Linear Guideway Research Articles

Varying stiffness and dynamic motion accuracy in a recirculating linear guideway

Varying stiffness and dynamic motion accuracy in a recirculating linear guideway

The effect of residual stress on the multi-step multi-point straightening with the three-dimensionally deformed linear guideway

The Multi-Step Multi-Point (MSMP) pressure straightening method is widely recognised for its effectiveness in manufacturing linear guideways. However, current theoretical analyses are limited to two-dimensional models, which oversimplify the complex nature of the straightening process. In reality, this process involves three-dimensional deformation and results in residual stress, adding complexity to the theoretical understanding of MSMP straightening. To address these challenges, this paper introduces an innovative MSMP straightening method specifically designed for three-dimensionally deformed linear guideways. It integrates both straightening and residual stress theories to thoroughly examine the impact of residual stress in various directions. Moreover, the paper develops a stroke-based straightening model that accounts for residual stress effects. Theoretical analyses are validated through comprehensive experiments, including bending and straightening tests. This research establishes a solid foundation for the study of pressure straightening three-dimensional deformed components.

Understanding human–robot interaction forces: a new mechanical solution

Nowadays, robots hold crucial roles in an increasing number of different fields, highlighting an ongoing transition to ever-closer collaboration between humans and machines. In this context, this new technological era has brought out safety issues and, consequently, robots need to be monitored with an appropriate control architecture and human–machine interaction forces should be correctly estimated. For this purpose, friction, inertia, external perturbation, and the intrinsic dynamic of the robots should be monitored. This specific work starts from the need to monitor human–robot interaction forces to ensure safety for users. A successful case study concerning the integration of additional sensors on a wrist robot that directly interacts with humans is shown. Its limits have been the inability to directly measure forces applied by users and the impossibility to know accurately the end-effector position. Firstly, introducing a force/torque sensor, the detection of the forces applied by the user to the robot has been enabled. The user’s force data have been used to measure force dissipation and, together with the smoothness of operation, to compare three different embeddable mechanisms. Moreover, the integration of a linear encoder allowed measuring the instantaneous end-effector position on a non-actuated linear guideway, consequently knowing the motor torque value and the force applied by the robot to the user. This has been compared to the interaction force estimated from the motor torques without the linear sensor. The error assessed between the force measured with the encoder and estimated without it is about 12.9%. These results demonstrate the importance of this new embedded system to detect human–machine interaction forces in an accurate way and prevent safety issues.

Research on nonlinear static and dynamic characteristics of linear guideway in machine tools considering carriage flexibility

Research on nonlinear static and dynamic characteristics of linear guideway in machine tools considering carriage flexibility

Linear permanent magnet electrodynamic suspension system: Dynamic characteristics, magnetic-mechanical coupling and filed test

This study investigates the dynamic electromagnetic characteristics and thermo-mechanical coupling effect of the linear permanent magnet electrodynamic suspension system (PMEDS) via high-speed test rig. Besides, a physical prototype weighing 1.5 tons along with a 50-m linear copper guideway is developed and tested. Firstly, the topology structure along with fundamental operation model is introduced, followed by establishing the analytical model. Subsequently, a multi-functional test rig is utilized to experimentally determine its speed characteristics, lateral stability, and vertical vibration, while also validating the simulation and analytical models. Additionally, thermo-mechanical coupling analysis is conducted through co-simulation, experimentation and calculation to determine the dependence of temperature on the levitation and drag forces. Finally, a prototype vehicle integrated with auxiliary components, is fabricated and tested on a copper guideway. The vehicle is suspended freely via levitation force in the air above 30 mm, with tested suspension height generally aligning with dynamic simulation results.

Vibration characteristics and reliability analysis of roller linear guideway workbench

Vibration characteristics and reliability analysis of roller linear guideway workbench

ESTIMATION OF MACHINE TOOL ACCURACY BASED ON MONTE CARLO SIMULATION USING MOVEMENT AXES GEOMETRIC ERRORS MODEL

Accuracy is one of the most important feature of a machine tool. Being able to estimate the overall accuracy of a machine tool represented by the total volumetric error can be a huge advantage in the design process. This paper provides overview of methods used for geometric error transfer modeling and volumetric error modeling. An error transfer rigid body model is derived and after that, a random linear guideway straightness error profile generator is proposed. This allows to simulate a movement axis with random straightness errors of rails and computed geometric errors of an assembled axis. Volumetric error of a 3-axis machine tool is then modeled using its kinematic scheme and homogenous transformation matrices with 21 kinematic errors. Using simulated axes as input to the volumetric model, an entire machine tool can be simulated. From that, the total volumetric error can be obtained and a Monte Carlo simulation carried out. This allows to analyze statistics of the total volumetric error and with slight input changes (rail straightness tolerance), a sensitivity analysis can be performed to determine the most influential errors in the machine tool.

