Improvement Of Machining Accuracy Research Articles

预应力下的结构模态计算

本文采用达朗伯原理建立动力学平衡方程，研究了梁类结构预应力下的模态计算方法，证明通过调节预应力，可有效改善结构的动态性能。本文通过有限元法计算比较正负预应力下桁架结构的变形和模态，提出预应力桁架可作为高速数控机床的横梁结构。在横梁内部施加预应力可大幅提高横梁的弯曲刚性。通过对桁架关键构件内应力的控制，可以使桁架内应力做到可调。根据加工参数的变化，优化调节桁架某些杆件的内应力大小及方向，使设备在加工过程中具有一定改变动态性能的能力，从而达到减小振动提高加工精度的目的。 Using D’Alembert’s principle to establish the dynamic equations to study the mode calculating method of class structure under prestressed, evidenced by adjusting the prestressing, can effec-tively improve the dynamic performance of the structure. Deformations and modal comparatively positive and negative prestressed truss structure by the finite element method is proposed as a beam structure of prestressed truss speed CNC machine tools. The bending rigidity of the internal beam can be improved significantly by prestressing the beam. Through the truss key component stress control, it can make the truss internal stress to be adjustable. According to changes of processing parameters, the size and the direction of the internal stress of certain truss rods are optimized and adjusted so that the device has the certain ability to change the dynamic performance to achieve the purposes of reducing vibration and improving machining accuracy.

A geometric accuracy design method of multi-axis NC machine tool for improving machining accuracy reliability

A geometric accuracy design method of multi-axis NC machine tool for improving machining accuracy reliability

The Application of Maglev Supporting Technology in NC Machine

Feed motion guides driven by linear motor in NC machine for industrial applications mostly adopt mechani- cal support and they easily produce wear because of impact and high speed. For above characteristic and the requirement of machining accuracy, application of maglev supporting technology in NC Machine is raised. By analyzing the structure of maglev feed motion guide, the mechanical model of single-degree-freedom and multi-degree-freedom magnetic sus- pension system is proposed. By MATLAB, the curve of stiffness and damper in steady state is gained from the two groups of PID parameters, so that the influence of the controller parameters on the stiffness and damper is obtained and the vibra- tion area of feed motion guides is made smaller. The conclusion can be reached that the performance of maglev feed mo- tion guides is optimized by adjusting the parameters of controller properly that has an important theoretical significance for improving machining accuracy of NC machine tools.

Study on a Wireless Temperature and Humidity Monitoring System for Workshop with Constant Temperature Based on SCM

A wireless temperature and humidity monitoring system for workshop with constant temperature based on AT89C52 Single chip microcomputer and nRF905 wireless microchip is studied. The system is consists of base station and slave station. Base station is mainly consists of temperature acquisition module, humidity acquisition module, wireless communicating module and communicating testing module. Good communication protocols play an important role in ensuring the correct monitoring data. So the network topology, communication data form, ad hoc networks protocol, mac protocol and data link layer protocols are discussed for commutation protocol to host computer software. The cost of the system is low and it has a large function area and a good performance. It is able to provide messages of workshop with constant temperature for improving machining accuracy and prolonging the life of equipment in machine shop.

Volumetric calibration in multi-space in large-volume machine based on measurement uncertainty analysis

Machining accuracy is a significant index to evaluate characteristics of machine tools. Error compensation has been proved as an effective method for improving machining accuracy. Error measurement and identification are the prerequisite and basis for compensation. In order to detect volumetric error and identify geometric error accurately in large machines, a new method including workspace segment and multi-lateration measurement principle using laser tracker is proposed. Firstly, a synthetic test in large-volume machine containing three steps is presented. The Monte Carlo approach is implemented for evaluating the measurement uncertainty of volumetric calibration. Uncertainty sources in the calibration process, such as laser tracker sensors, thermal drift, and machine repeatability, are introduced. In order to decrease measurement uncertainty, the measurement station is optimized. Workspace is segmented, and volumetric error is calibrated in multi-station. Total least square method is implemented to transform coordinates among different measurement systems into reference frame accurately. Finally, the accuracy of algorithms for geometric error identification is verified by comparing the test results with that measured using a laser interferometer. And the volumetric calibration accuracy is also verified through comparing X-axis positioning error tested by the laser interferometer and laser track in multi-station.

Modular spiral phase plate design for orbital angular momentum generation at millimetre wavelengths.

