制造技术与机床

Research on influence of cycloidal gear profile modification of robot RV reducer based on load carrying capacity and transmission efficiency optimization

WANG Chunguang, LUO Zhijiang, ZHANG Junfeng

2023, (11): 9-17. doi: 10.19287/j.mtmt.1005-2402.2023.11.001

[Abstract] FullText HTML PDF(2145KB)

Abstract:
In view of the current situation that the influence of cycloidal gear tooth profile modification is not considered in the conventional structure design of RV reducer, in order to realize the accurate dynamic structure design of RV reducer, a combined modification method of “negative movement distance-positive equidistance” or “positive movement distance-negative equidistance” of cycloidal gear profile of RV reducer is proposed based on the optimization of load carrying capacity and transmission efficiency. With the maximum load carrying capacity and maximum transmission efficiency as the optimization objectives, the key parameters which have a great influence on them are selected as the design variables, and the influence of tooth profile modification is considered to carry out the multi-objective optimization research on RV reducer. NSGA-Ⅱ algorithm is used to solve the problem, and the optimal parameter scheme of Pareto solution set is determined based on a multi-objective decision method combining TOPSIS and CRITIC. The results show that, compared with the original design, the influence of “negative movement distance-positive equidistance” or “positive movement distance-negative equidistance” modification on the meshing force is smoother than that “negative movement distance-negative equidistance” and “positive movement distance-positive equidistance” modification, and the tooth profile modification design is easier. After optimization, the transmission efficiency of cycloidal pin wheel is increased by 0.96%, the maximum engagement force is reduced by 35.98%, the transmission of the whole machine is more stable, and the dynamic performance of RV reducer is significantly improved.

Research on robot floating polishing actuator based on deep reinforcement learning algorithm

ZHANG Yiran, YANG Long, YUAN Bo, LI Changgeng

2023, (11): 18-22, 28. doi: 10.19287/j.mtmt.1005-2402.2023.11.002

[Abstract] FullText HTML PDF(1932KB)

Abstract:
To meet the constant force polishing needs of robots, this paper designs a floating polishing actuator and conducts research on polishing control algorithms. The structural design of the floating polishing actuator was carried out, and the force analysis and dynamic modeling of the floating polishing actuator system were carried out. On the basis of traditional PID control algorithms, the DDPG deep reinforcement learning algorithm is used to tune the PID control parameters. Conduct experimental verification of the constant force performance of the floating polishing actuator, and the experimental results show that the floating polishing actuator designed in this paper can meet the requirements of constant force control. By using the DDPG deep reinforcement learning algorithm to tune PID control parameters, the tedious parameter tuning steps are reduced, and it has better constant force control performance.

Performance optimization design and research of built-in V-type permanent magnet synchronous moto

CHEN Dehai, LI Zhiyuan, LAI Zhenggui, CHEN Zhiwen, LI Ming

2023, (11): 23-28. doi: 10.19287/j.mtmt.1005-2402.2023.11.003

[Abstract] FullText HTML PDF(1848KB)

Abstract:
In order to increase the output torque of the permanent magnet synchronous motor, weaken the torque ripple and cogging torque, and improve the operation stability of the motor, a new type of rotor magnetic barrier was designed, and a new type of permanent magnet synchronous motor with new rotor structure (NRS-PMSM) was proposed. On the basis of giving priority to the overall efficiency of the motor, the multi-objective sensitivity analysis method was used, select the key structural parameters that have a significant impact on the output torque, torque ripple, and cogging torque of the motor due to the rotor magnetic barrier, and use genetic algorithm to optimize the structural size parameters to obtain the optimal solution set. The electromagnetic performance of NRS-PMSM, including output torque, torque ripple, and cogging torque, was analyzed and calculated using finite element method. The simulation results showed that NRS-PMSM can increase output torque, weaken torque ripple, and cogging torque.

