Five-axis Machining Center Research Articles

Bionic optimization design for the crossbeam of a five-axis machining center based on honeycomb sandwich structures

Bionic optimization design for the crossbeam of a five-axis machining center based on honeycomb sandwich structures

Modeling, detection, and validation for geometric errors in machine tools

Abstract This study aims to enhance the spatial precision of five-axis machining centers through a comprehensive exploration of geometric errors, encompassing modeling, efficient detection, and compensation validation. Our approach begins with the establishment of a kinematic error model covering XYZ translational axes and AC rotational axes, providing an in-depth understanding of error origins and interrelationships. Utilizing a laser tracker, we conduct direct measurements of the geometric errors associated with translational axes, and a rotational axis error detection model is developed by using a ball bar, allowing for indirect analysis of rotational axis geometric errors. The validity of both the kinematic error model and error detection is further confirmed through practical on-machine measurements.

Investigation of Force-Controlled Polishing of Complex Curved PMMA Parts on a Machining Center

During the polishing process of complex curved PMMA parts, the polishing force is an important factor affecting the surface quality and optical performance. In this paper, a force-controlled polishing device integrated into a machining center to maintain the polishing force is investigated. In order to achieve the real-time active control of the polishing force, the linear voice coil motor and force sensors are used for motion and measurement. A compact structure was designed to couple the linear motion of the voice coil motor with the rotation for polishing. The force-controlled polishing system with a high real-time hardware architecture was developed to perform complex curved polishing path movement with precise force control. Next, the polishing force between the device and the workpiece was analyzed to obtain the mathematical model of the device. Considering the impact during the approaching phase of polishing, a fuzzy PI controller was proposed to reduce the overshoot and response time. To implement the control method, the controller model was established on Simulink and the control system was developed based on TwinCAT 3 software with real-time computing capability. Finally, a polishing experiment involving a complex curved PMMA part was conducted by a force-controlled polishing device integrated into a five-axis machining center. The results show that the device can effectively maintain the polishing force to improve surface quality and optical performance.

Design and grindability assessment with cup shaped electroplated CBN wheel grinding turbine disc slots of powder metallurgy superalloy FGH96

The machining surface integrity of aero-engine turbine disc slots has a significant impact on their fatigue life and service performance, and achieving efficiency and high-precision machining is still a great challenge. The high machining requirements of future aeroengine turbine disc slots will be difficult to satisfy using the broaching method. In addition, existing methods of slot machining face difficulties in ensuring surface integrity. This study explored a cup shaped electroplated Cubic Boron Nitride (CBN) abrasive wheel for profile grinding the turbine disc slots of FGH96 powder metallurgy superalloy. The matrix structure of the cup shaped abrasive wheel was designed and verified. A profile grinding experiment was conducted for fir-tree slots on a five-axis machining center. The accuracy and the surface integrity were analyzed. Results show that the key dimension detection results of the slots were within the allowable tolerance range. Meanwhile, an average surface roughness Ra of 0.55 μm was achieved, the residual stress was compressive, the plastic deformation layer thickness was less than 5 μm, and the hardening layer thickness was less than 20 μm. The research findings provide a new approach to machining the slots of aviation engine turbine discs and guidance for the high-quality processing of complex components.