The effect of carrier locking position on the dynamic characteristics of gapless miniature linear guideway

The analysis of the load position of the miniature linear guideway is very important for the dynamic friction characteristics of the linear motion equipment. In this paper, a miniature guideway dynamic friction coefficient tester will be designed. And the effect of load position, movement speed, and load on the friction force of linear guideway will be investigated according to the gapless. The experimental results show that the friction force will be dependent on the load position, load, and movement speed. Among them, the lowest frictional load position can be obtained at any speed of movement and load condition, which occurs at the central load position. The main reason for this is that the effect of the moment is minimum. On the same load position and movement speed, then load is proportional to friction. In the case of fixed load and load position, the effect of velocity on friction is positively correlated in the longitudinal offset position. The frictional force is aggravated by the unevenly distributed pressure on the inner ball due to the moment generated by the slider. At the same time, by observing the loading and the inclination angle of the carrier in the experiment with the laser displacement meter, it can be found that the inclination angle also tends to increase when the load increases.

Local subsidence behavior of linear guideway assembly resting on a rough elastic foundation

The accurate stiffness estimation of linear guideway assembly is determined by the structural deformation of carriage and supporting rail-pedestal-bolt joint. This paper proposes an analytical model to investigate the stiffness and local subsidence behaviors of linear guideway assembly. The different preload states between the upper and lower raceways are revealed, and the retraction behavior of carriage wing is found. Considering the local subsidence of the rail below a carriage, the proposed model reports the non-uniform load distribution along the finite-length rail, which is placed on the rough foundation and assembled by bolts. Loading tests are performed to verify the local sinking effect and the model accuracy. The developed model is promising to serve to the deformation error compensation.

Motorised System for Loading and Unloading of Press Dies in Press Machine

Abstract: The paper describes the use of a plate heat exchanger in transferring heat between two fluids. It explains that the design of a plate heat exchanger involves multiple heat transfer plates held together by a fixed plate and a loose pressure plate. These plates have a gasket arrangement that creates separate channel systems for the primary and secondary media, allowing for counter-current flow and effective heat transfer. To manufacture the corrugated plates, the text mentions the use of Hydraulic Press Machines with different capacities depending on the plate dimensions. The process involves changing heavy press dies, which is time-consuming and decreases overall plant efficiency. To address this issue, a proposed solution is to semiautomate the loading and unloading of press dies. A mechanical system is designed, comprising a table with rollers and linear motion guideways. The system utilizes a Ball screw mechanism powered by a servo motor and driven by a Worm Gearbox. The orientation of the motor, perpendicular to the line of motion, saves space and provides more working space on the workshop floor. In summary, the proposed solution aims to increase efficiency and safety by implementing a mechanical system for loading and unloading press dies in plate heat exchanger manufacturing, incorporating a Ball screw mechanism, servo motor, and Worm Gearbox.

Effects of nonlinear behaviour of linear ball guideway on chatter frequency of lathe machine tool

Linear ball guideways (LBGs) have several advantages for the precise positioning control of machine tools. However, the ball-groove contact behaviour leads to poor dynamic compliance, which induces a significant nonlinear behaviour of the guideway and a poor chatter stability. The nonlinearity complicates the chatter prediction due to the dependence of the contact stiffness. This approach aims to offer an industrially orientated method of estimation of chatter stability for structures based on LBG. Consequently, the present study first employs Hertzian contact theory to describe the ball-groove contact behaviour in the LBG of a lathe machine. Two static models are presented, both predict the LBG stiffness under different cutting loads. The first model describes is simplified, ignores the effects of the contact force on the deformation of the guideway components, even with that limitation depicts the main behaviour of the system. The second model is more precise and adopts a dynamic substructuring cosimulation method to incorporate the effects of structural deformation into the analysis. For both models, a linearisation approach is employed to analyse the dynamic behaviour of the system under static loading and define the dynamic compliance. The chatter frequencies of the LBG are estimated using the second model and are shown to be in good agreement with the experimental results. In general, the results of the analysis show that fundamental shifts in the frequency response of the LBG occur under specific values of the cutting force and gravity load. In other words, the results confirm that this method provides sufficient estimation of nonlinear behaviour of machine tool based on the LBG.

