Machine Tool Assembly Research Articles

A multi-objective model for integrated supplier order allocation and supply chain network transportation planning decision-making

Effective supplier order allocation (SOA) and transportation planning (TP) are critical for the smooth operation of supply chains, especially in dynamic markets with evolving customer demands. While previous research has made significant strides in addressing these areas individually, studies that integrate both aspects while considering a comprehensive set of objectives are limited. This study introduces an innovative multi-objective model that concurrently addresses total operational costs, supplier defect rates, sustainability performance, and supply chain network disruption risks. The model applies an augmented max–min approach of fuzzy multiple objective linear programming (AMM-FMOLP), which enhances overall utility while ensuring balanced performance across all objectives. The inclusion of all five objectives in the model is essential for a holistic evaluation of supply chain performance. The model’s effectiveness and practicality are validated through a case study involving a computer numerical control (CNC) machine tool assembly company, under various scenarios. Additionally, sensitivity analysis reveals how adjustments in supply chain structure can further improve performance. Moreover, the execution process of this study does not require expert intervention, making it a unique data-driven decision model particularly suitable for intelligent supply chain management and decision-support systems. This approach enhances the flexibility and resilience of supply chains, enabling them to effectively respond to unforeseen events and minimize their impact on business operations, especially in volatile global markets.

An energy consumption field model considering motion position errors for energy efficient machining on CNC machines:CNC programming perspective

Motion position errors, which are caused by factors such as machine tool assembly accuracy and thermal effects, often result in deviations in both machining energy consumption and precision, compared to what is expected. Furthermore, the degree of deviations dynamically varies with the machining schemes. These issues hinder the implementation of high-quality energy-saving machining. To address this challenge, an energy consumption field model is proposed, reflecting the impact of motion position errors on energy consumption and precision variations in different machining scenarios. Firstly, by analysing the conversion process from process plans to programming instructions, a dynamic cascading mechanism is revealed, driven by motion position errors that impact tool cutting trajectory offset, machining energy consumption and precision deviation. Subsequently, a dynamic quantification model for the cutting trajectory offset at the programming origin is established by correlating static geometric errors and dynamic spindle rotation errors with the programming origin coordinates. Finally, a transformation function is established by using the cutting trajectory offset as an intermediate variable to correlate motion position error, machining energy consumption and precision deviation. A spatial energy consumption field model is developed. Experimental results indicate that, while meeting precision constraints in the XYZ directions, a 10.96% reduction in energy consumption is achieved through the correction of programming origin coordinates.

Development of Machine Tool Disassembly and Assembly Training and Digital Twin Model Building System based on Virtual Simulation

In response to the issues of poor safety and insufficient training equipment in traditional machine tool assembly and disassembly training, this paper proposes a machine tool assembly and disassembly training system based on virtual simulation. The system utilizes Unity 3D to construct an interactive virtual training environment, achieving highly simulated simulations and teaching of the machine tool assembly and disassembly process. Additionally, the system is capable of establishing communication with actual machine tools, achieving bidirectional mapping between digital and physical spaces, allowing learners to observe the dynamic responses of machine tool models through the virtual environment. This virtual-real interaction mechanism enriches the application scenarios of the system, introducing digital twin technology into the virtual simulation of machine tool assembly and disassembly training. This paper also provides a detailed introduction to the design and implementation of core technologies such as the system's overall architecture, scene modeling, and virtual-real interaction, offering significant support for intelligent teaching in machine tool assembly and disassembly.

A case study of virtual CNC machine tool assembly and human-computer interaction techniques

When it comes to the virtual machine tool assembly process, there are problems such as assembly errors. Based on the general idea of correct assembly, it is proposed to innovate the assembly process by utilizing the enclosing box and separating axis theorem and GJK algorithm, so as to monitor the state of the detection process, which verifies the effective feasibility of the monitoring method and provides a new idea for the assembly process of virtual CNC machine tools.

