Machine Tool Design Research Articles

Dynamic stability of a paralle kinematic machine

Machine tool chatter causes machining instability, surface roughness, and tool wear in metal cutting processes. A stability lobe diagram based on the theory of regenerative vibration is an effective tool to predict and control the chatter. This paper presents the advances in the mechanical design of a parallel kinematic machine tool. The features that make it ideal for machining tasks, and that make unique in its own way, are highlighted. In addition, the description of the progress of this work will be focused on the analysis of the stability limitation for machining systems to derive the stability lobe diagram with modal analysis of the spindle. A vibratory model is developed by adding cutting forces and including analytical equations for the depth of cut and for the cutting speeds, both depending on the frequency of vibration. A step-by-step procedure provides a stability lobe diagram. The results show that it is relatively easy to provide a relationship between depth of cut and spindle speed. In turn, it makes it easy to compare machining processes under different cutting parameters and conditions.

Modular configuration design of a special machine tool for variable hyperbolic circular-arc-tooth-trace cylindrical gears

Abstract. In this paper, the machining principle of variable hyperbolic circular-arc-tooth-trace (VH-CATT) cylindrical gears is analysed, and a modular configuration design of this special machine tool is carried out. Based on the importance of parameter and knowledge dependence of rough set theory, the degree of influence of the index hidden in the data on the decision-making results is mined, and an algorithm for calculating the objective weight of the index is given. The comprehensive weight of the index is then obtained, combining the analytic hierarchy process. After obtaining the results of the index's comprehensive weight and module attribute classification, a module retrieval strategy is formulated using the fuzzy similarity priority ratio algorithm. Based on the modular division of this special gear-making machine tool, the modular configuration sequence of the machine tool using the depth-first search algorithm is determined. According to the module retrieval strategy and configuration sequence, a traversal of module instances is carried out, and a variety of modular configuration schemes of the machine tool is obtained, which provides a practical and efficient method for the rapid design of a special machine tool for VH-CATT cylindrical gears.

COMPUTER-AIDED DESIGN OF MECHATRONIC MACHINE EQUIPMENT LAYOUTS USING THE SOLIDWORKS SOFTWARE PACKAGE

The article proposes a technique for carrying out preliminary design of mechatronic machine tools using the SolidWorks computer-aided design system. This design system is the most popular in the engineering field and includes various add-ons for preliminary design.

Kinematic and Stiffness Modeling of a Novel 3-DOF RPU+UPU+SPU Parallel Manipulator

A novel 3-degrees of freedom (DOF) <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RPU+UPU+SPU</i> parallel manipulator (PM) is proposed in this study, and its complete kinematics and stiffness are studied systematically. First, the architecture description is discussed, and the inverse and the forward positional posture analysis are studied based on the constraints in the PM. Second, the Jacobian matrix, the velocity model, the Hessian matrix and the acceleration model are derived in explicit and compact forms. Third, based on the virtual work principle, the static model and the deformation decompose method, the stiffness model is built. Meanwhile, the stiffness matrix and the compliance matrix are obtained. Finally, the correctness of the models built in this study are verified by simulative PMs. This study is expected to provide new ideas for the design of PM machine tools.

Digital Model and Assembling of a Lathe

The article aims at developing a digital model of a lathe and the related technology for its assembling. The study is based on analyzing the service purpose and technological capabilities of modern modular machine tools, justification and development of the machine tool design according to the specified production conditions, and development of a technological process for assembling the proposed modular machine tool. The geometric modeling techniques and the design documentation were implemented to justify the rational choice of design parameters of the machine tool design and its spatial model. The proposed approach also considers structural elements and the relationships between them. As a result, a conceptual approach was proposed to design technological processes of lathe assembly with a wide range of technological capabilities. It allows implementation of the up-to-date strategy from idea to finished product at industrial enterprises. The practical significance of the obtained results for the machine-building industry is in the proposed practical recommendations for developing the technological process for assembling lathes.

