Machine Tool Body Research Articles

Modal Assurance Criterion as an iron cast and hybrid machine tool's body comparison tool

The paper presents the results of research on increasing the dynamic properties of the machine tool body. For this purpose, a hybrid body was manufactured, which was created by filling the free technological spaces in the cast iron body with a polymer concrete material. The modes of free vibrations, modal frequencies, amplitudes, and damping ratios were revealed using experimental modal analysis. In some cases, the amplitude value decreased by up to 68%, as well as the damping ratio increased by almost 109%. Then, using the MAC (Modal Assurance Criterion) method, the body with polymer concrete fillings was compared with the cast iron body to estimate the degree of similarity of the various modes of free vibrations of both structures. The obtained results in the range of 0.54–0.96 indicate high similarity between the vibration modes, which were revealed in both analyses.

Dynamic parameters identification for sliding joints of surface grinder based on deep neural network modeling

Dynamic parameters of joints are indispensable factors affecting performance of machine tools. In order to obtain the stiffness and damping of sliding joints between the working platform and the machine tool body of the surface grinder, a new method of dynamic parameters identification is proposed that based on deep neural network (DNN) modeling. Firstly, the DNN model of dynamic parameters for working platform-machine tool body sliding joints is established by taking the stiffness and damping parameters as the input and the natural frequencies as the output. Secondly, the number of hidden layers in DNN topology is optimally selected in order to the optimal training results. Thirdly, combining the predicted results by DNN model with experimental results by modal test, the stiffness and damping are identified via cuckoo search algorithm. Finally, the relative error between the predicted and experimental results is less than 2.2%, which achieves extremely high prediction precision; and thereby indicates the feasibility and effectiveness of the proposed method.

Dynamic properties of hybrid machine tool body – Theoretical and experimental investigation

Abstract The article presents theoretical and experimental investigation in order to obtain dynamic properties of hybrid machine tool body in comparison with cast iron body. For this purpose, the theoretical and experimental modal analyses were carried out. The influence of the mineral cast material for filling voids on the dynamic properties of the machine tool body was discussed. During the analysis, the modes and frequencies of free vibrations, the amplitude values and the damping ratios were compared. Despite lowering the free vibration frequency of the hybrid construction, compared to the cast iron body, in some cases, the dynamic properties were affected. This could be determined on the basis of decreasing the amplitude value of the transfer function (from 12.16% to 58.66%) and the increasing the vibration damping coefficient ratio (from 12.22% to 75.24%) in the case of a hybrid body as compared to a cast iron body. The final conclusions were drawn about the application of mineral casts in the construction of machine tools and its impact on the dynamic properties of the structure.

Optimized Design of Precision EDM Machine Tool based on CAE Simulation and Modal Testing Technology

For precision EDM equipment, in addition to the static stiffness of the body of the machine, the dynamic characteristics of the body and the ambient temperature are also the key factors that affect the machining accuracy of the workpieces. In this paper, through the modal simulation analysis of the machine tool that with the sheet metal shell, the weak points of the EDM machine tool are determined. Through thermal stress simulation analysis, the thermal deformation law of the workpieces mounting table is determined, and a solution to reduce thermal deformation is proposed. Through machine tool ODS (operating deflection shapes) test and analysis, the weak links of the machine tool's body in actual processing are determined. Through the above optimization analysis, the foundation has been laid for improving the dynamic and static accuracy of the precision machine tool. The research method in this paper makes up for the deficiency of the machine tool design method based on static stiffness.

Special Issue on Advanced Material Driven Design of Machine Tools

Special Issue on Advanced Material Driven Design of Machine Tools

The impact of support points during the measurement of machine tool bodies on Coordinate Measuring Machines

The article concern on the considerations regarding the influence of support points during measurement using coordinate measuring technique. The object of research, slide of the X axis of a five-axis numerically controlled machine CMX 70U from the portfolio of DMG MORI, produced at FAMOT Pleszew Sp. z o.o., set on the coordinate table of the measuring machine, using three- and four-point fixing. The aim of the research is to determine the optimal method of supporting the bodies, which in effect will reduce the measurement time and increase the efficiency of the process. The MES analysis available in the Creo software was used to calculate and graphically present the results.

