Controlled Machining Center Research Articles

On the milling strategy in machining curved surfaces based on minimum stress concentration by a 3-axis machining center

Three-axis computer numerical control machining centers are commonly used in machining due to their simple operations. When machining curved surfaces, the 3-axis CNC machining centers use interpolation line segment to fit the curved surfaces. The quality of the machined surface is affected by the length of the interpolation line segment. Sharp corners are formed at the junction of straight segments. The appearance of sharp corners will lead to increased stress concentration. To study the relationship between machined surface quality and interpolation straight line, this paper establishes the mathematical model of surface topography in ball-end milling multi-curved surfaces by a 3-axis milling center with considering the acceleration and deceleration controls. Based on the surface topography model, the stress concentration factor is analyzed in machining curved surfaces with different lengths of interpolation lines. The results show that the stress concentration factor decreases with the increase of the central angle when the length of interpolation lines and the radius of curvature are kept in constant, while decreases with the increase of the radius of curvature when the length of the interpolation lines and the central angle are held on. Moreover, the stress concentration factor increases as the length of the interpolation lines increases when the radius of curvature and the central angle are kept in constant. A method for selecting proper length of interpolation lines based on the stress concentration is proposed. In addition, the quality of the machined surfaces can be improved through the optimization of the tool path.

Influence of triangular rib on bending stress strength and tooth deflection for small size and high strength spiral bevel gear supported by ribs fabricated by five-axis controlled machining center

Influence of triangular rib on bending stress strength and tooth deflection for small size and high strength spiral bevel gear supported by ribs fabricated by five-axis controlled machining center

Consideration of features and the optimal form of rib of a small and high-strength spiral bevel gear fabricated using five-axis controlled machining center

Consideration of features and the optimal form of rib of a small and high-strength spiral bevel gear fabricated using five-axis controlled machining center

Consideration of features and the optimal form of rib of a small and high-strength spiral bevel gear fabricated using five-axis controlled machining center

Consideration of features and the optimal form of rib of a small and high-strength spiral bevel gear fabricated using five-axis controlled machining center

Investigation on machining accuracy with wireless tool holder under constant feed speed at milling point with a five axis controlled machining center considering approach path

Investigation on machining accuracy with wireless tool holder under constant feed speed at milling point with a five axis controlled machining center considering approach path

Improvement of machined accuracy under constant feed speed at milling point with a five axis controlled machining center considering approach path

We suggested a novel method to maintain a machined surface quality of a curved surface shape by synchronous motion between two linear axes and a rotary axis with the five-axis machining center. It was demonstrated that the proposed method made it feasible to prevent a machined error due to the quadrant glitch caused by friction of the ball screw and linear guide of feed drive system by the method. Moreover, in the previous report, we discussed the influence of servo characteristic difference between linear axis and rotary axis on the machined shape error to improve machined surface quality and suggested a method to reduce shape error of machined workpiece with an advanced control. However, we have not discussed the errors that influence the shape with this method and suggested an improved method based on non-machining motion. In the present report, we focused on using this method to develop a motion for cutting a circular shape, including approach path during actual machining. First, we developed a model formula for the shape error based on the predicted causes of error. Second, we validated our model based on NC data from an actual end-mill tool. We then determined the most appropriate processing method by comparing cutting results. The causes of error were identified as a circle radius decrement due to the circular interpolation motion of the two linear axes, relative angle difference between the linear and rotary axes, and eccentricity of the circular interpolation motion of the two linear axes because of the outside approach path of the machining tool. Finally, we confirmed an effect on reducing the shape error of the machined workpiece considering differences in the servo characteristics of the three axes by monitoring the cutting force with a wireless tool holder during machining. The results showed that the proposed method greatly decreased the shape error.

Consideration of optimizing rib shape for small size and high strength spiral bevel gear fabricated by five axis controlled machining center

Consideration of optimizing rib shape for small size and high strength spiral bevel gear fabricated by five axis controlled machining center

Study on cutting trace shape control of machined surface by radius end mill with five-axis controlled machining center

Study on cutting trace shape control of machined surface by radius end mill with five-axis controlled machining center

5軸制御マシニングセンタで創成する小型高強度ベベルギヤのリブ形状の検討

We have developed a small size and high strength spiral bevel gear fabricated by five axis controlled machining center. In the present report, we propose a novel spiral bevel gear with the rib at the end of tooth width to reinforce the tooth bending strength, which is machined with a ball-nose end-mill tool. We investigate the influence of the rib shape on the bending stress at the tooth root and the tooth deflection and demonstrate the effect of rib reinforcement at the proposed spiral bevel gear. As a result, a guideline is found to design the small size and high strength spiral bevel gear with the rib at the end of tooth width from a view of rib shape.