Analysis of the machine tool industry of modern Russia based on the «Anna Karenina method»

The machine tool industry is the most important industry, the state of which largely determines the level of development of mechanical engineering and the national economy as a whole. For the purposes of import substitution, it is necessary, in fact, to rebuild the machine tool industrial complex from bearing factories to machine tool assembly production, mobilize engineering personnel and begin to train new ones. Of course, Russian business alone, without the help of the state, cannot cope with this task. The work carried out a retrospective analysis of the machine tool industry in Russia. In particular, the article presents a table that examines the main indicators characterizing the development of the machine tool market in Russia. Based on the results of the analysis of the metalworking equipment market in the period from 2016 to 2020, a trend of stagnation in the volume of consumption of this equipment and the machine tool industry can be identified. To solve problems in the machine tool industry, it is proposed to use the method of industry mapping of the industry for the purposes of both monitoring the current state and assessing the needs of key enterprises and the industry as a whole in the near future. It is shown that the machine tool industry in Russia has become an excellent example illustrating the «Anna Karenina principle», especially in comparison with the world's largest economies; its current state is the result of many events that are described in the article. The authors are convinced that by producing domestic means of production, from machine tools and equipment to electronic machines, our country is able to provide itself with all the necessary products of its own production — from consumer goods to necessary agricultural equipment and defense products.

FRICTIONAL FORCE MODELING OF A MACHINE TOOL FEED DRIVE TELESCOPIC COVER

Telescopic covers are components which can have a potentially large impact on machine tool feed drive capabilities. Generally speaking, frictional force modelling is a well-established field of interest in which many approaches and challenges have been identified. This paper addresses frictional force modelling of machine tool feed drive telescopic covers. A sequential assembly approach and control system data acquisition are used for friction model parameter estimation and verification. Models of telescopic covers may be used in virtual machine tools. Furthermore, feed drive accuracy and dynamics may be enhanced by compensation of frictional forces in the control system. Other possible applications include component commissioning during machine tool assembly and predictive maintenance.

Effect of shape formation on the accuracy of grinding ends while compensating for machine tool errors

There are several general methods for correcting errors related to positioning the machine tool structural units. The task to achieve optimal manufacturing accuracy can be resolved by using a compatible solution to vector equations, a variation of the shape formation function, or applying a matrix of transfer coefficients. However, there is no mutual relationship between various calculation methods for the case of grinding flat surfaces. The methods should be simplified and tested for the elongated shape formation function while considering the links’ dimensions. This paper reports a study into the accuracy of grinding flat surfaces, determining and reducing the share of manufacturing errors. The content of variation matrices and transfer coefficients has been substantiated. The comparison of the orientation angles of the grinding machine headstock relative to the machine tool bed has demonstrated close results from all methods. These angles were taken as machine tool errors. The calculation error does not exceed 1.5 %. The experiments are consistent with the calculations. Different signs of the transfer coefficients in the orientation angles of grinding machine headstocks in the matrix make it possible to mutually compensate for the overall impact. The calculations have shown that the accuracy of the side-end machining is largely affected by a change in the orientation angle in the vertical plane. The effect exerted on the accuracy of individual mated parts by the machine tool structural units has been estimated. The calculations show that the error of positioning a part in the drum window acquires the highest absolute values and is random in nature, which requires a more accurate base positioning. The findings from both theoretical and experimental studies have been applied. The mathematical model makes it possible to determine the degree of scattering the end surface around the base plane via its variance. The measured trajectory provides diagnostic information about the sources of error in the machine tool assembly. A task to calculate the accuracy of the end-grinding machine tool can be solved for other models of machine tools in the same way

Study on the Stiffness, Longevity and Reliability of the Spindle Unit of Eclipse 300 CNC Lathe with Different External Load

The stiffness of the spindle assembly of machine tools in general and also CNC machines in particular is an important criteria to evaluate the quality of machining. The initial stiffness of the spindle assembly is due to pre-load. During operating, the spindle assembly is wear under the influence of external loads including cutting force and speed. It reduces the stiffness of the spindle assembly, as well as decreasing machining accuracy. This study presents the results of various stiffness of the spindle assembly under external loads in laboratory conditions. Based on the relationship between the stiffness and the amount of axial wear of the spindle assembly according to the working time, as well as the permissible stiffness limit to predict remaining time, reliability and time of adjusting the pre-load to maintain stability and machining accuracy.

