NC Milling Machine Research Articles

Research on Reliability of Positioning Error Measurement for NC Milling Machine

Laser interferometer is the common tool to measure the positioning error of CNC machine, and its measurement process will be affected by external factors. Therefore, it is very important to ensure the error accuracy which measured by laser interferometer for compensating the error of CNC machine tools. The positioning error of MVC850B CNC milling machine was measured by Renishaw laser interferometer. Firstly, the positioning error of it was measured in standard and actual environmental parameters, and measured results were comparatively shown in factors of temperature, air pressure and humidity. Secondly, the influence degree that in three conditions of feeding speed, interval distance and processing time was analyzed by the errors of reverse clearance and screw pitch cumulative. Finally, with the statistics of positioning errors measured in a certain period of time, this paper analyzed the reliability of positioning errors measured by laser interferometer and analyzed the variation of milling machine motion axis errors. Meantime, the possible location of machine errors can be predicted, and the positioning accuracy of CNC milling machine would be promoted.

DEVELOPMENT OF A HIGH-SPEED MIRROR-LIKE FINISH POLISHING TECHNOLOGY FOR MINUTE PARTS BASED ON A LINEAR MOTOR

As high speed, high acceleration and stable drive on machine tools is constantly growing in demand, the use of linear motors in machine tools has increased. On the other hand, in order to achieve a high degree of quality, the need for mirror-like finish surfaces on industrial products has also considerably increased. This research explores the use of linear motors to develop a high-speed fine polishing process that achieves a mirror-like finish surface on small parts. The first stage of this process consisted in developing a polishing device, which was composed of a NC milling machine, a linear motor drive and a polishing head. Specifically, a polishing head attached to a linear motor drive was coupled with the spindle of a NC milling machine. A substitute for a small linear motor drive was obtained from a commercially available shaver, while the polishing head was made of propylene. The polishing head elaboration process, linear motor drive properties, lapping agent and the optimum polishing conditions were investigated in several experiments. The evaluation consisted in the high-speed polishing of minute areas on flat surfaces using the selected optimum conditions. It is concluded that, (1) the proposed system was able to achieve a mirror-like finish surface, (2) when compared to polishing with an ultrasonic motor, the machining time of the proposed system was reduced by half, (3) the proposed system was able to achieve a mirror-like finish on a 3 mm square sided area.

Investigate on milling force of cryogenic cooling processing aluminum honeycomb treated by ice fixation

Aerospace metal honeycomb materials with low stiffness had often the deformation, burr, collapse, and other defects in the mechanical processing. They were attributed to poor fixation method and inapposite cutting force. This paper presented the improvement of fixation way. The hexagonal aluminum honeycomb core material was treated by ice fixation, and the NC milling machine was used for a series of cryogenic machining. Considering the similar structure of fiber-reinforced composite materials, the milling force prediction model of ice fixation aluminum honeycomb was established, considering tool geometry parameters and cutting parameters. Meanwhile, the influence rule on milling force was deduced. The results show that compared with the conventional fixation milling method, the honeycomb processing effect is improved greatly. The machining parameters affect order on milling forces: the cutting depth is the most important, followed by the cutting width, then the spindle speed and the feed. Moreover, too small cutting depth (ap = 0.5 mm) will cause insufficient cutting force, while ap > 2 mm with higher force will reduce the processing quality of honeycomb. Simultaneously, the honeycomb orientation (θ) has a great influence on processing quality. Using the model, the predicted and measured error values of the feed and main cutting force are all small in θ 90°, respectively, while they all exhibit the smallest error in θ = 60°. This bigger error mainly is due to unstable cutting force with obtuse angle. In addition, the tool rake angle has little influence on cutting quality in θ 90°. Furthermore, the calculation model successfully conforms to the main deformation mechanism and influences parameters of the cutting force in the milling process, and it can accurately predict the cutting force in θ < 90° and guide the milling process.