Control design of multi-station machine tool for aerospace special-shaped fastener processing

LI Xuexiao, LI Kuo, BI Xingrui

2023, (11): 29-33. doi: 10.19287/j.mtmt.1005-2402.2023.11.004

[Abstract] FullText HTML PDF(4572KB)

Abstract:
Aimed at the problems of process dispersion, low processing efficiency and precision,and poor consistency of finished products in the production of inner hole of special-shaped fasteners in the aerospace field,a multi-station special machine tool with ZMC406 motion controller as the control core is designed and developed.The machine tool is made up of mechanical structure,pneumatic system and electrical control system.The general requirements of the control system, each control system module, software and hardware design of the control system are described.Through the touch screen of the integrated industrial control machine with EtherCAT as the communication protocol to control the machining action of the machine tool and set the processing parameters, the centralized and automatic processing of the inner hole of the special fastener is realized.The actual processing and trial production results of the machine tool show that the production cycle of the machine tool is 8 pcs/min, and the pass rate is more than 99%. The machining precision and efficiency of the special-shaped fastener are improved, and the product consistency is good. Certain application and promotion value is included in the manufacturing field of aerospace special-shaped fastener.

Input-to-state stability analysis of linear motor motion systems

XU Yongming, CAO Xiangdong, LI Xu, LIU Haibo

2023, (11): 34-38. doi: 10.19287/j.mtmt.1005-2402.2023.11.005

[Abstract] FullText HTML PDF(921KB)

Abstract:
Linear motor is a typical direct drive system with high speed, high precision, and large thrust, which can be applied to high precision linear motor occasions in sophisticated equipment. However, the “zero transmission” property of linear motor motion system makes the disturbance factors including load variation and nonlinear friction force and so on, can act on the motion systems. It implies that disturbances can affect the performance and kinematic accuracy of systems. In this paper, the mode of linear motor motion systems with closed loop controllers is given and input-to-state stability analysis of the mode is considered. Based on the Lyapunov function method, an input-to-state stability criterion of linear motor motion systems can be obtained. The relationship between the controller gains and input-to-state stability is provided, which can provide auxiliary support for the selection of controller gains.

Simulation analysis and experimental research on laser quenching of H13 steel surface

MING Zhi, YAO Fangping, LI Jinhua

2023, (11): 39-46. doi: 10.19287/j.mtmt.1005-2402.2023.11.006

[Abstract] FullText HTML PDF(2333KB)

Abstract:
In order to study the influence of laser power on the surface modified layer of H13 steel after laser quenching and prepare the laser quenched modified layer under the optimal process parameters, the temperature evolution law of the quenching process of H13 steel was simulated by COMSOL, the depth of hardened layer was predicted, and the laser quenching experiment was carried out. The macroscopic morphology, microstructure evolution mechanism, elements and microhardness of H13 steel after laser quenching were analyzed by optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and microhardness tester. The results show that the depth of hardened layer predicted by simulation is basically consistent with the experimental results. The microstructure in the depth direction of the laser scanning area is refined obviously, and the hardness is gradient distribution. From the quenching surface to the inside, it is divided into phase transformation hardening zone, transition zone and matrix. The microstructure of phase transformation hardening zone evolves from original pearlite and ferrite to fine needle or lath martensite. When the laser process parameters are not selected properly, the phenomenon of overburning melting will be caused, which will affect the surface smoothness of the workpiece. When the laser power is 600 W and the scanning speed is 10 mm/s, the depth of the hardened layer can reach 0.41 mm, and the highest microhardness is 709.6 HV_0.3, which is about 3 times of the matrix.

Modeling and experimental study on ultrasonic milling force of Nickel-based superalloy

XIAO Qiang, FENG Zhenpeng, LIU Suoqiang

2023, (11): 47-52. doi: 10.19287/j.mtmt.1005-2402.2023.11.007

[Abstract] FullText HTML PDF(2231KB)

Abstract:
The work aim to study the influence of ultrasonic vibration on milling force and surface integrity of nickel base superalloy. According to the ultrasonic vibration characteristics, the ultrasonic vibration assisted milling force model is established and the key models of finite element analysis are introduced theoretically.In order to study the relationship between milling force and ultrasonic vibration amplitude and frequency, and single factor and multi factor orthogonal simulation cutting experiment are designed. The results show that when the ultrasonic vibration is applied to the milling cutter, the milling force decreases to a certain extent, and within a certain range, the ultrasonic current increases and the milling force decreases. In ordinary milling, the surface topography of the plough has clear scratch boundary, sharp surface protrusion and deep groove marks, and the adjacent cutting marks do not interfere with each other. After ultrasonic vibration, the surface morphology is more round and the transition of adjacent cutting marks is smooth.

