制造技术与机床

Research on 3D printing of continuous carbon fiber composite materials based on ultrasonic control of infiltration

DONG Chuanhe, SUN Xiaoyu, LI Wangxin, JIA Ruihao, ZHAO Xin

2024, (1): 13-18, 25. doi: 10.19287/j.mtmt.1005-2402.2024.01.001

[Abstract] FullText HTML PDF(4033KB)

Abstract:
To solve the problem of continuous carbon fiber reinforced 3D printing composite (C-CFRP) parts, which have lots of defects such as excessive internal voids and stress concentration, an ultrasonic online controlled printing method based on fused deposition modeling technology was proposed in this paper. Firstly, the tensile properties of C-CFRP wire were studied under ultrasonic vibration, which the amplitude were 0 μm, 10 μm, 20 μm, 30 μm, 40 μm and 50 μm. And, the tensile and bending properties of C-CFRP specimens were discussed under ultrasonic vibration, which the amplitude were 0 μm and 20 μm. Secondly, the cross-sectional morphology of C-CFRP wire was observed through a super depth of field microscope, and the microstructure of the fracture surface of C-CFRP parts was observed using a scanning electron microscope. Finally, the mechanism of melt resin infiltration into the fiber by ultrasonic controlled was analyzed. The results indicate that the mechanical properties of C-CFRP wire were first increased and then decreased with the increase of ultrasonic amplitude value. And the maximum failure load value of C-CFRP wire was 121 N under the amplitude reach 20 μm, which was 16% higher than that in the absence of ultrasound. The tension properties and flexural properties of composite parts were improved by 11% and 23%, under the amplitude was 20 μm, compared to the absence of ultrasound. This article provides a reference for the development of high-performance C-CFRP 3D printing technology.

Numerical simulation study of temperature field for laser melting deposition of 30CrNi2MoVA

DING Xinyu, LI Wei, ZHANG Yuhang, CHEN Longqing, WANG Zongping, YIN Ming

2024, (1): 19-25. doi: 10.19287/j.mtmt.1005-2402.2024.01.002

[Abstract] FullText HTML PDF(2138KB)

Abstract:
The 30CrNi2MoVA steel is commonly utilized in the manufacturing of military gun barrels. However, the harsh working conditions that these barrels are exposed to cause wear, cracks, and other types of damage to the surfaces of the steel parts. As a result, the laser melting deposition technology (LMD) is frequently implemented to repair these surfaces. The quality and mechanical properties of the parts are significantly influenced by the thermal behavior that occurs during the LMD process, as it affects the material structure evolution. To investigate these effects, a finite element model of the temperature field of 30CrNi2MoVA steel during the LMD process was developed using ABAQUS. This model was utilized to examine the temperature distribution law during the LMD process, and the influence of processing parameters on temperature field.The thermal history and heat transfer characteristics of thin-walled parts during deposition were analyzed, and relevant experiments were designed to verify the applicability of the model.The study revealed that the LMD temperature field has a comet-shaped pattern, and for every 100 W increase in laser power, the maximum temperature of the molten pool increases by about 40 ℃, while the scanning speed has an opposite effect. Moreover, as the deposition layers increase, the thermal accumulation effect intensifies, resulting in an increase in the peak temperature of the molten pool and a decrease in cooling rate.

Effect of additive manufacturing SLM process on the shape quality of Ti6Al4V surface texture

CUI Yunwei, TIAN Bin, WANG Ziyan, FENG Qingyuan, RAN Zhiyong

2024, (1): 26-31. doi: 10.19287/j.mtmt.1005-2402.2024.01.003

[Abstract] FullText HTML PDF(2702KB)

Abstract:
The work aimed to explore the influence of additive manufacturing SLM process on the shape quality of actual shape size and morphology of Ti6Al4V surface texture prepared by “one-step” method. Ti6Al4V titanium alloy samples with different theorical diameters and depths of surface textures were prepared by 3D metal printer under SLM technology. The shape quality of pit texture of titanium alloys were observed and analyzed. The results showed that for the pit textures, there were some incomplete melting titanium alloy powder particles at the edge and the bottom, which increased with the increasing of the texture diameter and depth. With the increase of theorical texture depth, the actual diameter and average diameter error of D400 pit texture increased first and then decreased, with the minimum average diameter error of 2.08%. And the average diameter error of D800 pit texture showed a downward trend, with the minimum average diameter error of 2.84%. Meanwhile, with the increase of theorical texture depth, the average depth error of D400 pit texture gradually decreased, with the minimum average depth error of 2.23%. But the average shape error in depth for D800 pit texture was larger than that in diameter. As a result, it was proved that Ti6Al4V titanium alloy with surface pit texture prepared by one-step method of 3D printing was feasible. Furthermore, the shape quality of actual pit textures in the diameter direction was better than that in the depth direction.