Development of Ultrasonic Vibration Assisted Micro Electrochemical Discharge Machining Tool

Background: The fabrication of microstructures with high machining quality is always difficult when it is concerned with non-conductive hard and brittle materials such as glass and engineering ceramics. It is reported in related papers and patents that Electrochemical Discharge Machining (ECDM) process is a good choice for machining non-conductive, hard and brittle materials. However, the machining performance of ECDM process, especially in the aspect of geometric accuracy and surface quality, needs to be greatly improved. Objective: The purpose of this study was to improve the machining quality of conventional ECDM process by introducing ultrasonic vibration to ECDM process, develop an Ultrasonic Vibration Assisted Micro Electrochemical Discharge Machining (UAECDM) tool, and investigate the improvements of the machining performance by means of comparative experiments. Methods: Firstly, the machining principle of UAECDM was investigated, and the effects of ultrasonic vibration are discussed with the analysis of the micro process. Secondly, the hardware system, which consists of a machine tool body, XY and Z axes, an ultrasonic spindle system and motion control system, was established; and the software system was developed based on the analysis of the overall workflow of the machining process. Finally, comparative experiments, including ECDM drilling, UAECDM drilling, ECDM milling and UAECDM milling, were carried out to reveal the improvements of the machining quality. Results: In the UAECDM group, a micro-hole with the inlet diameter of 133.2µm as well as the 3 × 3 array of micro holes was fabricated on the glass workpiece with 300µm thickness, and a microgroove with the width of 119.2µm was successfully milled on the glass workpiece. It is shown in both microscopic photographs and optical measurements that the microstructures fabricated by UAECDM have better machining quality compared with similar microstructures fabricated by ECDM. Conclusion: Based on comparative experiments and discussions of the results, it has been proved that the machine tool can meet the requirement of the ultrasonic vibration-assisted micro electrochemical discharge machining and can improve the geometric accuracy and surface quality significantly.

Layout and Number of Temperature Sensors for Precise Estimation of Steady-state Heat Quantities at Heat Sources in Machine Tool Bodies

Layout and Number of Temperature Sensors for Precise Estimation of Steady-state Heat Quantities at Heat Sources in Machine Tool Bodies

Teoretyczne badania właściwości dynamicznych łóż obrabiarki wykonanych z żeliwa i hybrydowego połączenia żeliwa z odlewem mineralnym

Teoretyczne badania właściwości dynamicznych łóż obrabiarki wykonanych z żeliwa i hybrydowego połączenia żeliwa z odlewem mineralnym

Cast Iron And Mineral Cast Applied For Machine Tool Bed - Dynamic Behavior Analysis

Abstract Cast iron and mineral cast are the materials most often used in the machine structural elements design (bodies, housings, machine tools beds etc.). The materials significantly differ in physical and mechanical properties. The ability to suppress vibration is one of the most important factors determining the dynamic properties of the machine and has a significant impact on the machining capabilities of a machine tool. Recent research and development trends show that there is a clear tendency to move away from the traditional iron casting to the mineral casting, due to better dynamic properties of the latter. However mineral cast as a structural material for the whole machine tools bed turns out to be insufficient due to its poor mechanical strength properties. The best solution should benefit from the advantages of the cast iron and mineral cast materials while minimizing their drawbacks. The paper presents numerical modal analysis of two lathe beds: the first one made of gray cast iron and the second one made of hybrid connection of cast iron and mineral cast. The analysis was conducted in order to determine the dynamic properties of two bodies of similar shapes made in the traditional (cast iron) and innovative hybrid (cast iron and mineral cast) technology. In addition, an analysis of the static structure rigidity of the two beds was performed. During the simulation studies it was found a significant increase in dynamic stiffness and static rigidity of the machine tool body made of hybrid connection of cast iron and mineral cast. The results of numerical simulations have confirmed the desirability of using hybrid construction because the dynamic properties of such a body are more advantageous in comparison with the conventional body made of cast iron.

