Actual Machining Process Research Articles

Real-time acquisition of machining task progress based on the power feature of workpiece machining

The real-time acquisition of machining task progress is one of the most important tasks of production management and is an essential aspect of manufacturing information. Targeted to the machining mode of mixed-category workpieces in job shops, a method for the acquisition of real-time machining task progress is proposed. The method is based on both the power feature of workpiece machining and the incremental learning Lagrangian support vector machine. First, the framework for this method is presented in a straightforward manner. Second, by analysing the characteristics of power change during the machining process, the power feature vector, which reflects the characteristics of workpiece machining, is designed for Lagrangian support vector machine. Then, based on the principle of incremental learning Lagrangian support vector machine, which can address the classification of mixed-category workpieces and the problem of an insufficient number of training samples for training the initial classifiers during the actual machining process, a detailed application of this method is constructed for workpiece classification and the acquisition of machining task progress. Finally, the effectiveness of this method is empirically tested by application to a case study.

A virus-evolutionary multi-objective intelligent tool path optimization methodology for 5-axis sculptured surface CNC machining

Sculptured surface machining is a material removal operation essentially adopted to manufacture complex products. Computing optimal tool paths with reference to ideally designed CAD models is indispensable to be able to suggest machining improvements in terms of high quality and productivity. The present paper proposes a new methodology based on a virus-evolutionary genetic algorithm for enhancing sculptured surface tool path planning through an automated selection of values for standard 5-axis end milling strategies' machining parameters to be decided upon in the context of a simulation-based; software-integrated, multi-objective optimization problem. The problem involves surface machining error as the first quality objective represented via the mean value of chordal deviations that tool path interpolation yields and effective radius of inclined tools that affects scallop. Machining time is the second quality objective entering the problem to assess productivity; whereas the number of cutter location points created for each tool path evaluation is also considered. Tool type, tool axis inclination angles as well as longitudinal and transversal steps are considered as the independent parameters in the case of 5-axis machining. Results obtained by conducting evaluation experiments and simulation tests accompanied by an actual machining process provided significant insight concerning the methodology's efficiency and ability of suggesting practically viable results.

High speed cutting of AZ31 magnesium alloy

Abstract Using LBR-370 numerical control lathe, high speed cutting was applied to AZ31 magnesium alloy. The influence of cutting parameters on microstructure, surface roughness and machining hardening were investigated by using the methods of single factor and orthogonal experiment. The results show that the cutting parameters have an important effect on microstructure, surface roughness and machine hardening. The depth of stress layer, roughness and hardening present a declining tendency with the increase of the cutting speed and also increase with the augment of the cutting depth and feed rate. Moreover, we established a prediction model of the roughness, which has an important guidance on actual machining process of magnesium alloy.

3D Simulation of the Ultra-Precision V-Groove Machine Tool

This paper develops a three dimensional (3D) simulation system with QT platform and OpenGL 3D library by adopting the driver and Aerotech’s linear motor as hardware platform and INtime and A3200 controller as the software platform. The system uses numerical control (NC) code syntax checking module to test the NC code syntax and applies 3D simulation module to display the actual machining process. The interference and collision detection module is built in this system to detect the problem during the actual processing. The system therefore contributes to avoiding the trial and tests for the ultra-precision machining process and improving the machining efficiency as well as reducing the loss of ultra-precision components of machine tool due to the collision.

Lightweight Design of the Welded Beam of Machining Center Based on Topology Optimization

From the perspective of statics, the deformation of welded beam under the action of gravity and cutting force was studied in the paper. During the actual machining process, vibration of welded beam and even the machine can be caused due to the change of cutting condition and interference from the outside. To avoid the natural frequency, and prevent the occurrence of resonance phenomena, welded beam modal was further analyzed; the first six natural frequencies and mode shapes of the beam were achieved. Statics and modal analysis are the basis of lightweight design of the welded beam based on topology optimization. The topology optimization model of maximum stiffness design and eigenvalue problem structural dynamics was established. Finite element model of beam and its components was established in hypermesh, and the optimization objective function, constraint function and boundary conditions were also set. Compared with the structure before optimization, the weight of the beam was reduced 10%, the lightweight design of the welded beam was achieved and the comprehensive performance of the beam was significantly improved.

