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A cost-effective stereolithography for medium-scale components is developed to fabricate 3D components with high build speed and resolution from photo-curable resin. The developed SLA utilizes a focused light beam of wavelength range (300 nm–700 nm) coming from the DLP projector and passes through the objective lens and finally imposed on the platform containing a layer of photo-curable resin. After focusing the light beam on the liquid resin layer, the photo-polymerization reaction occurs and the liquid resin becomes solid. Thus, the 3D object is fabricated layer by layer curing of liquid resin. The photopolymer used in this experimentation is polyethylene glycol di-acrylate and Irgacure 784 as photo-initiator. The Creo 3.0 software is used for modelling of 3D objects. A special MATLAB code is developed for slicing of the 3D model and displaying the sliced image one by one through DLP projector. The Arduino microcontroller with stepper motor and ball screw is used to control the motion of Z-stage platform. The Creation workshop software is also used to control motion of the Z-stage and period to display the sliced images through DLP projector. The medium-scale 3D objects with rectangular, square, and circular cross-sections are obtained by curing the aforementioned photo-curable resin. It is observed that the 3D objects are best cured for two seconds curing time with 0.1 mm curing depth along Z-axis.

Purpose For ball screw feed system, a sudden start or stop has a great influence on the transmission stiffness, so the axial stiffness mutation of feed system will occur. The purpose of this paper is to study the influence of acceleration on the transmission stiffness and dynamic characteristics of the ball screw feed system. Design/methodology/approach Taking the ball screw feed system as a research object, on the basis of the Hertz contact theory and the mixed element method, axial stiffness model and dynamic model are established. And the system stability was analyzed by the time history diagram and Phase-plane portrait diagram. The feed system was analyzed theoretically and experimentally, the experimental results are in good agreement with the model results. Findings Lead screw lead angle, preload, load and start acceleration affected ball-screw pair, bearing and transmission stiffness. And the load, nut contact stiffness, bearing contact stiffness, preload have a large effect on the transmission stiffness. The results show that a certain acceleration value will make the axial stiffness abrupt change. Originality/value This research provides a useful theoretical support for ensuring a good dynamic for the ball screw feed system.

Ball screws are the indispensable machine tool components and, as such, influence the positional accuracy of machine tools. The accuracy stability of machine tools is affected by thermal deformation of ball screws resulting from the increase in temperature. Inspired by the distinctive artificial muscle heat behavior, a bio-inspired ball screw was proposed. The proposed ball screw was based on the inner-embedded carbon fiber-reinforced plastic (CFRP), which restrains the axial expansion through the thermal contraction of CFRP. Additionally, a thermal conductor was mounted between the screw shaft and CFRP to improve the thermal conduction condition. Furthermore, both the simulation analysis and comparative experiments were carried out to compare the bio-inspired ball screw with the standard one. Two working conditions were considered to evaluate the effectiveness of the novel design, primarily in terms of reducing thermal deformation. Both results show that the proposed approach is effective and can be applied to reduce the thermal deformation of ball screws.

In numerical control machines, the thermal elongation of the ball screw influences the position accuracy. Different rotational speeds lead to different temperature changes at different positions in a ball screw system. In this paper, a new method is proposed to calculate the temperature rise of different positions when the ball screw is in the thermal equilibrium state. The thermal transmission of ball screws is analyzed, and the heat generation and transfer coefficient are calculated based on the laws of thermodynamics. The function between the temperature rise and position is built by solving the thermal equilibrium differential equations. The thermal elongation is obtained after the temperature rise is calculated. In order to prove the validity of this model, a series of detection tests are conducted to obtain the temperature rise of a ball screw and the thermal elongation under different rotational speeds. The experimental results show that the realistic temperature rise and the thermal elongation agree well with the theoretical values.

The sliding-rolling mixed motion behavior degrades the ball screw’s precision at different levels. Based on the sliding-rolling mixed motion between ball and screw/nut raceway, the ball screw’s precision loss considering different given axial loading and rotational speed working conditions was investigated. Since creep and lubrication relate to sliding and rolling motion wear, the creep and lubrication characteristics are analyzed under different working conditions. Besides, the precision loss was calculated considering the sole influence of sliding behavior between ball and screw and compared with the results from other current models. Finally, research on precision loss owing to the sliding-rolling mixed motion behavior was realized under given working conditions, and suitable wear tests were carried out. The analytical results of precision loss are in good agreement with the experimental test conclusions, which is conducive to better predicting the law of precision loss in stable wear period.

The combination of sliding/rolling motion can influence the degree of precision degradation of ball screw. Precision degradation modeling and factors analysis can reveal the evolution law of ball screw precision. This paper presents a precision degradation model for factors analysis influencing precision due to mixed sliding-rolling motion. The precision loss model was verified through the comparison of theoretical models and experimental tests. The precision degradation due to rolling motion between the ball and raceway accounted for 29.09% of the screw precision loss due to sliding motion. Additionally, the total precision degradation due to rolling motion accounted for 21.03% of the total sliding precision loss of the screw and nut, and 17.38% of the overall ball screw precision loss under mixed sliding-rolling motion. In addition, the effects of operating conditions and structural parameters on precision loss were analyzed. The sensitivity coefficients of factors influencing were used to quantitatively describe impact degree on precision degradation.

