Dynamic Performance Of Machine Tool Research Articles

Research on the Magnetorheological Finishing Technology of a High-Steepness Optical Element Based on the Virtual-Axis and Spiral Scanning Path.

Magnetorheological finishing (MRF) of aspherical optical elements usually requires the coordination between the translational axes and the oscillating axes of the machine tool to realize the processing. For aspheric optical elements whose steepness exceeds the machining stroke of the equipment, there is still no better method to achieve high-precision and high-efficiency error convergence. To solve this problem, an MRF method combining virtual-axis technology and a spiral scanning path is proposed in this paper. Firstly, the distribution law of the magnetic induction intensity inside the polishing wheel is analyzed by simulation, the stability of the removal efficiency of the removal function within the ±7∘ angle of the normal angle of the polishing wheel is determined, and MRF is expanded from traditional single-point processing to circular arc segment processing. Secondly, the spiral scanning path is proposed for aspherical rotational symmetric optical elements, which can reduce the requirements of the number of machine tool axes and the dynamic performance of machine tools. Finally, an aspherical fused silica optical element with a curvature radius of 400 mm, K value of -1, and aperture of 100 mm is processed. The PV value of this optical element converges from 189.2 nm to 24.85 nm, and the RMS value converges from 24.85 nm to 5.74 nm. The experimental results show that the proposed combined process has the ability to modify curved optical elements and can be applied to ultra-precision machining of high-steepness optical elements.

Qualitative research on the relationship between spindle vibration characteristics and bearing thermal load

The dynamic performance of machine tool is one of the most important factors affecting the machining accuracy. As the core part of machine tool, the dynamic performance of spindle directly determines the performance of machine tool. In this paper, the spindle of machine tool is taken as the research object, and the change of fit clearance between bearing inner and outer rings, rotating shaft and bearing seat caused by spindle bearing heat, and its influence on the stiffness of spindle system are analyzed. Based on Timoshenko beam theory and finite element method, this paper qualitatively analyzes the variation characteristics of spindle stiffness caused by bearing overheating and grease lubrication failure during high-speed machining.

Dynamic Performance Analysis of the micro-hole EDM Machine Tool

The EDM machine is special processing machine using the principle of EDM process of conductive materials. By means of modal analysis, ODS (Operational, Deflection, Shapes) analysis and order analysis, the static and dynamic performance parameters of the EDM machine tool are studied. According to the processing requirements, the structure of the machine tool is optimized, and the weak links are strengthened so as to reduce the aperture dispersion of the machined holes. Through the modal test this experiment firstly analyzes the natural frequency, damping ratio and modal shape in each mode of machine tool structure to understanding the characteristics of each order machine main mode. Then, through ODS (Operational Deflection Shapes) test, it analyzes the vibration characteristics of machine tool structure in operation condition. And it also analyzes the relation-shape between the vibration of rotating machinery and the speed of the machine through the order analysis to predict the vibration of actual machine tool structure in a certain band external or internal variety of vibration response. Finally, it makes a comprehensive study on the static and dynamic performance of machine tools, and provides a reference for the design and optimization of structure dynamic strength.

Structural design optimization of moving component in CNC machine tool for energy saving

Abstract With the increase of energy price and environment problem, the energy consumption of machine tool is attracting more attention. The moving components of machine tools consume a large amount of energy in the operating stage. Structure optimization of moving components is a key strategy for energy saving in machine tools design. Traditionally, structural optimization of machine tools is carried out for reducing energy consumption or improving static and dynamic performance. Given that these factors are important to the structure optimization in machine tools design, this paper presents a structural design optimization method for comprehensively considering energy consumption, static and dynamic performance of machine tool. Firstly, the energy consumption model of the moving components is proposed, and the structural performance indicators of the moving components are analyzed. Then, based on the experiment data obtained by uniform design method, five structure parameters that have great influence on performance indicators are selected as decision variables through sensitivity analysis. To improve the computation efficiency, approximation functional relationship between the five decision variables and the four performance indicators are built through response surface method (RSM). After that, an optimization objective is formulated by combining the four performance indicators through principal component analysis (PCA). Finally, a new hybrid algorithm which integrates Simulated Annealing (SA) and Particle Swarm Optimization (PSO) algorithm is developed to solve the structure optimization problem. Through calculation and analysis, it is found that there is a linear relationship between the moving part mass and energy consumption. The results show that the energy consumption of optimized structure is reduced while ensuring the static and dynamic performance.