Comparison of 4-axis and 5-axis Simultaneous Machining of Complex Shaped Blade

It is known that in multi-axis simultaneous control machining of complicated shape parts, machining accuracy may decrease due to synchronous error of the drive axes, and machining time may be longer due to excessive acceleration. In this study, in the machining using 5-axis control machining centers, in order to investigate the difference in machining accuracy and machining time depending on the number of drive axes simultaneously controlled, 4-axis and 5-axis simultaneous machining of a complex shaped blade are compared as a case study. As a result, it is found that the machining accuracy is better in the 5-axis simultaneous machining, but the machining time is shorter in the 4-axis simultaneous machining.

Development of Automatic Servo Tuning Function in Rotary Axis with DDM for Machine Tools and its Performance for Stable Machining

To advance technology of 5-axis control machining centers and future machine tools, it is essential to improve not only the performance of linear axes but also that of rotary axes. Therefore, direct drive motors (DDMs) employed for rotary axes of machine tools was developed by using the quality engineering and the FEM analysis of the electro-magnetic field. In this paper, the improvement impact on the performance of rotary axes from DDMs is described, and the influence of a workpiece position on the machine tool table on the kinematic performance is evaluated. Moreover, a novel method for tuning servo parameters automatically is proposed in order to improve the kinematic performance of a table axis with a workpiece which employs the DDM.

617 5軸制御マシニングセンタにより創成される小型高強度スパイラルべベルギヤの特性に関する考察(GS11,13 工作機械制御,研究討論セッション)

We have developed a small size and high strength spiral bevel gear fabricated by five axis controlled machining center. In the present report, we propose a novel spiral bevel gear with the rib at the end of tooth width to reinforce the tooth bending strength, which is machined with a ball-nose end-mill tool. We investigate the influence of the rib shape on the bending stress at the tooth root and the tooth deflection and demonstrate the effect of rib reinforcement at the proposed spiral bevel gear. As a result, a guideline is found to design the small size and high strength spiral bevel gear with the rib at the end of tooth width.

Current State of the Art of Multi-Axis Control Machine Tools and CAM System

<div class=""abs_img""><img src=""[disp_template_path]/JRM/abst-image/00260005/01.jpg"" width=""300"" />Asymmetric curved grooving</div> Multi-axis numerical control (NC) machine tools such as 5-axis control machining centers and 5-axis control multi-tasking machines are widely used in machine shops. NC data, which are prepared using computeraided manufacturing (CAM) systems, are used with multi-axis control NC machine tools that have a variety of advantages. This article describes the advantages ofmulti-axis control machining. The structure of CAM systems used for multi-axis control machining and the important role of collision avoidance in generating cutter location (CL) data are then explained. The transformation of CL data to NC data for use in machining, which is performed by a post-processor, is presented. Finally, an efficient machining method and unique shape creation via 6-axis control machining are explained. </span>

Dexterous machining aiming at high value-added products

It is important to establish a new approach of creating such value-added products as craftworks or applied arts, different from traditional way of achieving products with high quality and low price. Thus, the study deals with the first trial of creating artistic product shapes by means of multi-axis controlled multi-tasking machine tools or multi-axis controlled machining centers on the basis of mechanical cutting technology. The concept of creating high value-added products by devising cutting ways is named as “Dexterous Machining”. In the study, “Dexterous Machining” is classified into several areas and demonstrated. As a result, it is experimentally found that the concept of “Dexterous Machining” has the potential of creating high value-added products.

Development of a Measurement Complex for Automatic Adjustment of Tool Settings for Programmed Numerically Controlled Machine Tools

Results from the development of a complex for automated adjustment of tool settings outside a machine for high-speed and precision programmed numerically controlled machining centers are presented. Data on the features of the tools in the complex and the capabilities and metrological characteristics of the complex are presented.

Experimental study on brittle–ductile transition in elliptical ultrasonic assisted grinding (EUAG) of monocrystal sapphire using single diamond abrasive grain