Rigid body dynamics in optimization of the machine tool vibroisolation

Modern design of the machine tool treats the suspending parts as a crucial element of the effective vibration isolation. Therefore the suspending items are specifically developed and subjected to extensive tests before being applied on real objects. These elements ensure accurate levelling and appropriate vibration damping. Usually selection of inadequate support element causes intensive disturbing effects in machining. The paper presents dynamics analysis of the machine tool suspended on flexible mountings. The overall analysis is conceived on a rigid body dynamics. This method enables selection of an optimal supporting configuration. Further on such an effective suspension design prevents a need for expensive monitoring of the dynamic characteristics of the mechanical system, i.e. machine tool and supports. The paper explores dynamics of a real, flexibly supported machine tool. Results are obtained with the assistance of the SUPPORT software. Finally the theoretical and computational statements are approved throughout extensive site measurements on the machine tool body with appropriate instrumentation.

Kinematic Analysis of 5-UPS Parallel Machine Tool Based on Adams

In this paper, the kinematics of 5-UPS parallel machine tool is analyzed, and a kinematic analysis method combining kinematic analysis and computer kinematics software is proposed. Under the premise that the parallel machine tool sector parameters is known, firstly we use the vector method to establish a mathematical model of inverse kinematics, and in accordance with a U-shaped processing trajectory the inverse solution is calculated; Secondly, three-dimensional model of the parallel machine tool is modeled in Adams, and kinematic constraints are set correctly; Finally, the inverse kinematics solution of the mathematical model is used as the Adams drive input, then the positive solutions is carried out. Compared through the Adams simulation results with U-machining path, it is verified that the inverse solution of the mathematical model and parallel machine tool bodies both are correct, it has certain significance for Parallel machine tools and other parallel robot kinematics analysis.

Computer-aided alignment of castings and machining optimization

The presented publication demonstrates an accuracy assessment method for machine tool body casting utilizing an optical scanner and reference model of the machine tool body. The process allows assessing the casting shape accuracy, as well as determining whether the size of the allowances of all work surfaces is sufficient for appropriate machining, corresponding to the construction design. The described method enables dispensing with the arduous manual operation of marking out as well as shortening the time of aligning and fixing the casting body for machining. For the experimental setup, four rotary indexing table castings were investigated according to the method principles. The geometric accuracy of each casting was examined by comparing their scans with the computer-aided design model, and the machining allowances were evaluated to determine casting qualification for machining. The nominal volume of material to be removed was established and subsequently optimized to reduce the volume to be machined. Thus, a rapid method of aligning a casting in a machine tool according to the planned optimized distribution of machining allowances was developed. For the set of measured castings, it was proven that their poor geometric quality precluded the possibility of further machining according to standard marking out instructions. However, by following the presented methodology, it was possible to successfully process the entire set while reducing the overall volume of the material removed by 4.5–9.6%, as compared with nominal values. The obtained results ultimately confirmed that manual marking out could be eliminated from the casting assessment process.

Evaluation of accuracy and reproducibility of the optical measuring system in cast machine tool body assessment

Evaluation of accuracy and reproducibility of the optical measuring system in cast machine tool body assessment The hereby presented study puts forth the fundamentals of an innovative technology enabling rapid assessment of machine tool cast shape by elimination of manual marking out requirement and machining surplus minimization. The new technique is based on optical measuring system utilization for the design of virtual cast models and their comparative analysis with structural models. Two small scale machine tool body casts were selected for the investigation. The measurements were conducted in triplicate series for each cast labeled with reference markers, by means of Atos GOM II optical scanner. For further comparison, one of the casts was additionally scanned without labeling. Flatness parameters of selected cast surfaces were determined for geometric accuracy evaluation and the scanned cast shapes were compared with reference models. The comparison results were recorded as multicolored maps projected upon the experimental cast and reference model surfaces. Practical map interpretation was further elucidated and the surplus sizes on the machined surfaces were assessed accordingly. Comparative analyses of individual models were demonstrated for all measurement series of both casts, affording reproducibility evaluation of optical scanning system measurements. Economic viability of the proposed technology market implementation was unequivocally established, as it provides for considerable reduction in the cast machining scale as well as the quality control of 100%.