In today's fast-moving and competitive world, the engineering applications are evaluated based on the precise and accurate results. The intense need for precision motion is achieved with the help of deflection of beams in compliant mechanism. A special class of mechanism is referred to as compliant mechanisms that are based on the rigidity and mobility of a component, which lead to greater precision without affecting its accuracy. Major failures of compliant mechanism are due to in plane and out of plane movement of compliant beams for the repetitive use. Life of compliant mechanism needs to improve for large deflection values. Motion is created by molecular deformation with bending of beams in elastic zone. Compliant mechanism are used in modern techniques such as micro-nano processing microscopy, biomedical scanner are existing mechanisms for precision scanning. Available biomedical scanner is using ball screw mechanism to achieve X directional and Y Directional scanning range. Ball screw mechanism provides 0.5 mm displacement in single stroke which takes so much times to stabilize the image. Compliant mechanism provides displacement of 0.1 mm in step. Biomedical scanner required X and Y Direction scanning range of 6 mm which we can achieve by using compliant mechanism. In present paper Experimental and Numerical analysis of compliant mechanism is done for linear motion which is used in biomedical scanner. Static structural analysis on Compliant mechanism is performed to get linear displacement values with steel, Titanium alloy and Aluminium alloy. Modal analysis of Compliant mechanism is performed to get natural frequency of system with steel, Titanium alloy and Aluminium alloy for better stability of mechanism we can operate Compliant system below that resonance frequency. By using Compliant mechanism we will get smooth range of motion over ball screw mechanism.

Modeling and modal analysis method based on receptance coupling are proposed for a vibration mode of a ball screw feed drive system, which cannot be determined by axial and torsional modal shape curves through a traditional method. In this study, the mathematical model for ball screw feed drive system is obtained by improved receptance coupling. The natural frequencies of different assembly states are calculated in the modeling process. The vibration modes of the feed drive system are determined by comparing the natural frequency distributions of different assembly states for a detailed analysis of the dynamic characteristics of the feed drive system. In the proposed method, a self-developed ball screw feed drive system is selected to study the influence of worktable position, worktable mass, and screw lead on the dynamic characteristics of the ball screw feed drive system. A change in the worktable position mainly affects the vibration of the ball screw itself. A change in the worktable mass mainly affects the coupling vibration between the ball screw and the rotor or bearing. The screw lead has an opposite influence on axial and torsional vibrations of the feed drive system, and the stability of the feed drive system improves with the screw lead. The validity of the proposed method is verified by the case study.

Among the errors in precision machining, thermal error has been recognized as the most significant error. The heat of the nut in the feed drive system plays an important role in the thermal error generated by the feed drive system. To better estimate and further understand the increase in temperature and thermal deformation of the ball screw during operation, a new correlation equation for the frictional torque of the nut is proposed and determined in this study for the calculation of the frictional torque of the nut and the heat generated by the nut at different feed velocities and nut temperatures. In this study, a set of devices for measuring the frictional torque of the nut under different feed velocities and different nut temperatures is designed and established. Various experimental conditions are designed to measure the frictional torque of the nut at different feed velocities and different nut temperatures to establish a correlation equation for the frictional torque of the nut. In addition, for further confirmation, the method for measuring the frictional torque of the nut used in this study is compared with the method using a handheld digital force gauge. The correlation equation for the frictional torque of the nut established in this study is based on the LuGre model and the formula of the frictional torque due to the viscosity of the lubricant of the bearing at different temperatures. The results show that the root-mean-square error between the frictional torque of the nut calculated by the correlation equation and that measured experimentally is 0.0301 N-m, indicating that the correlation equation for the frictional torque of the nut proposed in this study is accurate and feasible.

At present, one of the most pressing issues is the problem of improving electromechanical drive reliability, specifically, eliminating the possibility of jamming in the ball screw. The paper proposes an engineering solution designed to replace expensive imported ball screws. We analysed alternative designs intended to improve electromechanical drive reliability. We proposed and patented a ball screw design featuring a separator, in which the nut acts as a piston. The structure consists of a smooth cylindrical body and a slotted separator, its slots positioned along a helical line with a step equal to the thread lead. The body and the separator are coaxial and rigidly fixed together at the separator end faces so that the rolling elements remain in contact with the screw thread surfaces, the internal smooth cylindrical surface of the nut body and the surfaces of the separator slots. The ball screw design proposed, which features a nut with no internal threading, significantly simplifies the structure and its manufacturing technology. We built a model of an electromechanical drive equipped with a recirculating ball screw in order to determine static and dynamic properties of an electromechanical drive containing a ball screw featuring a separator. We compared the strength of the ball screw designs considered. As the ball screw featuring a separator is simpler and more reliable, the results of our analysis and the properties of an electromechanical drive equipped with the design proposed show that it is a promising solution to the import substitution problem concerning recirculating ball screws

Based on the structure analysis and the working principle of cylindrical giant magnetostricve actuator (CGMA) for ball screw preload, a thermal error suppression method using oil cooling system to control the temperature is proposed. Firstly, the heat transfer model and thermal circuit model of CGMA are established; next, the steady-state temperature model and the thermal expansion displacement model of cylindrical giant magnetostrictive material (CGMM) are obtained according to the heat-transfer rules and loop analysis method in circuit analysis; finally, the design parameters of the oil-cooling temperature control system are determined by combining thermal circuit model analysis with finite element simulation analysis. Such optimization method saves a lot of computation and provides a simple way for the design of oil cooling structure. In addition, a test platform for the CGMA is established. The experimental results indicate that the measured temperatures are in good agreement with the simulation results under forced oil cooling, and the relative error is less than 5%, which proves the rationality of the temperature control system. Moreover, the output accuracy and stability of the CGMA is significantly improved with proposed oil cooling method, which further confirms the thermal error suppression method is effective. As a result, this study provides a basis for the application of CGMA in the precise adjustment of double-nut ball screw preload.