This study is carried out to investigate the material removal characteristics in elliptical ultrasonic assisted grinding (EUAG) of monocrystal sapphire using single diamond abrasive grain. The scratching experiments are performed to develop a fundamental understanding of the ductile–brittle transition mechanism during EUAG of monocrystal sapphire. An elliptical ultrasonic vibrator attached with a sapphire substrate was set up on a multi-axis CNC controlled machining center equipped with a single point diamond tool. The vibrator was constructed by bonding a piezoelectric ceramic device (PZT) having two separated electrodes on a metal elastic body, and an elliptical ultrasonic vibration was generated on the end-face of the metal elastic body when two phases of alternating current (AC) voltages with a phase difference are applied to their respective electrodes on PZT. In scratching experiments, the effects of ultrasonic vibration on the critical depth of cut ac for the ductile–brittle transition region and the material removal ratio, i.e., the ratio of the removed material volume to the machined groove volume, fab, are investigated by the examination of the scratching groove surfaces with SEM and AFM. The obtained results show that the critical depth of cut in EUAG is much larger than that in conventional grinding without vibration (CG), and even the bigger vibration amplitude leads to a greater improvement. Although the values of fab in the ductile–brittle transition region in both EUAG and CG are less than 1, that in EUAG is bigger than that in CG. Furthermore, as the vibration amplitude increases, the value of fab is increased to eventually be close to 1. These show that it is prone to achieve a ductile mode grinding in greater vibration amplitude. It was also found that in the process there are two kinds of material removal modes, i.e., continuous cutting and discontinuous cutting modes, which are determined by the relationship between values of vibration amplitude and depth of cut. This study validates that the elliptical ultrasonic assisted grinding method is highly effective in ductile mode machining of hard and brittle materials.

Accuracy Evaluation of 5-Axis Machining Center Based on Measurements of Machined Workpiece – Evaluation of Accuracy of 5-Axis Controlled Machining Center –

A new method for evaluating the geometrical accuracy of a 5-axis Machining Center (MC) based on the measurement results of the machined workpiece has been developed. The strategy behind our method is to utilize, because of its accuracy, a Coordinates Measuring Machine (CMM) as a master gauge. Thus, the machine operator machines the workpiece and a technologist of precise measurement takes the measurements. In our study, non-rotational machining is utilized to copy and trace the machine trajectory on the workpiece, minimizing the machining error. The profiles of the machined workpiece are measured and evaluated by a CMM, and the geometric errors of the machining center are extracted. Themeasurement results are sufficiently accurate compared to those taken using the square master gauge calibrated by CMM previously. In this report, the machining setup, including workpiece design, tool design, and cutting conditions, is proposed, and the experimental procedures and results of the evaluation are given.

Gloss Estimating Method of Finished Surface Machined by Ball Nose End-Milling under Constant Contact Angle with a Five-Axis Controlled Machining Center

In recent years, studies have been conducted about creating metal moulds using a five-axis controlled machining centre with ball end milling. Most of these reports concern the programming of CAM based on geometry. However, there have been few reports related to polish-less finished surface. Furthermore, a specular surface like a mirror and finishing under a constant angle between ball end milling and the work piece have not been investigated. Therefore, this paper deals with the gloss of the machined surface when feed rate and pick-feed rate are changed to maintain constant surface roughness considering tool run-out under the condition that the angle between the tool and work piece in contact are inclined at 15. However, by changing the combination of feed rate and pick-feed rate, various specular changes and direction of disposition of reflected light were obtained. Therefore, we suggest a new method of evaluating the gloss of these finished surfaces. Comparing results by the proposed method with ones by a glossmeter, it is clear that an appropriate ratio of feed rate and pick-feed rate is important for obtaining finished surface. Moreover, it is demonstrated that the proposed method is effective for estimating the gloss of the machined surface.

Influence of Hydraulic and Interference-fit Tool Holders on Tool Wear and Hole Quality in the Drilling of Al-Si Cylinder Heads

The present work compares the performance hydraulic and interference-fit tool holders in the machining of Al-Si cylinder head components produced by pressure casting for the automotive industry by analyzing tool wear as well as geometry, roughness and tolerance of the produced holes. Uncoated WC + Co cutting tools were applied and the drilling operations were carried out at a Huller computer numerical controlled machining center. Tool wear was characterized by applying optical and scanning electron microscopy and geometry of the holes was followed for parts 1 to 11500. The investigations revealed that, while no significant difference in tool wear could be detected, better results with respect to hole diameter, roundness and surface roughness were obtained for the drills fixed by thermal interference.

Study on the Improvement of Motion Accuracy of 5 Axis Control Machining Center (Measurement of Alignment Errors of the Rotating Axis and their Compensations)

The five-axis machining center with the table-on-table structure has newly been developed, and verified that the alignment accuracy of the rotating axis is easier to be ensured when the motion range of the rotating axis is larger. For the table-on-table type machine structure, it is practically very difficult to completely eliminate the alignment errors of the rotating axis even when the machine is sufficiently accurately assembled. The study deals with the method to enhance the motion accuracy with NC error compensation, based on the errors measured by using DBB. The alignment errors of the rotating axis on five-axis controlled machining centers are measured by using three different methods, and the results are compared. It found that remained alignment errors can be drastically reduced by conducting NC error compensation, whose amount is calculated on the basis of measured alignment errors.