Design- and control-concept for compliant machine tools based on controller integrated models

The paper presents a novel design- and control-concept for machine tools aiming for lightweight design. A Kalman-filter containing a model of the mechanical structure is applied. The Kalman-filter calculates the dynamic dislocation of the machine tool body with respect to the tool-center-point and its velocity. Dislocation and velocity are used for the correction of the CNC's setpoint values. Experimental results show, that the dynamic dislocation had been reduced considerably. This allows for a compliant design contrary to the established design-concept of stiff frames. The concept is proposed for direct-drive machine tools used for micro-milling.

Research on VSR Process for Large Machine Tool Body

In order to improve effect of VSR（vibration stress relief）for large machine tool body, the VSR process parameters must be optimized. This paper studies mechanism of VSR and determination principle of process parameters. Using finite elements method, the vibration modal analysis of large machine tool body are applied to determine VSR frequency, exciting position, supporting position and detecting sensor position. Based on analysis above, the harmonic response analysis is applied to work out relationship between exciting force and dynamic stress. In this way, the exciting force can be determined. The experiment result shows the determination method of VSR process parameter in this paper is feasible and effective. This method is worthy of application and dissemination for large size castings.

E19 工作機械熱源熱量を高精度に推定するための温度センサ配置方法(OS1 最新工作機械(4))

An increase in frictional heat due to increases in rotational speed and feed rate causes the thermal deformation of machine tools, resulting in a decrease in machining accuracy. To establish a method for reducing the thermally induced machining errors of machine tools, recently the authors have proposed a method to estimate the heat flux acting upon a machine tool body by solving inverse problems. By using the quasi-steady state temperature rises of the body, the heat flux at the heat source was estimated with sufficient accuracy for practical use. To improve the estimation accuracy of the heat flux, the effects of both the number of temperature measurement points and their positions on the accuracy were examined with the orthogonal arrangement of the temperature evaluation points. S/N ratios and factorial effects at each temperature measurement points were evaluated by the optimum solutions of heat flux estimations. These values are useful for an index in determining a layout of temperature sensors to estimate the heat values at heat sources.

Heat Flux Estimation at Heat Sources of Machine Tools by Solving Inverse Problems

An increase in frictional heat due to the increase in rotational speed and feed rate causes thermal deformation of machine tools, resulting in a decrease in machining accuracy. To establish a method for reducing thermally induced machining errors of machine tools, a method has been proposed to estimate the heat flux acting upon a machine tool body by solving inverse problems. Experiments were carried out with the cross slide of a machine tool. Using the heat flux estimated at the heat source, the temperature rise of the body in a steady state could be obtained with sufficient accuracy. Effects of both the number of evaluating and measuring points of the temperature on the estimation accuracy were also examined experimentally. More accurate estimation of the heat flux requires that the number and position of both temperature measurement points and candidates for heat sources are selected considering how the machine tool is actually operated.

C33 Heat Flux Estimation at Heat Sources of Machine Tool by Solving Inverse Problems(Evaluation of machine tool performance)

For establishing a method to reduce thermally induced machining errors of machine tools, a method has been proposed to estimate the heat flux acting upon the machine tool body by solving inverse problems. Experiments were carried out with the cross slide of a machine tool. Using the estimated heat flux at the heat source, the temperature rise of the body in a steady state could be obtained with sufficient accuracy. More accurate estimation of the heat flux requires that the number and position of both temperature measurement points and candidates for heat source are selected considering the machine tool operation.

Direct and „Intelligent” Monitoring of Thermal Distortions

Machine tool thermal distortions (TD) can account for up to 70% of the total machining error in finishing operations. The diminishing of this negative influence on machining accuracy is very hard to achieve due to complexity of thermal distortion phenomenon and changeable character of machine tool working cycles. There is a growing need of TD monitoring techniques that would enable good compensation of such errors. The most frequently used approach to TD monitoring is to measure temperature of the machine tool body and to predict TD using artificial intelligence (AI). The paper describes a direct method of TD monitoring by the use of novel sensors measuring local displacement (SMLD) and AI based on neural networks.