Experimental study on laser cavitation micromodeling of 304 stainless steel

LIN Sihao, WANG Guan

2023, (11): 53-58. doi: 10.19287/j.mtmt.1005-2402.2023.11.008

[Abstract] FullText HTML PDF(3344KB)

Abstract:
This article conducted experimental research on laser cavitation micro modeling of 304 stainless steel, focusing on the influence of three main factors: laser focus position, laser energy, and laser action frequency on the surface micro modeling of 304 stainless steel. The morphology of the surface micro modeling of 304 stainless steel was observed and measured using a laser confocal microscope, and relevant theories were used to analyze the experimental phenomena and results in detail.

Analysis and modeling of dynamic positioning error of XY table of object - oriented CNC machine tool

YANG Hongtao, XUE Qingtao, LI Li, LIU Shiping

2023, (11): 59-66. doi: 10.19287/j.mtmt.1005-2402.2023.11.009

[Abstract] FullText HTML PDF(1805KB)

Abstract:
In order to study the effect of cutting force and speed on the dynamic positioning error of XY table of CNC machine tool, the dynamic error characteristics of XY table under the influence of cutting force were analyzed comprehensively. The accurate calculation model of dynamic positioning error components caused by error sources such as ball screw assembly, guide rail system, table surface and friction force is established, and the theoretical model of XY table dynamic positioning error is derived. According to the theoretical model, cutting force, speed and friction are the main sources of dynamic positioning error of XY table. The theoretical model of dynamic positioning error under cutting force is analyzed, calculated and simulated, and the validity of the theoretical model is verified. It is proved that the cutting force has an effect on the dynamic positioning error of the table, and the dynamic positioning error is minimum when the table moving speed is 4 mm/s under different cutting force, and the speed is defined as the best moving speed. The results of this study lay a good foundation for setting up the positioning error prediction and compensation model of NC machine tool to improve the machining accuracy.

An optimization method for numerical control small line fitting and speed planning

MIAO Rui, ZHANG Yonglin

2023, (11): 67-74. doi: 10.19287/j.mtmt.1005-2402.2023.11.010

[Abstract] FullText HTML PDF(2220KB)

Abstract:
In numerical control machining, arc fitting and spline fitting have curvature mutation, high computational complexity and machining speed fault. A fitting method using sine curve instead of arc curve was proposed to solve the problem. The three-dimensional four-leaf clover shape path set by ourselves was taken as the object for simulation analysis. The results show that both sinusoidal arc interpolation and arc interpolation have the advantages of high computational accuracy; the full length of sinusoidal arc interpolation's transition edge length is increased to 147.5%~218% of arc interpolation while the curvature is kept continuous. When limited by the same transition length, the Angle range of sinusoidal arc interpolation is increased by about 29%~46%. In the follow-up velocity planning, the backtracking method in velocity foresight is added, and the velocity fault and acceleration and acceleration overrun problems are solved.

Equivalent variable domain fuzzy PID control with non-origin symmetry in the theoretical domain

FAN Kangsheng, YANG Guangyong, WU Dafei, XU Tianqi

2023, (11): 75-81. doi: 10.19287/j.mtmt.1005-2402.2023.11.011

[Abstract] FullText HTML PDF(1952KB)

Abstract:
The traditional variable domain fuzzy PID controllers need to contraction-expansion the internal domain of the fuzzy controllers, which has high design complexity and is difficult to implement. A control strategy is proposed to solve this problem. This control strategy does not change the internal domain of the fuzzy controller, but changes the input and output of the fuzzy controller to achieve the equivalent variable domain effect. In addition, in view of the limitation that the current method of the domain contraction-expansion is only applicable to the origin symmetric domain, a method is proposed to determine the position of the variable in the non-origin symmetry domain after the domain contraction-expansion. An equivalent variable-domain fuzzy PID controller is designed for a system that uses a servo motor and a ball screw as the drive mechanism. The feasibility of the equivalent variable domain fuzzy PID controller is verified by Matlab/Simulink simulation comparison experiments. And the experiments demonstrated that the equivalent variable domain fuzzy PID controller has faster response speed, stronger anti-interference ability and better control performance than the traditional fuzzy PID controller, PID controller and traditional variable domain fuzzy PID controller.