Dimensionality Reduction of High-Fidelity Machine Tool Models by Using Global Sensitivity Analysis

Abstract Models that are able to accurately predict the dynamic behavior of machine tools are crucial for a variety of applications ranging from machine tool design to process simulations. However, with increasing accuracy, the models tend to become increasingly complex, which can cause problems identifying the unknown parameters which the models are based on. In this paper, a method is presented that shows how parameter identification can be eased by systematically reducing the dimensionality of a given dynamic machine tool model. The approach presented is based on ranking the model’s input parameters by means of a global sensitivity analysis (GSA). It is shown that the number of parameters, which need to be identified, can be drastically reduced with only limited impact on the model’s fidelity. This is validated by means of model evaluation criteria and frequency response functions which show a mean conformity of 98.9% with the full-scale reference model. The paper is concluded by a short demonstration on how to use the results from the GSA for parameter identification.

Design and Simulation of CNC Milling Machine on Matlab

The development and revision of milling machines and components are continuous. With the help of computer technology, we can simulate some activities in a manufacturing system. The main purpose of a simulation is to understand and imitate the behavior of a particular manufacturing system on a computer, before hardware creation, thereby reducing the amount of testing and experimentation in the field. By using a virtual system, less material is wasted and the constraints on the actual operation of the machine in the field can be minimized. In the field of milling machinery, various modeling and simulation methods have been introduced so far. Today, the manufacture of a machine tool can no longer use the time-consuming and costly manufacturing and testing of physical prototypes to detect weak points and then optimize the design. In contrast, the current machine tool design process uses "virtual prototyping" technology to reduce the cost and time of hardware testing and iterative improvements to physical prototypes. The model of a milling machine can be simulated in Matlab simulations through analytical methods using various compositions. The presented virtual modeling methods and milling machine tool simulations make it possible to design, perform complex analyses, test, optimize, and use various types of control structures. in the computer simulation.&#x0D; Keywords: Milling Machine, CNC Miling Machine, Matlab

METHOD FOR SAFE EXPERIMENTAL TESTING OF MACHINE TOOL USABLE SPINDLE POWER

The regenerative chatter during milling is a consequence of the machine tool dynamic compliance and the specific setting of the cutting process. The basic request on the machine structure is to enable a stable cut with dominant portion of the installed spindle power. In order to improve the dynamic properties of newly-designed machine tools, the machine tool structures are optimized using various advanced simulation methods and are made of various advanced materials. The final design should be tested experimentally. The test of usable spindle power provides important feedback on the machine tool design. The testing of large machine tools is time consuming due to the significantly varying machine dynamic compliance dependent on the working space. Due to the installed high power and large diameter tools used, the occurrence of chatter might be dangerous with a high risk of machine tool damage. The article presents a method for the safe and time-effective experimental testing of the machine tool usable spindle power. The method is based on the experimental identification of the cutting force coefficients and the experimental identification of machine tool behavior with the support of extrapolation models based on identified experimental data. The dynamic compliance is measured within a rough network of measurement points in the machine working space. The measured dynamic compliance results are characterized by a model based on modal identification data. Only a few cutting tests are done for the cutting force coefficient identification. Finally, a map of the usable spindle power is calculated. This approach makes it possible to calculate the results with respect to the real machining process and the current machine tool conditions across the whole working space in an acceptable time. The approach is demonstrated on a real case study.

A device to reduce positioning errors due to the machine tool compliance

One of the main problems that large machine tool designers must face is the onset of deflection and vibration due to the forces involved during the process: the own weight of the elements of the machine, the cutting forces and the inertial forces. The last ones are especially relevant in the case of large and heavy machine tools with cantilever elements as rams or columns. To counteract these forces, the present work proposes the use of an inertial device, based on the rotation of two eccentric mases around the same axis. Hence, a simplified dynamic model of a column is first developed, and tested during a standard face milling operation. Then, the dynamic model of the device is also developed, and a Computed Torque Control is proposed to govern the action of the device. The simulations show that the use of this device has the potential to reduce drastically the effect of the inertial forces and even the lower frequency components of the cutting forces.