MACHINE TOOL DISTORTION ESTIMATION DUE TO ENVIRONMENTAL THERMAL FLUCTUATIONS ― A FOCUS ON HEAT TRANSFER COEFFICIENT

Thermally induced errors have been approached in multiple ways due to the influence these have over the positional accuracy of a machine tool. Here, approaches regarding environmental thermal fluctuations surrounding a machine tool remain to be explored in detail. These fluctuations have been explored in terms of the heat transfer coefficient and thermal radiation of the machine shop walls, as well as in terms of seasonality and varying thermal gradients. This paper presents additional considerations regarding environmental temperature perturbations, as heat transfer coefficient fluctuations in the machine shop were thought to play a significant role in machine tool thermal deformation a broader term for these phenomena, environmental thermal fluctuations, was defined and evaluated. Specifically, an environmental thermal data survey of a machine shop was explored. This data was then applied to a NC milling machine and a CNC jig borer FEM analyses and compared to experimental data. FEM simulations were then used to demonstrate that convection regimes and heat transfer coefficient values at a machine shop have a significant influence over machining precision. Here, under maximum and minimum heat transfer coefficient values, the NC milling machine and CNC jig borer simulations results showed an error of cut difference up to 36.5 μm and 18.17 μm, respectively. In addition, as the importance of the heat transfer coefficient was highlighted, considerations regarding machine tool surface color were deemed relevant and were described.

A new damage diagnosis approach for NC machine tools based on hybrid Stationary subspace analysis

This paper focused on the damage diagnosis for NC machine tools and put forward a damage diagnosis method based on hybrid Stationary subspace analysis (SSA), for improving the accuracy and visibility of damage identification. First, the observed single sensor signal was reconstructed to multi-dimensional signals by the phase space reconstruction technique, as the inputs of SSA. SSA method was introduced to separate the reconstructed data into stationary components and non-stationary components without the need for independency and prior information of the origin signals. Subsequently, the selected non-stationary components were analysed for training LS-SVM (Least Squares Support Vector Machine) classifier model, in which several statistic parameters in the time and frequency domains were exacted as the sample of LS-SVM. An empirical analysis in NC milling machine tools is developed, and the result shows high accuracy of the proposed approach.

Modeling and experiment of surface error for large-aperture aspheric SiC mirror based on residual height and wheel wear

In the grinding process of large-aperture aspheric silicon carbide mirror, the wear of grinding wheel affects the surface accuracy seriously due to high hardness of silicon carbide and large diameter of aspheric mirror. Therefore, establishing surface error model of large-aperture aspheric silicon carbide mirror taking the wear of grinding wheel into account is of great significance to improve the processing quality and the imaging quality of aspheric mirror. The spiral grinding method is chosen to grind large-aperture aspheric SiC mirror in this work. The surface error of large-aperture aspheric silicon carbide mirror is established based on residual height and radial wear of grinding wheel using the grinding ratio as a bridge. The influence of grinding parameters on surface error is analyzed based on theoretical model. The results show that surface error increases with the increase of the rotation radius of workpiece and feed velocity of wheel, while it decreases with the increase of rotation velocity of workpiece and arc radius of wheel. The influence of the rotation velocity of workpiece and feed velocity of wheel is greater than that of the rotation radius of workpiece and arc radius of wheel. The regression equation of grinding ratio is established through grinding experiment, and the correlation coefficient is 0.9774 which verifies the reliability of the regression equation. Furthermore, the complete formula of surface error is acquired based on regression equation of grinding ratio. Finally, the grinding experiment of large-aperture aspheric silicon carbide mirror is carried out on the five-axis NC milling and grinding machine tool of HZ-091 type, and the error between measured value of grinding experiment and prediction value of theoretical model is less than 20%, which indicates that the theoretical model is reliable.

클라우드 기반 3D 프린팅 활용 생산 시스템 통합 연구

After the US government declared 3D printing technology a next-generation manufacturing technology, there have been many practical studies conducted to expand 3D printing technology to manufacturing technologies, called AMERICA MAKES. In particular, the Keck Center, located at the University of Texas at El Paso, has studied techniques for easily combing the 3D stacking process with space mobility and expanded these techniques to simultaneous staking techniques for multiple materials. Additionally, it developed convergence manufacturing techniques, such as direct inking techniques, in order to produce a module structure that combines electronic circuits and components, such as CUBESET. However, in these studies, it is impossible to develop a unified system using traditional independent through simple sequencing connections. This is because there are many problems in the integration between the stacking modeling of 3D printers and post-machining, such as thermal deformations, the precision accuracy of 3D printers, and independently driven coordinate problems among process systems. Therefore, in this paper, the integration method is suggested, which combines these 3D printers and subsequent machining process systems through an Internet-based cloud. Additionally, the sequential integrated system of a 3D printer, an NC milling machine, machine vision, and direct inking are realized.