Ball screw mechanisms (BSMs) are used as accuracy transmission components in a wide range of industries and are characterized by their high accuracy. More specifically, the positioning accuracy of BSM has a significant effect on the accuracy of machine tool. Based on the macro-micro multiscale method, an exponential prediction model for the BSM positioning accuracy was developed considering time-varying working conditions (load and rotational speed) and feed modes. Since the accuracy degradation is mainly caused by wear, a microscopic approach was proposed to describe the positioning accuracy retention and the microscopic wear process was investigated. The sliding contact of the asperities between the ball and raceway was analyzed, and the microscopic wear behavior of the asperities was determined. Considering the time-varying working conditions, the BSM positioning accuracy characteristics were obtained under the normal feed mode by conducting suitable tests. The exponential wear model used the wear index to describe the wear status based on the positioning accuracy measurement. The accuracy loss value and the prediction index of positioning accuracy were determined based on an exponential model, and the effective lifetime of the BSM was predicted. Finally, the exponential prediction model was used in negative/positive skew feed distribution, and the effective lifetime determined.

The accurate model of the load state for all balls under multidirectional load is very helpful for the design process of ball screws. The contact deformation model of the ball screw without consideration of the stress difference of all balls is inaccurate. In this paper, a novel contact load model of the ball screw is established by considering coupled axial, radial load to study the elastic deformation displacement and position accuracy. The deviation and variation of axial elastic deformation with the dimension errors of all balls are investigated to obtain the influence of load state on the precision sustainability of the ball screw. The position precision including travel deviation and variation by considering load distribution of all balls is studied under the different load conditions. In addition, a new working bench is designed to study the position precision of the ball screw. The experimental study is carried out to obtain the relationship between the position precision and the contact load state of all balls, which is a reference to compensate for the precision loss of the ball screw.

PurposeThis paper aims to provide thermal elastohydrodynamic lubrication (TEHL) contact model to study all balls’ lubrication performance of the ball screw when the multidirectional load is applied.Design/methodology/approachA new TEHL contact model combining the multidirectional load and the roughness surface texture is established to describe fatigue life of the ball screw. Meanwhile, the authors use the Reynolds equation to study the lubrication performance of the ball screw.FindingsWhen the multidirectional load is applied, contact load, slide-roll ratio and entrainment velocity of all balls have a periodic shape. The TEHL performance values at the ball-screw contact points including contact stress, shear stress, minimum film thickness and temperature rise are higher than that at the ball-nut contact points. The TEHL performance values increase with the increase of root mean square (RMS) except for the film thickness. In addition, the radial load of the ball screw has a significant effect on the fatigue life.Originality/valueThe results of the studies demonstrate the new TEHL contact model that provides the instructive significance to analyze the fatigue life of the ball screw under the multidirectional load.Peer reviewThe peer review history for this article is available at:https://publons.com/publon/10.1108/ILT-03-2020-0097/

Ball-Screw is a mechanical actuator that transforms the rotational motion of the motor into a linear motion of drive. The ball-screw is commonly used in industrial precision machines and due to this very reason it had been a common topic of research for many scholars, as precision in motion renders to precision in work directly. In this paper, some of the work done by different research scholars on different parametric aspects of ball screw had been discussed alongside optimization of ball screw diameter. The aspects which had been reviewed are elastic deformation & stiffness in ball screw, feed velocity and preloading, preload control in ball screw and various other aspects of preloading such as loss detection. Furthermore, the Finite elemental method had been applied to find the suitable diameter of the ball screw to render minimum deflection and stress value possible with the chosen material.

Purpose The study of vascular mechanics is important. The purpose of this paper is to present an apparatus to measure the biomechanical properties of blood vessels, which can be used for tensile test and fatigue test. Design/methodology/approach This equipment consists of a mechanical test platform, a hardware circuit based on FPGA and control software. The torque generated by stepper motor is converted to axial force by ball screw, and the vascular specimen is stretched axially. The tension is measured by a load cell, and the displacement is recorded by a grating displacement sensor. Findings According to the results of calibration experiment and stability experiment, the linearity error of the system is 0.251, the hysteresis error is 0.047, the repeatability error is 0.185, the comprehensive error is 0.315 and the standard deviation of the output is less than 0.01 N. A test of animal vascular mechanical properties was carried out, and the results are consistent with the theory. Originality/value This apparatus is designed to measure biomechanical properties of blood vessels, and the results of experiments indicate that it is stable and reliable. This work is valuable for studying vascular disease and testing artificial blood vessels.