Influence of the positioning accuracy given by the positioning encoder of the CNC machine tools

The CNC machine tools are present at a large extent worldwide, for machining by cutting all kinds of work pieces. Their machining accuracy and quality are crucial to obtaining very accurate and intricate work pieces. The accuracy of a CNC machine tool is given by the quality of each and every kinematic linkage/coupling in its structure. This work aims at researching the influence of several constructive and functional factors on the positioning accuracy of a kinematic coupling in the structure of a CNC machine tool. The influence caused by noncompliance with the Abbé principle on the positioning accuracy of a feed kinematical linkage is analysed into detail, both at idle and load running. Out of this research useful conclusions are resulting for the CNC machine tool designers and builders, with respect to optimising several constructive factors, such as the location of the position encoder, location of the ball screw, stiffness of the directional guideways etc., in order to improve the accuracy of the CNC machine tool. The results of the theoretical research have been validated through experimental trials, confirming the impossibility of full compliance with the Abbé on the CNC machine tools.

A comprehensive nonlinear dynamic model for ball screw feed system with rolling joint characteristics

Modern tendency of machine tools design requires more accurate model to predict the system dynamics, in order to anticipate its interaction with machining process. In this paper, a comprehensive dynamic model of ball screw feed system (BSFS) considering nonlinear kinematic joints is introduced to investigate the varying dynamic characteristics when worktable is subjected to combined load from six directions. The load–deformation relationship of each kinematic joint is dealt with a set of translational and angular spring elements. The nonlinear restoring force function of each joint involving coupling displacement is calculated. Based on the lumped mass method, the analytical 18-DOF dynamic equation is formulated by the analysis of the interaction force between joints. Model verification tests are conducted. The worktable response exhibits the abundant and fascinating nonlinear phenomena arising in nonlinear joint and coupling effect. The nonlinear behavior behaves significant difference owing to the variations of excitation, platform position, screw length, preload and damping of joints. Thus, the model is promising for comprehension of machine dynamic behavior and for development of sophisticated control strategy.

Electrical System Design and Fault Analysis of Machine Tool Based on Automatic Control

Automatically controlled machine tools have been used extensively in the industrial field, and fault analysis methods have garnered increasing attention. This paper first describes the software and hardware design of a machine tool and then presents a fault analysis of the machine tool. The fault types of machine tools are analyzed. A signal is obtained from a vibration sensor, the characteristic value is extracted, and the fault is analyzed using a back-propagation neural network (BPNN). The experimental results show that the BPNN yields the best performance when the structure is 8-9-8, and its recognition rate is 97.22% for different types of faults. Meanwhile, the recognition rate of naive Bayes is only 76.73%, and that of a support vector machine is only 85.55%, which is significantly lower than that of the BPNN. The results show that the BPNN is effective in fault analysis and can be promoted and applied more extensively.

ENHANCEMENT OF SPECIALISED VERTICAL TURNING LATHE ACCURACY THROUGH MINIMISATION OF THERMAL ERRORS DEPENDING ON TURNING AND MILLING OPERATIONS

Achieving high workpiece accuracy is a long-term goal of machine tool designers. There are many causes of workpiece inaccuracy, with thermal errors being the most dominant. Indirect compensation (using predictive models) is a promising strategy for reducing thermal errors without increasing machine tool cost. A modelling approach using thermal transfer functions (a dynamic method with a physical basis) embodies the potential to deal with this issue. The method does not require interventions into the machine tool structure, uses a minimum of additional gauges and its modelling and calculation speed is suitable for real-time applications with fine results with up to 80% thermal error reduction. Advanced machine tool thermal error compensation models have been successfully applied on various kinds of single-purpose machines (milling, turning, floor-type, etc.) and implemented directly into their control systems. This research reflects modern trends in machine tool usage and as such is focused on the applicability of the modelling approach to describe specialised vertical turning lathe versatility. The specialised vertical turning lathe is adequately capable of carrying out turning and milling operations. Calibration of the reliable compensation model is a real challenge. The applicability of the approach during immediate switching between turning and milling operations is discussed in more detail.