Proof of concept measurements of a modular spiral phase plate design able to generate millimetre wavelength beams with an azimuthal mode number of l = ±10 are presented. The plate is comprised of ten single modules that interlock to create the full plate assembly, allowing improved machining accuracy compared to standard techniques. Therefore, this design could be used in millimetre wavelength systems that require the manipulation of large OAM modes. The plate was manufactured from polypropylene (index of refraction n ≈ 1.5), and was measured at 100GHz. A three dimensional field scanner was used to measure three near field surfaces behind the plate. Intensity measurements showed the expected OAM intensity ring, and phase measurements showed ten phase dislocations, implying proper functionality.

Kinematic Analysis of Ultrasonic Vibration Assisted Micro End Grinding

A new processing method, ultrasonic vibration assisted micro end grinding (UAMEG), is proposed to improve micro grinding technology, aiming at machining of brittle-rigid material micro components. Trajectories of adjacent two abrasive were modeled and simulated to perform kinematic investigation and mechanism analysis. The critical condition of regular high-frequency abrasive-workpiece separation (AWS) is obtained and proved to be: the frequency coefficient (K) is a positive integer. The effect of K is investigated. Cutting force and temperature reducing, smooth chip evacuation, tool life prolongation and machining accuracy improvement can be achieved in UAMEG from the kinematics point of view.

Development of 2-axis hybrid positioning system for precision contouring on micro-milling operation

A 2-axis hybrid positioning system was developed for precision contouring on micro-milling operation. The system was developed to overcome the micro-positioning limitations of conventional linear stage positioning system on machine tools. A 2-axis flexure hinge type piezoelectric stage was added on a standard milling machine to obtain better machining results. The control method used for the hybrid system was active error compensation type, where errors from linear stages are cancelled by the piezoelectric stage motion. Positioning experiments showed an improvement of machine accuracy which was confirmed by the machining results. A micro-pillar was fabricated for the validation of long-range and high-precision contouring capability. The system was successfully implemented on micro-milling machining to achieve high-precision machining results.

Adaptive feedrate interpolation with multiconstraints for five-axis parametric toolpath

A good adaptive feedrate will be helpful for improving machining accuracy and efficiency, as well as avoiding the excess of the machine’s physical capabilities and feed fluctuations during machining. Therefore, it is highly desirable to consider the constraints of geometric error, cutting performance, and drive constraints in the feedrate scheduling of the parametric curve interpolator for five-axis computer numerical control machining. In this paper, a novel multiconstraints feedrate scheduling method is proposed for the parametric curve interpolator in five-axis machining. In the method, the feed optimization model is first built with the constraints of geometric error, the maximum feedrate and acceleration of cutter tip, and the maximum feedrate and acceleration of five-drive axes. Then, the relations between each constraint and the cutter tip feedrate are derived by means of near arc length parameterization. After that, a linear programming algorithm is applied to obtain the optimal feed profile on the sampling positions of the given tool path. Finally, illustrated examples are given to validate the feasibility and applicability of the proposed feedrate scheduling method. The comparison results show that the proposed method has an ability of the simultaneous guarantees of geometric accuracy, cutting performance, and drive characters of machine tools.

The Use of Response Surface Methodology to Optimize Parameter Adjustments in CNC Machine Tools

This paper mainly covers a research intended to improve the circular accuracy of CNC machine tools and the adjustment and analysis of the main controller parameters applied to improve accuracy. In this study, controller analysis software was used to detect the adjustment status of the servo parameters of the feed axis. According to the FANUC parameter manual, the parameter address, frequency, response measurements, and the one-fourth corner acceleration and deceleration measurements of the machine tools were adjusted. The experimental design (DOE) was adopted in this study for taking circular measurements and engaging in the planning and selection of important parameter data. The Minitab R15 software was adopted to predict the experimental data analysis, while the seminormal probability map, Plato, and analysis of variance (ANOVA) were adopted to determine the impacts of the significant parameter factors and the interactions among them. Additionally, based on the response surface map and contour plot, the optimal values were obtained. In addition, comparison and verification were conducted through the Taguchi method, regression analysis to improved machining accuracy and efficiency. The unadjusted error was 7.8 μm; through the regression analysis method, the error was 5.8 μm and through the Taguchi analysis method, the error was 6.4 μm.

