Rotary Axes Research Articles

Geometric Error Identification and Analysis of Rotary Axes on Five-Axis Machine Tool Based on Precision Balls

This paper presents the design of a precise “ball-column” device to efficiently and accurately measure the geometric error terms of both rotary axes of the five-axis machine tool. A geometric error measurement method of spherical contact was proposed based on the influence of the geometric error term from a five-axis machine tool rotating axis on the integrated geometric error of the machine tool. A multiple degree of freedom, step-by-step contact method based on on-machine measure for measuring the spherical center point is proposed, and the solution formula of each geometric error term of the rotating axis is established, respectively. This method can identify 12 geometric errors based on the influence of one rotating axis on another rotating axis after long term operation. The spatial error field of the five-axis machine tool was constructed by analyzing the error law of the two rotating axes of machine tools based on various positions and postures. Finally, after the comparison of the experiment, the results showed that the accuracy of the developed error measurement device reached 91.8% and the detection time was as short as 30–40 min.

Design of a six-degree-of-freedom geometric errors measurement system for a rotary axis of a machine tool

This paper proposes a new kind of non-contact optical measurement system, which combines with a polygon mirror and a conical lens to achieve the purpose of simultaneously measuring six-degree-of-freedom (6 DOF) geometric errors for a rotary axis of a machine tool. At the beginning, we used the Zemax software to construct the proposed optical structure and observe the change of light spots on the detectors. Then, we built the proposed optical structure on the Matlab software by using the skew-ray tracing method, which used to present the actual condition of light spot change and compare with the simulation results. Then, we designed the appropriate fixtures to place the system structure on a rotary axis in a laboratory environment. After completing the laboratory-built prototype, we analyzed the effects of different geometric errors on the detectors at different angular positions of a rotary axis of a machine tool. The proposed measurement system simultaneously measured 6 DOF geometric errors of the rotary axis, and the experimental results were compared with those of two dial gauges by using the measurement method of ISO 230–7. The experimental results show that the maximum deviation ranges of the radial motion error in X axis, the radial motion error in Y axis, the tilt motion error around X, and the tilt motion error around Y are ±4.7 µm, ±6.0 µm, ±3.6 arcsec, and ±8.1 arcsec, respectively.

A dynamic two-axis interpolation test with linear and rotary axes in five-axis machine tool

This paper presents a new dynamic two-axis interpolation test method for dynamic accuracy calibration of rotary axis in a five-axis machine tool based on the double ball bar(DBB). The proposed method only requires synchronous movement of a single rotary axis and a single linear axis which is parallel to the average line of the rotary axis. The measurement trajectory is a spatial curve formed by the intersection of spherical and cylindrical surface, which are the reachable operating space of the DBB and the reachable operating space of the two moving axes, respectively. Compared to the circular tests described in ISO10791.6, which need at least three axes to synchronize motion, the proposed method can be effectively applied to the matching of servo parameters and the adjusting of the dynamic errors of the rotary axis, without the interference of additional linear axes. Meanwhile, the error trajectory pattern obtained by this method has the characteristics of orthogonality and regular variation, which is similar to the circular test of linear axis. So it can guide the calibration and optimization of rotating axis conveniently and effectively. Simulation results show that the proposed method can effectively identify the inverse error, scaling mismatch error, servo mismatch error, squareness error, and other error sources of the rotary axis. The proposed method is verified through experiments on a five-axis machine tool.

Dressing technology of arc diamond wheel by roll abrading in aspheric parallel grinding

In order to dress arc diamond wheel in aspheric parallel grinding efficiently and precisely, a novel truing technique by roll abrading with silicon carbide wheel was proposed. The rotary axis of diamond wheel and dressing wheel were orthogonal. Based on X/Y/Z three-axis linkage controlling, the diamond wheel moved around the outer cylindrical surface of the dressing wheel. In this process the dressing wheel abraded the surface of arc diamond wheel. After analysis of geometric relationship between diamond wheel and dressing wheel, the mathematical model of motion trajectory during the truing process was established. And the dressing efficiency and accuracy were analyzed theoretically. The width of dressing wheel was a key parameter affecting the precision of diamond wheel and dressing efficiency. Then, experiments of truing a type of resin-bonded arc diamond wheel were carried out. The arc error, radial runout error, and radius fluctuation decreased from about 110 μm, 290 μm, and 10 mm to 4 μm, 1.5 μm, and 0.2 mm respectively by the dressing process within 7 h. And the abrasive grains on the surface of diamond wheel had a better cutting edge. At the end, a large-scale aspheric lens was machined by this diamond wheel. The P-V of form error was below 4 μm. All the experiments verified that this new approach was feasible, and this truing technique had been applied in ultra-precision grinding of large-aperture aspheric lens, which improved the overall processing efficiency.