Research on preheating temperature control for selective laser sintering based on modified predictive fractional-order PID

CUI Hao, GUO Yanling, XIAO Yaning, JIANG Chenglei, LI Jian, WANG Yangwei

2024, (1): 32-40. doi: 10.19287/j.mtmt.1005-2402.2024.01.004

[Abstract] FullText HTML PDF(3543KB)

Abstract:
In response to the problems of nonlinear uncertainty and time delay lag of the preheating temperature control in the selective laser sintering (SLS) process, a modified predictive fractional-order proportional-integral-differential (FOPID) algorithm for temperature control is proposed in this study. The designed controller firstly integrates the Smith predictor to eliminate the oscillations generated by the pure time lag chain, which is considered to improve the robustness of the controlled system. Then, a new novel sensitive parameter self-tuning method called EAOCBO is proposed to provide the optimal design of model parameters for the predictive FOPID controller. Aquila optimizer (AO) is a bionic intelligent algorithm, in order to overcome its shortcomings of the imbalance exploration and exploitation phase and ease to be trapped in the local optimum, the leader updating mechanism from COOT bird optimization, adaptive switching factor, and refracted opposition-based learning are introduced in the original algorithm. On the nine IEEE CEC2017 test functions, the optimization performance of EAOCBO is significantly enhanced compared to the other compared algorithms. In order to verify the effectiveness of the proposed EAOCBO-predictive FOPID controller, its dynamic response characteristics under unit step signal are simulated and analyzed by Matlab/Simulink software and further applied to the sintering machine to carry out the actual forming experiment. The results show that the proposed controller has lower regulation time and steady state error compared with other advanced FOPID controllers, which indicates its excellent response speed and control accuracy. Moreover, the EAOCBO-predictive FOPID controller can also precisely control the preheating temperature and improve the uniformity of the temperature field in practical applications, which in turn boosts the dimensional accuracy of the forming parts.

Study on the influence of power supply types on discharge craters in short electric arc-electrochemical hybrid machining

HU Guoyu, WANG Jiahao, ZHOU Jianping, ZHANG Shengsheng, FU Fei

2024, (1): 41-47. doi: 10.19287/j.mtmt.1005-2402.2024.01.005

[Abstract] FullText HTML PDF(2596KB)

Abstract:
The size of the discharge craters affects the consistency of the machined surface topography, and the height of the bump and the recast layer of the craters have important effects on the quality of the machined surface. In this paper, based on the short electric arc-electrochemical hybrid machining method, a single discharge experiment was carried out on titanium alloy TC4 under two common power supply types, DC and pulse, and the size and influence rule of single discharge craters in the short electric arc-electrochemical hybrid machining under two power supply types were analyzed. The variation of plasma discharge channel during arc discharge is studied by combining the waveform collected from single discharge crater experiment with the simulation model of arc discharge process. The results show that the difference of the size and influence law of DC and pulse discharge craters is related to the arc breaking mode, and the different arc breaking mode affects the plasma discharge channel. Dc arc tends to break through the movement of fluid medium and the change of electrode distance, while pulsed arc breaks through the change of voltage and electrode distance after pulse. These two arc breaking methods not only affect the size and morphology of the craters, but also affect the electrochemical corrosion effect after arc breaking.

Influence of the intensity of ultrasonic rolling on surface strengthening features of 25CrMo4 axle steel

WANG Chaoyang, HUANG Qiaomei, QIN Rongbin, DING Zhimin

2024, (1): 48-52. doi: 10.19287/j.mtmt.1005-2402.2024.01.006

[Abstract] FullText HTML PDF(1957KB)