Multi-objective optimization design and performance analysis of machine tool worktable filled with BFPC

In order to explore a new way to improve the static and dynamic performance and lightweight of machine tool, the machine tool worktable filled with basalt fiber polymer concrete (BFPC) is designed, which take a worktable of vertical machining center as the research prototype and meet the stiffness and light weight as the constraint conditions. The static, dynamic performance weight of prototype structural columns are simulated and analyzed by using Workbench software. Taking the width and height of rectangular hole of worktable filled with BFPC as design variable, taking the maximum stress and maximum strain of prototype worktable as constraint conditions, taking maximum of the first three order natural frequency and the lightest mass of worktable filled with BFPC as object function, the sensitivity histogram and response surface of each parameter are acquired by using optimization design. Then the best width and height of rectangular hole of worktable filled with BFPC are finally determined. The static and dynamic performance, quality and the first three order natural frequencies of the optimized filling structure are compared with the prototype structure. Finally we can know that the static, dynamic performance of the machine tool can be improved by using worktable filled with BFPC and ensuring light weight.

Dynamic Modeling and Optimal Design of a Horizontal Machining Center Based on Experimental Modal Analysis

The modeling and optimization of machine tool’s dynamic performance remains to be a grand challenge in machine tool design. In this paper. In order to identifying the concentrated modals of a horizontal machining center, a combined experiment modal analysis method is proposed. A FEA dynamic model accurate in frequency and mode shape is built and verified by comparing with EMA results. Based on the model the optimization of frame structure is made, Simulation results shows the optimized frame enhances the dynamic performance of machine tool.

Dynamic Characteristics Analysis of the Feeding System Based on Conjoint Interface

Because the key factors of the dynamic performance of the machine tool are related to the characteristics of the conjoint interface, the feeding system as an important part of the machine tool, which contains typical rolling conjoint interface and fixed conjoint interface, so in order to study the dynamic performance of machine tool better, the modal analysis is carried out on the feeding system. In this paper, the finite element model simulation and test methods will be combined. First, making a finite element analysis of the feeding system to obtain its corresponding mode and frequency; Secondly, the actual modal test experiment is carried out, and the result is compared with the simulation result through the follow-up data processing; Finally, the causes of the error are analyzed, and the correctness of the method is verified.

An iterative feed rate scheduling method with confined high-order constraints in parametric interpolation

Feed rate scheduling of complex tool path is critical for improvement of processing efficiency by fully exploiting the dynamic performance of machine tool in CNC machining. To overcome the complexity and low efficiency of conventional feedrate scheduling algorithm in computation, an iterative feed rate optimization method is proposed. In this work, the constraints that can reach the third-order derivative of motion in trajectory and drive system are established according to the differential operation of tool path and the feed rate profile. Besides, the feed rate expressed in the form of B-spline curve is adjusted iteratively by raising the control points from a zero-speed velocity curve. Specifically, in each iteration process, the control points are raised one by one through binary search technique to approach the permissive maximum with the constraints bounded. The iteration process terminates when the maximum increment of control points is less than the predefined threshold and then a near time-optimal feed rate is achieved. The scheduled feed rate derived by the iterative optimization method possesses both superior time-optimality and enough motion smoothness to the constraints without leading to excessive computation load. At last, the validity of the proposed method is verified by the simulation cases and the experiments.

