Rolling Guideway Research Articles

Damping in ram based vertical lathes and portal machines

Chatter vibrations originated by the machine structure are a major limitation for the productivity of ram based machines performing heavy duty operations. Consequently, the damping of the machine structure has a capital importance. It is known that interfaces and guideways are the main origin of damping. Recently, the use of active dampers has been introduced in industry. In this work, the damping of hydrostatic and rolling guideways with and without active damping has been experimentally identified and compared using receptance coupling. The results show that hydrostatic guidance can introduce 3–4 times more damping than a roller based system. However, the introduction of active damping is a game changer enhancing damping more than 30 times.

Effect of off-sized balls on contact stiffness and stress and analysis of the wear prediction model of linear rolling guideways

The characteristics between the rolling balls and raceways are the key to study a linear rolling guideway (LRG). In this paper, the contact stresses of an LRG with off-sized balls incorporating the variation of the contact angle are given by the established LRG joint model. Moreover, the effect of the location, number, and the deviation degree of the off-sized balls on the stress distribution are studied. In addition, the contact stress distribution between the balls and raceway for different arrangement cases of the off-sized balls are analyzed. The random arrangement case can improve the stiffness and service life of the LRG. Based on the Archard wear theory, the wear prediction model of the LRG is established and the displacements and angular displacements of the slider caused by wear in reciprocating motion are obtained. The effectiveness of the contact stiffness and wear prediction model of the LRG is verified by simulations and analysis.

An analytical model of static stiffness for linear rolling guideway considering the structural deformations of carriage

To solve the deformations and stiffnesses changes of linear rolling guideway under different loads, and to provide reference for the structural design of the carriage, this paper presents an analytical model of three-degrees-of-freedom static stiffness for linear rolling guideway considering the structural deformations of the carriage. In this study, first, the contact loads and elastic deformations between balls and raceways caused by external loads and preload were obtained by Hertz contact theory. The elastic deformations between balls and raceways were described by the change of the curvature centers of the carriage raceways. Next, according to the constraints and loading conditions of the carriage, the elastic beam theory was introduced, and the structural deformations of the carriage under the contact loads were equivalent to the deformations of two cantilever beams. Then, the external loads and the displacements of the carriage were derived by the static equilibrium conditions of the carriage. At last, the proposed equivalent model of carriage structure deformations was validated by comparing the calculated deformations of the carriage with those from a commercial program under various loading conditions, and the accuracy of the static stiffness model proposed in this paper was further verified by the experimental results in the reference. The results show that the calculated structural deformations of carriage matched the deformations calculated by a commercial program well. Also, with relative errors of 4.4–17.5%, the calculated stiffnesses using the model proposed in this paper more closely matched the measured stiffnesses. Clearly, there is a better match between the calculated results of the proposed model and the measurements than with the conventional rigid model.

Full-load analysis model and experimental study on the static characteristics of linear rolling guideway joints

Linear rolling guideways have been widely used in machine tools. The overall performance of machine tools is directly influenced by the linear rolling guideway characteristics. In this study, a contact model for a single ball–raceway joint surface is established based on the fundamental characteristic parameters of the joint surface, which are obtained experimentally. Based on this model, a novel full-load analysis model of the linear rolling guideway joint is proposed, and six linear rolling guideway-joint stiffness types, namely the tangential, normal compressive, and normal tensile stiffnesses and the pitch, yaw, and roll angular stiffnesses, are obtained. Testing devices are developed for the six stiffness types. The stiffnesses of the medium preloaded HJG-DA35AA, HJG-DA45AA, and HJG-DA55AA linear rolling guideways are achieved using the developed testing devices, and the results obtained from the full-load analysis model are approximately consistent with the experimental results.

Hybrid modeling and analysis of multidirectional variable stiffness of the linear rolling guideway under combined loads

In the working process of high-speed multiaxis machine tools, inertial loads due to high feed acceleration and time-varying gravity loads due to changing configuration of multiaxis structure result in time-varying complex loads applied to linear rolling guideway. Existing models cannot efficiently represent the effect of complex loads on multidirectional stiffness variation of linear rolling guideway. In this paper, a hybrid model of multidirectional stiffness of linear rolling guideway and the solving algorithm are proposed. The complex loading conditions of linear rolling guideway in high-speed multiaxis machine tool structure are considered. And contact flexibilities between rolling balls and grooves are modeled with the effect of elastic deformations of runner block and rail. The proposed model can calculate the multidirectional stiffness with high accuracy. Meanwhile the differences between the stiffness characteristics in different directions are represented correctly. The variations of multidirectional stiffness of linear rolling guideway under time-varying combined loads are analyzed. This study provides an effective way to comprehensively evaluate the stiffness characteristics of linear rolling guideway which can contribute to the dynamic analysis and active design of high-speed machine tool structure.