Development and Research of Information System Elements for Passengers Drive Comfort Improvement

Abstract Preliminary theoretical analyzes have been made, which show that heavy acceleration reduces comfort are available. This applies both to the acceleration when starting and stopping. High levels of acceleration are most common when braking. An analysis of passenger comfort based on accelerometer data and a survey was conducted. The speed of travel, the acceleration in the direction of accelerometer X axis, the rotation axis C have a significant influence on the degree of passenger discomfort. The results obtained complement and partly improve those from the available literature with a model using only one linear and one rotary axis, by which the discomfort is described with sufficient accuracy. A regression model has been obtained, which is a suitable basis for building a driver assistance system to provide passenger comfort in public road transport. A model of a “Driver Assistant” microprocessor system based on studies is proposed.

Geometric deviation evaluation for a five-axis flank milling tool path using the tool swept envelope

The geometric deviation is a fundamental concern of five-axis flank milling tool path planning. The determination of the tool swept envelope (TSE) is a very important issue for geometric deviation evaluation because the machined surface is formed by the TSE. Envelope condition is usually utilized to calculate the swept profiles on the cutter surfaces to construct the TSE. The envelope condition presumes the velocity of any point on the tool axis trajectory surface does not vanish. However, it will vanish if the tool axis trajectory surface is not regular. If the swept profiles are still integrated directly to form the TSE when the tool axis trajectory surface is not regular, a wrong result is returned and it will affect the geometric deviation evaluation as well. Kinds of research have largely overlooked this problem. This research presents a robust TSE modeling method and an efficient geometric deviation evaluation method using the TSE. First, the two rotary axes movements are considered to define the tool axis trajectory surface. Then, based on the tool axis trajectory surface and the cutter geometry, cutter’s swept profiles are determined by using the envelope theory of sphere congruence. By utilizing the proposed method to detect outlier tool positions, the TSE is decomposed into multiple surface patches according to the outlier tool positions. To deal with the tool path self-intersection issue, surface patches of the TSE and the cutting tools at the outlier tool positions are represented as triangular facets. Finally, the geometric deviation for a flank milling tool path is calculated via the discrete vector model of the design surface. Examples are given to demonstrate the validity of the proposed methods.

Influence of linear-axis error motions on simultaneous three-axis controlled motion accuracy defined in ISO 10791-6

Five-axis machine tools, which combine three linear axes and two rotary axes, are required for accuracy in machining complex shapes. In this paper, to clarify the influence of simultaneous three-axis control motion measurements as specified in ISO 10791-6, the measured results using a ball bar and R-test are compared. As the motion trajectories of the linear axes are not identical in both measurement devices, it is expected that the error motions of the linear axes cause different measurement results depending on the measurement devices. Thus, the squareness errors between the linear axes and the error motions of the linear axes are assumed as error factors that influence the measured results in this study. A mathematical model of a five-axis control machine tool that considers the error motions and squareness errors of the linear axis is constructed, and the influence of those error factors on motion accuracy is examined using an experiment and a simulation. As a result, the squareness errors and error motions of the linear axis are observed to greatly affect simultaneous three-axis controlled motion accuracy.

Design and Kinematic Analysis of a Novel Machine Tool With Four Rotational Axes and One Translational Axis

Abstract Due to their superior machining quality, efficiency, and availability, five-axis machine tools are important for the manufacturing of complicated parts of freeform surfaces. In this study, a new type of the five-axis machine tool was designed that is composed of four rotary axes as well as one translational axis. Given the structure of the proposed machine tool, an inverse kinematics analysis was conducted analytically, and a set of methods was then proposed to address the issues in the kinematic analysis, e.g., the singularity and multi-solution problems. Compared with traditional five-axis machine tools, which are typically composed of three linear axes and two rotary axes, the proposed machine tool exhibited better kinematic performance with machining parts with hub features, such as impellers, which was validated by simulations and real cuttings.

