis ball end cutting tool. We then determine machining evaluation from which the results of machining experiments are determine using a tilted tool axis ball end cutting tool. We propose calculation of optimum indexing angle candidates for machining surfaces using normal vectors of surfaces and cutting edges. We then show machinable area evaluation for the calculated indexing angle based on inverse offset method with a state flag. We then give examples demonstrating the effectiveness of our proposal.

Optimal Structure Design Methodology for Compound Multiaxis Machine Tools - I - Analysis of Requirements and Specifications -

The functionality of compound multiaxis machine tools is becoming increasingly versatile as NC lathes evolve. A single compound multiaxis machine tool functions as a 2-axis NC lathe and as a 5 axis machining center. The compound multiaxis machine tool executes machining such as inclined surface and gear cutting, conventionally executed by dedicated machines with special jigs and fixtures. A survey has shown that most machining executed by conventional compound multiaxis machine tools consists of basic drilling and milling on the orthogonal plane, indicating that compound multiaxis machine tools specifications should be designed to meet these requirements. To improve competitiveness and return investment over conventional NC lathes and machining centers, productivity required for a compound multiaxis machine tool is derived based on the machining time of typical parts on conventional machines. Here, we address systematic analysis and methodology to determine compound multiaxis machine tool specifications from the viewpoints of quality and cost.

Special Issue on Multiaxis Control and Multitasking Machine Tools

Machine tools using numerical control (NC) devices are typical mechatronics products and a powerful way to automate plant production. The introduction of multiaxis control and multitasking machine tools to workshops is growing to meet the requirements of highly efficient, precision machining of a variety of complex products and mold dies. The increase in the number of control axes and multitasking capability in one chucking process enable machine tools to manufacture complex products efficiently and accurately. Given the strong attention and interest multiaxis control and multitasking machine tools are attracting, it is about time to introduce the current state of the art of these tools and their practical and applicable technologies, especially in Japan. This special issue covers the development of 5-axis control machining centers, machine tools having multispindle heads with 5-axis control, 5-axis control CAMs, accuracy evaluation for 5-axis control machine tools, and more. We thank the authors for their interesting papers to this special issue, and are certain that both general readers and specialists will find the information they provide both interesting and informative.