Virtual metrology frame technique for improving dynamic performance of a small size machine tool

This paper presents a novel concept, a virtual metrology frame, for enhancing the dynamic performance of a machine tool with a flexible structural frame. The dynamic properties of a machine are directly affected by the stiffness of its frame, and its reference system; thus, by having an unstressed metrology frame, superior dynamic capabilities can be achieved. The developed concept does not require physical components associated with metrology frame; hence it is ideal for machine tools with requirements for small footprint and ultra-precision performance. The concept relies on an accelerometer based dynamic displacement feedback technique, where the accelerometer is used as a precision frame displacement sensor. The concept does not require a complex controller, and was realized in an off-the-shelf CNC controller. The concept was demonstrated on a linear motion system, a simplified version of a compact size CNC machine, and its servo bandwidth and dynamic stiffness were improved by 36% and 70% respectively, which are the key parameters for improving the machining accuracy.

Stiffness and damping model of bolted joint based on the modified three-dimensional fractal topography

The machine tools are consisted of many parts and most of them are connected by the bolts. Accurate modeling of contact stiffness and damping for bolted joint is crucial in predicting the dynamic performance of machine tools. This paper presents a modified three-dimensional fractal contact model to obtain the stiffness and damping of bolted joint. Topography of the contact surface of bolted joint is fractal featured and determined by fractal parameters. Asperities in microscale are considered as elastic, elastic–plastic, and full plastic deformation. The expand coefficient ψ is introduced to the size-distribution function of asperities. The real contact area, contact stiffness, and damping of the contact surface can be calculated by integrating the microasperities. The relationship of contact stiffness, damping, fractal dimension D, and fractal roughness parameter G can be obtained. Experiments are conducted to verify the efficiency of the proposed model. The results show that the theoretical mode shapes are in good agreement with the experimental mode shapes. The relative errors between the theoretical and experimental natural frequencies are less than 3.33%, which is less than those of the W-K model and L-L model. The presented model can be used to accurately predict the dynamic characteristic of bolted assembly in the machine tools.

Surface Polishing of Hardened Grey Cast Iron with a Compliant Abrasive Filament Tool

Sliding guideways play a critical role in the accuracy and dynamic performance of machine tools. Discontinuous jerking motion occurs due to wringing if the guides are too smooth, but excessive wear results is the surface is too rough. The current fabrication approach uses large and expensive grinding machines that place logistical restrictions on production. A higher productivity milling process, using cubic boron nitride (CBN) tooling has been attempted, but this process does not achieve the necessary surface quality. Secondary finishing using a spindle mounted abrasive filament tool could be implemented as a post process to improve surface quality. This study determined the relationship between number of passes and Spk, Sk, and Svk areal functional parameters for three types of filament tools.

Research on Optimization of Column Structure Design for Dynamic Performance of Machine Tool

Research on Optimization of Column Structure Design for Dynamic Performance of Machine Tool

Virtual System to Simulate the Performance of Various Categories of Machine Tools during the Design Stage

This paper presents a simulation system designed to evaluate the static and dynamic performance of machine tools. The design considerations of the evaluation system are discussed and the system is then employed in order to compare between various categories of milling machine's structure adapted for end milling operation. The machine performance is identified in terms of static loop stiffness in both x and y directions, mode shapes, and frequency response function (FRF) at tool center point (TCP). The advantage of such a reliable model is that it could replace the many experimental tests that must otherwise be carried out each time the parameters affecting the machine tool performance are changed.

Investigation on the Influence of Machine Tool Dynamics on the Wavefront Gradient of KH2PO4 Crystals

The root mean square gradient (GRMS) is a key parameter for KH2PO4 crystal of low-frequency wavefront, which affects the focusing performance in the inertial confinement fusion (ICF) system. The large wavelength waviness on the machined surface has significant influence on the GRMS. In this paper, the influence of the large wavelength waviness on the GRMS and the main sources resulting in the large scale ripples are analyzed based on dynamics analysis of the machine tool. The dynamic performance of machine tool is optimized and the reasonable dynamic stiffness region is obtained. Furthermore, the machined and the tested results validate the usefulness of the theoretical analysis.

