Evolution of methods of assessing the accuracy of metal-cutting machines

The evolution of concepts of accuracy and attainable machining accuracy are considered. The physical aspects of accuracy are discussed. The changes in the level of precision since 1800 are outlined, with predictions of what is attainable in the future. The energy barrier to accuracy is analyzed for various cutting technologies.     

Optimal materials for the manufacture of metal-cutting machines

With the goal of improving machine-tool design, attention focuses on the possibility of manufacturing the components of metal-cutting machines from effective new nonmetallic materials that not only meet all the current requirements on such machines but also in most cases improve their performance. The best results are obtained with metal–concrete structures in which the nonmetallic binder consists of modified cement with chemically active additives. Results from materials science are compared with multiyear production tests of metal-cutting machines based on metal–concrete components, which are characterized by stable performance over time. On that basis, an effective new approach is proposed for the modernization of machine tools at the end of their effective working life, without replacing the fundamental structures. The design of the basic structures is analyzed. The production of metal–concrete components in a specialized department of the manufacturing plant is recommended.     

Trends in research on metal-cutting machines

This review covers the current state and prospects for the design of metal-cutting machines, including numerically controlled machines. The characteristics of common mechatronic modules are considered. The structure of metal-cutting machines is outlined, and means of complying with operational requirements are presented.     

Patterns of thermal behavior of metal-cutting machines

The basic methodological principles relating to the thermal behavior of metal-cutting machines are outlined. Standard formulas for the relative displacement of the shaping tools are presented and analyzed.     

Classification of metal-cutting machines by energy efficiency

Methods of determining the energy efficiency of machine tools are analyzed, including methods based on the input energy balance, the expenditures in machining, and energy losses in the shaping structure of the machine tool. The energy efficiency may be assessed in terms of the energy ratio of the physical processes within the machine tool. On that basis, metal-cutting machines may be classified by energy efficiency.     

Diagnostics of metalworking machines

Diagnostics of machine-tool damage on the basis of the change in trajectory of the blank’s axis and the cutter trajectory is considered.     

A microcomputer-based controller for milling machines

The design and development of a microcomputer-based servo motor controller is presented. The control procedure is implemented within the microcomputer so that it can be modified easily. Indeed, the flexibility introduced by the software rather than the usual emphasis on hardware makes the control package extremely attractive for machine retrofits or the custom machine-tool market. Enhancements to a standard model of servo motor, the use of sampled-data techniques and a custom-developed interface card made it possible for one particular machine tool to achieve positional accuracies of the order of 0.0005″ at the machine's maximum feedrate of 30 in min⁻¹.     

Thermal behavior of components in metal-cutting machines

The thermal behavior of components in metal-cutting machines is considered, and corresponding formulas are derived. Characteristics of standard components are determined, and their ranges are noted.     

Analysis and Synthesis of Dynamic Characteristics of Machine-Tool Equipment Based on Rotary Linear Modules

The use of mechatronic rotary linear modules in manipulators of machine-tool equipment is considered. A solution to the inverse position problem is presented, and the kinematic capabilities of a device based on mechatronic rotary linear modules for machine-tool equipment are evaluated. Dynamic equations have been derived used to evaluate the dynamic characteristics and the precision of the finishing of complex surfaces by the example of the machining of a gas-turbine engine blade feather.     

Precision and efficiency of metal-cutting machines

Approaches to improving the design of metal-cutting machines are discussed. The most important problems relating to the precision, thermal processes, dynamic modeling, and diagnostics of metal-cutting machines are considered.     

Systems approach to the design of technological equipment for metal-cutting machines

The design of technological equipment for metal-cutting machines is considered, for the example of machining and monitoring attachments. Their design on the basis of a systems approach is outlined. The principles and technology for systems design of technological attachments are briefly outlined.     

Modal control in the supply drives of metal-cutting machines

Modal control of the transverse supply drive in a numerically controlled lathe is considered. The control method is based on stabilization of the elastic deformation with change in thickness of the cut margin, so as to ensure a constant value within the motor??s armature chain.     

评定机床颤振稳定性的新方法

本文考虑了进行机床动态试验时切削宽度连续变化这一时变因素对机床颤振稳定性的影响。由于切削宽度的连续变化,给切削过程引入了新的反馈因素,从而影响机床颤振稳定性。稳定性条件不仅与机床结构有效动柔度的实部有关,而且与相应的虚部及结构主振频率有关。因而传统理论不再适合做为评定机床动态性能的理论依据。本理论给出的稳定性条件,包含了切削工艺参数、工件材料及形状、机床结构动力学参数对机床颤振稳定性的影响,更符合实际地描述了颤振建立的客观条件,是建立新的机床动态性能评价指标的可靠理论基础。     

Optimal machining cycles for numerically controlled metal-cutting machines

The design of optimal automatic machining cycles for numerically controlled metal-cutting machines is considered, in theoretical terms. Dynamic programming permits the optimization of an unlimited number of control parameters for all the machining operations in numerically controlled metal-cutting machines.     