The Multi-Station Clamp Device of the Long Truss Girder End Parts Processing

The Long girder end parts are one of the types structure in aerospace equipment, the complex structure parts, machining parts. Usually the parts be processed on the NC milling machine, through the analysis of processing craft, design a kind of quick change type, Multi-station clamp device, instead of processing the parts on the multi-axis nc machine tool; at the same time of guarantee machining accuracy, in order to improve the production efficiency and reduce the cost of production.

NC Machine Tools Fault Diagnosis Based on Kernel PCA andk-Nearest Neighbor Using Vibration Signals

This paper focuses on the fault diagnosis for NC machine tools and puts forward a fault diagnosis method based on kernel principal component analysis (KPCA) andk-nearest neighbor (kNN). A data-dependent KPCA based on covariance matrix of sample data is designed to overcome the subjectivity in parameter selection of kernel function and is used to transform original high-dimensional data into low-dimensional manifold feature space with the intrinsic dimensionality. ThekNN method is modified to adapt the fault diagnosis of tools that can determine thresholds of multifault classes and is applied to detect potential faults. An experimental analysis in NC milling machine tools is developed; the testing result shows that the proposed method is outperforming compared to the other two methods in tool fault diagnosis.

The Tool Setting Skills of Round Parts in NC Milling

This article focuses on the tool setting methods and techniques of disk parts and hole parts , in order to improve the precision and efficiency of the tool setting, so as to improve NC milling machining quality and machining efficiency of Nc milling.

Analysis on the NC Milling Machining Precision and the Error

the numerical control milling process design is on the basis of ordinary milling process design, combining with the characteristics of CNC milling machine, give full play to its advantages. CNC milling process design is the key to reasonable arrangement of process route, to coordinate the relationship between the CNC milling process and other process, determine the content and steps of NC milling process make the necessary preparations for programming. NC milling machining process analysis is related to the effectiveness and success or failure, is one of the important preparations before programming. This article will mainly for NC milling machining precision and machining error analysis and research.

Fast Discretization Algorithm of Densely Subdivided NURBS Curves

This paper develops a discretization algorithm for non-uniform rational B-spline (NURBS) curves. The algorithm is used for CAM software which is developed for HNC-3000 five-axis woodworking NC milling machine. Functions from the CAM software divide the NURBS into dense segments with equal arc length by vertex set p1, p2pn. The algorithm simultaneously considers chord error δ and curvature of the NURBS curve to maximize the arc length of the segments to get vertex set p'1, p'2 pm'. The algorithm can be described as f (p1, p2pn, δ) = (p1', p2'pm'). The complexity of the algorithm is O (n).

Machining of NURBS Surfaces Using Three-Axis NC Milling Machine

Three-axis NC milling machines must carefully consider the surface interpolation algorithm and the cutting tool compensation method to achieve precise NURBS surface machining results. This study thus analyzed NURBS surface functions and developed a tool compensation method to efficiently compensate for the radius and length offsets of the cutting tool used for NURBS surface machining. A NURBS surface machining test performed on a vertical machining center further validates the proposed approaches.

Design of Machine Tool Setting and Parameter Optimization

To solve the existing problems in the NC machining process, the optimization design of cutting parameters in NC milling machine with genetic algorithm. With the maximum production efficiency as the optimization objective, the spindle speed, feed speed, milling width, depth and other parameters as optimal variables, establishes the optimization mathematical model of machine tool. The optimization results show that: parameters optimization can significantly improve the processing efficiency, and bring economic benefits for enterprises

Research on Dynamics Simulation of CNC Milling Machine Based on Virtual Prototyping

In this paper, design and analysis of the main structure of milling machine has been done. In order to obtain the parameters of servo control system, the automatic control theory, system modeling, simulation, and virtual prototyping technology and so on are used in this paper. It has built 3D virtual prototype model and control systems of the CNC milling machine on ADAMS and MATLAB platform respectively ,as well as processed united simulation on ADAMS and MATLAB. Through the control of workbench's speed simulations, simulation results are obtained, by which the reasonability and validity have been testified. The method can be applied to the design and adjustment of NC milling machine.