As one of the most important part of the machine tool, thermal behaviors of the ball screw feed drive system has great effect on the positioning accuracy and machining accuracy. Finite element method is widely used for simulating the temperature of the ball screw under various working conditions. In this paper, in order to improve the simulation accuracy, the moving heat loads are considered in the finite element model, and the response surface methodology is proposed to optimize the boundary conditions. The correctness and effectiveness of the method are verified by experimental data. In addition, according to the temperature simulation results of the ball screw feed drive system, thermal equilibrium is defined and the factors which have influenced on it are analyzed.

Temperature in the cutting zone during dry machining has a significant effect on the tool life and surface integrity of the workpiece. This paper describes a comprehensive research on the cutting temperature in dry machining of ball screw under whirling milling by using infrared imaging. The effects of tool parameter and geometric parameter of workpiece together with the cutting parameters on the maximum and average temperatures in the cutting zone were analyzed in full detail. The influencing degree of these parameters on the maximum and average temperatures was affected by the value ranges of the parameters. In addition, the regression model and back propagation (BP) neural network model were proposed for predicting the maximum and average temperatures in the cutting zone. The verification of the predictive models showed that compared to the regression model, BP neural network model could predict the cutting temperature with high precision. The R 2 of BP neural network model for predicting the maximum and average cutting temperatures in the cutting zone was higher than 99.8%, and the mean relative error and root mean square error were less than 4% and 19%, respectively.

The ball screw system operates under the coupling condition of external loads, preloads, and thermal loads, and its thermo-mechanical characteristics significantly affect its dynamics performance. Therefore, a thermal-mechanical real-time dynamics model is necessary. In this work, the screw systems thermo-mechanical coupling mechanism was first analysed. Second, a new dynamic thermal network model for the screw system with moving heat excitation was proposed using the position of the moving nut obtained by FANUC Open CNC API Specifications (FOCAS), which can rapidly determine the transient temperature field. Based on this model, a new thermo-mechanical coupling real-time dynamics model of the screw system was established. The influence of temperature on dynamics characteristics was analysed using the dynamics model, and the results showed that the system preload caused by thermal elongation of the screw decreases with an increase in temperature. The system preload caused by the thermal deformation of the bearing increases with an increase in temperature. The total preload of the system depends on the interaction between the thermal deformation of the screw and the axial thermal deformation of the bearing. Additionally, the system stiffness and natural frequency variation relative to the increase in temperature and position of the carriage were obtained. Thermo-mechanical dynamics performance experiments of the feed system were carried out to validate the effectiveness of the proposed model.

Structural health monitoring (SHM) of the ball screw of machine tools relies on the repeated observation of the damage-sensitive features. The natural frequency is a characteristic inherent to the structure that is more robust than other signal features as a SHM index. However, a major problem is that regular changes in the operating conditions, such as the feed speeds, the worktable positions and other uncertain complex boundary conditions, also affect the natural frequencies, and these factors may mask the subtle variations induced by structural damage. Therefore, it is necessary to adopt an effective method to eliminate those effects to avoid false alarms during structural damage monitoring. In this article, Bayesian ridge regression modelling methods are developed to eliminate the effects of the worktable different positions and feed speeds on the natural frequencies. The proposed method can model the natural frequencies that are simultaneously affected by two dimensional operational factors and provide a rigorous quantitative assessment of the uncertainties associated with the complex boundary conditions of the ball screw drive system and the inevitable estimation errors. First, the different worktable positions and feed speeds were tested on the experimental bench to verify the proposed method. Then, two novel criteria were used as damage warning signals, which can reduce false alarm. Finally, this method was applied to monitor the wear of a ball screw of a CNC machining centre in an automobile factory. The validity of the method was provend using actual monitoring results.

The feed system of CNC machine tool has the characteristics of multiple heat sources and strong time-varying heat generation rate of each heat source. However, previous studies have paid little attention to the time-varying heat generation rate of each heat source, so it is difficult to accurately predict the temperature rise and thermal error of the lead screw. In this paper, Monte Carlo (MC) simulation-integrated FEM method was used to capture the heat generation rate of each heat source in the feed system. Consequently, relationship of the ratio of each heat source to the total heat generation rate of the system with the running time was obtained. Then, based on heat ratios of the heat sources, the torque current of the servo motor in the feed system was proposed to calculate the heat generation rate of each heat source. Finally, based on the finite difference method of one-dimensional heat conduction equation, numerical prediction model for thermal error of the lead screw was put forward. Finally, the accuracy and validity of the calculation model were verified by comparing with the experimental results.

The thermal characteristic of the ball screw feed drive system has great influence on machining accuracy as its thermal deformation would induce the positioning deviation. In this paper, finite difference method was applied to simulate the temperature distribution and thermal growth of the ball screw feed drive system under various working conditions. When simulating, the nut was considered a moving heat source, and the boundary conditions were optimized based on response surface methodology. By comparing the simulation results with the testing data, it was verified that the accuracy of the simulation could be improved by using the proposed method.