Improved Method for Synchronizing Motion Accuracy of Linear and Rotary Axes Under Constant Feed Speed Vector at End Milling Point – Investigation of Motion Error Under NC-Commanded Motion –

A 5-axis machining center (5MC) is noted for its synchronous control capability, making it a feasible tool for quickly and accurately machining complicated three-dimensional surfaces such as propellers and hypoid gears as it is equipped with a direct-drive (DD) motor in the rotary axis. The current research work identified the necessity of improving both the accuracy of the machined shape and the consistency of the free-form machined surface. A method for maintaining the feed speed vector at the milling point by controlling two linear axes and the rotary axis of a 5MC to improve the quality of the machined surface was investigated. Additionally, a method was proposed for reducing the shape error of machined workpieces by considering differences in the servo characteristics of the three axes. The shape error was significantly reduced by applying the proposed method using a precedent control coefficient determined via calculations. To maintain the feed speed vector at the milling point in the machining of complex shapes, rapid velocity change in each axis is often required, leading to inaccuracy caused by torque saturation at a DD motor in the rotary axis. The results of this study indicate that torque saturation can be evaluated via simulation and that the machining accuracy and consistency can be improved by accounting for these errors using the proposed precedent control coefficient method.

Effect of CAD/CAM Post Process on S-Shaped Machining Test for Five-Axis Machining Center

ISO 10791-7, the test standard for machining centers, was revised in 2014 to add the test method for five-axis machining centers. However, an S-shaped test was additionally proposed as an accuracy test of aircraft parts from China immediately before the establishment of the test standard. In an ISO meeting, various problems such as creating three-dimensional models and evaluation items have been indicated for the proposed test method. By revising these problems, the standard was finally completed and will be introduced as an informative annex soon. However, it is still an inappropriate test method from the viewpoint of performance inspection for machine tools. In this research, the S-shaped test method draft proposed in September 2016 is tested using two types of five-axis machining centers and commercial CAM software. Consequently, a hidden problem is revealed, that is, an abrupt movement that affected the final result is added to the machine because the rotation direction of the rotary axes is not ideal. This is attributed to the performance of the CAM software’s post processor that converts from CL data to NC program. This study provides some insights into avoiding the problem and obtaining better test results.

АВТОМАТИЗОВАНЕ ВИРОБНИЦТВО ВІДВОДІВ СКЛОПЛАСТИКОВИХ ТРУБОПРОВОДІВ

A promising direction in the production of high-pressure pipelines is the use of composite materials with special properties. Characteristics of composite products are set by reinforcement schemes and the use of various binders. The stability of the strength characteristics significantly depends on the stability of the process of laying reinforcing fibers. The development of automated technological systems of production, ensuring the stability of the process, is an urgent task. A method of fiberglass pipe bends manufacturing by the method of pre-impregnated tape winding on a folding mandrel. To implement this method the problem of developing technological equipment, equipment and methods of adjustment are solved. The proposed solution provides the formation of a branch from the inner surface. The kinematic scheme of the equipment realizes the rotation of the tape stacker around the axis of the cross-section of the mandrel and the longitudinal-angular displacement of the mandrel relative to the stacker, which provides the possibility of cylindrical and spiral stacking of the tape. The installation of tap winding, which is a three-axis CNC machine that implements the proposed scheme, is described. The rotation of the coils with tape around the mandrel is provided with a hollow rotary axis – stacker. Moving the mandrel relative to the stacker is provided by its installation on a movable platform. Following the proposed method of manufacturing bends, the outer surface of the collapsible mandrel ensures the formation of the inner surface of the branch, including the connecting-butt surfaces. Rules for the choice of the surface of the connector mandrel, ensuring its extraction from the manufactured branch is formulated. A method for programming winding operations has been developed. A method for determining the parameters of the control system of the CNC system is given, which specifies the structure of laying the tape and the wall thickness of the outlet. A procedure is described for setting up a tap manufacturing operation consisting in changing the relative position of the installation elements and the mandrel fixing devices. The use of traditional for CNC systems approaches to adjust the coordinate systems ensures the accuracy of the initial position is not worse than 0.1 mm.

A novel differential kinematics model to compare the kinematic performances of 5-axis CNC machines

A 5-axis CNC machine is similar to two cooperating robots, one robot carrying the workpiece and one robot carrying the tool. The 5-axis CNC machines are designed in a large variety of kinematic configurations and structures. Comparing different 5-axis kinematic configurations plays an important role in machine selection and optimal machine design. In this sense, the present study proposes a new mathematical model to analyze and compare the kinematic performances of the 5-axis machines. First, a generalized kinematic chain of 5-axis machine is treated as a unified kinematic chain of two collaborative robots in order to formulate a generalized differential kinematics model of the machines. Second, four important properties of the kinematics model are proved in a generalized case so that quantitative parameters characterizing the kinematic performances of the machines can be evaluated effectively. Last, six typical groups of 5-axis CNC configurations are compared through the evaluated parameters. In addition, it has been shown that, by using the properties of the kinematics model, the forward and inverse kinematic equations for the rotary axes of any 5-axis machine can be formulated in an effective and simplified manner that could be useful for developing the postprocessors for any 5-axis machine.