Abstract:
In order to improve the service life of train axle. The work aims to research the surface morphology and roughness, surface hardness and its depth, surface residual stress and surface microstructure of the specimen after different treatment. The influence of rolling and ultrasonic rolling treatment with different loads on the surface strengthening characteristics of 25CrMo4 axle steel was explored. The results show that compared to grinding specimen, both rolling and ultrasonic rolling reinforcement improve the surface flatness of the specimen, the surface roughness of low-load ultrasonic rolling specimen was the lowest, reaching 0.2 μm; After high-load ultrasonic rolling, the plastic deformation layer obtained on the surface of the specimen is the deepest. The surface hardness of high-load ultrasonic rolling specimen is the largest, reaching 370 HV_0.1 and forming a hardened layer with a depth of about 150 μm. Both the surface of the rolling specimen and the ultrasonic rolling specimen produce high residual compressive stress. Conclusion: rolling and ultrasonic rolling treatment increase the surface hardness and its gradient, produce high residual compressive stress and reduce the surface roughness of 25CrMo4 axle steel, which will have a favorable effect on the improvement of fatigue performance. However, excessive load will increase the axle roughness, which has an adverse impact on the improvement of its fatigue performance.

Research on machine tool precision heightening device of ultrasonic roller extrusion actuator

LU Yibiao, WANG Xiaoqiang, TIAN Yingjian, LING Yuanfei, SHI Qingsong, ZHANG Xu

2024, (1): 53-58. doi: 10.19287/j.mtmt.1005-2402.2024.01.007

[Abstract] FullText HTML PDF(3483KB)

Abstract:
In order to solve the problem that the ultrasonic roller extrusion device is in ultrasonic machining, because the execution tool is in the vertical height direction of the machine tool, the extrusion head always cannot be in the same horizontal line with the central axis of the workpiece, resulting in long processing preparation and difficult height adjustment. A mechanical design method that can not only meet the height adjustment of ultrasonic roller extrusion actuator but also use a precision height adjustment device that is not limited by the machine tool. The worm gear mechanism is used to achieve height direction adjustment, and at the same time the wedge is load-bearing, which can withstand huge loads under the clamping of the tool holder, protect the internal parts, nuts and spring plates to stabilize the members, ensure that the device avoids movement during operation and increases stability. Finally, through test comparison, it is concluded that the height adjustment time of the rolling head after using the device is shortened to less than 30 s, the measured roughness of the workpiece is reduced by 7%, and the diameter deviation is reduced by 50%～67%. It can meet the ultrasonic machining under different working conditions, and achieve precise control of tool height adjustment, which greatly solves the needs of ultrasonic roller extrusion actuator height adjustment when working in different machine tools.

TC4 surface finishing turning 3D simulation and verification

DOU Weitao, SHI Lichen, KANG Kai, HAN Feiyan, LU Zhuqing, WANG Zhe

2024, (1): 59-66. doi: 10.19287/j.mtmt.1005-2402.2024.01.008

[Abstract] FullText HTML PDF(4736KB)

Abstract:
In order to analyze the effects of cutting speed, feed rate and depth of cut on chip morphology, cutting force and residual stress during finishing turning of titanium alloy wire by centerless lathe. The simulation software ABAQUS is used to establish a 3D finite element finishing turning model based on the centerless lathe, and the experimental design is compared with the simulation results. In the process of turning titanium alloy, high rotational speed will form shorter C-shaped chips, which is conducive to the separation and fracture of chips. Due to the increase of spindle speed, the friction between workpiece and tool decreases and the cutting force decreases with the increase of spindle speed. As the feed speed increases, the amount of feed per revolution increases, the workpiece removal increases, and as the feed speed increases the cutting force increases, and as the depth of cut increases, the cutting removal increases, so the cutting force cutting depth increases and increases. The process of turning titanium alloy needs to increase the speed to reduce the cutting force, which is conducive to the cutting process. At the same time, the feed rate is small, easy to generate C chips, which is conducive to the turning process.

Nonlinear dynamics model of cylindrical grinding and experimental verification

FENG Chao, ZHANG Jinfeng, XU Zhiling, WANG Baoyi

2024, (1): 67-72. doi: 10.19287/j.mtmt.1005-2402.2024.01.009

[Abstract] FullText HTML PDF(1563KB)

Abstract:
Grinding chatter was a strong vibration between grinding wheel and workpiece, which reduced the surface quality of workpiece and accelerated grinding wheel wear. The key to solve the problem was improving the stability of grinding system. Firstly, the nonlinear dynamic model was established according to the dynamic macroscopic structure of cylindrical grinding, and the nonlinear dynamic equation was deduced, Faddeev algorithm was used to linearize the nonlinear dynamic equation to calculate the system characteristic values, and stability prediction was carried out to obtain the factors which affecting the system stability. Then, taking feed speed and grinding wheel length as an example, Matlab was used to draw the parametric stability chart with different values of each factor, and the time domain response chart and eigenvalue location chart corresponding to each parameter at the turning point of state change were studied, it was founded that the grinding process changed from unstable to stable when the feed speed increased from 10 mm/min to 12 mm/min, and the grinding process changed from stable to unstable when the length of the grinding wheel increased from 12 mm to 14 mm; parametric stability chart, time domain response chart and eigenvalue location chart were compared, and the conclusions obtained were consistent, which proves the correctness of the model finally.