Synthetic Analysis and Simulation of One-Side Processing Profile Error of Globoidal Cam

Aiming at globoidal cam one-side machining errors in addition to programming error, there exists combined effects of a number of the original errors, such as, machine motion error, tool error, fixture error and et al. On basis of the analysis of the principle of one-side processing, the theoretical calculation synthetic model of the one-side machining profile normal error is established based on the multi-body system error modeling theory and spatial mechanism conjugate meshing principle. And by applying Newtons iterative method and simulations in Matlab, the law of comprehensive influence of each original error on globoidal cam profile normal error is revealed. The simulation results verify the correctness of the theoretical calculation error synthetic model, and a scientific proof is provided for further improving machining accuracy of one-side machining of globoidal cam.

Characteristics of ultrasonic complex vibration for hole machining in brittle materials: Comparison of longitudinal and complex vibration sources

Ceramic materials have the advantage of abrasion resistance, heat resistance, and corrosion resistance compared with metal materials. The combination of ultrasonic vibration and polishing slurry has been shown to be an effective method for machining holes in brittle materials. However, conventional ultrasonic methods use only longitudinal vibration. Complex vibration sources with diagonal slits have been applied to ultrasonic motors and ultrasonic welding; in contrast, few studies have been conducted on ultrasonic machining using complex vibration and polishing slurry. Removal rates and machining accuracy are expected to be improved by using ultrasonic complex (longitudinal-torsional) vibration. Therefore, we have developed a new method using polishing slurry together with ultrasonic longitudinal and torsional vibration sources with diagonal slits for hole machining of brittle materials. Torsional vibration is considered to improve the processing of the hole side of ceramic materials such that the polishing slurry can circulate more easily. We assume improvement of removal rate and machining accuracy for that reason. In experiments, soda-lime glass is used as the processing material in ultrasonic complex vibration or ultrasonic longitudinal vibration, and machining time is measured to assess the hole machining characteristics.

Intelligent Control for a Robot Belt Grinding System

A robot belt grinding system provides promising prospects for relieving hand grinders from their noisy work environment, as well as for improving machining accuracy and product consistency. However, for a manufacturing system with a flexible grinder, controlling the robot to perform precise material removal from free-form surfaces is a challenge. In the belt grinding process, material removal is related to a variety of factors, such as workpiece shape, contact force, and robot velocity. Some factors of the grinding process, such as belt wear, are time-variant. To achieve the desired removal in the grinding process, an intelligent control method for the industrial robot is proposed in this paper. First, an adaptive grinding process model that can track discontinuous changes in working conditions is constructed to precisely predict material removal in accordance with in situ measurement data. With incorporated prior knowledge, the method considerably improves model accuracy, which worsens when new samples from an in situ measurement are insufficient or are unevenly distributed under new working conditions. After this, an online trajectory generation method for the robot control parameters is proposed. By calculating the optimal control parameters in real time, the control transition process is shortened and its negative effect on grinding quality is reduced. Finally, the preliminary grinding experiments validate the workability and effectiveness of the proposed control method.

Improving machining accuracy of electrochemical machining blade by optimization of cathode feeding directions

Electrochemical machining (ECM) is well-established in certain areas, such as the aerospace, defence, and medical industries for machining complex parts. ECM is an effective way to produce compression blades. However, with advances in the development of aero engines, the accuracy of blades becomes higher and their shapes have also become more complex. Thus, considerable attention has been devoted to improving the machining accuracy of blades by ECM. In blades machined by ECM, the angle between the cathode feeding directions and the normal of the anode profile greatly affects the accuracy of the ECM process, and it is determined by the angle combination of the anode installation and the cathodes feeding direction. It is very important to determine the best angle combinations that could minimise the angle between the cathode feeding directions and the normal of the anode profile. The present paper focuses on the optimization method of the angle combinations of the cathode feeding directions and anode installation. A theoretical model describing the optimization method of the cathode feeding directions and position of the anode was developed, and the experimental investigations were conducted in order to evaluate the rationality of the optimization method. The results show that with the optimized combination of the cathode feeding directions and position of the anode, the maximum angle between the cathodes feeding directions and the normal of the anode profile is minimised and the inter-electrode gap between the cathode and anode is more uniform. Thus, the machining accuracy could be clearly improved and the maximum errors of the convex part and concave part were only 0.054 and 0.047 mm, respectively.