Die Zustandsüberwachung von Anlagen, Maschinen und deren Bauteilen ist eine zentrale Thematik von Industrie 4.0. Unvorhergesehene Ausfälle von Werkzeugmaschinen sind häufig auf den Verschleiß und das daraus resultierende Versagen von Kugelgewindetrieben zurückzuführen. Aufgabe dieser Arbeit ist die frühzeitige Detektion von Oberflächenschäden auf der Kugelgewindetriebspindel mit einem elektromechanischen Kamerasystem in Kombination mit Deep-Learning-basierten Modellen, um entsprechende Wartungsmaßnahmen abzuleiten. Condition monitoring of plants, machines and their components is a central topic of Industry 4.0. Unforeseeable failures of machine tools are often caused by wear, resulting in failure of ball screws and subsequent surface disruptions. This article describes how image-based monitoring of ball screws by an electronic camera system in combination with deep learning-based models enable the early detection of surface disruptions and to derive appropriate and preventive maintenance measures.

The article presents compensation of thermal errors of a computerized numerical control (CNC) axis. A partial differential equation (PDE) model of ball screw temperature distribution was utilized. The model takes into account non-steady-state localized heat sources and the effect of heat conduction between the screw and the machine body. To tune and validate the model, temperature distribution of the axis was measured on-line during its operation. The change of the model parameters related to the change of the axis movement velocity was presented. The article shows, that utilization of the thermal PDE model to compensate thermal errors, though effortful, is beneficial, but noticeably less accurate than the utilization of compensation based on the measured temperature values.

Ball screws are the driving components used to convert the rotational motion into linear motion in precision equipment. However, the machining accuracy of precision equipment is directly determined by the positioning accuracy of the ball screw. The authors analyze the precision sustainability of preload double-nut ball screws with raceway wear. A new wear model combining the modified Archard theory and the iterative interpolation method is established to analyze the variations in wear depth. A new model considering the coupling relationship between raceway wear and preload loss is proposed to study the precision life of the double-nut ball screw. In addition, a novel running test bench is designed to verify the precision sustainability of ball screws. The precision sustainability of the ball screw is analyzed during its life cycle, and these results match the theoretical values obtained by using the wear model.

A spindle feed system is continuously subjected to cutting forces, cutting heat and frictional heat during machining processes, which interact to form a complex, nonlinear and thermal-force coupling field. The coupling field causes deformations and vibrations of the mechanism that affect the machining accuracy. Therefore, determining the thermal-force coupling dynamic characteristics of the mechanism is beneficial, as it lays the theoretical foundations for accurate error compensation and the design and optimization of the spindle feed system. The deformation of the spindle feed system in actual working processes is approached by modeling, simulation and verification. Based on the theory of mechanics and heat transfer, the models for the transient milling force and the temperature field are established to obtain the real-time, dynamic cutting force and the associated heat values. A thermo-mechanical coupling model is also deduced, and the deformations generated by the cutting force and heat are simulated using the finite element method. Moreover, the thermo-mechanical coupling deformations of the system are emulated. The above deformation results are tested and confirmed. This paper establishes the deformation rules under the cutting force and cutting heat as well as their associated coupling effects. When studying thermo-mechanical coupling, the initial deformations of the ball screw are dominated by the cutting forces. The effects of heat on the X-direction deformations gradually exceed the effects of the cutting forces. The Y-direction deformations are primarily caused by the forces, with little influence from the heat. The Z-direction deformations are mainly caused by the heat, with negligible influence from the forces.

This paper aims to investigate the load distribution and contact stiffness characteristics of the single-nut ball screw pair (SNBSP). First, the transformed relationship of coordinate systems is established. Then, the whole rolling elements load distribution model of the SNBSP is presented. Based on this, the whole rolling elements contact stiffness model is obtained. Applying the Newton–Raphson iterative method to solve the model, the normal force of rolling elements and the contact angles between balls and raceway surface are determined. The calculation results are reasonably consistent with those of the half pitch model. Then, the local contact stiffness and global contact stiffness are obtained. Furthermore, the effects of axial load and structural parameters of the SNBSP on the normal contact force, contact angle, and local and global contact stiffness are discussed using numeric analysis. Finally, a dynamic model of the z-axis feed system with time-varying axial stiffness is established, and the accuracy of the model is verified by experiments.

Double-nut ball screws bear the action of bidirectional pretightening force, leading to the deformation of the contact area between the ball and the raceway. Under this condition, it is important to analyze and calculate the static stiffness of the ball screw. However, the conventional calculation method is inaccurate. Hence, a new method for the static stiffness analysis of a double-nut ball screw is proposed. Through the structural analysis of the ball screw and internal load distribution, a load deformation model was established based on the Hertzian contact theory. Through the load analysis of the ball screw, a static stiffness model of the ball screw was established and applied to a case study and a finite element simulation. The rigidity of THK double-nut ball screws used in the X-axis feed system of a high-stiffness heavy-duty friction stir welding robot (developed by the research group) was calculated. When the workload was lower than 1.1 × 104 N, the slope of the double-nut static stiffness curve increased significantly with the increase in the workload, and when the workload was greater than 1.1 × 104 N, its upward slope tended to stabilize. The simulated and experimental stiffness curves were in good agreement; when the external axial load was greater than 2.8 × 104 N, the stiffness value calculated using the finite element method gradually converged to the theoretical value; and when the axial load reached 3.0 × 104 N, the simulation and test curves matched well. The analysis method of the double-nut ball screw was found to be concise and accurate, and the stiffness curves calculated using the two methods were consistent. The simulation analysis of the static stiffness presented herein is expected to aid the design of double-nut ball screws of high-rigidity heavy-duty equipment.