Research on the full lifecycle maintenance system of industrial equipment based ontrusted identification

CHANG Saike, SUN Wenlei, LIU Zhiyuan, LU Cheng, BA Yinjun, ZHANG Kezhan

2023, (11): 82-89, 94. doi: 10.19287/j.mtmt.1005-2402.2023.11.012

[Abstract] FullText HTML PDF(4659KB)

Abstract:
After analyzing the maintenance process of industrial equipment throughout its entire lifecycle, the management of lifecycle maintenance information for industrial equipment is realized. This paper introduces a system for the full lifecycle maintenance of industrial equipment, rooted in trusted identification. Initially, using the AHP hierarchical analysis method, the research calculates the weight values for the entire process indicators of the full lifecycle maintenance system. Consequently, a platform for tracing the quality information of industrial equipment maintenance via industrial internet identification resolution gets established. Then,a mini-program for the industrial equipment maintenance information tracing system has been developed. In the end, validation occurs through the traceability of key component information of the beam-pumping unit, recording an average query time of 66.932 ms, meeting equipment maintenance needs. This research offers insights and references for the full lifecycle maintenance of industrial equipment.

The PLC program design of energy monitoring system for induction quenching machine

LEI Jun, CHEN Zhichu, LUO Min

2023, (11): 90-94. doi: 10.19287/j.mtmt.1005-2402.2023.11.013

[Abstract] FullText HTML PDF(7451KB)

Abstract:
In this paper, the energy monitoring system scheme for induction quenching machine based on PLC is proposed. The communication data format between the upper computer and the PLC are provided. The PLC related main program and interruption program are designed. Functions are fufilled, including the collection of DC voltage and current during induction heating, scale transformation, calculation of heating time and power, alarm setting, on/off control, etc. Through on-site running, the entire PLC control program can work well and get accurate result.

Structure optimization of workpiece tray of bearing steel ball polishing machine

YUAN Hao, WU Yanbin, FU Tianhao, SUN Yongjie, MENG Yudong

2023, (11): 95-100. doi: 10.19287/j.mtmt.1005-2402.2023.11.014

[Abstract] FullText HTML PDF(4281KB)

Abstract:
For the roundness of the whole ball batch after grinding the bearing steel ball billet can reach the ball grade required by industry, and the quality is consistent, optimize the tray mechanism to achieve continuous, uniform and complete loading of the ball flashing machine. The motion of the ball billet in the plate mechanism was analyzed, and two key factors affecting the uniformity and continuity of the ball billet were obtained: the inclination angle of the transporting materials plate and the ball baffle. The influence of various factors on the uniformity and continuity of ball loading was simulated by EDEM software, and the best combination parameters of ball loading effect were obtained: the slope of the loading plate was 8° and the slope of the baffle plate was 40°; the feeding mechanism is tested under this combination parameter, and it is found that there is no steel ball accumulation at the ball outlet. The uniform and complete effect of the plate mechanism loading material is good, and it can meet the operating requirement.

Research on flexible fixture of annular thin-walled parts based on clamping layout

HAN Jun, SHEN Weidong, ZHAO Zhenyao, DONG Bingyang, SHAO Shuai, PANG Nannan

2023, (11): 101-106. doi: 10.19287/j.mtmt.1005-2402.2023.11.015

[Abstract] FullText HTML PDF(2273KB)

Abstract:
Thin-walled parts are widely used in aerospace, electronic communication, automobile industry and other fields. Factors affecting parts machining deformation are clamping, cutting parameters, parts internal residual stress, can be selected by the appropriate cutting parameters and fixtures to reduce parts deformation. The fixture is one of the main factors affecting the deformation of thin-walled parts, but the design and manufacture lack of scientific theory guidance, which can not predict the performance. Aiming at a ring thin-wall part in the clamping due to the unreasonable clamping way caused the clamping deformation of the part is too large, a special fixture which can restrain the deformation of the part is developed. The binding force of the parts was calculated, and the influence of different clamping layout on the deformation of the parts was simulated by finite element software. The working principle and travel of special fixture are analyzed. The processing procedure was established and the actual processing was carried out. The research shows that the maximum deformation of parts is controlled within 0.05 mm by using special clamping layout, which is of great significance for improving the accuracy of parts.