Influence of lubricant on nonlinear vibration characteristics of linear rolling guideway

Linear rolling guideways are widely used in precision mechanical systems such as robots and machine tools. Clarifying the natural vibration characteristics of a linear rolling guideway is important for improving the performance of mechanical systems, because the dynamic characteristics of the guideway strongly influence the dynamics and posture accuracy of mechanical systems. This study focuses on the natural vibration characteristics of linear rolling guideways. We discuss both the nonlinear relationship between friction and natural vibration, and the influence of the lubricant specification on the nonlinearity of nonlinear natural vibration. Additionally, the effects of the lubricant specifications on the damping ratio are different for different vibration modes, owing to the differences between the damping mechanisms.

Design of dynamic error detection system for grating scale

Grating scale is a closed-loop detection and control tool for precision machine tools, and its accuracy detection needs a higher precision detection platform. There are two kinds of commonly used detection platform guideways: sliding guideway and rolling guideway. Because of the contact of points or lines, the error caused by the guideway itself is obvious. In order to reduce the error of the platform itself, the air-floating guideway with small friction resistance and no vibration relative to the motion is used as the support mode, and the air pressure is debugged according to the smoothness of sliding. The static accuracy detection method of grating sensor is comparatively mature, but there is no effective solution for its dynamic accuracy detection. To solve this problem, we developed a dynamic error detection system of grating scale based on high-precision grating scale. The experimental results show that the system can detect the dynamic accuracy of grating scale, and has high detection efficiency. It is suitable for mass rapid measurement in practical work.

EXPERIMENTAL RESEARCH REGARDING THE INFLUENCE OF THE FRICTION FORCE FROM LINEAR ROLLING GUIDEWAYS ON THE POSITIONING PRECISION OF KINEMATIC FEED CHAINS USED ON CNC MACHINE TOOLS

<p>Friction represents one of the major sources of disturbing forces which affect the functioning of the kinematic feed chains from CNC machine tools. Its influence reflects on the positioning precision values, having a negative impact on the table movement and leading to stationary errors, stick-slip motion and trajectory errors. The present paper presents an experimental analysis regarding the influence of the friction forces which appear in the linear rolling guideways on the positioning precision of kinematic feed chains. The rolling guideways present the advantages of a good behavior in terms of axis stability at low speeds and also for achieving high positioning speeds. Concerning the friction coefficient values, rolling and hydrostatic guideways are most suitable for the construction of high speed and high precision kinematic feed chains; in these cases, the friction coefficient has small values, which maintain quasi-constant against the feed rate. </p>

A newly developed zero-gravity vertical motion mechanism for precision machining

Gravity load deteriorates positioning performance on a vertical motion stage. A counterweight or a fluidic cylinder is conventionally used for gravity compensation; however, these solutions may induce new problems. This paper presents a novel zero-gravity vertical motion mechanism for precision machining. The proposed mechanism employs a linear motor and the magnet yoke has rolling guideway, thus the yoke is also used as counter mass. Because inertia of the moving parts is doubled for disturbance, the mechanism can effectively minimize the influence of machining force. The performance evaluation results confirm that the mechanism provides superior driving characteristics to vertical motion stages.

Evaluation Method for Vibration Characteristics of Rolling Guideway Influencing on Dynamic Stiffness of Machine Tool

Evaluation Method for Vibration Characteristics of Rolling Guideway Influencing on Dynamic Stiffness of Machine Tool

Stripe theory based numerical method for solving asymmetrical hysteresis of friction force in linear rolling guideways

Linear rolling guideways (LRGs) play an important role in precision engineering. In the pre-rolling region, the hysteretic friction force exerts great impacts on the positioning accuracy. Numerical and experimental studies of the hysteresis of friction force are presented in this paper. A model, which is based on the stripe theory and the simplified theory of rolling contact, is built to describe the transient hysteresis of the friction force. Then, the model is modified by taking the anelasticity effect into consideration. Experimentally, a linear motor direct-drive setup is utilized to measure the transient asymmetrical hysteresis of the friction force in the pre-rolling region of an LRG. The influences of the pre-rolling displacement and the dwelling time on the asymmetrical hysteresis of the friction force are studied. The numerical and experimental results are well correlated, which shows good accuracy of the model. The transient asymmetrical hysteresis of friction force in the pre-rolling region of LRGs can thus be determined using the model.

OS0610 転動体の接触状態が転がり案内の減衰に及ぼす影響

Rolling guideways are widely used in machine tools. In rolling guideways, rolling elements move raceway groove between rail and carriage. Commonly, rolling guideways have two or four rows, eight rows' are getting a lot of attention as high rigidity and damping. Eight-row guydeways have more and smaller rolling elements than others. However, the influence of the number and diameter of balls on its damping has not been clarified. Thus, this paper describes the influence of number and diameter of balls on its damping using damping measurement apparatus. In this apparatus, it is possible to measure the influence of design variable of rolling guideways respectively. In consequence, the number of balls is more relevant to dynamic characteristics of rolling guideways than diameter of balls.