Ball screws used for high-speed feed systems generate friction heat, which affects the preload and supporting system stiffness, and further, the dynamic characteristics of the screw system are modified and negative effects on the positioning accuracy are produced. Therefore, a thermal dynamic model for investigating dynamic performance variation with temperature is needed. First, a new dynamic temperature model of a hollow cylinder with varied heat flow was proposed based on the heat transfer theory. By using the thermocouples to read the real-time surface temperatures of heat sources, this model can be used to obtain the real-time temperature field of the supporting bearings and nut, and by using the FOCAS function to read the real-time position of nut, a finite difference heat transfer model with real-time moving heat sources was established. Based on this model, the dynamic thermally induced preload and stiffness models of the system were obtained. Second, a real-time thermal dynamic model of the ball screw system was achieved. Finally, an inverse identification method of the heat excitation was proposed. Through measuring dynamic characteristics of the feed system in machine tools, the real-time thermal dynamic models of the screw system were validated. It provided the theoretical and practical foundation for real-time monitoring and controlling of dynamic characteristics of preloaded ball screw systems.

Energy-harvesting shock absorbers (EHSAs) have been introduced in the last decade as a viable technology for improving the performance and durability of electric and/or hybrid vehicles. However, in order to gauge the potential that can be obtained from this technology in different environments, the computational models that are used should behave as close to reality as possible. One of the limiting factors in EHSAs, in terms of recoverable energy, is frictional losses between its moving parts. Depending on the friction losses, the dynamics and efficiency of the system will vary. This paper presents a method of identifying the friction parameters in a ball-screw energy-harvesting shock absorber (BS-EHSA) system for subsequent computational simulation. In addition, it shows qualitative and quantitative results of how these friction parameters could affect the comfort and adhesion of the vehicle, as well as the generated power and energy efficiency of the BS-EHSA.

To improve the simulation accuracy of the traditional transient thermal characteristics analysis model (TCAM) of the ball screw feed drive system (BSFDS), the optimization method of the thermal boundary conditions (TBCs), including the thermal loads, the convective heat transfer coefficient and the thermal contact resistance (TCR), was proposed. A multi-objective and multi-parameter optimization model was established based on the hybrid response surface (HRS) and a multi-objective genetic algorithm (MOGA) was developed to optimize the above TBCs. To simulate the thermal characteristics of the BSFDS under different working conditions, the generality of the method was extended to predict the TBCs under different feed rates. To validate the effectiveness of the method, the thermal characteristic experiments of BSFDS were conducted. The results showed that the simulation error for the temperature field was reduced from 25% to 10% and that the simulation error for the thermal elongation was reduced from 30% to 11%.

A real-time wear measurement system for tripod type Constant Velocity (CV) joints is proposed in this study. Adhesive wear on tripod type CV joints is very crucial to the life time of CV joints but it is very difficult to measure the wear depth of a tripod type CV joint separate from the drive shaft assembly. The wear measurement system developed in this study can measure the wear depth of a tripod type CV joint in real-time as it applies kinematics and forces to the CV joint. In order to apply the same motions as the motions of an actual CV joint, kinematics of the CV joint has been analyzed. As a result, reciprocating stroke and yaw motions have been completely implemented in the system. The wear measurement system comprises four parts. The first part is for applying normal forces to a set of spherical roller and housing track. One servo motor, spur gear and ball screw sets were employed to generate and augment the normal forces. The second and third parts are for applying reciprocating stroke and yaw motions, respectively. These parts synchronize with each other to make the same motion profiles as the actual CV joint. The fourth part is for measurement. This part consists of load cell and rotary encoder to measure the surge normal forces caused by the flaking phenomena and the wear depth caused by the adhesive wear. In the case of the encoder, the wear depth is augmented by the ball screw and spur gear sets so 0.18°/μm of measurement resolution can be achieved. For the validation of the system, a tripod type CV joint was selected, and its wear depth was measured by the system and the results were compared with the wear depth measured by a profilometer.

In this paper, a nine degree-of-freedom dynamic model of the ball screw feed system considering the contact nonlinearity between balls and raceways is established to analyze the vibration characteristics. The position relationship between raceway centers for the ball screw and bearings is determined by using the homogeneous coordinate transformation, and then the restoring force functions along the axial and lateral directions are derived. The dynamic equations of the feed system are solved by using Newmark method, and the proposed model is verified by the experimental method. Furthermore, the effect of the excitation amplitude on the axial vibration of the feed system is investigated by the frequency-amplitude curve and 3-D frequency spectrum. With the increase of excitation amplitude, the dynamic response of the feed system exits the softening, hardening type nonlinearity and jump phenomenon. Additionally, the effects of the initial contact angle, length of screw shaft and number of loaded balls on the axial vibration of the feed system in the resonance region are discussed. The results show that the dynamic model established in this paper is suitable for improving the machining accuracy and stability of the ball screw feed system.