Forward and reverse trajectory features fused GRU neural network for hysteresis characteristics modeling of joint

DANG Xuanju, ZHANG Yichen

2023, (11): 107-115. doi: 10.19287/j.mtmt.1005-2402.2023.11.016

[Abstract] FullText HTML PDF(3480KB)

Abstract:
To address the problem of high-precision modeling of the complex hysteresis characteristics exhibited by the flexible joints of low-cost and lightweight industrial robots without load torque sensors, the motor drive current is used to indirectly reflect the change of load torque, and the relationship between drive current and torsion angle is employed to describe the hysteresis characteristics of flexible joints, the forward and reverse trajectory features -based GRU neural network hysteresis model is proposed. The features specific to the forward and reverse trajectory features in the joint hysteresis characteristics are fused into the GRU neural network. The Kalman filter-based current increments are used to extract the features of the forward and reverse trajectory to describe the multi-valued characteristics exhibited by the forward and reverse trajectory features in the current-torsion angle hysteresis characteristics. The historical prediction results are taken as the new information input model to construct a dynamic GRU neural network hysteresis model with memory capability and nonlinear mapping ability. The experimental results verify that the proposed flexible joint hysteresis model has good prediction ability and high model accuracy.

Research on evaluation methods of cnc machine tool machining consistency

LI Dandan, WANG Junjian, ZHAO Qinzhi, BIAN Yachao, CUI Yingjie, HU Yu

2023, (11): 116-122. doi: 10.19287/j.mtmt.1005-2402.2023.11.017

[Abstract] FullText HTML PDF(924KB)

Abstract:
According to the connotation of machining consistency, a method is proposed for evaluating the machining consistency of CNC machine tools by utilizing the fluctuation degree of technical indicators in this paper. Firstly,the methods of absolute fluctuation method and relative fluctuation method are derived and calculated in detail. To address the inclusion of multiple indicators in actual machining accuracy, a multi-index evaluation model is established, and the dimensionless processing is conducted using the CRITIC valuation method. The objective weight of each indicator is determined by calculating the correlation coefficient matrix and information content; subsequently, the comprehensive consistency evaluation result is obtained by weighting and summing the volatility of each indicator. To verify the feasibility of the evaluation method, a consistency study is performed on CNC machine tools. Several key accuracy indicators for typical machining parts were selected, the fluctuation of individual indicators and the comprehensive consistency of multiple indicators were evaluated, and different applicable methods for different accuracy indicators were proposed. Finally, the evaluation rules for machining consistency of CNC machine tools are summarized, providing a unified quantitative technical means for evaluating the consistency level of the same type of machine tool products.

Experimental study on cutting force in high speed milling of 20CrMnTi hardened steel

ZHAO Haonan, JIN Chengzhe, ZHANG Wenrui

2023, (11): 123-128. doi: 10.19287/j.mtmt.1005-2402.2023.11.018

[Abstract] FullText HTML PDF(3119KB)

Abstract:
In order to study the influence of cutting parameters on the cutting force of high-speed milling of 20CrMnTi hardened steel, this paper adopts the orthogonal experimental method to conduct high-speed milling experiments. The collected raw data are processed, and the range analysis of the data results is conducted to obtain the impact of cutting parameters on the milling force and the optimal cutting parameters. The influence of cutting parameters on cutting force is obtained by using a single factor test method. The research results show that the milling depth is the primary factor affecting the cutting force F_x in the X direction during the milling process of hardened steel, with the feed per tooth having a relatively small impact, and the cutting speed having the smallest impact; For the Y direction cutting force F_y, the milling depth has the greatest impact, followed by the cutting speed, and the feed per tooth has the smallest impact. When the cutting speed increases from small to large, the cutting forces F_x and F_y decrease as the speed increases; When the feed rate per tooth increases from 0.05 mm/z to 0.13 mm/z, the cutting forces F_x and F_y show an upward trend; The cutting force F_y increases rapidly with the increase of the milling depth. Although the cutting force F_x also shows an upward trend, the growth rate is lower than F_y.