OS0609 転がり案内を模擬した接触減衰評価装置の試作

OS0609 転がり案内を模擬した接触減衰評価装置の試作

Impact of certain engineering methods on results of computational analyses of rolling guideway subassemblies

Impact of certain engineering methods on results of computational analyses of rolling guideway subassemblies

Influence of nonlinear spring behavior of friction on dynamic characteristics of a rolling guideway

The friction of rolling guideways in the prerolling region displays hysteretic behavior known as nonlinear spring behavior (NSB). NSB deteriorates motion accuracy and causes vibration in the feed direction. Therefore, the influences of NSB on the dynamic characteristics of rolling guideways should be clarified. This paper describes the influence of NSB on the dynamic characteristics of a rolling guideway. A simple friction model is constructed based on the Masing rule. Because the proposed friction model is described with only three parameters, the factor that inherently affects the dynamic characteristics can be clearly identified. To clarify the influence of NSB, the impulse response, frequency response, and steady state motion are analyzed by numerical analysis. According to the results, the dynamic characteristics in the feed direction depend only on the change rate of friction in the prerolling region, which is introduced to the friction model as the shape factor, n. The stiffness and damping are high when the change rate of friction is high in the prerolling region. The frequency response function is force- dependent, and its tendency is varied by n. The frequency response function includes harmonic and super harmonic resonances. When the carriage is excited with a frequency lower than that of the super harmonic resonance, a displacement spike (quadrant glitch) is observed. Additionally, the nonlinearity cannot be ignored when the carriage is excited with a frequency lower than the harmonic resonance. Finally, an experiment with a roller guideway is conducted to prove the validity of the analysis. The resonance frequency and compliance at the harmonic resonance measured by the experiment accurately conform to the analytical results.

Statics modeling and analysis of linear rolling guideway considering rolling balls contact

The linear rolling guideway is composed of rail, carriage, rolling balls, and other accessories and contains a large number of rolling interfaces between the rolling balls and the grooves. For such a complex nonlinear mechanical system, it is very significant to obtain the statics deformation and vertical stiffness under different loads for the structural design of guideway and mechanical analysis of Computer Numerical Control (CNC) machine tool. Therefore, the focus of this study is on the development of statics modeling techniques of the linear rolling guideway by analytical and finite element methods, considering the rolling balls contact. First, an accurate statics analytical modeling method was proposed by using the Hertz contact theory and revision of experiment results. Then, on the basis of considering contacts between rolling balls and grooves, the precise finite element modeling was studied. To improve the efficiency of analysis, the full finite element model of guideway was replaced by the component finite element model. At last, the created analytical and component finite element models were applied to analyze the effects of load and preload on the statics characteristics of single ball and the whole guideway system. The proposal of current study may provide a reference to create the precise dynamics model of linear rolling guideway.

B18 転がり出し領域における摩擦が転がり案内の送り方向動特性に及ぼす影響(OS2 最新機械要素技術(1))

B18 転がり出し領域における摩擦が転がり案内の送り方向動特性に及ぼす影響(OS2 最新機械要素技術(1))

Study on the Static and Dynamic Characteristics of Linear Rolling Guideway

Linear rolling guides are widely used in the NC machine tool, and usually the NC machine tool's characteristics shall been influenced by the characteristics of the guide greatly. The HSR series of liner rolling guides are taken as the research object of the paper. The methods of constructing the dynamic finite element analysis models are studied. The contact element is applied to simulate the characteristics of junction surfaces during the static characteristic analysis. The spring damping element is applied during the dynamic characteristic analysis. The static stiffness, natural frequencies, modal shapes and other characteristics are obtained by finite element analysis. Then the experiments of linear rolling guide are carried out and verified the model that had been built and calculation results of finite element analysis.

Experimental characterization of disturbance force in a linear drive system with high-precision rolling guideways

This paper describes a characterization method of disturbance force in a linear drive system supported by high-precision rolling guideways. Disturbance force is divided into the friction component and other disturbance force. Experimental characterization method to analyze effect of global position, effect of micro-position and effect of table velocity is suggested. With stop-dwell-go and reversal motions, characterization experiment and analysis are conducted on a positioning system consists of a linear motor and rolling guideways. Firstly, global disturbance force depends on global position and stick and slip friction components are characterized. Secondly, stick friction force is separated from stick and slip friction force in the micro-region. Thirdly, influence of the velocity is analyzed. Finally, a modified single bristle model, which describes friction characteristics in the micro-regime, is shown to simulate the measured disturbance force.

Dynamic Performance Analysis of a Machine Tool Considering Linear Rolling Guideway

The linear rolling guideway is one of the most essential parts of the machine tool. So it is very important to analyze the dynamic-static characteristic of the machine tool by considering rolling guideway for the study of the effect on machinery function. The research is based on a NC machine tool produced by a certain plant of machine tools. In this study, methods of simulating the rolling guideway support were studied; and the configuration of the spring damper elements of the bearing supports were investigated. The finite element analysis on the CKS6125 machine tool was used to confirm its dynamic characteristics. The finite element analysis models were validated by some experiments.