Geometric errors characterization of a five-axis machine tool through hybrid motion of linear-rotary joints

Position independent geometric errors (PIGEs) of rotary axes, which are caused by imperfections during assembly of machine tools, are proved to be one of the major error sources of a five-axis machine tool. In this paper, PIGEs’ characterization method through hybrid motion of linear-rotary axes using a double ball bar (DBB) is proposed. The coordinated motions involving the motion of a linear and rotary axes are designed, namely, the XC, YC, and ZB motion pairs. The comprehensive error model of the machine tool is established using the screw theory based on the machine tool topology. The asynchronization between the synthetized velocity of the spindle tool cup relative to the workpiece tool cup during the coordinated motions has been resolved based on optimal motion trajectories. The PIGEs are identified using the particle swarm optimization method and simulated using the comprehensive machine tool model. A compensation strategy of the identified errors is proposed using the machine inverse kinematics. The effectiveness of the proposed characterization method is proved by the compensation results.

A linear model for the machine tool assembly error prediction considering roller guide error and gravity-induced deformation

In assembly, error prediction and control according to the error state of the machine parts are the key links to ensuring the accuracy of the entire machine tool. In this study, an assembly error modeling method considering the error of the roller guide and gravity-induced deformation is proposed. First, based on the Hertz contact theory, a nonlinear error propagation model for the roller guide to the moving part is proposed. With this model, the analytical relationship between the straightness error of the guide rail and the errors of the moving part can be established. Then, after the linearization of the guide error model, a machine assembly error model considering the guide error is proposed. This model expresses the linear relationship between the error of the rolling joint surface and the error of the machine tool after the final assembly. Additionally, considering the influence of gravity deformation of structural parts, the gravity deformation is extracted by the finite element analysis method and added to the model by linear superposition. As a result, the model corresponds more with the practical assembly process. Finally, an assembly error prediction method of the precision horizontal machining center is presented, and a case is studied to demonstrate the validity of the proposed model and method.

Assembly consistency improvement of straightness error of the linear axis based on the consistency degree and GA-MSVM-I-KM

Fluctuation on the assembly quality of the linear axis of machine tools (LA-MT) at the same batch is urgent problem need to be solved in assembly of machine tools. In this paper, a new concept of assembly consistency degree was introduced for defining the fluctuation degree of assembly quality. Based on assembly consistency degree, a hybrid machine learning method, genetic algorithm optimized multi-class support vector machine and improved Kuhn–Munkres (GA-MSVM-I-KM) was proposed for improving assembly consistency of LA-MT. The assembly of linear axis of a three-axis vertical machining center was regarded as an example, and the assembly consistency influence factors on straightness error of Y-axis (SE-YA) were analyzed through the Kruskal–Wallis statistical method. The main factors affected on the assembly consistency of SE-YA turned out to be the machining errors of bed and the assembly team technical levels. Based on this, the assembly consistency improvement model was established. Then, the prediction model of SE-YA based on assembly experiment data and genetic algorithm optimized multi-class support vector machine (GA-MSVM) was constructed, and I-KM method was applied for improving assembly consistency of SE-YA. The results show that the GA-MSVM-I-KM method can effectively enhance the assembly consistency of SE-YA, and the assembly consistency degree is reduced from 0.19 to 0.08.