Prediction of main cutting force and optimization of process parameter in gear skiving

YANG Guowan, WEN Zijin, CHEN Yongpeng

2023, (11): 129-136. doi: 10.19287/j.mtmt.1005-2402.2023.11.019

[Abstract] FullText HTML PDF(1942KB)

Abstract:
Taking the gear skiving process as the object, the changing law of cutting force is studied, and predictive optimization of cutting forces, and a parameter control method for optimizing the process is proposed. Firstly, according to the kinematic theory of gear skiving, the solid models of workpiece and cutter are constructed, and the response data of cutting force in the process of single-tooth cutting are obtained through simulation experiments; secondly, the main cutting force prediction model is established based on multiple linear regression method, and the influence law of three process parameters on the main cutting force is analyzed: cutting speed, feed amount and axis intersection angle between tool and workpiece; finally, the main cutting force is used as Finally, the process parameters were optimized based on genetic algorithm with the main cutting force as the constraint condition and the highest machining efficiency as the target. The results show that the single and multiple process parameters with the greatest influence on the main cutting force are the feed and feed-axis intersection angle, respectively, and the error between the optimized predicted value and the simulation result is within a reasonable range, which verifies the validity of the prediction model. The research method and results provide an important reference for improving the machining quality and tool life of gear turning process.

Research on the formation rule of surface grinding affected layer of hardened GCr15 steel

GUO Jien

2023, (11): 137-140, 160. doi: 10.19287/j.mtmt.1005-2402.2023.11.020

[Abstract] FullText HTML PDF(2161KB)

Abstract:
The affected layer generated during the grinding process of hardened bearing steel has a direct impact on the performance of the parts, in order to improve the processing quality and efficiency of bearing parts, this paper conducted an experimental study on the formation law of affected layers in surface grinding hardened GCr15 bearing steel, the effects of grinding parameters on grinding force, grinding temperature, and affected layer thickness during the grinding process were studied, and the microstructure of the affected layer was observed. the variation law of microhardness of the affected layer was explored. Research has shown that the grinding force and grinding temperature increase with the increase of cutting depth, and the cooling method has a significant impact on the tangential grinding force; the heating rate during the grinding process is as high as 104 ℃/s, and the cooling rate is also up to 103 ℃/s; temperature is the main factor affecting the formation of the affected layer, and the thickness of the dark layer increases with increasing temperature, high temperature is a necessary condition for the formation of the white layer, after the grinding temperature exceeds the nominal phase transition temperature (745 ℃), the thickness of the white layer suddenly increases, and the ratio of the thickness of the dark layer to the white layer is greater than 4; the hardness of the white layer is higher than that of the substrate, and the surface hardness increases with increasing cutting depth, reaching a maximum hardness of 1057 HV, while the dark layer softens, with a minimum hardness of only 492 HV.

Research on the active control method of worm wheel grinding tooth surface texture

TIAN Xiaoqing, WU Zhonglei, TANG Jianping, YOU Tongfei, HAN Jiang, XIA Lian

2023, (11): 141-147. doi: 10.19287/j.mtmt.1005-2402.2023.11.021

[Abstract] FullText HTML PDF(2198KB)

Abstract:
Aiming at this phenomenon that gears produce regular and mutually parallel tooth surface textures along the tooth direction during grinding are more likely to cause large gear meshing noise, a tooth surface texture active regulation method based on multi-axis synchronous additional motion of a flexible electronic gearbox was proposed. Firstly, the mathematical models of tooth surface and grinding wheel surface and tooth surface texture angle were established. Secondly, the additional motion was applied to the motion axis to establish the relationship between tooth surface texture angle and additional motion polynomial coefficient.Then, the sensitivity matrix combined with least squares estimation was used to determine the additional motion polynomial coefficient of the motion axis to obtain the target texture angle. Finally, the gear grinding texture after additional motion of the motion axis was simulated and compared with the texture generated by conventional machining and low noise shifting technique. The simulation results show that the method of additional motion of the motion axis can obtain the tilted irregular tooth surface texture, which proves the feasibility of this method.