Application of Accuracy Engraving Technique in the Complex Curved Surface Mould Processing

The advantages of the precise carving techniques in complex curved surface mould processing are studied. The small tools of carved machine can realize the small size processing which is unachievable for CNC and NC milling machine. The method using accuracy engraving machine to manufacture complex curved surface mould with small features is proposed, so the speed of mould processing is accelerated, the cost of new product development is decreased, the rapid manufacturing is realized and the traditional design method using only CNC and milling machine is improved. Finally, this method has been applied to the processing of a plastic mould and the application method is expounded.

Development of Parrametric Modeling for the Spindle of NC Milling Machine Based on ANSYS

With the development of manufacturing technology, modern CNC machine tools are greatly improved in machine processing range, dynamic performance, the processing precision and reliability with the help of the modern design technology, process intensification and the new function part. The research object is mainly based on a CNC milling machine spindle system, using ANSYS software for the spindle of machine tool modeling, and then puting the design parameters into the already built parameterized model. It is known that the spindle is in high speed operation of the deformation and vibration characteristics by analyzing, the some unreasonable parameters were improved using some assumptions, so that the spindle is more stable and reliable in high speed and super high speed running dynamic performance, thus improving the processing precision fastly. Through the model analysis, this step is simplified in manufacturing prototype, thereby simplifying the cost, shorten the design cycle.

Investigations on model-based simulation of tool wear with carbide tools in milling operation

This paper deals with tool wear in milling operation using carbide tools. The main purpose of this work is to define a model-based procedure for forecasting tool-wear progression during cutting operation by using machining simulation. Firstly, a multi-axis machining simulation algorithm is proposed based on DEXEL model and local area update method. NC milling machining process simulation software NCToolWearSim is realized by using Visual C++ and OpenGL. The developed process simulation software is used to simulate the cutting process. Secondly, tool-wear simulation algorithm in the machining process is presented with tool-wear model and machining simulation algorithm and is implemented into the machining simulation software NCToolWearSim in order to evaluate the tool wear and to update the tool geometry. The tool-wear value is estimated according to the established tool-wear model from experienced tool-wear data. Thus, tool-wear progression can be visualized in milling operation by using NCToolWearSim. Finally, experimental tests, performed milling integral wheel with carbide tools, were used to calibrate and validate the correctness of tool-wear simulation process based on the tool-wear model.

Grey Correlation Analysis-Based Comprehensive Dynamic Characteristics Evaluation of NC Machine Tool

The dynamic characteristics of the NC machine are the important technical indicators of NC machine performance, and the precision of existing machine's dynamic characteristics evaluation analysis that based on structural dynamics modeling and simulation is poor. For this problem, this paper presents NC machine dynamic characteristics evaluation methods based on Grey Correlation Analysis. This method, by measuring the vibration signal of feature points in NC machine and making 1/3 octave spectrum analysis for vibration signal, can obtain the characteristics data sequence of vibration signal. Through the grey correlation analysis method, calculate the relevancy between the characteristics data sequence of each vibration signal and that of ideal dynamic characteristics, and quantitatively evaluate the dynamic characteristics of machine tools according to the size of the grey correlation. Took three same type NC milling machines as study objects, designed the cutting vibration resistance experiments, used this paper's method for the evaluation analysis of the comprehensive dynamic characteristics of NC milling machine, and obtained the evaluation results which is in line with the actual dynamic characteristics of machine tools, and verified the evaluation method of comprehensive dynamic characteristics that proposed in this paper.

Application of Path Control Method with Minimum Desired Point Search to NC Milling Machines

Application of Path Control Method with Minimum Desired Point Search to NC Milling Machines