Calibration and Optimization for Spindle-Tilting Type Five-Axis Machine Tools with Inclinable Head AB Based on Compensation of Rotation Axis Direction Error

To solve the five-axis machining accuracy problems that caused by assembly precision and direction error of rotary axes of inclinable head in high precision five axis machine tool. By selecting the five axis machine tool with inclinable head AB, GMC1230u, as the research object and analyzing the causes of the inclinable head error, the kinematics relationship of the rotation center position error and axis tilt error is established. By that, the direction vectors of each rotation axis and the position vector of rotation center are calculated based on the regression analysis of on-line measurement of the tool center point position and the calibration of five-axis RTCP function parameters is also accomplished. Finally, the compensation for inclinable head error in five-axis machine tools is fulfilled efficiently and remarkable improvement of RTCP machining accuracy is achieved.

How to Guarantee the Machining Accuracy of the Improved Numerical Control Machine

Advancing the machining accuracy of machine tool is one of aim of numerical control machine improving . There are many effecting machining accuracy factors of economical numerical control machine tool driven by a stepper motor . The way of improving machining accuracy and compensation method were put forward in this paper .

Finite Element Static Stiffness Analysis of the A/C Axes Bi-Rotary Milling Head

A/C axes bi-rotary milling head is an important functional component in gantry type five-axis CNC machine tool. The static characteristics affect directly the machining accuracy of machine tool. The paper investigates the static stiffness of A/C axes bi-rotary milling head in gantry type five-axis CNC machine tool XK2320-5X developed by a domestic company. Because this product developed depend on the experience of designers, the machining accuracy of A/C axes bi-rotary milling head of primitive XK2320-5X type cannot meet the accuracy requirement under actual working conditions. On the basis of structure design, the static stiffness analysis of the milling head under two working conditions is carried out using finite element method. The deformations of the main mechanical parts in the milling head are obtained. The analysis results indicate that the static stiffness in direction X is the weakest of the milling head and the milling head shell is the most important factor of deformation. The work done provides foundation for further structure design and machining accuracy improvement of A/C axes bi-rotary milling head.

4th Step Model Analysis for High Speed and High Precision Servo System

With the continuous improvement of computer numerical control (CNC) system processing speed and machining accuracy, traditional low step mathematic model can not express the high speed movement character any more. Therefore, an integrate model for servo system is established and simplified with reason, upon which a 4th step model which embodies high speed movement character of servo system is reasoned out. By the emulation analysis of numerical control system which uses normal PID controller, the phenomenon that responds curves deteriorated with the improvement of servo system speed when servo system controller works with the same PID parameter is detected. When primary PID theory is not suitable to high speed servo system, the 4th step model should be solved in order to obtain the best parameters in terms of high speed motion. A pole planning method is proposed to optimize important parameters for high speed 4th step model of servo system, because it is very difficult to get the accurate solutions of high step equation. Sequentially, the high speed machining servo system parameters which make respond characteristics without oscillation or overshoot are obtained. Simulation proves that this method is useful and successful.

In-situ Inspection Error Compensation for Machining Accuracy Improvement of Complex Components

In order to improve in-situ inspection accuracy of complex surface components, error factors influencing the inspection accuracy of the on-machine inspection system are discussed and error compensation methods are studied. The main errors of the inspection system are analyzed which contain geometric error of machine tools, pre-travel error of the inspection system and radius error of measuring probe. The geometric error model of a three-axis numerical control machine tool is established and each individual error value is identified and obtained through laser interferometer. For the pre-travel error of the inspection system, a radial basis function algorithm based prediction method is proposed and implemented. Based on the distribution of the pre-travel probe error obtained, an real-time compensation of the error can be performed during the actual inspection process. Considering the probe radius and its compensation of the contact-type measuring system4, a new algorithm is developed to improve the calculation accuracy of the normal vector which will affect the compensation accuracy. To verify the effectiveness of the proposed method, a complex part is exampled. Through the comparison of the in-situ inspection result with that of the CMM measurement, the proposed inspection system can achieve a great improvement of the inspection accuracy.

Study on Superposed Magnetic Field ECM of Square Hole

To improve the Electrochemical Machining accuracy and little stray corrosion of shaping hole, one scheme is adopted to carry on the technical experiment, which inserted the permanent-magnet into the core of cathode in the square hole separately. Compared with the experiment of Electrochemical Machining without magnetic field, the magnet around the core of cathode inlaid with the magnet is in favor of improving machining accuracy under the same processing parameter, and helpful to reduce the stray corrosion.