Design of multipurpose mechanical Machine

This paper focuses on designing of Multi-Purpose Mechanical Machine. The research specializes in design and development of multi-purpose machine tool which is able to perform multiple operations like drilling, cutting and grinding simultaneously and can also performs one operation at a time as per the requirement. The functions of machine tools are to transform the raw substances with the help of machining operation to finished part with precise geometry, dimensions and surface quality. The call for is increasing to provide elements with high standard at minimal cost, the machine tools are required to have better machining, precision and speed. This research paper proposed a machine which can perform operations like drilling, cutting and grinding simultaneously which means that industrialist have no need to purchase different machines for different operational task.

Methodology for the design of a reconfigurable guillotine shear and bending press machine (RGS&amp;BPM)

Purpose In manufacturing, dedicated machine tools and flexible machine tools are failing to satisfy the ever-changing manufacturing demands of short life cycles and dynamic nature of products. These machines are limited when new product designs are introduced. The solution lies in developing responsive machines that can be adjusted or be changed functionally when these change requirements arise. These machines are reconfigurable machines which are becoming the new focus, as they rapidly respond to product variety and volume changes. A sheet metal working machine known as a reconfigurable guillotine shear and bending press machine (RGS&amp;BPM) has been developed. The purpose of this paper is to present a methodology, function-oriented design approach (FODA), which was developed for the design of the RGS&amp;BPM. Design/methodology/approach The design of the machine is based on the six principles of reconfigurable manufacturing systems (RMSs), namely, modularity, scalability integrability, convertibility, diagnosability and customisability. The methodology seeks to optimise the design process of the RGS&amp;BPM through a design of modules that make up the machine, enable its conversion and reconfiguration. The FODA is focussed on function identification to select the operational function required. Two main functions are recognised for the machine, these being cutting and bending; hence, the design revolves around these two and reconfigurability. Findings The developed design methodology was tested in the design of a prototype for the reconfigurable guillotine shear and bending press machine. The prototype is currently being manufactured and will be subjected to functional tests once completed. This paper is being presented not only to present the methodology by to show and highlight its practical applicability, as the prototype manufacturers have been enthusiastic about this new approach. Research limitations/implications The research was limited to the design methodology for the RGS&amp;BPM, the machine which has been designed to completion using this methodology, with prototype being manufactured. Practical implications This study presents critical steps and considerations in the development of reconfigurable machines. The main thrust being to explore the best possibility of developing the machines with dual functionality that will assist in availing the technology to manufacturer. As the machine has been development, the success of the design can be directly attributed to the FODA methodology, among other contributing factors. It also highlights the significance of the principles of RMS in reconfigurable machine design. Social implications The RGS&amp;BM machine is an answer for the small-to-medium enterprises (SMEs), as the machine replaces two machines with one, and the methodology ensures its affordable design. It contributes immensely to the machine availability by eliminating trial and error approaches. Originality/value This study presents a new approach to the design of reconfigurable dual machines using principles of RMS. As the targeted market is the SME, it is not limited to that as any entrepreneur may use the machine to their advantage. The design methodology presented contributes to the body of knowledge in dual reconfigurable machine tool design.

Effect of metal foam on vibration damping and its modelling

The use of metal foams for damping vibrations of mechanical structures has found interesting applications in machine tools and its components. Indeed, undesired vibration is one of the most detrimental causes that limit the machine performance in terms of the maximum achievable material removal rate MRR. Although positive results were presented in some research works, a methodology for predicting the damping properties of such materials in the machine tool design phase using finite element codes is still missing. In order to bridge this gap, in this paper, an experimental procedure for identifying the damping contribution of the aluminum metal foam to the hosting structure is proposed. The experimental data are even used to develop a model for predicting the damping. The procedure is further validated on a dummy structure.

