|
| |
|
|
PREDICTION OPERATIONAL ACCURACY OF THE CNC MACHINING CENTRE
Michalíček, Michal ; Blecha, Petr (referee) ; Skýpala, Milan (referee) ; Marek, Jiří (advisor)
The main research topic of this dissertation thesis deals with the influence of the working accuracy related to large CNC machines on the required workpiece properties. The state-of-the art has constantly been developed and the customer’s requirements directed to manufacturers of the machine tools are increasingly demanding. There is required a high accuracy, reliability, shortening delivery times etc. The manufacturer is expected to fulfill all the customer’s requirements. The machining accuracy is dependent, among others, on the positioning accuracy of a machine tool that represents the position of the cutting tool relative to a workpiece. The accuracy of a particular machine tool is therefore a limiting factor concerned with reaching the highest accuracy and quality of a workpiece. Acceptance test procedures are initially realized within a manufacturing shop floor and then within a customer environment. The main subject of the testing procedures is to verify. basic properties of a machine tool such as basic dimensions of a machine, strokes in all respective coordinates, machine travels and spindle speeds. A machining of a workpiece with a desired precision specified by the customer is also performed. In this thesis, a new methodology to calculate and determine errors concerned with machining on vertical lathes is proposed with the aim of predicting the machining accuracy of CNC machine tools. The objective of this work was to determine the influence of machining accuracy of a CNC machine in connection with a subsequent geometrical accuracy of a workpiece. Considered position of a tool relative to a workpiece will be affected by errors concerned with a kinematical inaccuracy, geometrical errors and errors related to machining forces. A vertical lathe SKIQ 30 produced by TOSHULIN, a.s. has been used as a testing machine on which the proposed methodology has been verified. During processing various calculations in this thesis there has been found out that the machining inaccuracy of the machine – main topic of interest – is influenced by the machining conditions such as cutting conditions, material to be machined and even the setting of working positions of the machine. For instance, a position of the cross slide is determined by a workpiece height and a position of the lathe carriage that is determined by a workpiece diameter and a travel of the slide that is also determined by a workpiece height. It can be stated then that to predict the machining accuracy of work pieces, it is important to know the behavior of the machine in its all range of working envelope. Based on the information acquired about the behavior of the machine, it can be determined an appropriate position for a workpiece setting that allows utilizing the maximum reachable accuracy with respect to the stiffness and geometrical accuracy of the machine tool. An appropriate setting of initial working position may influence the subsequent geometrical accuracy of a workpiece.
|
|
|
Methodology of machine tool’s electric drive system modeling
Pruša, Radomír ; Černohorský,, Josef (referee) ; Kurfűrst, Jiří (referee) ; Huzlík, Rostislav (advisor)
The present dissertation is focused on the methodology of modelling of the machine tool drive. The initial chapters contain a review of the current state of knowledge in the field of drive modelling with a focus on the electromagnetic part, thermal field and drive control. The acquired overview and orientation in the subject matter has enabled the development of a systematic analysis on the topic of modelling the machine tool axis drive. The follow-up work was aimed at obtaining the appropriate quality of the output parameters, according to the subsequent use of the results. The reason for this approach is to ensure only a minimum of input parameters. At the same time, the individual parameters must be readily available or easily measurable. The actual methodology of the drive modelling method was also based on the described strategy. The basic building blocks were chosen to be the warming of the machine, the energy balance, the setting of the control structure and, last but not least, the positioning accuracy. The applied methodology was also verified at the end of the thesis under different operating conditions, which were adapted to multiple drive variations.
|
|
|
EFFECT OF GEOMETRICAL PRECISION MACHINING CENTERS ON THE DESIRED CHARAKTERISTICTS OF THE GOODS
Holub, Michal ; Demeč, Peter (referee) ; Hýbner, Břetislav (referee) ; Pernikář, Jiří (referee) ; Marek, Jiří (advisor)
The main subject of this doctoral thesis is the influence of the geometrical accuracy of large CNC machine tools on desired features of produced work pieces. Doe to globalized market environment and competition producers of machine tools have changed their strategy for delivery of their products to customers. The main issue is not only to deliver a machine tool as such; supporting instructions related to the technology of the cutting process on the machine tool are of great importance. When taking delivery, the customer can see a new machine tool that will produce by him specified work piece with a desired accuracy. In the proposed thesis, a development of a novel methodology of measuring vertical lathes for prediction of chosen geometrical parameters of work pieces is introduced. The main goal of this work has been to determine the influence of the geometrical accuracy of selected design groups of a vertical lath on the future geometric accuracy of the work piece. The proposed methodology has been developed and verified on a selected vertical lath SKIQ30 produced by TOSHULIN, a.s. For identification of chosen parameters of the vertical lath a measuring system using latest measuring technologies has been applied. The basic tool for measured data processing has been a set of statistic methods for prediction of behaviour of measured design groups of the machine. The foundation for statistical processing has been calculation of geometrical deviations obtained from algorithms designed for proposed measurement methodology. The proposed measurement methodology for vertical lathes has been divided into two parts. In the first part, the methodology of measurement and evaluation of linear axes is solved, where a measuring system Laser Track has been used. The employment of the system Laser Track turned out to be very suitable. Conclusions related to the accuracy of the measuring device have been drawn in the thesis. The second part of the proposed methodology is represented by observation and description of the rotating disk, where non-contact position transducers have been used. In the course of the doctoral dissertation it has been observed that the studied (with respect to the geometry) behaviour of the machine is significantly affected by the cutting conditions. To these belong the loading of the rotating disc by the mass of the work piece, angular velocity of the rotating disc and the operating time of the machine. Based on these observations it can be stated that for prediction of work piece features it is essential to know the behaviour of the machine tool in the whole range of the operating speeds and loading of the rotating disc. A part of the proposed methodology for measuring vertical lathes seems to be very suitable for a design of a diagnostic system that could be applied on large rotating disc. Furthermore, it is recommended to extend the doctoral thesis in order to develop a unit for compensation of geometrical errors on rotating discs of vertical lathes.