Being a critical factor affecting the motion accuracy of precision machine tools, structural thermal elongation of precision ball screw unit is generally caused by the comprehensive influence from heat generations of screw-nut pair / bearings and time-varying ambient temperature. To resist 2 thermal disturbances above to guarantee precisely the original length of screw shaft, an active coolant control strategy is proposed in this paper. This strategy is based on an empirical model: For the slender and long tubular structure of screw shaft, the screw shaft temperature is approximately equal to its recirculating coolant temperature. The reason is that the intensive forced coolant convection is capable of eliminating screw shaft temperature rises caused by friction heat generations and ambient air convections. Based on this premise, screw coolant temperature can be consistently controlled by an active strategy, further to correct the thermal elongation of screw shaft. It can be experimentally verified that the thermal variations of machine positioning accuracy caused by the active coolant control strategy are not more than 10µm, which are lower than traditional strategy. Besides, based on detected structural temperatures of precision ball screw unit, the empirical model above is further proved to be reliable by FE simulation method.

The coefficient of friction (COF) is a key factor to estimate the performance of ball screws. Pieces of research focus on the experimental study of the COF, leading to the COF chosen empirically in many studies. To acquire the COF of the ball screw, a measuring system is conducted to detect the friction torque under different preloads and rotational speeds and the effects of the applied axial load and rotational speed on the COF are analyzed. By the curve fitting method, the Stribeck curve of the ball screw is obtained. The experimental results show that the lubricating state can be divided into two categories: the mixed lubrication state and the elastohydrodynamic lubrication state. This study is beneficial to choose a suitable working condition for a different performance of the ball screw.

The amount of lubricating oil supply of ball screw mechanism is adjusted only by artificial experience in the computer numerical control (CNC) feed system, which lacks scientific basis and theoretical guidance. On the one hand, the raceway of ball screw mechanism is worn frequently, on the other hand, lubricating oil is wasted and environment is polluted. To meet the requirements of green manufacturing, realize reasonable and accurate lubrication, and improve the accuracy retention and reliability of the ball screw mechanism, it is necessary to study intelligent lubrication control method of the ball screw mechanism based on the actual lubrication state online perception. Firstly, the calculation methods of contact characteristics, oil film thickness distribution, and friction coefficient with the vary of lubrication degradation process were established based on the theory of fractal and point-contact elastohydrodynamic lubrication (EHL) theory. Subsequently, according to the quasi-static force balance equation under the constant screw speed operating condition, the calculation method of friction torque of the ball screw mechanism with the varies of lubrication state was proposed, and the law of friction torque with lubrication degradation process in different screw speeds was determined. Finally, the online monitoring experiment on the lubrication degradation process of the ball screw mechanism was implemented based on the linear relationship between the friction torque of the ball screw mechanism and the current of the driving motor under the no external load and constant screw speed conditions, and the experimental results verified the correctness of the theoretical analysis.

In a vertical machining centre (VMC) heat generation occurs due to the movement of the machine tool components. This heat generationand surrounding air temperature create temperature rise in the machine tool. Due tothe temperature rise, the tool centre point (TCP) displaces which leads to inaccuracy and loss of precision in machined components. VMC base is one of the major componentsof a machine tool contributing to TCP displacement. In VMC base, thermal deformation of the guideway is caused by heat generation of linear motion bearing, and thermal deformation of the feed drive system is caused by ball screw movement. Further, the ball bearing also contributes to TCP displacement. Epoxy granite is used as a replacement for conventional cast iron in VMC base due to its better dynamic characteristics. But the lower thermal conductivity of epoxy granite, makes the heat to concentrate in a localised region which creates structural deformation. The present work focuses on determination of heat generation due to the frictionof linear motion bearing and feed drive system, the corresponding temperature rise and deformation of the VMC base. A mathematical model based on transfer function is also developed to predict thermal errors.

In a ball screw mechanism, the lead error is not only the key parameter to evaluate the precision, but also an important parameter to determine the load distribution. In this paper, a model is proposed to predict the load distribution related to the lead errors. The mechanical analysis of a double-nut ball screw is conducted to investigate the effect of the lead errors on the balls’ contact deformations and contact angles. Based on the Hertz contact theory, the equations to predict the preload and no-load drag torque are established, and the amplitude of the preload is obtained when the rotational speed is low. To verify the model, various experiments are conducted to measure the lead errors and the no-load drag torques of the ball screw by changing the screws with different accuracy levels. The experimental results show that the preload and no-load drag torque rise when the lead error increases in a double-nut ball screw. Besides, the relative errors between the experimental value and the theoretical value are less than 10%. This proves that the model can predict the preload and the no-load drag torque influenced by the lead error well, which is beneficial to the design of the double-nut ball screw for a certain preload.

The no-load drag torque is a crucial factor in the design phase to estimate the power required by the electric motor in electro-mechanical actuators (EMA). This paper focuses on the analysis of the drag torque contribution generated in preloaded double nut ball screws of EMAs. In literature its value is commonly estimated with a linear relationship with respect to the preload level. However, many other parameters play a role in determining the friction torque, such as operating speed, temperature and geometry. A sensitivity analysis on these parameters is presented by means of simulation results obtained from a high-fidelity multibody dynamic (MBD) model, capable of describing the full three-dimensional dynamics of each subcomponent and the presence of full film, mixed or boundary lubrication between mating elements. The results have been interpreted with a physics-based approach highlighting a strong dependency of the drag torque on temperature basing on the lubricant’s viscosity. This parameter also influences the drag torque speed dependence, which resulted to be more pronounced for low operating temperatures. An experimental test bench is being constructed to validate the model results.