Optimization of Control Gains in Numerical Control

It is frequently the case that the feed rate indicated in a numerical control (NC) program does not obtain in actual machining processes and the cutting tool does not path the points indicated in the NC. A reason underlying such problems is that control gains are not optimized, which causes issues with acceleration and deceleration in the control of machine tools. To address these problems, in this paper, we propose a method for the optimization of control gains using the MATLAB and Simulink software by considering the weight of the workpiece, the controlling distance, and the controlling speed. Simulations confirmed the effectiveness of our proposed optimization.

Experimental Study on the Dynamic Performance of a New High-Speed Spindle Supported by Water-Lubricated Hybrid Bearings

The dynamic performance of a new high-speed spindle supported by water-lubricated hybrid bearings is experimentally studied on a test rig. The present design allows the speed of the spindle up to 30,000 rpm, with a bearing internal diameter of 40 mm, which makes it possible to simulate many actual machining processes. Some experiments have been presented to study the mechanical and thermal behaviors of the spindle and its supporting hybrid bearings. The maximum temperature rise is less than 15°C with a speed of 30,000 rpm and a water supply pressure of 2.5 MPa. The spindle radial run-out of the rotational frequency is about 1 µm. Stability of the spindle system has been improved. The experimental results indicate that water-lubricated hybrid bearings are valuable choices to replace ceramic bearings and air bearings as support for spindles under high-speed, high-precision, and heavy-load machining conditions.

A method of measuring tool tip vibration in turning operations

The tool tip vibration measurement has a great significance for online surface topography prediction and active vibration control. Many measurement methods have been developed. However, most of these methods are difficult to be applied in actual machining process for the following problems: the chips and cutting fluid will cause damage to the sensor or distort its measurement results and the sensor must be installed again when replacing the cutting tool. In order to overcome the above problems, this paper proposes an indirect measurement method: the vibration of the tool tip is obtained from the vibration of the measurement point on the turret. The relationship between the tool tip vibration and the turret measurement point vibration is obtained through impact tests. The vibration of the measurement point on the turret is measured via an accelerometer, which is easy to install. The measurement point is so far away from the cutting area and chip evacuation zone that the accelerometer and its measurement results will not be affected by the chips and cutting fluid. The accuracy of the measurement method is checked by comparing the calculated tool tip vibration calculated from the vibration of the turret measurement point to the directly measured results, which is measured via an accelerometer installed below the tool tip. The comparison results show that the calculated tool tip vibration at main frequencies as well as low frequencies has a high accuracy. Moreover, the effectiveness of the measurement method is verified through machined surface profile.

Optimization of Control Gains in Numerical Control

It is frequently the case that the feed rate indicated in a numerical control (NC) program does not obtain in actual machining processes and the cutting tool does not path the points indicated in the NC. A reason underlying such problems is that control gains are not optimized, which causes issues with acceleration and deceleration in the control of machine tools. To address these problems, in this paper, we propose a method for the optimization of control gains using the MATLAB and Simulink software by considering the weight of the workpiece, the controlling distance, and the controlling speed. Simulations confirmed the effectiveness of our proposed optimization.

Development of Online Real-Time Collision Free Machining Using Simulation with CNC Openness

In recent years, 5-axis machine and multi-tasking machine have seen wide spread use. These tools can contribute to the enhancement of machining efficiency and precision. Conversely, their complex motion can cause numerous collision accidents between machines, tools, materials, and other parts. To prevent such accidents, it is now common to verify numerical control (NC) data using a machine motion simulator before performing the actual machining. However, the actual machining process is not always conducted in the expected manner. In some cases, the machining process is manually defined or altered, possibly causing a collision accident. In the present study, an online real-time collision free system was developed for the prevention of unexpected collisions. The effects of using this system are described in this article.