Effect of process parameters on the densities and cracking defects of SLM formed NiTi alloys

XU Chen, LI Zhiyong, ZHANG Wei, ZHENG Fu, CHAI Mingxia

2023, (11): 148-153. doi: 10.19287/j.mtmt.1005-2402.2023.11.022

[Abstract] FullText HTML PDF(1819KB)

Abstract:
In this paper, the effects of laser power and scanning speed on the density and crack defects of NiTi alloy samples in selective laser melting (SLM) were investigated by all factor tests, and the effects of process parameters on the forming quality were evaluated comprehensively by the energy mass density. The results show that with the increase of energy density, the induced density increases first and then decreases, and the surface of the sample changes from microscopic crack defect to no defect and then to macroscopic crack defect. When the physical mass density is between 75 J/mm³ and 95 J/mm³, the density is maintained above 99.7%. With the increase of laser power or the decrease of scanning speed, the density of the sample increases first and then decreases. By exploring the influence of laser power and scanning speed on the forming quality of the sample with the same physical mass density, it is found that when the laser power is greater than or equal to 270 W, scanning speed is greater than or equal to 900 mm/s, laser power is less than or equal to 90 W, scanning speed is less than or equal to 300 mm/s, the density of the sample is lower than 99.5%, and keyholes and micro-cracks appear. When the laser power is 180 W and the scanning speed is 600 mm/s, the density is higher than 99.5% and there are no obvious defects.

Multi-objective optimization of vertical five-axis machine tool ram based on CCD

WANG Songming, LIAO Yinghua, LI Lei, LIAO Xinyu, LI Kun

2023, (11): 154-160. doi: 10.19287/j.mtmt.1005-2402.2023.11.023

[Abstract] FullText HTML PDF(2228KB)

Abstract:
The ram has a significant influence on the machining accuracy of the vertical five-axis machine tool. In order to improve the static and dynamic characteristics of the ram, a multi-objective genetic algorithm optimization based on the central composite design is proposed in combination with the arrangement of the ram ribs. On the basis of the original ram structure, five different rib layout structures were designed. The parametric model was established in SolidWorks, and the total deformation, first-order natural frequency and mass were used as evaluation indexes. Statics and modal analysis were carried out in Workbench. The well structure was selected as the optimal scheme by comprehensive analysis of finite element simulation data. The sensitive size was obtained by sensitivity analysis and the Central Combination Design was carried out. The response value of the test point was obtained in Design-Expert. The response surface model was built and the multi-objective optimization of the well ram was carried out. The optimization results show that the maximum total deformation of the ram decreases by 23.25% and the first-order natural frequency increases by 10.89% when the total mass increases by 3.32%.

Geometric accuracy optimization of the main axis of vertical machining center

LI Lei, XU Yun, WANG Songming, ZHANG Jiahu, CHEN Ting

2023, (11): 161-165. doi: 10.19287/j.mtmt.1005-2402.2023.11.024

[Abstract] FullText HTML PDF(1619KB)

Abstract:
In order to improve the geometric accuracy of the spindle axis of vertical machining center, a structural compensation scheme was proposed, that is, the geometric error of the spindle axis after assembly was obtained by finite element analysis of the whole machine, and the perpendicularity error between the spindle axis and the X and Y axis motion and the parallelism error between the Z axis motion were reduced by adjusting the column predip Angle and the headstock inclusion ratio. Taking a certain type of vertical machining center as an example, sample points were selected by Latin hypercube sampling method, and the geometric accuracy response surface function model of spindle axis was constructed according to the sample point data, and multi-objective genetic algorithm was used for optimization. The results show that with the optimized design scheme, the perpendicularity error between X and Y axes and the parallelism error between Z axis axes are reduced to achieve the purpose of optimization.

Internal helical gear grinding error on-line monitoring and compensation

FU Wenhua, WANG Huiliang, JIANG Chuang

2023, (11): 166-171. doi: 10.19287/j.mtmt.1005-2402.2023.11.025

[Abstract] FullText HTML PDF(4078KB)

Abstract:
Taking the grinding of internal helical gears by CNC machine tools as the research object, the machining error and compensation problems in the grinding process are studied. Firstly, through the principle of homogeneous coordinate transformation, the homogeneous coordinate transformation matrix with errors between the workpiece and the tool is derived, and the geometric error model in the machining process is obtained. Secondly, the on-line monitoring of machine tool machining error is realized by using the built-in signal synchronous acquisition method, and the main error sources are compensated by the software compensation principle. Finally, through the gear detector, the tooth surface before and after error compensation is detected, and the tooth surface error after compensation is reduced. This experiment provides data theoretical support for improving the machining accuracy of machine tools.

