5-axis NC Research Articles

Machine-Learning-Based Model Parameter Identification for Cutting Force Estimation

Recently, there has been an increased demand for precise monitoring of the milling process using machine tools through a simple and cost-effective method. Accurate estimation of cutting forces is highly effective for this monitoring, and one approach is the modeling of tool spindles and tables of a machine tool. To model machine structures, well-known methods involving the use of impulse hammer response or structural analysis exist. However, the complex modeling is hard to achieve when using the impulse response. Moreover, it is often considerably difficult to achieve the modeling with structural analysis because the preparation of the accurate model and highly complicated calculations are required. Therefore, in this study, we propose a new monitoring method to identify model parameters of the machine structure and estimate cutting forces. First, a simplified assumed structure is prepared based on locations where sensors can be mounted. Next, measurement data during actual milling process are collected through the acceleration sensors mounted on the tool spindle and the dynamometer for the cutting force attached to the table. Subsequently, model parameters are identified from these data using machine learning. A 3-axis NC milling machine was used to evaluate the application range of the model parameters by changing cutting conditions, milling direction, cutting tools, and materials. The model parameters identified using the proposed method were equivalent to those using the impulse response. Furthermore, even in cases where the impulse response was difficult to identify, suitable model parameters were identified using machine learning. Finally, we confirmed that the proposed method can accurately achieve in-process monitoring of cutting forces in the X, Y, and Z directions.

Analysis of Milling Force and Optimization of Milling Trajectory for the NC Machining of Small Integral Impeller

In order to reduce the deformation of small integral impeller and improve the surface quality of blade in the process of NC machining, the influence of trajectory parameters on the milling force in the process of impeller NC finishing is studied and the orthogonal experiment with trajectory parameters as the main influencing factor is designed. In Deform 3D process simulation system, the physical dynamic simulation of NC milling force is carried out, the influence rules of the trajectory parameters on the milling forces in X, Y and Z directions are analysed, and then the range analysis method is used to optimize the simulation data to get the optimal combination of the trajectory parameters. Taking the actual production of a small integral impeller as an example, the trajectory parameters before and after optimization are respectively applied to 5-axis NC machining and the data of product inspection show that the optimized trajectory parameters not only improve the rigidity of the blade root and reduce the overall deviation of the blade, but also verify that the small milling force is obtained after the optimization of the trajectory parameters for the finish machining aiming at the surface quality and the optimization scheme of the trajectory parameters proposed in this paper is feasible.

Design and application of a biconjugate closed-end cylindrical single-cam pair

A biconjugate closed-end cylindrical single-cam pair refer to a cylindrical cam pair that control two roller followers. Based on the theory of space conjugated surface and vector revolving, by analyzing the conjugation relation between two rollers and cam surfaces of a biconjugate closed-end cylindrical single-cam pair, the parameter equations of the moving path of the axis of the left and right rollers that envelope the cam surface are established. Taking the minimum clearance between the roller and cam surfaces as the optimization objective, the parameter equation was optimized by adjusting the coefficient of the parameter equations of the left and right rollers without changing the structural size of the cam pair, and the optimized equation can be directly used as the tool path of cam machining. Finally, the cam was machined by a 5-axis NC machining center, and the optimized effect was verified by measuring the clearance between the work face of the cam and the rollers after the assembly of the cam, swing rods, and other parts. The obtained results showed that the clearance between the work face of cam and rollers were significantly reduced after optimization, indicating that the optimization method of cam is reasonable.

Screening and optimization method of defect points of G code in three axis NC machining

ABSTRACT G code is the input of the CNC system, and its quality affects the machining accuracy and efficiency. However, the G code generated by CAM has some defect points, which will seriously affect the processing quality and efficiency. To solve this problem, this paper proposes a method to screen and optimize the defect points of the G01 format G code of three-axis machining. First, a rough screening method based on the geometric characteristics of the trajectory is constructed. Second, a precise screening method through trend trajectories and box plot to screen out defect points is constructed. Finally, the NURBS curve is used to restore and discretize trajectories to obtain new points of G code. Two cases and experiments are used to verify the optimization effect. The experiments results show that after screening and optimization, the geometric characteristics of the two G codes, such as curvature and the difference between adjacent line segments, are obviously improved. The curves of setpoints speed and acceleration are smoother, the setpoints jerk is reduced, and the vibration is weakened. The processing time of the two G codes is shortened by 4.07% and 9.85% when the feed speed is 3000 mm/min and 2000 mm/min, respectively.