Thermal characteristics analysis and experimental study on the high-speed spindle system

In order to avoid the sudden failure of high-speed spindles in the actual machining process caused by an excessive temperature rise at the design stage, a three-dimensional (3D) finite element analysis (FEA) model was proposed to conduct transient thermal-structure interactive analysis of a high-speed spindle. The FEA model considered thermal contact resistance (TCR) at solid joints and bearing stiffness to improve the accuracy of traditional thermal models which ignored TCR. However, TCRs at solid joints and bearing stiffness were often ignored in traditional thermal models of high-speed spindles. This caused inaccuracies in traditional thermal models. The heat generation of the built-in motor was calculated based on the efficiency analysis method proposed by Bossmanns and Tu [1]. Based on the quasi-static mechanics analysis of rolling bearing, the heat generation and stiffness of bearings were calculated by applying the Newton-Raphson algorithm to improve the convergence. The Weierstrass-Mandelbrot (W-M) function, a function of fractal parameters, was used to characterize the rough surface morphology of bearing rings. The fractal parameters were identified by the structure function method and the measurement data of bearing ring’s surface morphology, and a contact mechanics model was developed to calculate the contact parameters used in the model of TCR. Then, a new predictive model for TCR was proposed based on M-T model. The above boundary conditions were applied to the FEA model, and thermal equilibrium experiments were conducted to validate the effectiveness of the model. The results showed that the FEA model was much more accurate than the traditional model which ignored TCRs at solid joints and bearing stiffness.

Influences of roller diameter error on contact stress for cylindrical roller bearing

The rollers of rolling bearings usually have certain geometrical error in actual machining process and, in the past, the mechanics analysis and computation of rolling bearing did not take into account the influences of this error in general. A cylindrical roller bearing is taken as the research object in this paper and a calculating model has been established by mechanical analysis, which can analyze the contact stress between rollers and raceways, as well as the axis orbit by taking into account the rollers’ error. Influences of rollers’ error on the contact stress of the rollers and raceways and the axis orbit have been studied by a concrete example numerically. The variation curves of maximum contact stress and axis orbit of the bearing were plotted and explained in detail.

Identification of kinematic errors of five-axis machine tool trunnion axis from finished test piece

Compared with the traditional non-cutting measurement, machining tests can more accurately reflect the kinematic errors of five-axis machine tools in the actual machining process for the users. However, measurement and calculation of the machining tests in the literature are quite difficult and time-consuming. A new method of the machining tests for the trunnion axis of five-axis machine tool is proposed. Firstly, a simple mathematical model of the cradle-type five-axis machine tool was established by optimizing the coordinate system settings based on robot kinematics. Then, the machining tests based on error-sensitive directions were proposed to identify the kinematic errors of the trunnion axis of cradle-type five-axis machine tool. By adopting the error-sensitive vectors in the matrix calculation, the functional relationship equations between the machining errors of the test piece in the error-sensitive directions and the kinematic errors of C-axis and A-axis of five-axis machine tool rotary table was established based on the model of the kinematic errors. According to our previous work, the kinematic errors of C-axis can be treated as the known quantities, and the kinematic errors of A-axis can be obtained from the equations. This method was tested in Mikron UCP600 vertical machining center. The machining errors in the error-sensitive directions can be obtained by CMM inspection from the finished test piece to identify the kinematic errors of five-axis machine tool trunnion axis. Experimental results demonstrated that the proposed method can reduce the complexity, cost, and the time consumed substantially, and has a wider applicability. This paper proposes a new method of the machining tests for the trunnion axis of five-axis machine tool.

The Research of Five-Axis NC High Efficient Machining Technology for UAV Integral Impeller

In this paper, a very detailed process analysis for UAV integral impeller was made. According to the specific processing requirements, the appropriate CNC machine, blank and cutting tools have been choosing. In the rough machining process, various machining strategies have been used for comparing and analyzing, finally a more efficient roughing method with the accurate machining parameters will be obtained. At the same time the machining method have been improved and the processing parameters also have been determined in the semi-finishing process. Through the simulation processing in VERICUT, the possibility of the existence of interference which is usually occurred in the actual processing can be ruled out and the program optimization will be finished in the meantime. Finally, using intelligent three-coordinate measuring machine the consequence will be verified and inspected in the actual machining process.

Hypoid Gear Three-Dimensional Modeling with Pro/E

For hypoid gear which processed by HFT (hypoid gear formate tilt) method, geometry parameters and machining parameters of hypoid gear were calculated by using Gleason card. According to the actual machining process and meshing principle, tooth surface equation was derived by coordinate transformation. Then the discrete coordinates points of tooth surface were obtained by using MATLAB tools and projection transformation principle, and data were saved in ibl format. At last the 3-demensional model of hypoid gear were established by importing the ibl format data in Pro/e.