Design method of high speed toolholder with positioning cone surface containing sectionally drilled holes

CHEN Jianchao, ZHANG Ziming, RONG Jiran, DING Mingchao, WANG Jiachun, LI Kaiyan

2024, (1): 73-79. doi: 10.19287/j.mtmt.1005-2402.2024.01.010

[Abstract] FullText HTML PDF(2009KB)

Abstract:
According to the analysis results of the connection performance of the high-speed toolholder under different interference amounts and the distribution law of the cone surface contact stress at different speeds, a design method of the high-speed toolholder with cone surface containing sectionally drilled holes is proposed. The cone surface is divided into three equal sections according to the length of the generatrix on the cone, and a set of blind holes are evenly distributed circumferentially at each section. By adjusting the number and size of the blind holes, the cone surface of the toolholder reaches a certain flexibility. The influence of blind hole opening parameters on the contact stress and flexibility of the toolholder cone surface is elucidated, and the parameter optimization range is proposed. The design case of cone segmented opening based on HSK-E50 is given, and the limit speed and contact stress distribution are analyzed by FEM. The results show that compared with the prototype toolholder, the limit speed of the new toolholder is increased by about 10.79%, and the contact stress distribution of the cone surface is significantly uniform.

Experimental study on the roughness of milled 20CrMnTi steel machined surface

ZHOU Haochun, JIN Chengzhe, ZHANG Wenrui, LIU Wei

2024, (1): 80-84. doi: 10.19287/j.mtmt.1005-2402.2024.01.011

[Abstract] FullText HTML PDF(2413KB)

Abstract:
The effect of cutting parameters on the machined surface roughness during high-speed milling of 20CrMnTi hardened steel with CBN straight-shank flat-bottomed end mills was studied by orthogonal test method. The effect of the cutting parameters on the surface roughness was tested by analyzing extreme differences, and the main influencing factors were clarified. The law of the influence of cutting parameters on the surface roughness was determined using the one-factor test method. A model of the relationship between cutting parameters and surface roughness based on an exponential function was created. Error analysis between the surface roughness obtained from the predictive model and the test results shows that the fixed model can more accurately predict the surface roughness. The test results showed that: the effect of each factor in descending order is the milling depth, feed per tooth, cutting speed; surface roughness increases with increasing feed per tooth and milling depth, and decreases with increasing cutting speed.

Research on coordinated motion trajectory planning method of dual robots with different constraints

SU Hepeng, MIAO Hongbin, LI Mengqian, SHEN Guangpeng, YU Lang

2024, (1): 85-92. doi: 10.19287/j.mtmt.1005-2402.2024.01.012

[Abstract] FullText HTML PDF(2524KB)

Abstract:
With the widespread use of industrial robots in all walks of life, a single robot can no longer meet the requirements of large-scale workpiece handling, complex welding, and hole shaft assembly. In the research of dual robots, the most important problem is how to ensure that the motion between the two robots meets the time and space constraints, that is, the coordination of multiple movements of the two robots. In this paper, the cooperative motion under tight and loose constraints is analyzed by using the examples of cooperative handling and collaborative writing of two robotic arms, and the kinematic coordination relationship is analyzed, and the robot constraint relationship is studied through the workpiece or main body motion trajectory to construct a two-machine collaborative system. Stability verification is carried out in Matlab, and the proposed theory is verified for reliability.

Development and experimental study of bus digital module applied to machine tool processing

JING Juan, JIN Weifeng

2024, (1): 93-99. doi: 10.19287/j.mtmt.1005-2402.2024.01.013

[Abstract] FullText HTML PDF(1879KB)

Abstract:
In order to meet the requirements of real-time and stability in the process of signal acquisition and transmission in the machining of CNC, such as the hardware limit signal of axis movement, gas signal,water signal, tool measurement signal and others, and to establish communication with programmable controllers for data exchange to detect and control digital signal. This article designs and develops a digital module with the EtherCAT communication protocol which is based on Ethernet technology. The software and hardware design of the digital module and the execution process of the data interaction program is studied. Experiments are conducted in conjunction with the standard EtherCAT communication master station TwinCAT to demonstrate that the developed digital module can establish communication and transmit data with the master station normally, and maintain synchronization with the communication cycles in EtherCAT bus.A tool measurement scheme for machine tools was designed based on digital signal detection in machine tool processing. The results showed that the calculation of tool wear errprs based on the real-time response to measurement input signal by the digital module met the requirements of machine tool processing. The digital module has practical engineering value and achieves the research purpose.