Feasibility of 8-Shaped Motion Test for Five-Axis Machining Center

ISO 10791-7, which specifies the machining accuracy test standard for machining centers, and ISO 10791-6, which specifies the interpolation motion test standard, were revised in 2014 to include five-axis machining centers (5-axis MCs). In addition, cone frustum test, which has been used as the National Aerospace Standard (NAS), was revised and introduced in these ISO standards. However, prior to the establishment of these standards, an aircraft manufacturing company in China proposed S-shaped machining test to measure the accuracy of the test piece of an aircraft. This was adopted as an informative annex of ISO 10791-7 in 2020. Furthermore, in 2019, China proposed a method related to S-shaped machining test and a method of 8-shaped interpolation motion test. Since the S-shaped test requires high acceleration and deceleration in some sections, the test results depend on the performance of the computer-aided manufacturing (CAM) software; therefore, it is not efficient in determining the accuracy of the machine tools. In contrast, in the 8-shaped motion test, the tip of the spindle moves based on a sine curve; consequently, high acceleration/deceleration does not occur. Since the tip of the cutting tool is fixed, a device called R-test is used to measure the position of the center of reference ball using three displacement sensors. In this study, we have discussed the feasibility and problems of the 8-shaped motion test. First, the motion of the machine in the figure “8” motion test is clarified. Next, the definition of the parameters necessary to create the NC programs is outlined. In addition, we have proposed a method in which suitable conditions are set for simultaneous 5-axis feed on a 5-axis MC. Finally, the results of an actual test are applied to the 5-axis MC to confirm that no major problems exist.

Analysis and Control of Precision Machining Error for Spatial Angle Parts of Remote-Sensing Camera

Aiming at the problem of low machining accuracy of remote-sensing camera parts with spatial angle, this study analyzed the causes from human, machine, material, method, environment, and measurement, and proposed an experimental analysis method based on the spatial rotation of machine tool spindle according to the linkage machining function of the five-axis machining center. The cutting experiment was carried out through the self-built benchmark of the machine tool, and the machining errors of the machine tool spindle with different spatial angles were studied. The precision machining of the parts with spatial angles was realized by taking measures such as machine tool correction and numerical control program compensation. The experiment proved that this method is feasible and effective.

Studies on the Numerical Control Programming for Multi-Axis Machining of Turbomolecular Pump Rotor

Turbomolecular pumps (TMPs), boasting advantageous high pumping rates, stability, and cleanliness, have been widely used in the semiconductor and photoelectric industries. In the aviation industry, the lightweight rotors of turbomolecular pumps can enhance the performance of generators. With technological advancements and increased industrial performance demands, various designs for turbomolecular pump rotors utilizing twisted and curved blade surfaces have been proposed. This increase in complexity runs parallel with machining difficulties. Contact and noncontact reverse engineering equipment was used to reconstruct a computer-aided design (CAD) model of turbomolecular pump rotors. The machining of thin and long blades, cutting tool arrangement, and toolpath was planned. Postprocessing was used to convert the toolpath into numerical control (NC) programming codes, which were combined with solid model cutting simulation software to verify the efficacy of the generated machining NC program for turbomolecular pump rotors. A five-axis horizontal machining center (CK type) with aluminum alloy AL6061-T6 was used to conduct actual machining tests measuring the efficiency of the machining methods. The rapid prototyping (RP) blocks can be creatively used as a jig and stuffed between the blades to suppress the chatter problem during processing, and the roughness of the surface of the blades can be reduced from 4.4 μm to 1.3 μm. The processed rotor can meet the flow test requirements, and the overall research can be used as a reference for the industry.

ОСОБЕННОСТИ ПРИМЕНЕНИЯ МНОГОКООРДИНАТНЫХ ШЛИФОВАЛЬНЫХ СТАНКОВ С ЧПУ ДЛЯ ПОВЫШЕНИЯ ПРОИЗВОДИТЕЛЬНОСТИ, КАЧЕСТВА И ТОЧНОСТИ ОБРАБОТКИ ДЕТАЛЕЙ И УЗЛОВ АВИАЦИОННЫХ ГАЗОТУРБИННЫХ ДВИГАТЕЛЕЙ