The Improved Modal Analysis of Driving Shaft for Machine Tool Based on Finite Element Model

With the continuous development of machine tool technology, the machine design requires more and more work for the precision and high quality direction. The design of the driving shaft for the whole machine tool has a very important influence. To improve the ability to make rational analysis and accurate dynamic performance of machine tool, this paper presents an analysis method of modal improved driving shaft based on the amount of calculation, the flow and the external factors are improved, the method can improve the design level of machine tool, making full analysis and detailed characteristics of the whole machine, for further improvement of the machine has a reference role in science.

A Prediction Method for Dynamic Performance of Machine Tool Joint Surfaces

The method for dynamic modeling of joint surfaces is proposed to predict dynamic performance of machine tool accurately by virtual material layer elements in this paper. For this process, the numerical relations of contact stiffness and virtual material layer parameters are obtained by finite element theory, and the finite element model is founded by virtual material layer elements and multiple point constrain technique (MPC). Modal analysis of a simple model under different contact stiffness is carried out. It has shown the relative errors between theoretical natural frequencies and simulated ones of this model are less than 2%.

Fuzzy Adaptive PID Control for Parallel Machine Tool

The hydraulic control system, which is important composition of parallel machine tool, is a high order, nonlinear, parameter uncertain system, which seriously affect dynamic performance of machine tool, So it is very difficult to gain good performance with traditional control. By making a single-channel control of parallel machine tool as the research object, a fuzzy adaptive PID controller is proposed based on the traditional PID control and fuzzy control theory. Using the Fuzzy PID controller, PID parameters can real-time change and the system has good adaptive ability and robustness. System dynamic simulation is made by the MATLAB. Simulation results reveal that the performance of this adaptive fuzzy PID controller is much better than the conventional PID controller, even in the external disturbance and system conditions changing, this controller has the the characteristics of fast response and good robustness.

Facing the Dynamic Performance of Machine Tools for the Optimization of Column

Structure Dynamic Design theory, including its core analysis of the results of the mechanical properties and structure optimization, in order to ensure the reliability of the structure, improve the use of equipment reliability, improve efficiency provides a strong theoretical support. By the method of variable analysis focuses on the reinforcement plate column, door-type column constrains represented by a single-ended cantilever dynamics with different structures, parameters of the relationship, and for YK2275 column structure is optimized, make the first three natural frequencies varying degrees of increase, an average of 10%.

Development of a dynamic performance test on the lathe.

With increasing demands on automatic and high-capability manufacturing, the dynamic performance of machine tools becomes more important for a cutting system. However, no proper standard has yet been established to estimate the dynamic performance. In this paper, the relationship between compliance of the cutting system and the commencing point of chatter vibration is checked with impulse excitation and cutting tests on some cutting systems. Then, a practical and reliable test method of the dynamic performance of the lathe is investigated. The results obtained from this study are as follows : (1) It was proven that there is a mutual relationship between the compliance characteristic of the cutting system and the commencing point of chatter vibration. (2) The relationship between the commencing point of chatter vibration and feed rate, in other words, exciting force, is clarified quantitatively under several cutting conditions. (3) The possibility of estimation for several lathes is confirmed on the dynamic performance with this method.

CJ89-35. A new method to assess the stability in the dynamic performance of machine-tool : By Xiao Youyi and Peng Zemin (Tianjin University, Tianjin, China). Chinese J. Mech. Engng25, No. 3 (Sept., 1989), pp. 24–30

Characterization of functional outcome in animal stroke models is essential to improve preclinical drug screenings. Operant procedures showed promising results for the identification of long-lasting functional deficits. In particular, a suppression of lever-pressing in high ratio schedules has been consistently found in rodent models of ischemic stroke. In the present work, we attempted to replicate these isolated observations, by submitting C57Bl/6J mice to a progressive fixed-ratio schedule of reinforcement three weeks after MCAO or sham surgery. Results showed a significant lever-pressing impairment in the MCAO group. Motivational factors (longer post-reinforcement pause, lesser appeal for food rewards) seemed accountable for the deficit, while motor abilities appeared preserved. These findings resemble fatigue-like states experienced by stroke survivors and may be used as long-term measures of behavioral outcome following experimental stroke.