Existing methods of parameters identification do not consider the torsion characteristics of a ball screw and the worktable position simultaneously. Therefore, this paper proposes a multi-position identification method based on receptance coupling. Firstly, the mathematical model of the feed drive system is established by the improved receptance coupling, and this model considers both axial and torsional vibration of the ball screw. Secondly, the identification equation is established by minimum error of the modal parameters of multiple worktable position, and differential evolution algorithm is used to calculate the stiffness and damping of the joint. Finally, the self-developed ball screw feed drive system is used for experimental study. The maximum error of the first four orders of natural frequencies predicted through multi-position identification results is 2.95%, and the multi-position method is more robust than the common method identification at one position. The experiment study showed that the proposed method is accuracy and necessity.

Ball screws have been investigated by several researchers from a theoretical point of view because the intrinsic complexity of experimental investigation of these mechanisms. Most of the models developed so far have been developed in quasi-static conditions ignoring inertia terms and time variability of operating conditions. A detailed multibody dynamic model of a double nut preloaded ball screw is presented in this paper, taking into account the full dynamic of each subcomponent as well as the mutual interactions. A 3D contact model is introduced, considering Hertzian normal contact and a simplified friction model based on grease lubrication. This model takes into account the time variability of the operating conditions and it is suitable to be used for prognostic and model-based design approaches. The results of dynamic simulations in presence of backlash are presented to highlight the model’s capabilities.

A low-cost stereolithography (STL) apparatus was developed to produce highly precise, three-dimensional (3D) structures from broad selection of functional materials, especially photopolymer resin. The developed stereolithography apparatus (SLA) utilizes focused light beam of wavelength range (300–700 nm) coming from the DLP projector and passing through the objective lens over the surface of a photocurable resin, which undergoes photopolymerization and forms solid structures. The photopolymer used in this STL system was polyethylene glycol di-acrylate and photoinitiator was Irgacure 784. The Creo 3.0 software was used for modelling of 3D object. A special MATLAB code was developed for slicing of the 3D CAD model. The Creation Workshop software was used to control the z-stage motion with the help of Arduino microcontroller, stepper motor, and ball screw. It also controls time period to display the sliced images through DLP projector and settling period. The experiments were successfully performed to built hexagonal cross-section and pyramid objects with 0.1 mm curing depth and two seconds curing time. The pyramid object with maximum 120 numbers of layers with 12 mm maximum dimension along Z-axis was build.

Machine tools are required to realize high precision and high efficiency machining by various industry sectors. A machine tool has some driving systems to position cutting tools and workpieces, and hence driving units are required high speed and precision positioning. However, high speed feed motion causes thermal deformation due to generated heat at friction surfaces such as guideway, feed screw, and bearings, it deteriorates positioning accuracy of driving units. Thermal deformation of a ball screw is one of large error factors of lower positioning accuracy, and a cooling system for reducing thermal deformation is installed into machine tools. Since the cooling system needs additional cost and space in machining systems, a new method for minimizing thermal deformation is required. In this study, a new structure of ball screw is proposed in order to meet these requirements. A new ball screw which has a core pipe made of CFRP was developed. CFRP is one of composite materials which have light weight and low thermal expansion. This paper presents analysis results of a simplified FEM model of the ball screw and the basic experimental results of the developed ball screw. These results confirmed that the proposed ball screw was applied to high performance positioning system in machine tools.

To determine the thermal deformation of ball screw in actual working condition, a novel method for determining thermal deformation of ball screws in complicated working condition is proposed based on G-code and finite-element (FE) method. In the complicated working condition, it is difficult to obtain and import the nut movement into FE model due to the complex nut movement. In this research, the nut movement is directly determined from G-code by MATLAB code programming. The nut location is recorded with time in a file. The thermal parameters can be determined according to the nut speed with time as well. In the implicit FE analysis, the nut location is read from the input file instead of nut location calculation before every time step. And then, the effect of factors, such as working condition and materials, on thermal deformation reduction of ball screw is studied. The thermal deformation reduction of ball screws under different rotational speed, actual working condition, and different axial elastic modulus of composites is discussed, which can provide the guidelines to evaluate the thermal deformation reduction and design the composite in improved ball screws.

Precision locknuts are widely used in rotary machinery especially the machine tools operating in high speed with high precision. The flank-locking locknut studied in this paper is mainly employed in spindle and ball screw assemblies of machine tools to secure the preloading in the bearings required for better structural stiffness. In service the locknuts often suffer corrosion from the harsh machining environment. The possible effects of corrosion on the surface morphology of locknut, such as flatness and roughness, and its performance were investigated. The locknut was submerged in a 5% NaCl solution following ASTM B895 standard for different durations- 1, 2, and 4 h to speed up the possible corrosion. The treated locknut was then undergone assembling test following ISO 2320 standard. The flatness and roughness on the end face and threads were measured along with microscopic examination. It was found that with increasing duration of corrosion, the surface flatness and roughness became worse. However, the tightening constant of the locknut showed a positive correlation with the increased surface roughness raised by the corrosion treatment.