Research progress of ultrasonic elliptical vibration cutting difficult-to-machine materials

SUN Yuhan, ZHANG Yijia, YANG Yanzhao, JIANG Zhenfeng, FU Xiuli

2024, (1): 100-107. doi: 10.19287/j.mtmt.1005-2402.2024.01.014

[Abstract] FullText HTML PDF(3400KB)

Abstract:
Ultrasonic elliptical vibration cutting has the cutting advantage of intermittent cutting characteristics, and has become a hot spot of research and application at home and abroad. It especially is used in high-performance manufacturing and processing fields of brittle materials, composite materials and other difficult-to-machine materials. At present, the mechanism of this technology and its adaptation process to difficult-to-machine materials are still immature, and need to be further explored and practiced. The unique advantages of ultrasonic elliptical vibration cutting in machining such as low cutting temperature, low cutting force, low damage, high dimensional accuracy and good surface integrity, are expounded in this paper based on analysis of the mechanism and characteristics of ultrasonic elliptical vibration cutting and the factors affecting the surface quality. The application in the fields of difficult-to-machine materials such as plastic materials, brittle materials and composite materials is summarized, providing a reference for the subsequent study of ultrasonic elliptical vibration cutting technology.

Workshop multi-object scheduling under fuzzy processing time and rewards-punishments grey target decision

HAN Wenying, ZHAO Mingjun, CHUN Lan, BA Teer

2024, (1): 108-114. doi: 10.19287/j.mtmt.1005-2402.2024.01.015

[Abstract] FullText HTML PDF(1169KB)

Abstract:
To achieve multi-objective optimization scheduling of flexible workshops under fuzzy processing time conditions, an optimization method based on neighborhood dynamic selection NSGA-II algorithm and a decision method based on weighted grey target theory were proposed. A multi-objective optimization scheduling model was established using fuzzy set theory for the workshop scheduling problem under fuzzy processing time conditions. In terms of scheduling optimization, the NSGA-II algorithm selection strategy was improved, and a multi-objective optimization method for workshop scheduling using neighborhood dynamic selection NSGA-II was constructed. In terms of decision-making, the reward and punishment operator was introduced into the grey target decision-making theory, and this method could determine the optimal result in the sense of information entropy. Through production case verification, compared with the standard NSGA-II algorithm, chaotic mapping NSGA-II algorithm, and double-layer genetic algorithm, the Pareto solution set of the neighborhood dynamic selection NSGA-II algorithm is in a dominant position, indicating that the optimization ability of this method is the strongest. The optimal scheduling scheme determined by the weighted grey target theory satisfies both time and logical constraints, which means it is a feasible scheduling scheme. The experimental results indicate that the optimization and decision-making methods proposed in this paper are feasible and they also have certain advantages.

Remote access method for FANUC CNC system PMC based on intranet penetration

YE Liangliang, LUO Min, FAN Junshan

2024, (1): 115-123. doi: 10.19287/j.mtmt.1005-2402.2024.01.016

[Abstract] FullText HTML PDF(9496KB)

Abstract:
To address the issue of remote access to FANUC CNC system PMC within an internal network, a method for remote access to FANUC CNC system PMC based on intranet penetration is proposed. This method utilizes four intranet penetration tools including “peanut shell” software, NATAPP, frp, and “peanut shell” hardware box to achieve the objective. The specific configuration methods for each tool in practical usage are elaborated in detail. A comparative analysis is conducted on the application scenarios, advantages, and disadvantages of these four methods. These approaches exhibit characteristics of low cost and high efficiency, providing guidance and reference for achieving remote access to FANUC CNC System PMC.