The paper is aimed at improving the productivity, quality and accuracy of manufacturing gas turbine engine parts and assemblies for the modern growing passenger aviation transport based on the use of technical capabilities of modern multiaxis CNC grinding machining centers. The paper shows the results of successful application of a five-axis CNC grinding machining center MFP-050.65.65 made by Magerle (Switzerland), which allows reducing by five times the number of operations, universal machines, special devices and cutting tools by increasing the number of machined surfaces for one set of nozzle blades of an aviation gas turbine engine. Simultaneously with a significant increase in the productivity of machining various multidirectional surfaces of the nozzle blades due to the use of new highly porous grinding wheels and rational modes of deep grinding, a higher burn-free quality of the ground surfaces is ensured and an important task is solved to increase the accuracy of the flow sections of the turbine nozzle apparatus with the combined use of CNC system and special software for correcting errors of part casting surfaces during their installation, turning and deep grinding of the base surfaces. The developed new technology of nozzle blades machining was introduced for the first time in the Russian Federation at the Aviadvigatel enterprise for manufacturing nozzle blades of modern newly produced gas turbine engines.

Fault monitoring and diagnosis of motorized spindle in five-axis Machining Center based on CNN-SVM-PSO

A spindle fault diagnosis method based on CNN-SVM optimized by particle swarm algorithm (PSO) is proposed to address the problems of high failure rate of electric spindles of high precision CNC machine tools, while manual fault diagnosis is a tedious task and low efficiency. The model uses a convolutional neural network (CNN) model as a deep feature miner and a support vector machine (SVM) as a fault state classifier. Taking the electric spindle of a five-axis machining centre as the experimental research object, the model classifies and predicts four labelled states: normal state of the electric spindle, loose state of the rotating shaft and coupling, eccentric state of the motor air gap and damaged state of the bearing and rolling body, while introducing a particle swarm algorithm ( PSO) is introduced to optimize the hyperparameters in the model to improve the prediction effect. The results show that the proposed hybrid PSO-CNN-SVM model is able to monitor and diagnose the electric spindle failure of a 5-axis machining centre with an accuracy of 99.33%. In comparison with the BP model, SVM model, CNN model and CNN-SVM model, the accuracy of the model increased by 10%, 6%, 4% and 2% respectively, which shows that the fault diagnosis model proposed in the paper can monitor the operation status of the electric spindle more effectively and diagnose the type of electric spindle fault, so as to improve the maintenance strategy.

Tool wear condition monitoring method of five-axis machining center based on PSO-CNN

The effective monitoring of tool wear status in the milling process of a five-axis machining center is important for improving product quality and efficiency, so this paper proposes a CNN convolutional neural network model based on the optimization of PSO algorithm to monitor the tool wear status. Firstly, the cutting vibration signals and spindle current signals during the milling process of the five-axis machining center are collected using sensor technology, and the features related to the tool wear status are extracted in the time domain, frequency domain and time-frequency domain to form a feature sample matrix; secondly, the tool wear values corresponding to the above features are measured using an electron microscope and classified into three types: slight wear, normal wear and sharp wear to construct a target Finally, the tool wear sample data set is constructed by using multi-source information fusion technology and input to PSO-CNN model to complete the prediction of tool wear status. The results show that the proposed method can effectively predict the tool wear state with an accuracy of 98.27%; and compared with BP model, CNN model and SVM model, the accuracy indexes are improved by 9.48%, 3.44% and 1.72% respectively, which indicates that the PSO-CNN model proposed in this paper has obvious advantages in the field of tool wear state identification.

Reduction in the Volumetric Wear of a Ball Polishing Tool Using Ultrasonic-Vibration-Assisted Polishing Process

Ultraprecision freeform polishing using a bonnet or a felt ball mounted on a polishing head plays an important role in the mold and lens production industries. The volumetric wear of a bonnet or a felt polishing ball is still a problem to be solved. The objective of this study was to develop an ultrasonic-vibration-assisted ball polishing process on a CNC machining center to improve the surface roughness of a STAVAX mold steel and to reduce the volumetric wear of the polishing ball. The optimal combination of the ultrasonic-vibration-assisted ball polishing parameters for a plane surface was determined by conducting the Taguchi L18 matrix experiments, ANOVA analysis, and verification experiments. The surface roughness of the polished specimens was improved from the burnished surface roughness of Ra 0.122 μm to Ra 0.022 μm. In applying the optimal plane surface ball burnishing and vibration-assisted spherical polishing parameters sequentially to a fine-milled and burnished aspherical lens surface carrier on a five-axis machining center, the surface roughness of Ra 0.014 μm was obtainable. The improvement in the volumetric wear of the polishing ball was about 62% using the vibration-assisted polishing process compared with the nonvibrated polishing process.