Nonlinear error control of five-axis machining singular region

Aiming at the singular problem of large nonlinear error caused by the extreme change of rotation in five axis NC machining of complex surface. An optimization algorithm of tool path in singular region is proposed. Taking a-c double turntable five axis linkage NC machine tool as an example, firstly, the mathematical models of tool local milling ability, machining bandwidth and tool axis inclination are established. Based on the two constraint models, the mechanism of singularity and the size of singular region are analyzed, and it is proposed to adjust the side angle with the tool contact as the rotation center to avoid the singular region. The modified tool axis vector that does not meet the accuracy is interpolated recursively according to the interpolation principle. This method solves the problem of large nonlinear error caused by the extreme rotation of the rotating axis in the singular region on the basis of meeting the requirement of no curvature interference. At the same time, the processing bandwidth before and after modification is guaranteed to remain unchanged. Simulation results show that the algorithm can effectively detect the singular region and improve the machining quality in the singular region.

Research on nxug10.0 impeller automatic programming and DMU50 five axis machining center

Taking nxug10.0 software as the platform and impeller as an example, this paper analyzes the structural characteristics and processing difficulties of impeller, reasonably formulates the NC processing scheme, and uses nxug10.0 impeller processing module to plan the tool path, generate the tool path file, and simulate the processing to verify the correctness of the tool path. The NC program of impeller is generated by special post processor and uploaded to DMU50 five axis NC machining center to complete the actual processing of impeller. Through the detection of impeller, the results show that the impeller fully meets the design and use requirements.

Designing and manufacturing of desktop type 5-axis NC precision grinder and its fundamental grinding characteristics

Designing and manufacturing of desktop type 5-axis NC precision grinder and its fundamental grinding characteristics

Generating Machining Directions for 5-axis NC Machining of Cycling Helmet’s Mold Components

Mold components for producing a cycling helmet are one of the most complex parts encountered in 5-axis NC machining. One important factor namely machining direction is used not only for checking collision, but also for reducing machine setup and shaping surface with low curvature variations. This paper focuses on how to minimize the total number of machining direction in 5-axis NC machining of cycling helmet’s mold components. In the proposed method, the machining direction candidates are generated using a regular placement method. V-maps are also used to select the machining direction through cascade filter of V-maps. Genetic algorithm is also used in order to identify the initial machining direction. Moreover, blockage solver and agglomeration method are applied in sequence to update the machining direction results. Additionally, to evaluate the performance of the proposed method, a CAD model for the cycling helmet mold components is created and used as a model of implementation. The computational result shows that the CAD model can be machined using the minimum number of machining directions. A 5-axis NC machine is also used to really produce the mold components.

Manufacturing and Performance Evaluation of Desktop Type 5-axis NC Precision Grinder

Manufacturing and Performance Evaluation of Desktop Type 5-axis NC Precision Grinder

Optimization method of tool axis vector based on kinematical characteristics of rotary feed axis for curved surface machining

Complex surface parts are widely used in the industrial applications, and 5-axis NC machining with ball-end cutter is the commonly adopted method for curved surface parts. Due to the additional rotary feed axis comparing with 3-axis NC machining, the tool orientation control is complex for curved surface machining. With the more complexity of curved surface parts, it is a known problem that the large incoherent movement of the rotary feed axis will easily appear in curved surface machining, which may even be beyond the kinematical performances of the rotary feed axis in machine tool, so as to affect the machining quality of curved surface parts. In order to overcome this issue, an optimization method of tool axis vector based on the kinematical characteristics of the rotary feed axis for curved surface machining is proposed. Firstly, the optimizing interval of the toolpath for tool axis vector is selected based on the relationship between the rotation angle of rotary feed axis and the accumulation arc length of toolpath. Then, the equalization method of tool axis vector based on the quaternion method is used to optimize the tool axis vector with the kinematical characteristics of rotary feed axis. Finally, the angular change curve of rotary feed axis with the optimized angular value and cumulative arc length is adjusted by the principle of least-squares fitting after the local optimization of tool axis vector. Simulation and experiment on test parts are carried out to verify the validity of the proposed method, and the achievements are significant to improve the processing quality of complex curved surface parts.