A Method for Diagnosing the Performance of the Dropping Mechanism in the High-Precision Absolute Gravimeter

The absolute gravimeters used in gravity measurements have wide applications across disciplines. The precision of a classical free-fall absolute gravimeter is limited by the performance of its dropping mechanism. The mismatch between the linear bearings and guideways can give rise to vibrations in measurement and lead to errors in the gravity results. To detect this problem, this research develops a diagnostic approach based on the current analysis of the motor that drives the dropping mechanism. Several dropping chambers are tested under gravity measurement within 12 hours to calculate the uncertainty of the mean and be tagged as qualified or unqualified. The status of the dropping mechanism is assessed by applying four parameters of the current data in the time and frequency domains during steady motion and feature coefficients of transient current under wavelet packet decomposition (WPD). The proper ranges of the parameters are identified through comparative experiments. Empirical evidence confirms the feasibility of the parameters and coefficients used to determine whether a gravimeter dropping mechanism meets the requirement of precision around 1 micro Gal. In addition, the analysis based on continuous wavelet transform (CWT) proves its potential to locate the faults in the unqualified dropping mechanism. The proposed diagnostic approach can be applied within 20 times of motor current acquisition, which makes it practicable and helpful in improving and achieving high-precision gravity measurement.

Fabrication of wear-resistant PA6 composites with superior thermal conductivity and mechanical properties via constructing highly oriented hybrid network of SiC-packed BN platelets

Herein, a strong extensional and shearing field was introduced to construct highly oriented hybrid networks of silicon carbide (SiC)-packed boron nitride (BN) platelets to fabricate high-performance wear-resistant PA6 composites. Results show that in-plane and through-plane thermal conductivity (TC) of the prepared PA6 composites with a total filler loading of 20 wt.% reached 1.31 and 0.35 W/(m K), 352% and 25% higher than those of pure PA6, respectively. It is attributed to the highly oriented hybrid network that facilitates the formation of efficient thermal conductivity pathways. Temperature monitoring results during friction confirm that high TC favors the friction heat dissipation performance. Meanwhile, the yield strength of PA6 composites increased by 39.1% and they still have excellent ductility with an elongation at break of 207.1%. Finally, the wear rate of PA6 composites decreased sharply by 92.5%. This method can be used to manufacture advanced linear bearing and guideway parts, etc.

Nonlinear dynamic model for linear guideway with crowning subjected to external load in five directions

The motion accuracy of linear guideway is adversely affected by ball passage vibration (BPV) when rolling balls within carriage move in a loop. Reduced vibration amplitude can be realized by a carriage with crowning design by now. However, few dynamic models are availability for the BPV analysis when linear guideway is subjected to actual external load in five directions. In this paper, a nonlinear dynamic model is proposed to investigate the periodic micro fluctuation of linear guideway with crowning subjected to load in five directions. The idea of coordinate transformation is adopted for the easier derivations of time-dependent and piecewise restoring force function. The different contact states of each ball are described in detail due to load distribution. The numerical simulation is employed to deal with equation of motion and discuss the effects of ball grouping, external load, preload and carriage speed. Experiment is also conducted for the verification of proposed model. The analytical model developed here is promising to clarify the mechanism of BPV from a dynamic perspective and serve the walking parallelism accuracy monitoring of linear guideway.

Detection method of springback for linear guideway straightening using digital image correlation.

The guideway deformation control of the straightening process is the basic method to ensure straightening accuracy. The prediction of and compensation for springback in the straightening process of a guideway adopts mostly numerical analysis and finite element analysis methods instead of experimental methods because of the measuring difficulty of actual springback. In this paper, a method is proposed to detect bending deformation during the straightening process, which provides a reference for the relevant manufacturing processes. Digital image correlation measurement technology is adopted for the detection of bending springback, which can measure the full-field displacement distribution without contact and with high precision. The experimental results show that digital image related technology can very accurately detect the deformation of the guideway straightening stroke and bending springback deformation. This study can help to control bending deformation during the straightening process and ensure straightening accuracy, providing a reference for real-time monitoring of straightening force.