Compensation of Thermally Induced Errors in Five-Axis Computer Numerical Control Machining Centers Equipped With Different Spindles

Abstract Thermally induced errors are the dominant source of inaccuracy in machine tools today and are often the most difficult type of error to reduce. Software compensation of thermally induced displacements at the tool center point (TCP) is a widely employed error reduction technique due to its cost-effectiveness and ease of implementation. Transfer function (TF)-based compensation methods lead to promising results, as has been shown in previous studies. Furthermore, machine tool manufacturers frequently offer the same type of machine tool equipped with different spindle units. This leads to different thermal deformation behavior depending on the specific spindle unit mounted in the machine tool. To demonstrate this difference, experimental research is carried out on three five-axis computer numerical control (CNC) machining centers of the same type equipped with three different spindle units. The experimentally obtained thermal errors at the TCP of three machine tools with different mounted spindle units are compared, showing a significant variation in thermal errors in the Z-direction depending on the spindle unit. The research presented in this paper shows a dynamic approach to thermal error compensation of five-axis CNC machining centers considering different spindle units. System identification theory is applied to build dynamic thermal error models for three different spindle units based on calibration experiments. Subsequently, the evaluation of model performance through spindle spectrum tests shows that a reduction in thermal error of up to 85% was achieved in the Z-direction after compensation.

Improved Synchronous Motion of Linear and Rotary Axes While Avoiding Torque Saturation Under a Constant Feed Speed Vector at the Endmilling Point – Investigation of Motion Error Under Numerical Control Commanded Motion –

A five-axis machining center is known for its synchronous control capability, allowing complicated three-dimensional surfaces, such as propellers and hypoid gears, to be quickly created. Prior research has shown that it is necessary to improve not only the machined shape accuracy but also the machined surface roughness of free-form surfaces. Therefore, in this research, we aimed to maintain the feed speed vector at the endmilling point by controlling two linear axes and a rotary axis with a five-axis machining center to improve the machined surface quality. In previous research, we suggested reducing the shape error of machined workpieces (referred to as shape error in this research) by considering the differences in the servo characteristics of the three axes in the machining method. The shape error was significantly decreased by applying the proposed method, which uses a parameter (referred to as precedent control coefficient in this research) determined by calculation, rather than trial and error. Moreover, to maintain the feed speed vector at the endmilling point when machining complex shapes, a rapid velocity change in each axis is required, causing inaccuracy owing to torque saturation. The results of the experiments and simulations of previous research indicated that torque saturation can be evaluated via simulation. In this research, to reduce the shape error while avoiding torque saturation when movement has high angular velocity, we developed a theoretical method to obtain the most suitable precedent control coefficient of each axis by using a block diagram that considers torque saturation. Therefore, both shape error reduction and torque saturation avoidance can be realized by using the proposed method.

Study on the spindle axial thermal error of a five-axis machining center considering the thermal bending effect

Spindle axial thermal error is one of the main sources affecting the accuracy of a machine tool. It is important to study this error with respect to thermal optimization design and thermal error compensation. The column thermal bending effect mainly caused by spindle rotating is an important factor affecting the spindle axial thermal error, but it is often ignored in current research. In this paper, a novel modeling approach to studying the spindle axial thermal error of a five-axis machining center that considers the thermal bending effect was proposed. Experiments with different thermal boundary conditions were conducted to decouple this error. The thermal deformation coefficients of the column were effectively identified by using both the axial and radial thermal error data. Then, a physically-based model including the error component caused by the thermal bending effect was established. The complicated evolution process of the measured spindle axial thermal error can be explained by the proposed model. The thermal bending angles can be also effectively predicted to quantify the thermal bending behaviors. Furthermore, compared with three typical data-driven models, the proposed model shows better performance in predicting the axial thermal error. The proposed modeling method helps in better revealing the formation mechanism of the spindle axial thermal error. And the proposed model shows a good application prospect for error compensation because of its generalization ability and simplicity.