A Method of Improving Accuracy of Lapping Main Cylinder of Brake-Pump

This paper analyzes the existing problems of acting lapping pressure in lapping internal holes of main cylinder of brake-pump with solid abrasives, proposes a new type of solid abrasives supporting method, namely, three supportting points acting lapping pressure method. The method improves pressure distribution between solid abrasives and the surface of the machined workpiece,which is favorable to increase cylindricity of machined hole.Through actual machining process, new method is demonstrated increasing cylindricity accuracy of machined holes of main cylinder significantly.

Optimization of Cutting Conditions of YG15 on Finish Cutting in WEDM Based on Taguchi Method

Wire electrical discharge machining (WEDM) is extensively used in the mold, instrument and manufacturing industries, and rough cutting operation in WEDM is treated as a challenging process because improvement of more than one machining performance measures viz. metal removal rate (MRR), roughness (Ra) are sought to obtain a precision work. In this paper, first of all, a set of Taguchi experiment (L18 21×34) is carried out based on the Taguchi method. Secondly, two groups of ANOM are completed to obtain the influence trends of each parameters on material removal rate (MRR) and roughness (Ra), respectively. Eventually, three groups of best process parameters combination are acquired to meet high material removal rate (MRR) and low roughness (Ra) simultaneously, it can provide guiding significance to actual machining process.

A study of the fabrication of v-groove structure in ultra-precision milling

V-groove structure is the key component for the alignment of fibres in the fibre array connector. This paper presents an investigation on the application of ultra-precision multi-axis machining technology in the fabrication of v-groove component. Ultra-precision raster milling (UPRM) is one of the multi-axis machining technologies which provide a new solution and more freedom to produce v-groove structure as compared with the precision grinding technology. In this paper, the cutting strategy is developed to schedule the material removal process, select cutting parameters and plan tool paths for v-groove machining in UPRM. Based on the study of the factors affecting machining efficiency, a novel model for machining time prediction is built for the fabrication of v-groove taking into consideration the acceleration and deceleration time of the ultra-precision machine. An integrated system is developed for the machining of v-groove structure in UPRM. Experiment is conducted to produce two different types of v-groove structures in UPRM. The experimental results show that the increase of feed rate decreases the surface quality and the core pitch tolerance of v-groove structure produced by raster milling process reaches to sub-micrometre. The developed model provides a precise machining time prediction for the actual machining process.

Research on Rework Strategies for Reconfigurable Manufacturing System Considering Mission Reliability

Rework strategies that involve different checking points as well as rework times can be applied into reconfigurable manufacturing system (RMS) with certain constraints, and effective rework strategy can significantly improve the mission reliability of manufacturing process. The mission reliability of process is a measurement of production ability of RMS, which serves as an integrated performance indicator of the production process under specified technical constraints, including time, cost and quality. To quantitatively characterize the mission reliability and basic reliability of RMS under different rework strategies, rework model of RMS was established based on the method of Logistic regression. Firstly, the functional relationship between capability and work load of manufacturing process was studied through statistically analyzing a large number of historical data obtained in actual machining processes. Secondly, the output, mission reliability and unit cost in different rework paths were calculated and taken as the decision variables based on different input quantities and the rework model mentioned above. Thirdly, optimal rework strategies for different input quantities were determined by calculating the weighted decision values and analyzing advantages and disadvantages of each rework strategy. At last, case application were demonstrated to prove the efficiency of the proposed method.

Study and Implementation of CNC Lathe Machining Simulation System

Virtual manufacturing technology is used to simulate the computer numerical control (CNC) lathe, virtual prototype of the CNC lathe is established. In the simulating process, the explain module and the check module of the CNC code are analyzed, the differential radial dynamic scaling technology is used to simulate the workpiece forming process, then the motion simulation of the virtual CNC lathe system is realized, and the system is drived by the CNC code. The machining process and workpiece forming process can be observed directly in the virtual environment, so the correctness of the CNC code can be checked in advance to avoid the interference, collisions or other problems in the actual lathe processing and reduce the the scrap rate of the workpiece and tool in the actual machining process.