Condition Monitoring of Machine Tool Feed Drives: A Review

Abstract The innovations propelling the manufacturing industry towards Industry 4.0 have begun to maneuver into machine tools. Machine tool maintenance primarily concerns the feed drives used for workpiece and tool positioning. Condition monitoring of feed drives is the intermediate step between smart data acquisition and evaluating machine health through diagnostics and prognostics. This review outlines the techniques and methods that recent research presents for feed drive condition monitoring, diagnostics and prognostics. The methods are distinguished between being sensorless and sensor-based, as well as between signal-, model-, and machine learning-based techniques. Close attention is given to the components of feed drives (ball screws, linear guideways, and rotary axes) and the most notable parameters used for monitoring. Commercial and industry solutions to Industry 4.0 condition monitoring are described and detailed. The review is concluded with a brief summary and the observed research gaps.

Rolling resistance model for estimation of friction fluctuation in linear ball guideways

Linear ball guideways are widely employed in machine tool drive systems. Friction fluctuation of linear ball guideways causes fluctuations in the feed rate that results in contour errors in synchronous motions while using several feed drives. In this study, a practical model of rolling resistance is proposed for a model-based design of the raceway profile that realizes a smooth feed motion. In the proposed model, the rolling resistance is obtained from the preload and two contact angles at the upper and lower raceways. The preload variation is represented by a simplified spring model. The validity of the proposed model is experimentally verified. The variation in the rolling resistance is influenced by the phase difference between the upper and lower raceway profiles. The resistance variation can be decreased by setting the phase difference to the half period of the profile component. The experimental results indicate that the fluctuation components of the rolling resistance, with a wavelength longer than the contact diameter between the ball and raceway, can be correctly estimated. The estimation error for the shorter-wavelength component is not a crucial issue because the rolling resistance fluctuation is small for such a component. The verification results show that the proposed model can provide an effective guideline for the raceway profile design to reduce the rolling resistance fluctuation to an acceptable level.

Flatness on-machine measurement system of chemical mechanical polishing process for large-caliber tin plates

In planar optics machining, surface flatness is a critical requirement for making high-quality optical devices. Chemical mechanical polishing (CMP) is an important process of smoothing surfaces for hard and brittle planar optics. Thus, there are growing interests in developing high-precision flatness on-machine measurement system for tin plate CMP process. However, the traditional evaluation measurement cannot meet the measurement accuracy requirement of approximate 2 μm. In this study, we propose an effective on-machine measuring system for the large-caliber optical tin plate, which consists of linear guideway, rotary table, and measuring sensor. In the system, the straightness error of the guideway and the axial runout error of the rotary table are compensated using a spiral method and the Keyence LK-G5000 measuring sensor. First, the spiral measuring path is formed by the movement of the line guideway and rotary table, which can prevent from multiple calibration. Then, the 3D flatness error of the dressing process is measured by linear movement of the LK-G5000 and the rotation of the tin plate. After the primary measurement process, the obtained 3D flatness error is compensated for straightness and axial runout error in sequence. To verify the accuracy of the flatness measurement, the tin plate is dressed by the natural diamond tool according to the measured 3D flatness error. After the dressing process, the peak-valley value of the remeasured flatness error can achieve 2.12 μm through a single-step dressing. The experimental results provide the accuracy and reliability of the high-precision on-machine flatness measurement system for the large-caliber tin plate.

Designing control algorithm and experimental validation for piezo stepping actuator

Piezo-stepping actuator is one device that produces large displacement while some voltage is applied to it or vice-versa by micro-meter accuracy and nanometer resolution. The displacement in stepper actuators happens with steps. A linear stepping movement of the base of the actuator is proposed in this paper. A linear stepping motion of the piezo actuators is achieved with four sets of push–pull actuators and four sets of lock release actuators. The designed stepper actuator produces linear displacements. The design and control of the stepper actuators are explained in the paper. A trapezoidal signal is being generated from the triangular wave moreover this is implemented as the input for the smooth functioning of a stepping actuator. Control operation of push–pull and lock-release actuators was performed and for various input displacements the experimental displacements of actuators were achieved and the results were plotted. Control operation of Push-pull and lock release assembly was conducted for varying input displacement and corresponding experimental displacement is measured and also the results were plotted. The actuator assembly was proficient in driving the linear guideways.

Model and nonlinear dynamic analysis of linear guideway subjected to external periodic excitation in five directions

Model and nonlinear dynamic analysis of linear guideway subjected to external periodic excitation in five directions