|
|
| |
|
|
PREDICTION OPERATIONAL ACCURACY OF THE CNC MACHINING CENTRE
Michalíček, Michal ; Blecha, Petr (referee) ; Skýpala, Milan (referee) ; Marek, Jiří (advisor)
The main research topic of this dissertation thesis deals with the influence of the working accuracy related to large CNC machines on the required workpiece properties. The state-of-the art has constantly been developed and the customer’s requirements directed to manufacturers of the machine tools are increasingly demanding. There is required a high accuracy, reliability, shortening delivery times etc. The manufacturer is expected to fulfill all the customer’s requirements. The machining accuracy is dependent, among others, on the positioning accuracy of a machine tool that represents the position of the cutting tool relative to a workpiece. The accuracy of a particular machine tool is therefore a limiting factor concerned with reaching the highest accuracy and quality of a workpiece. Acceptance test procedures are initially realized within a manufacturing shop floor and then within a customer environment. The main subject of the testing procedures is to verify. basic properties of a machine tool such as basic dimensions of a machine, strokes in all respective coordinates, machine travels and spindle speeds. A machining of a workpiece with a desired precision specified by the customer is also performed. In this thesis, a new methodology to calculate and determine errors concerned with machining on vertical lathes is proposed with the aim of predicting the machining accuracy of CNC machine tools. The objective of this work was to determine the influence of machining accuracy of a CNC machine in connection with a subsequent geometrical accuracy of a workpiece. Considered position of a tool relative to a workpiece will be affected by errors concerned with a kinematical inaccuracy, geometrical errors and errors related to machining forces. A vertical lathe SKIQ 30 produced by TOSHULIN, a.s. has been used as a testing machine on which the proposed methodology has been verified. During processing various calculations in this thesis there has been found out that the machining inaccuracy of the machine – main topic of interest – is influenced by the machining conditions such as cutting conditions, material to be machined and even the setting of working positions of the machine. For instance, a position of the cross slide is determined by a workpiece height and a position of the lathe carriage that is determined by a workpiece diameter and a travel of the slide that is also determined by a workpiece height. It can be stated then that to predict the machining accuracy of work pieces, it is important to know the behavior of the machine in its all range of working envelope. Based on the information acquired about the behavior of the machine, it can be determined an appropriate position for a workpiece setting that allows utilizing the maximum reachable accuracy with respect to the stiffness and geometrical accuracy of the machine tool. An appropriate setting of initial working position may influence the subsequent geometrical accuracy of a workpiece.
|
|
|
EFFECT OF GEOMETRICAL PRECISION MACHINING CENTERS ON THE DESIRED CHARAKTERISTICTS OF THE GOODS
Holub, Michal ; Demeč, Peter (referee) ; Hýbner, Břetislav (referee) ; Pernikář, Jiří (referee) ; Marek, Jiří (advisor)
The main subject of this doctoral thesis is the influence of the geometrical accuracy of large CNC machine tools on desired features of produced work pieces. Doe to globalized market environment and competition producers of machine tools have changed their strategy for delivery of their products to customers. The main issue is not only to deliver a machine tool as such; supporting instructions related to the technology of the cutting process on the machine tool are of great importance. When taking delivery, the customer can see a new machine tool that will produce by him specified work piece with a desired accuracy. In the proposed thesis, a development of a novel methodology of measuring vertical lathes for prediction of chosen geometrical parameters of work pieces is introduced. The main goal of this work has been to determine the influence of the geometrical accuracy of selected design groups of a vertical lath on the future geometric accuracy of the work piece. The proposed methodology has been developed and verified on a selected vertical lath SKIQ30 produced by TOSHULIN, a.s. For identification of chosen parameters of the vertical lath a measuring system using latest measuring technologies has been applied. The basic tool for measured data processing has been a set of statistic methods for prediction of behaviour of measured design groups of the machine. The foundation for statistical processing has been calculation of geometrical deviations obtained from algorithms designed for proposed measurement methodology. The proposed measurement methodology for vertical lathes has been divided into two parts. In the first part, the methodology of measurement and evaluation of linear axes is solved, where a measuring system Laser Track has been used. The employment of the system Laser Track turned out to be very suitable. Conclusions related to the accuracy of the measuring device have been drawn in the thesis. The second part of the proposed methodology is represented by observation and description of the rotating disk, where non-contact position transducers have been used. In the course of the doctoral dissertation it has been observed that the studied (with respect to the geometry) behaviour of the machine is significantly affected by the cutting conditions. To these belong the loading of the rotating disc by the mass of the work piece, angular velocity of the rotating disc and the operating time of the machine. Based on these observations it can be stated that for prediction of work piece features it is essential to know the behaviour of the machine tool in the whole range of the operating speeds and loading of the rotating disc. A part of the proposed methodology for measuring vertical lathes seems to be very suitable for a design of a diagnostic system that could be applied on large rotating disc. Furthermore, it is recommended to extend the doctoral thesis in order to develop a unit for compensation of geometrical errors on rotating discs of vertical lathes.
|
guest ::