Structural optimization design and analysis of test analysis and optimization design of natural marble bed for precision vertical grinding machine

YU Ronghua

2024, (1): 124-129. doi: 10.19287/j.mtmt.1005-2402.2024.01.017

[Abstract] FullText HTML PDF(2790KB)

Abstract:
In order to solve the problem that the performance of cast iron bed is close to the material limit, the natural marble bed of a precision vertical grinding machine is studied in this paper. Firstly, the basic structure of precision vertical grinding machine is introduced, and the modal simulation of natural marble bed structure is carried out by finite element method. Then the vibration test of the bed is carried out to verify the correctness of the simulation model. Finally, the structure optimization design of natural marble bed is carried out based on ANSYS topology optimization module. The results show that the total deformation, the equivalent stress, the mass of natural marble bed are reduced by 23.8%, 15.07%, 1.01% respectively, which proves the feasibility and superiority of natural marble as a grinding machine bed material.

A method for evaluating the assembly process capability of machine tool feed mechanism based on Bootstrap-C_pu

HUI Yang, NIU Boya, SHI Jianmeng, MEI Xuesong

2024, (1): 130-135. doi: 10.19287/j.mtmt.1005-2402.2024.01.018

[Abstract] FullText HTML PDF(1345KB)

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The assembly process of the machine tool feed mechanism is the process of forming its assembly quality. Due to the influence of the 5M1E factor, the assembly process capability of the feed mechanism may be insufficient, which can lead to significant fluctuations in the assembly quality of the feed mechanism, and even unqualified products. Therefore, based on the theory of $ {C_{pu}} $ and Bootstrap, a method for evaluating the assembly process capability of the feed mechanism based on Bootstrap was constructed and applied in practice. The results showed that under 95% confidence, the assembly process capability of the feed mechanism of this batch of machine tools was sufficient, and the assembly quality fluctuation was small.

The influence of relative inclination of inner and outer rings on the life ofcylindrical roller bearings

WEI Yangang, DUAN Tongjiang, YAO Jinchi, LV Haiting

2024, (1): 136-142. doi: 10.19287/j.mtmt.1005-2402.2024.01.019

[Abstract] FullText HTML PDF(1580KB)

Abstract:
Using the Romax Designer engineering analysis software to model the overall gearbox of a large MW wind turbine, a large amount of analysis and calculation were conducted on the contact stress, modification effect, and bearing life of the cylindrical roller bearing of the gearbox output shaft under different relative inclinations of the inner and outer rings according to the classic rolling bearing theory and the basic idea of the "slicing method". The focus is on analyzing the ISO/TS 16281 lifespan of bearings, analyzing the impact of the inclination of the inner ring relative to the outer ring on the ISO/TS 16281 lifespan, and the impact on the lifespan of bearings under the optimal convex measurement of unmodified and logarithmic modification. The ISO 281 lifespan and ISO/TS 16281 lifespan are also compared. The research results indicate that regardless of whether the bearing is modified or not, the inclination of the inner ring relative to the outer ring has a significant impact on the ISO/TS 16281 lifespan of the bearing. Moreover, the larger the inclination, the shorter the service life of ISO/TS 16281, and the larger the corresponding optimal modification convex magnitude, the better the corresponding modification effect, and the greater the increase in the rated service life of ISO/TS 16281:2008. Under the same relative inclination of the inner and outer rings, the lifespan of ISO/TS 16281 differs significantly from that of ISO 281. The research results can provide reference for the optimization design of cylindrical roller bearings.

Research on liquid nitrogen cooling process for quenching 20CrMnMo alloy steel workpieces

YANG Hong, LI Zili, FAN Xiaobin, LI Shen, ZHANG Zhongqiang

2024, (1): 143-150. doi: 10.19287/j.mtmt.1005-2402.2024.01.020

[Abstract] FullText HTML PDF(2166KB)

Abstract:
The existing production line still relies on empirical process parameters as a guide for the cold assembly process of 20CrMnMo alloy steel workpieces after quenching, leading to a lack of systematic design methods for the cold assembly process equipment. It is urgently necessary to reveal the time-varying laws of workpiece temperature and deformation during assembly. This article conducts experimental studies on the low-temperature thermal properties of 20CrMnMo material after quenching. Based on this, numerical investigations were carried out on the temperature and deformation variations over time for several typical workpieces in the cold assembly process. The results showed that under the same operating conditions, the rates of workpiece temperature change and deformation increased with the size of the workpieces. The time-varying laws of workpiece temperature and deformation were confirmed through experiments, and the simulation results were found to be in good agreement with the experimental results. Based on the machining errors of the workpieces and the precision requirements of assembly, accurate prediction of assembly time for the cold assembly process can be achieved. The research findings will provide a theoretical basis for the study of material thermal properties and the precise setting of key parameters for the cold assembly process.