Study on the tool setting method of micro-milling tool based on in-line holography

Aiming at the various shortcomings of existing tool setting methods, this paper proposes a coaxial holographic tool setting method for tiny tools. Based on the research and analysis of the principle of holographic imaging and the key issues of holographic images, a set of holographic tool setting detection device for micro milling tool was built, and the micro milling tool measurement was carried out on the five-axis machining center using standard tools. experiment. Experimental results show that the tool setting device can efficiently perform tool setting detection of micro-milling tool. Compared with the measurement results of the high-precision external presetting instrument, the relative error of the contact tool setting instrument is 0.033%, and the relative error of the holographic tool setting prototype is 0.007%, which is more effective in realizing the tool setting of tiny tools. Detection. This result verifies the feasibility of the coaxial holographic tool setting method for micro tool, that is, holographic measurement can be used for high-precision tool setting of micro milling tool.

Condition for machining feasibility for a five-axis machining center

Recently, five-axis machining centers with non-orthogonal rotation axes have been developed to achieve a high stiffness and large machinable area. Although such machine tools can expand the manufacturing field, adopting not only orthogonal axes, but also non-orthogonal axes, requires generalization of conventional form-shaping theory. Moreover, since it is not possible to imagine simultaneous five-axis movement of machine tools with non-orthogonal axes, it is important to analyze the validity of the developed machine tools with non-orthogonal axes using generalized form-shaping theory by a structure analysis method. In the present paper, generalization of the form-shaping function is first performed, and the conditions whereby machining centers with non-orthogonal axes can achieve every position and posture are clarified for an index showing the validity of the machine tool structure. Finally, the machining feasibility is verified for a machine tool structure with non-orthogonal axes using the derived conditions.

Position error reduction of tool center point in multi-tasking machine tools through compensating influence of geometric deviations identified by ball bar measurements

A method to compensate the influence of geometric deviations on tool center point (TCP) for a multi-tasking machine tool is proposed in this paper. Some methods to compensate geometric deviations of a rotary axis in five-axis machining centers have been proposed. However, due to the special topological structure of multi-tasking machine tools, the identification and compensation methods for geometric deviations are different from those of the five-axis machining centers, which have been seldom researched until now. In this paper, the main attention is paid to analyze the eccentricities of the trajectories measured by a ball bar under simultaneous three-axis motions and to reduce the influence of the identified geometric deviations on the position error of TCP by the compensation method. It is divided into two sequential subtasks. At first, the geometric deviations are identified by using the eccentricities of measured trajectories. A simple and practical measuring procedure is proposed to identify geometric deviations of rotary axes existing in a multi-tasking machine tool. For the second step, a method is proposed by modifying the original NC code according to the kinematic chain model of the targeted machine tool to compensate the influence of the existing geometric deviations on TCP. An experiment is conducted on a multi-tasking machine tool with a swivel tool spindle head in the horizontal position. The repeatability of the measured eccentricities based on three experimental results is also investigated to reduce the influence of measuring error on the identified results. As a result, the corresponding values of geometric deviations after the compensation are less than 2.2 arcseconds or 2.4 μm. It is concluded that the influence of geometric deviations on TCP is compensated effectively, and the position error of TCP is reduced significantly.