Algorithm for Designing Reconfigurable Equipment to Enable Industry 4.0 and Circular Economy-Driven Manufacturing Systems

In the paradigm of industry 4.0, manufacturing enterprises need a high level of agility to adapt fast and with low costs to small batches of diversified products. They also need to reduce the environmental impact and adopt the paradigm of the circular economy. In the configuration space defined by this duality, manufacturing systems must embed a high level of reconfigurability at the level of their equipment. Finding the most appropriate concept of each reconfigurable equipment that composes an eco-smart manufacturing system is challenging because every system is unique in the context of an enterprise’s business model and technological focus. To reduce the entropy and to minimize the loss function in the design process of reconfigurable equipment, an evolutionary algorithm is proposed in this paper. It combines the particle swarm optimization (PSO) method with the theory of inventive problem-solving (TRIZ) to systematically guide the creative potential of design engineers towards the definition of the optimal concept over equipment’s lifecycle: what and when you need, no more, no less. The algorithm reduces the number of iterations in designing the optimal solution. An example for configuration design of a reconfigurable machine tool with adjustable functionality is included to demonstrate the effectiveness of the proposed algorithm.

Design and development of a five-axis machine tool with high accuracy, stiffness and efficiency for aero-engine casing manufacturing

In order to satisfy the machining requirements of aero-engine casing in modern aviation industry, this paper investigates three main issues during the design and development process of a five-axis machine tool with high accuracy, stiffness and efficiency, including whole structure design, key components design, and supporting stiffness design. First, an appropriate structure of five-axis machine tool is determined considering the processing characteristics of aero-engine casing. Then, a dual drive swing head and a compact motorized spindle are designed with enough drive capability and stiffness, and related structure, assembly method, cooling technology, and performance simulation are given in detail. Next, a design method of supporting stiffness of guide is proposed through the deformation prediction of the spindle end. Based on above work, a prototype of machine tool is developed, and some experiments are carried out, including performance tests of swing head and motorized spindle, and machining of a simulated workpiece of aero-engine casing. All experimental results show that the machine tool has satisfactory accuracy, stiffness and efficiency, which meets the machining requirements of aero-engine casing. The main work can be used as references for engineers and technicians, which are meaningful in practice.

A novel transient infrared-thermography based experimental method for the inverse estimation of heat transfer coefficients in rotating bearings

Heat Transfer at moving bearing interfaces is a key parameter for the thermal characterization and design of high precision machine tools and electrical engine systems for e-mobility application. Yet, the majority of experimental approaches use tactile sensors to obtain the required temperature information for the calculation of heat transfer coefficients. However, only a limited amount of sensors can be placed in the investigated system, also including significant measurement uncertainties, long investigation times, and providing only access to local temperature information. To overcome these shortcomings, a novel method is presented, using infrared thermography to obtain transient and spatially resolved temperature information of bearing front surfaces. The recorded temperature data is used in an inverse evaluation algorithm, to determine the heat transfer coefficient, considering for modeling heat conduction as well as convective fluxes due to rotating components. Finally, experimental temperature data and calculated heat transfer coefficients are presented, discussing further the effect of low angular velocities on the heat transfer. It is shown, that this method is capable to detect changes in heat transfer coefficient due to variations in rotational speed which was not possible with existing methods. Concluding, this approach can be used in future work to focus in detail on the influence of different rolling elements, geometry and interstitial media.

Quality scale the design of a metal-cutting machine

A method is proposed for assessing the quality of a working structure, based on its study as a thermodynamic system, in contrast to its accepted assessment in a static state. This interpretation requires the use of an indirect method for assessing the quality of the structure during operation. Keywords: machine tool design, design quality, measurement unit, quality scale. dmitriev@bmstu.ru