Research on the Error Averaging Effect in A Rolling Guide Pair

By studying the effects of geometric precision on kinematic accuracy, an error mapping model has been established, based on the hypothesis that a motion pair and its installation surface are rigid. However, when using this assumption, there is a significant error induced in high-precision computer numerical control (CNC) machine tools as compared with reality. One of the most important reasons for this error is failing to consider the error averaging effect of motion pair elements. Therefore, this work examines a high-precision horizontal machining center as its research object, and analyzes the error averaging mechanism of a rolling guide pair under a deformation of the rolling elements. The carriage bearing forces caused by guideway straightness errors are obtained by constructing a geometric error model of a single carriage. The relationship between guideway straightness errors and carriage bearing forces is described by a transfer function in the spatial frequency domain, and its characteristics are analyzed. It quantifies the so-called error averaging effect of the rolling guide system and, on this basis, a static model for four carriages is established to reflect the error averaging effect of the rolling guide pair on the position and orientation errors of the motion pair. In addition, it is found that the wavelengths and phase differences of guideway errors affect this error averaging mechanism, but the amplitude and preload have little influence thereon. The experiment result shows that the kinematic straightness errors in the x- and y-directions were approximately 1/3 to 1/2 of the guideway straightness errors in the corresponding directions. The results can be used to guide the precision design and assembly of machine tools.

Research on Geometric Precision Compensation of NC Machining Tools Based on Modified 9-line method

In the process of precision compensation of NC machine tools, the traditional 9-line method has such principle error as error compensation of the rolling angle, because of difference from the coordinate system of the laser measurement and machine tool manufacturing. Secondly, the method has a poor robustness because the measurement noise and the repeatability of the machine tool are included in the measurement. Thirdly, the compensation model can only be used for the error compensation, and cannot be used for the precision design and the precision control and process optimization in the process of the machine tool assembly. In the paper 9-line method is modified based on error compensation model reconstructed, computer simulation research and empirical analysis. Compared with the experimental results, it is proved that the new method can correct three points of the traditional nine line method, and improve the accuracy of the roll angle error.

Diversity of assembly error migration and its solution model for heavy duty machine tool

Aiming at the ever-changing assembly error along with operation in the large scale assembly space, the diversity of machine tool assembly error migration and its operation route are characterised by making use of the correspondence relationship between joint surface error and operation distance. The formation and retention of assembly error are respectively revealed by the forward migration and the reverse migration of assembly error. Furthermore, the delayed step function of assembly error migration is constructed to recognise the potential control operation of error migration. Based on the response surface method, the solution model of assembly error migration is established to reveal the diversity of assembly error migration process and the effect of multiple operations. Finally, the design method of assembly process about heavy duty machine tool is proposed, and its effectiveness is verified by gantry-moving type turning-milling machining centre.

Diversity of assembly error migration and its solution model for heavy duty machine tool

Aiming at the ever-changing assembly error along with operation in the large scale assembly space, the diversity of machine tool assembly error migration and its operation route are characterised by making use of the correspondence relationship between joint surface error and operation distance. The formation and retention of assembly error are respectively revealed by the forward migration and the reverse migration of assembly error. Furthermore, the delayed step function of assembly error migration is constructed to recognise the potential control operation of error migration. Based on the response surface method, the solution model of assembly error migration is established to reveal the diversity of assembly error migration process and the effect of multiple operations. Finally, the design method of assembly process about heavy duty machine tool is proposed, and its effectiveness is verified by gantry-moving type turning-milling machining centre.

Simulation and analysis for accuracy predication and adjustment for machine tool assembly process

This article presents an approach to investigate the variation propagation of machine tools due to the geometric errors produced in assembly process and determine a pre-adjustment method in assembl...