Precision measurement method of “cradle-type” five-axis machining center

This study mainly measures the accuracy of closed impeller machining machines in aerospace. However, this machining center is different from others and belongs to a “cradle type” five-axis machining center. The measuring difficulty of cradle-type five-axis machining center is that the error accuracy of X, Y, Z, B, and C axes can meet the requirements when the Y-axis moving speed reaches 80 m/min and the maximum acceleration is 10 m/s2; and the C-axis maximum angular acceleration is 1.25 rad/s2; and the maximum angular velocity is 60 rpm. Therefore, the 24 theoretical models of accuracy error measurement for cradle type are derived at first. Combined with the theoretical model, the straightness of X, Y, and Z and the positioning accuracy of X, Y, Z, B, and C axes are measured by laser interferometer. In X, Y, Z, and C axes detection, two methods are adopted and compared. Then, the overall processing accuracy is measured through trial-cutting parts. The measurement results show that the second way (with temperature sensor) is better than the first measurement. Compared with the device without normal temperature sensor, the measurement of X-axis repeated positioning accuracy and positioning accuracy are improved by 8.5% and 23.6%, respectively. The positioning accuracy of Y-axis is improved by 16.7%. The repeated positioning accuracy and positioning accuracy of Z-axis are improved by 78.9% and 72.1%, respectively. The repeated positioning accuracy and positioning accuracy of the C-axis are improved by 20.4% and 7%, respectively. At the same time, it is also measured that the repeated positioning accuracy of B-axis is 15 μm. Finally, through the processing and testing of the trial-cutting parts, the processing error of the inclined cone table profile is 20 μm, which is far less than the design parameters of the original cradle-type five-axis machine tool. It provides efficient theoretical guidance and practical reference for similar five-axis machine tool measurement methods in the future.

Thermal error prediction of motorized spindle for five-axis machining center based on analytical modeling and BP neural network

To ensure the stability of precision of the motorized spindle for five-axis machining center, the thermal error of five-axis machining center was investigated, and the temperature rise-thermal deformation model of a thin-wall ring type rotary elastomer was built on the basis of thermo-elastic property. Thus, a model of radial thermal error was con-structed. The relationship between radial error and axial error was also investigated in this paper and the total radial errors were gotten. In addition, the thermal error of the motorized spindle of five-axis machining center was measured by the ball bar in the experiment of thermal error. The motorized spindle total radial error was achieved by this experiment and radial total error analytical model. Finally, a BP neural network algorithm was introduced for thermal error prediction of five-axis machining center, and the precision of prediction of these models was compared and analyzed. The analysis shows that this method is practical and effective.

Research on a Five-Axis Machining Center Worktable with Bionic Honeycomb Lightweight Structure.

The processing of high-precision aerospace parts requires not only ultra-precision machine tools, but also high-efficiency processing. However, in order to realize high-efficiency processing, besides optimizing the system and process parameters, some subversive research can also be done on the machine tool structure. In this paper, the lightweight research is mainly carried out on the structure of machine tool worktable. The traditional workbench is very “heavy” and “slowness”. If the traditional workbench is subverted and reformed to reduce the weight, the processing efficiency will be improved qualitatively. Therefore, this paper studies the lightweight worktable of CFRP (carbon fiber reinforced polymer) in combination with the biological “honeycomb” shape. At first, the tensile, bending, compressive and laminar shear analysis of CFRP were carried out, and the comprehensive parameters were obtained. Simultaneously, the theoretical research and the honeycomb structure simulation and verification of CFRP worktable are carried out. The results show that the HACT (honeycomb arrangement of circular tubes) is 18.51% better than the SACT (straight arrangement of circular tubes) and 45.05% better than the OW (original worktable) by comparing and analyzing the weight of the three modes (HACT, SACT and OW). The actual weight of bionic honeycomb lightweight worktable is 1100 kg, while the simulation result is 1080.25 kg, with an error of 1.8%. Meanwhile, it is analyzed that the original workbench weight of the five-axis machining center is 2023 kg, while the simulation result is 1998.6 kg, with an error of 1.2%. The lightweight degree is reduced by 45.05%. However, the actual lightweight degree has been reduced by 45.63%. The error between simulation and actual is less than 1.3%. This kind of structural transformation has brought forward cutting-edge innovations to the machine tool processing industry. It provides a reference scheme for related enterprises in the future equipment renovation.