Mechanism of residual stress formation and controllable process in plane grinding GT35

FU Tianzhang, LI Yuan, CHEN Ming, YIN Luan, LI Lijie, YANG Jidong

2024, (1): 151-157. doi: 10.19287/j.mtmt.1005-2402.2024.01.021

[Abstract] FullText HTML PDF(2121KB)

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The quality problems of steel bonded cemented carbide GT35 parts, such as gyroscope motor bearing sleeve, such as surface cracking and dimensional deformation, often occur due to the improper control of micro-stress during machining, the production of gyroscope has brought no small trouble. In order to investigate the influence of surface grinding process parameters on surface residual stress and realize the controllable process scheme of low residual stress machining, the formation mechanism of GT35 residual stress in surface grinding was analyzed, the grinding experiments were carried out with KP-36 precision grinder, and the factors such as the grinding wheel linear speed, the depth of radial grinding, the workpiece feed speed and the type of grinding wheel bond were analyzed, the residual stress was measured by X-ray diffraction. The results of the experimental study show that, in the process parameters of GT35 steel-bonded cemented carbide surface grinding, the influence degree of radial grinding depth is 49%, the feed rate of workpiece is 25%, the type of binder is 16%, and the linear speed of grinding wheel is 10% The residual stress is minimum when the workpiece feed rate is 18 m/min, and the residual stress of resin bonded grinding wheel is 10% less than that of bronze bonded grinding wheel. GT35 material parts plane grinding residual stress controllable process plan is to use bronze bond diamond grinding wheel and choose 0.002 mm radial grinding depth, 18 m/min workpiece feed speed and 30 m/s grinding wheel linear speed.

Application of origin offset method in NC trimming of tooth profile of grinding roller

QIN Xiangguo, ZHANG Ziying, WU Zhiwei

2024, (1): 158-163. doi: 10.19287/j.mtmt.1005-2402.2024.01.022

[Abstract] FullText HTML PDF(1688KB)

Abstract:
As one of the main methods of gear machining, worm grinding wheel has the advantages of high processing efficiency, stable processing performance and high product quality, which is suitable for mass and specialized gear machining. The diamond grinding wheel is the main dressing tool of worm grinding wheel, and its manufacturing precision spacing determines the machining quality of the gear. Because the diamond grinding roller is made of the hardest material known to man, it is very difficult to trim the tooth profile. Due to the serious loss of dressing tools, optical guidance and manual intervention are mainly used in engineering to achieve machining. This method has low manufacturing accuracy and is difficult to adapt to today’s human needs for gear processing accuracy. For this reason, this paper analyzes the characteristics of tool loss when grinding roller tooth shape trimming, and puts forward a CNC trimming method based on origin offset, and verifies the feasibility of the method through engineering practice.

Thermodynamic simulation and surface morphology study on ultrasonic powder mixing EDM

DONG Yinghuai, ZHANG Shaojian, WANG Yan, NIU Yuebo, ZHOU Wen

2024, (1): 164-170. doi: 10.19287/j.mtmt.1005-2402.2024.01.023

[Abstract] FullText HTML PDF(3133KB)

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In order to study the effects of ultrasonic vibration and powder mixing on EDM, an ultrasonic powder mixing EDM heat transfer model was established based on heat transfer theory, combining ultrasonic and powder mixing characteristics. Based on the established heat transfer model, a transient thermodynamic simulation of the material removal process by ultrasonic powder mixing EDM was carried out, and the accuracy of the simulation results was verified through experiments. The simulation and experimental analysis of the four machining methods, namely, ordinary EDM, ultrasonic EDM, powder mixing EDM and ultrasonic powder mixing EDM, show that the efficiency of ultrasonic powder mixing EDM is 23%, higher than that of ordinary EDM. The addition of mixed powder and the application of ultrasound can reduce carbon build-up on the machined surface and improve surface quality. The addition of the powder mix can make the discharge craters more regular, resulting in a reduction in surface roughness. The average reduction in surface roughness is 8.9%, compared to normal EDM. The average reduction in surface roughness of ultrasonic powder blending EDM compared to normal EDM is 4.3%.