Study of the Effect of Tool Orientation on Surface Roughness in Five-Axis Milling of 300M Steel

The tool position deviation will affect the surface quality, especially for ultra high strength and high hardness materials, such as aircraft landing gear, engine impeller of high strength and high hardness of the hard machining aviation parts. The 300M steel is a kind of low alloy medium carbon martensitic reinforced super high strength steel, which is a common material for aircraft landing gear workpiece. The material has a strength of 1900-2100 MPa and hardness of 50 HRC after heat treatment. This material is a typical difficult-to-machine material and can produce large cutting resistance in cutting, resulting in larger tool deviation and vibration, and affects the surface quality of workpiece. Aiming at its complex processing technology, it is particularly important to study the relationship between the surface quality and the process parameters in multi axis milling. The tool orientation, which is represented by the lead angle and the tilt angle of the tool, is representative and influential process parameter. Therefore, experimental study is conducted to reveal the relationship. The surface roughness of the workpiece after multi axis NC machining is measured accurately. The effect of tool orientation on surface roughness is analysed based on the experiment data. The result shows that it is of great significance to optimize the tool orientation, which is represented by the lead angle and the tilt angle of the tool, to improve surface quality.

The Extremely Efficient New Model in Milling of Complicated Surfaces in 5-Axis Machining for 3-Dimensional Contact

Although most of the 5-axis NC milling machine tool producers declare that their machine poses the function of 5-axis simultaneous machining, and most of the commercialized CAD/CAM software was reported it can support the 5-axis simultaneous machining, but there are very few analyses about their machining efficiency. I hope that the reader would be interested to know how the new method is highly effective. The paper did a good job in motivating the problem mentioned here. The model of this paper is extremely efficient ant. This is a highly effective way of surface machining. There are also some areas that need improving. The mathematic presentation is not clear, but much more pages are needed, if the authors like to make it clearer. In the resent paper “The Extreme Efficiency of the New Model in Milling of Complicated Surfaces” we discussed the extreme efficiency of the new model in milling of complicated surfaces in 5-axis machining for 2-dimensional contact. While this time let’s discuss the same problem but much complicated one, 5-axis machining for 3-dimensional contact. As the research activities conducted by Dr. Liu Huran opened a new field and wide horizons in 5-axis machining of sculptured complicated surfaces using mathematical theories, and according to the interesting results presented in paper, Dr. Liu Huran is strongly encouraged if he can submit a similar work but this time with a new title that corresponds to the purpose [1].

Study on Tool Interference Checking for Complex Surface Machining

In order to solve the problem of complex and low efficiency of tool interference detection algorithm for five axis NC processing of complex surface, new tool interference detection algorithm is proposed based on space three dimensional coordinate system transform principle, the surface points was calculated in tool local coordinate system in the tool projection region to judge whether occurred interference, this method can detect local interference and global interference, it greatly reduce the calculation, and improve the detection efficiency and NC processing efficiency. The calculations of tool axis rotation and angular is given to avoid interference. The feasibility and effectiveness of the proposed method are verified by an example.

RESEARCH ON THE MANUFACTURING AND EVALUATION METHOD FOR A CURVE-FACE GEAR

Curve-face gear is a new type transmission device combining the common transmission characteristics of non-circular gears and face gears, which can transfer the motion and power between the intersecting shaft and staggered shaft. Given the complexity of the tooth generation of curve-face gear, 1) some machining methods, including three axis NC machining method , five-axis CNC machining method and the combined processing method of additive manufacturing and five-axis CNC machining, were introduced. 2) Based on space gear meshing theory and the machining principle, the machining models of curve-face gear were established.In order to verify the accuracy of the obtained gear, tooth surface measurement was applied, a new accuracy evaluation method for pitch deviations and tooth profile deviation of curve-face gear was processed. The results show that the tooth surface accuracy of the curve-face gear is high. The design of the curve-face gear, and its processing methods have been verified.