Through Life Analysis for Machine Tools: From Design to Remanufacture

Increasing awareness of environmental burden calls for a sensible transition of manufacturing from the traditional mode where products have only one cycle of service life after being produced to a sustainable mode where multiple cycles of service life are enabled through material recovery, reuse, and remanufacture. As both the means for product generation and a product of modern manufacturing processes, machine tools have been increasingly viewed as a critical element for improving through life and consequently, sustainability. This paper examines the life cycles of machine tools and recent advancement in extending their life cycles. A life cycle is defined as starting from the design, proceeding through the stages of manufacturing and usage, and completing by the end of the service life. Modular design techniques that facilitate the manufacture and assembly of machine tools and analytical methods for reliable machine state estimation and remaining service life prediction are presented. Extension beyond completion of the first service life is enabled by recover and recycle of material from worn/broken machines, and redesign methods that reduce the amount of new materials to be used for making the same product in the subsequent re-manufacturing processes to ultimately realize materials reuse. Opportunities and challenges for sustainable manufacturing in the context of cloud manufacturing are also highlighted.

Layout evaluation at earlier stages of machine tool design:form-shaping function-based approach

Some important parameters of the machine tool layout have to be selected in the early stages of design when a shortage of information makes application of the finite element method impractical. As a computer-aided tool in these stages, the form-shaping function (FSF)-based approach can be used. It allows evaluation of the kinematic and geometric errors and compliance issue static deformations, which contribute significantly to the total machining error as applied to precision machine tools. The FSF-based methodology gives important information allowing layouts’ comparison and structure optimization under uncertainty in requirements and limitations relating to the designed machine under strong time constraints. Six different layouts of a turning center are investigated to compare the effect of geometrical errors and compliance of machine structure on part accuracy in the range of less than five microns. Motion errors of machine tool components were measured by laser equipment during machine tool assembly and inspection. Compliance-induced errors are included in the evaluation to take into consideration cutting forces. Obtained data were used as the input for simulation of machining a sample workpiece—a sphere whose size, position, and form errors are used as criteria for layout comparison. Since the FSF-based results correlate well with the experimental data, the developed approach can be considered as an effective tool for application in the early stages of machine design.

Interface contact pressure-based virtual gradient material model for the dynamic analysis of the bolted joint in machine tools

Bolted joints have significant influence on the dynamic characteristic of the machine tool assembly. This study proposes a new modeling method using virtual gradient material. On the basis of Hertz contact theory and fractal geometry theory, the relationship between contact stiffness and normal contact load is deduced. The contact pressure distribution at the interface is obtained through finite element contact analysis. An orthogonal material model is introduced to describe the properties of virtual material. The virtual material is divided into several layers, and the elastic modulus and shear modulus in each sub-layer are derived based on Hooke’s Law. Both experimental and theoretical results for a bolted lap structure are obtained. The experimental results are compared with theoretical ones in terms of qualitative comparison of similar mode shapes and quantitative comparison of corresponding natural frequencies. The comparison shows that the theoretical first three-order vibration mode shapes are in good line with the experimental ones. The relative errors of corresponding natural frequencies between the virtual gradient material model and the experiment are less than 9%, which are smaller than those between the traditional virtual uniform material model and the experiment. The proposed virtual gradient material method would be useful to accurately model the bolted joint in CNC machine tools.

A new position independent geometric errors identification model of five-axis serial machine tools based on differential motion matrices

Five-axis position independent geometric errors (PIGEs), which are caused by imperfect assembly of machine tools, need to be identified and compensated in order to improve the accuracy of machined parts. In traditional PIGEs identification model based on differential motion matrices (DMM), PIGEs elements are defined in the local frames attached to the previous axis, which is inconvenient to do redundance analysis. In order to fully but un-redundantly identify five-axis PIGEs, this paper proposes a new PIGEs identification model based on DMM in the global coordinate frame. The transfer matrix which realizes the transformation of PIGEs between global and local definitions is derived at first. Then the Jacobian function of the tool center motion errors related to PIGEs defined in the global frame is calculated and adopted for PIGEs identification with the least-square algorithm. For the proposed PIGEs identification model in the global frame, the minimum set of PIGEs can be easily found to make sure full but un-redundant identification, by properly setting up the machine tool coordinate frame using the method of ISO 230-1:2012. The proposed new Jacobian function and PIGEs identification model in the global frame are verified through simulation and experiments with ball-bar tests.