Parametric time-domain methods for non-stationary random vibration modelling and analysis — A critical survey and comparison

A critical survey and comparison of parametric time-domain methods for non-stationary random vibration modelling and analysis based upon a single vibration signal realization is presented. The considered methods are based upon time-dependent autoregressive moving average (TARMA) representations, and may be classified as unstructured parameter evolution, stochastic parameter evolution, and deterministic parameter evolution. The main methods within each class are presented, and model “structure” selection is discussed. The methods are compared, via a Monte Carlo study, in terms of achievable model parsimony, prediction accuracy, power spectral density and modal parameter accuracy and tracking, computational simplicity, and ease of use. Comparisons with basic non-parametric methods are also made. The results of the study confirm the advantages and high performance characteristics of parametric methods. They also confirm the increased accuracy and performance characteristics of the deterministic, as well as stochastic, parameter evolution methods over those of their unstructured parameter evolution counterparts.     

Design of special machine-tool attachments

The automated design of special machine-tool attachments for the machining of high-tech parts and assemblies in order-based production is considered theoretically and experimentally. New models and methods are discussed.     

非圆齿轮线切割加工数控程序计算机辅助设计研究

非圆齿轮,特别是螺线形非圆齿轮的切齿加工,在没有专用机床的条件下是非常困难的。本文作者利用计算机和数控线切割现代手段加工成一对阿基米德螺旋线形非圆齿轮。为了在线切割机床上进行齿形加工,必须计算出非圆齿轮每个齿的渐开线齿廓坐标。在计算中我们没有用标准渐开线方程,而是根据圆柱齿轮的啮合原理,找到齿面法线与节圆交点跟齿面之间的几何关系,利用这种关系算出每个齿的齿廓坐标,然后编成数控程序,由计算机打印出来并穿成孔带,由线切割机床加工成非圆齿轮。     

Estimation of the accuracy of Taylor length scale measurements by two-point LDV in reciprocating engines

The accuracy of the direct measurement of the Taylor length micro-scale by two-point laser Doppler velocimetry in a motored engine is analysed. The probe volume length, the portion of the correlation curve used to fit a matching parabola and the ratio between the integral and Taylor length scales of the turbulent field are the basic parameters of the present analysis. A second order model of compressed turbulence is used to predict the theoretical evolution of the integral and Taylor length scales in a reciprocating engine during the compression and expansion strokes without combustion. This prediction permits us to estimate the uncertainty on the measured length scales by simulating the finite length of the probe volumes. Finally, the application of the theoretical analysis in a real motored engine is presented and an attempt to remove bias from experimental Taylor scale has been made.     

An integrated computer-aided decision support system for die stresses and dimensional accuracy of precision forging dies

Precision forging is a field in which decision support systems can be effectively and widely applied and depends on knowledge and rules derived from the past experience of forging die design engineers. Precise components are becoming quite important in attempts to reduce cost and improve reliability. There are thus many application areas in which the rules themselves become inherent to the parts or the processes. In forging die design, dimensional accuracy is one of the main goals. The load carrying capacity and life of any forged product is greatly affected by its dimensional accuracy. To predict the precise dimension of the part and determine the die dimension for precision forging, it is necessary to analyze the factors which affect dimensional accuracy. Dimensional evolution of die and product should be analyzed at each stage of forging. In this study, both radial and tangential stresses are encountered in the determination of die stresses since cylindrical workpieces were used. In order to sustain dimensional accuracy of the forging die, differences between the forging product and the die insert such as elastic die expansion and product contraction are presented.     

The effect of interface friction on the inplane flexibilities of machine tool joints

The effect of interface friction between contact surfaces on the flexibilities of machine-tool joints is studied. The joint flexibility is determined by applying unit load successively at one end of the joint while keeping the other end fixed. Only plane problems have been taken up for consideration. A finite element based numerical procedure is used for solving the problem. Results are presented for the care of a hypothetical machine tool joint and dovetail joint for various values of friction coefficient. It is observed that the decrease in flexibility is only 15% for values of friction coefficient μ = 0.2.