Extrinsic calibration and kinematic modelling of a laser line triangulation sensor integrated in an intelligent fixture with 3 degrees of freedom

This article presents the kinematic modelling for the extrinsic calibration of a laser line profile sensor integrated in an intelligent fixture. It aims to characterize the real 3D shape of flexible parts when they are clamped to ensure suitable stiffness for machining processes, aiding to define the machining path to improve the precision of the process. This tool consists of two linear axes and a rotary axis (3 DOF) which enables scanning the area of the part to be processed automatically. In order to carry out the accuracy evaluation of the intelligent fixture, some methods present in the state of the art have been considered and compared. Moreover, in order to design and identify the most suitable calibration procedure a previous simulation process is carried out based on sensitivity analysis. To complete the study, a test piece has been scanned with the intelligent fixture and compared with an external metrological frame employed as a ground truth. In addition, a characterization of the geometric performance of the fixture's linear actuators is carried out to check the geometric performance and its influence on the extrinsic calibration process accuracy. The results of this article show the importance of performing simulation processes in order to define the best measurement scenario for extrinsic calibration. Besides, it demonstrates the influence of the method used to perform extrinsic calibration in order to obtain good precision in the measures, where the geometric performance of the drives have a decisive influence.

Geometric accuracy enhancement of five-axis machine tool based on error analysis

The characteristics of geometric error affect both the positions and orientations of a five-axis machine tool, which are very important for precision manufacturing. It is necessary to conduct quantitative analysis for the above characteristics to improve the precision of the five-axis machine tool. In this paper, the synthetic volumetric error model of the five-axis machine tool with a turntable-tilting head has been established, which describes the effect of 43 geometric error terms on position and orientation error vector intuitively. The multidimensional output of geometric error vectors in the workspace of the machine tool is sufficiently taken into account, and global quantitative sensitivity analysis is introduced to determine the effect of each geometric error on the precision of the machine tool. The results showed that geometric errors of the rotary axes are dominant sensitivity factors, reaching 59.32 and 51.59% of sensitivity indices of the position and orientation error vector, respectively. Furthermore, geometric error terms that are noncritical and critical are extracted according to the result of mutual information analysis. Those geometric errors were removed from the geometric error compensation model, which are at the same time insensitivity errors and nonsignificant geometric errors. The geometric error compensation results show that the accuracy of the machined parts with complex curved surfaces was improved 56.22% after error compensation based on sensitivity and mutual information analysis. This research provides a feasible methodology for analyzing the effect of geometric errors and determining the compensation values of the machine tool.

Ultrasonic Non-Destructive Testing System of Semi-Enclosed Workpiece with Dual-Robot Testing System.

With the rapid development of material science, more and more workpieces, especially workpieces with complex curved surfaces, are being made of composite materials. Robotic non-destructive testing (NDT) systems for complex curved surface composite material parts are being used more and more. Despite the emergence of such flexible NDT systems, the detection of semi-enclosed parts is also a challenge for robotic NDT systems. In order to overcome the problem, this paper establishes an NDT solution for semi-enclosed workpieces based on a dual-robot system of synchronous motion, in which an extension arm is installed on one of the robots and presents a trajectory planning method that always ensures the extension arm is parallel to the rotary axis of a semi-enclosed workpiece and that the ultrasonic probes are perpendicular to the workpiece surface. Trajectory analysis experiments and ultrasonic NDT experiments utilizing the optimal water path distance determined by simulation result of multi-Gaussian beam model for two types of semi-enclosed workpieces are performed with the dual-robot NDT system. Experimental results prove that the dual-robot NDT scheme functions well and the planned trajectories are correct. All the hole-shaped artificial defects with diameters ≥3 mm are detected by using 2.25 MHz ultrasonic probes through the transmission testing method. Vivid 3D C-scan image of a small diameter cylindrical workpiece based on the testing result is provided for convenience of observation.