Analysis of static and dynamic stiffness characteristics of two type of ball screw feed systems with different support modes

FENG Yuhai, SU Fang, ZHAO Cong, WANG Chensheng

2023, (11): 172-179. doi: 10.19287/j.mtmt.1005-2402.2023.11.026

[Abstract] FullText HTML PDF(1994KB)

Abstract:
Ball screw feed system is an important part of CNC machine tool, and its static/dynamic stiffness has an important effect on the machine tool performance and stability. In the working process, the static/dynamic stiffness of the ball screw feed system changes with the stroke. In order to study the static/dynamic stiffness characteristics of the ball screw feed system with different support modes, the lumped mass method was used to establish a dynamic model, and the static/dynamic stiffness variation of the system within the stroke was studied. The influence of the mass and placement of the workpiece on the static/dynamic stiffness of the system was also concerned. The re`sults show that in the negative stroke, the static/dynamic stiffness of the system with fixed supports at both ends decreases first and then increases with the increase of stroke; the static/dynamic stiffness of the system with one end fixed and one end floating support decreased continuously. Compared with the two, the dynamic stiffness of the system with two ends fixed support was more sensitive to the mass and placement of the workpiece, that is, the natural frequency changed relatively large. The results can be used to guide the optimal design of the ball screw feed system and the selection of the mass and placement of the workpiece during the working process.

Design and optimization of hydrostatic plain bearing for precision grinding machine motorized spindle

HAN Shaoyan, CAO Yang, JIA Qian, HAN Haiyan, LI Xiao

2023, (11): 180-185. doi: 10.19287/j.mtmt.1005-2402.2023.11.027

[Abstract] FullText HTML PDF(1093KB)

Abstract:
In order to improve the grinding accuracy, the design and optimization of hydrostatic bearing of motorized spindle were studied from the point of view of motorized spindle. The hydrostatic plain bearing is designed with four oil chamber structure and orifice throttling mode. The main design parameters include throttling ratio, radius clearance, return groove width and sealing surface width. The stiffness calculation model of the small-orifice throttling hydrostatic bearing was established, and the influences of throttling ratio, radius clearance, return groove width and sealing surface width on the support stiffness of the hydrostatic bearing were analyzed. Orthogonal experiment was used to optimize the design of bearing throttling ratio, radius clearance, return groove width and sealing surface width, and the primary and secondary order of influence of the above four parameters on bearing stiffness was obtained through range analysis, so as to obtain the optimal parameter combination. The results show that when the radius clearance is 0.04 mm, the orifice throttling ratio is 1.8, the width of the oil return groove is 12 mm, and the width of the oil sealing surface is 20 mm, the bearing oil film stiffness is the maximum. The research results of this paper can provide reference for improving the precision of high precision machining machine tools.

The influence of test bench support on the recognition accuracy of dynamic characteristic coefficient of sliding bearings

XU Fan, TANG Jie, CHEN Runlin, DU Chen, CUI Yahui, LIU Kai

2023, (11): 186-192. doi: 10.19287/j.mtmt.1005-2402.2023.11.028

[Abstract] FullText HTML PDF(1682KB)

Abstract:
There are many factors affecting the test accuracy of the dynamic characteristics of sliding bearings, among which the test bed parameters are very important and need to be considered. In this paper, the inverted dynamic characteristic test bench is taken as the research object. The influence of supporting parameters on the test accuracy of sliding bearing dynamic characteristic is analyzed. Based on the positive and negative problems of dynamics, the testing process of sliding bearing dynamic characteristics is simulated by simulation method, and the evaluation method of dynamic characteristics identification accuracy is proposed. Considering the different excitation frequency, the influence law of support stiffness and support damping of the test bench on the identification accuracy of the main stiffness and main damping of bearing is studied. The reasonable excitation frequency and support parameter range are determined according to the analysis results. The results show that the vibration frequency of the inverted bearing dynamic characteristic test bed is recommended to be between 30~280 Hz. The bearing stiffness should be greater than the stiffness of the bearing under test. The greater the bearing stiffness, the better the bearing dynamic characteristic identification accuracy. The value of support damping almost does not affect the recognition accuracy.

Download CenterMore

LinksMore

2023 No. 11

Journal DynamicsMore

Top ViewMore