Surface defect detection of metal sheets based on optimized Faster R-CNN algorithm

KONG Siman, ZHOU Chenyang, WANG Jiahua, LI Lin, SUN Jianzhi

2024, (1): 171-178. doi: 10.19287/j.mtmt.1005-2402.2024.01.024

[Abstract] FullText HTML PDF(2016KB)

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Traditional image processing methods have low efficiency in detecting surface defects of various metal sheets during the production process, making it difficult to meet the needs of industrial production. In order to improve the accuracy of metal sheet surface defect detection, a metal sheet surface defect detection method based on optimized Faster R-CNN algorithm is proposed. Using the residual network ResNet50 as the backbone feature extraction network. Firstly, the Feature Pyramid Network and Deformable ConvNets v2 are fused to improve the detection ability for small objects and irregular defects. Then, RoI Align and K-means++ clustering algorithms are used to optimize the candidate boxes and achieve precise defect localization. Finally, the proposed model is applied to multiple experiments in the NEU-DET dataset. The experimental results shows that the mAP of the optimized Faster R-CNN algorithm on this dataset is 78.7%, which is 7.7% higher than the original network, and its detection performance is better than SSD, YOLOv5s, and YOLOv7 object detection algorithms.

Aluminum surface defect detection method based on improved YOLOv5s

XIE Kun, FANG Kai, CHEN Juan, YANG Zhaoling

2024, (1): 179-184. doi: 10.19287/j.mtmt.1005-2402.2024.01.025

[Abstract] FullText HTML PDF(1357KB)

Abstract:
In view of the current problems of low detection accuracy of aluminum surface defect detection algorithms in practical engineering applications and being not lightweight enough and difficult to deploy, an aluminum surface defect detection method based on improved YOLOv5s is proposed. This algorithm is based on the classic YOLOv5s model, and integrates the ShufflenNetV2-Block algorithm into the backbone network to reduce the computational complexity of the model; then adds an SE attention mechanism to focus attention on defect-related areas and better distinguish between categories. The difference between them improves classification performance and detection efficiency; finally, the loss function is optimized and SIoU (S-intersection over union) is used to replace CIoU to improve network positioning accuracy. The results show that the detection accuracy of pinhole and spot defects is improved by 8.3% and 8.4% respectively compared with the original YOLOv5, and the mAP value is increased by 6.4%, which improves the defect detection accuracy and reduces the size and memory of the model, making it more convenient. Mobile terminal deployment effectively improves the problem of missed detection during the manufacturing process.

Research on the measurement method of crankshaft coaxiality error based onthree-dimensional point cloud

DOU Yaping, ZHENG Shu, YANG Zhifei, REN Huiru, GU Xuhui, SUI Wentao

2024, (1): 185-190. doi: 10.19287/j.mtmt.1005-2402.2024.01.026

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Abstract:
Aiming at the requirement of rapid inspection of crankshaft journal coaxiality, a method of visual measurement of coaxiality error based on 3D point cloud is proposed. In this paper, a laser scanner is applied to obtain the 3D point cloud model of the part to be measured, and the point cloud slices of equally spaced journals are calculated. After that, the Pratt-RLTS method is proposed to obtain the center of each point cloud slice, and then the common reference axis is obtained by the least squares method according to the center of each slice, which finally realizes the measurement of the coaxiality error. The experimental results show that the circle fitting method in this paper is more accurate and stable than the least squares circle method, the least-inclusive circle method, and the RANSAC method, etc. The average value of the maximum absolute error compared with the results of the coordinate measuring machine (CMM) is no more than 4.8 μm, which can satisfy the practical needs of fast and efficient measurement of the crankshaft coaxiality error.

Study on vision measurement technology for holes on textured composite skin inpolluted environment

LI Bo, ZHANG Shaokun, GAO Xin, YU Zhiyong, LU Renhua

2024, (1): 191-196. doi: 10.19287/j.mtmt.1005-2402.2024.01.027

[Abstract] FullText HTML PDF(5498KB)

Abstract:
Reinforced carbon fiber composite skin is generally connected to aircraft skeleton parts through connection holes. The hole position is crucial for ensuring the joint strength. In order to achieve efficient online measurement of hole position on textured composite skin in polluted environment, this paper designs a machine vision device, and image algorithm is also proposed. Accurate extraction of hole edge is realized by rapid positioning of hole area and edge search around hole wall. The hole position is calculated based on image algorithm, laser beam calibration and spot coordinate. The online measurement experiment of hole on skin test piece is carried out. Compared with common image algorithm, the proposed image algorithm has better adaptability. The experiment result shows that measuring error of hole position is less than 0.05 mm, while the system can measure 12 holes per minute.

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2024 No. 1

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