Reliability Design of an Electronic Cam Curve for Flying Shear Machine in Short Materials Cutting

The structure and the production process for flying shear machine are introduced first. Then, a quintic polynomial is applied to the design of an electronic cam system for the rotary knife axis in short materials cutting. The dimensionless equation for a quintic polynomial cam curve is deduced. Finally, the curve is plotted with the cam constructor integrated into Siemens engineering development software SCOUT and it is tested with a laboratory platform, which consists of a motion controller SIMOTION and motor drivers SINAMICS S120. The results show that the running stability of the flying shear machine and the position control accuracy of the rotary knife can be effectively improved by using the curve designed in this paper.

Sensitivity analysis of relationship between error motions and machined shape errors in five-axis machining center - Peripheral milling using square-end mill as test case -

Five-axis machine tools, consisting of three translational axes and two rotary axes, are increasingly being used for complex surface machining. This paper proposes a new sensitivity analysis method to elucidate the relationship between the tool trajectory error and the error motions of the feed axes. Based on the free-curve trajectory during simultaneous five-axis machining, a surface coordinate system is created for each tool center point, to define the tool trajectory and the trajectory errors. Then, a novel sensitivity coefficient is defined to investigate the relationship between the trajectory error and the error motions. It is shown that the proposed sensitivity analysis method can successfully determine whether the trajectory is sensitive to the error motions, based on sensitivity analyses performed during conic frustum machining and S-shaped machining tests. Moreover, the sensitivity analysis method can also predict the effects of the error motion source, such as the reversal errors. In the future, we intend to study other types of machining processes, such as ball-end milling, as well.

Method of improving synchronisation of motion accuracy of rotary axis and linear axes under a constant feed-speed vector of end-milling point

ABSTRACTA five-axis machining centre is noted for its synchronous control capability that makes it feasible to create complicated three-dimensional surfaces such as propellers and hypoid gears quickly. As stated in this research, it is necessary to improve not only the accuracy of the machined shape but also the roughness of the machined surface of free-form surfaces. Therefore, in this study, it is aimed at maintaining the feed-speed vector at the milling point by through controlling two linear axes and a rotary axis to improve the machined surface quality. In addition, a method was suggested for reducing the shape error of machined workpieces by considering the differences in the servo characteristics of the three axes. The shape error was greatly decreased by applying the proposed method of using parameters (referred to as the precedent FF coefficient in this paper) determined by calculation instead of by trial and error. Moreover, to decrease the shape error, even in machining complex shapes that exhibit high angular velocity, the motor load, which is a key factor in the shape error, served as the focus, and a block diagram that considers the motor load was developed. The shape error can be evaluated via the simulation.

Dynamics Model of Backhoe Devices Considering Excavation Load for Hydraulic Excavators

This paper presents a new dynamic model of backhoe devices considering excavation load so as to study the dynamic characteristics when the backhoe device is excavating. The dynamic model for the backhoe device was derived in matrix form by using Lagrange equation. The program of fourth-order Runge-Kutta method was coded in MatLab software so as to solve the dynamic model. Then taking composite excavation conditions as examples, The proposed dynamic model was used to calculate the counterforce of the kinematic pairs at all hinge points and solved the rotational movement laws (such as angular displacement, angular velocity, etc.) of the main components of backhoe devices around their rotary axes. In order to verify the correctness of the dynamic model, experiments of composite excavation conditions were done by using an XG822FL excavator, and the results of the experiment demonstrated that the proposed dynamic model is correct and effective to calculate the counterforce of kinematic pairs and solve the rotary movement laws of main components during the course of excavation, which can be used to predict the counterforce of kinematic pairs during the design process of backhoe device.

Uji Kinerja Surface Scanner 3D Menggunakan Sensor VL53L0X dan Mikrokontroler ATMEGA8535

Digital data recording of the geometry of 3-dimensional objects require a 3D scanner tool which are mostly using an imagery sensor. However there is hardly used information of scanned result, named color. Imagery sensor requires high spesification processing unit as capable as a personal computer for data acquisition processing. This research aims to build a 3D surface scanner using a time of flight laser ranging sensor and to develop its simple function to become more valuable device. Using point to point displacement method, the sensor measures the distance between the outermost point of the object and the sensor surface perpendicularly, once when one measurement is done then the object to be rotated along with the rotary table. The prototype was built using the VL53L0X sensor and ATMEGA8535 microcontroller as a motor controller for rotary table and vertical axis. Scanned data is sent from the microcontroller to the computer to be visualized in real time. The results show that the VL53L0X sensor is suitable for scanning convex objects but it is not capable to handle objects with multiple cavities.