Analysis on Influence of Perpendicularity Error of Five Axis NC Machine Tool Error Modeling Accuracy and Complexity

In this paper, proved that the Perpendicularity Error in as a translation error element modeling and as the angle error element modeling on the error precision of the model and modeling of complex different influence degree. For multi axis machine tools, from the complexity of angle error modeling process, as modeling complexity is less than the translational error as the angle error the modeling, error of perpendicularity accumulate, distinguish the complexity is more obvious, mainly the additional angle error matrix in the modeling the matrix. Compensation from the point of view, this study shows that, for only need displacement compensation of the machine tool, the compensation effect of two kinds of the modeling results are the same, but for multi axis machine tool needs angle compensation, compensation matrix as the angle error the modeling accuracy obtained is higher than that of as translational displacement. Comprehensive analysis, this paper puts forward in multi axis machine tool error synthesis the modeling priority when the verticality error as a translation error the modeling.

The NC Machining Method and Application of Three Axial Impeller Based on Cimatron Software

With the development of China's manufacturing industry, the multi axis NC Machining Technology is rapidly popular. In the case of impeller shaft processing, this paper introduces the NC machining method and of three axial impeller based on Cimatron software, It is important practical significance and reference value to realize multi axis machining by the three axis CNC equipment.

Study on Performance of Integral Impeller Stiffness Based on Five-axis Machining System

Integrated stiffness characteristics of machine tool, cutters in various postures and distribution of impeller blade will affect the machining system in processing impeller with complex and thin-wall sculpture surface, and have further effect on machining accuracy of blade. Base on the theories of multi-body small deformation, the point of transfer matrix and the Jacobi matrix, the integrated stiffness model of machining system is established by space force ellipsoid in 3D particular to 5-axis NC machining center. The force ellipsoid method is used to analyze the effect of machine tool joints, cutter and joint of tool holder/cutter on the integrated stiffness field of machining system. And then, the integrated stiffness field distribution of impeller blade in cutting plane is analyzed. Finally, this theoretical model can be effectively optimized path of machining of integral impeller, which is tested by optimization experiments of working table posture.

Research on five axis NC Machining Simulation Based on VERICUT

The structure of five axis machine tool is complex and expensive, especially in the processing of complex and sophisticated parts. It is prone to produce the phenomenon of overcutting or undercutting between the machine parts and the knives or the machine tool , which will cause serious damage or even grievous scrap on the machine tool . With the help of VERICUT 7.0 Simulation of NC machine tool, you can modify and optimize the NC program code, shortening the real processing time required and improving the economic benefit of the company remarkably.

Brushless Servomotor’s Thermal Behavior Computer Assisted Evaluation for a Linear Motion NC Axis Experimental Stand

The paper presents works carried out by the authors in the field of NC axes’ structural and functional optimization. This paper includes the results obtained by using a MathCAD application (developed in the doctoral thesis of the second author) for the servomotor's thermal behavior computer assisted evaluation. The analyzed servomotor is included in the driving system of a linear motion NC axis experimental testing stand, (existing in MMS department from EMTS Faculty). The NC axis of the experimental stand integrates a FAGOR brushless servomotor, a 1:1 ratio belt drive intermediary transmission, a ball screw - bearings assembly (lead screw - ball nut - bearings) and a driven element guided through a ball rail system. The MathCAD application was developed in order to perform specific calculation for servomotor's thermal energy dissipation and maximum operating temperature evaluation, and allows to perform the assisted final check and optimum selection of the electrical driving servomotors based on these results. The paper presents, through some screenshots from running the MathCAD application, the computer assisted evaluation procedure and results of the brushless servomotor's thermal behavior analysis corresponding to analyzed NC axis (included in the experimental stand).

Active precision design for complex machine tools: methodology and case study

Machine tool design starts with the determination of performance specifications. Precision of the NC axes is an important aspect of machine tool design. Conventionally, the precision specification of machine tools is empirically determined, resulting in poor designs with insufficient or excessive precision. To provide a cost-effective precision specification for complex machine tools, such as gear cutting machines, an active precision design approach is proposed to generate the specification of the positioning repeatability of NC axes to meet the designated working precision requirements of the machine tools. The methodology consists of error analysis and precision design in four steps: (1) workpiece surface formation modeling in terms of the motion axes and layout of the machine tool, and the generating principle of workpiece features; (2) workpiece machining error modeling based on the workpiece surface formation model by considering kinematic errors of the NC axes of the machine tool; (3) workpiece machining precision modeling via the machining error model; and (4) precision allocation according to the required workpiece precision and the machining error model. The methodology is demonstrated and validated through a case study of precision design for a six-axis CNC spiral bevel gear milling machine.