This paper focuses on model development for computer analysis of the thermal behavior of an externally driven spindle. The aim of the developed model is to enable efficient quantitative estimation of the thermal chara...This paper focuses on model development for computer analysis of the thermal behavior of an externally driven spindle. The aim of the developed model is to enable efficient quantitative estimation of the thermal characteristics of the main spindle unit in an early stage of the development process. The presented work includes an experimental validation of the simulation model using a custom-built test rig. Specifically, the effects of the heat generated in the bearings and the heat flux from the bearing to the adjacent spindle system elements are investigated. Simulation and experimental results are compared and demonstrate good accordance. The proposed model is a useful, efficient and validated tool for quantitative simulation of thermal behavior of a main spindle system.展开更多
With hard turning, which is an attractive alternative to existing grinding processes, surface quality is of great importance. Signal processing techniques were used to relate workpiece surface topography to the dynami...With hard turning, which is an attractive alternative to existing grinding processes, surface quality is of great importance. Signal processing techniques were used to relate workpiece surface topography to the dynamic behavior of the machine tool. Spatial domain frequency analyses based on fast Fourier transform were used to analyze the tool behavior. Wavelet reconstruction was used for profile filtering. The results show that machine vibration remarkably affects the surface topography at small feed rates, but has negligible effect at high feed rates. The analyses also show how to control the surface quality during hard turning.展开更多
Today＇s production systems are demanded to exhibit an increased flexibility and mutability in order to deal with dynamically changing conditions, objectives and an increasing number of product variants within industr...Today＇s production systems are demanded to exhibit an increased flexibility and mutability in order to deal with dynamically changing conditions, objectives and an increasing number of product variants within industrial turbulent environments. Flexible automated systems are requested in order to improve dynamic production efficiency, e.g. robot-based hardware and PC-based controllers, but these usually induce a significantly higher production complexity, whereby the efforts for planning and programming, but also setups and reconfiguration, expand. In this paper a definition and some concepts of self-optimizing assembly systems are presented to describe possible ways to reduce the planning efforts in complex production systems. The concept of self-optimization in assembly systems will be derived from a theoretical approach and will be transferred to a specific application scenario---the automated assembly of a miniaturized solid state laser--where the challenges of unpredictable influences from e.g. component tolerances can be overcome by the help of self-optimization.展开更多
Cutting super alloy is a highly sensitive manufacturing process regarding the complex thermo-mechanical interactions in the cutting zone,which finally determine the capability of the process in order to reach economic...Cutting super alloy is a highly sensitive manufacturing process regarding the complex thermo-mechanical interactions in the cutting zone,which finally determine the capability of the process in order to reach economic requirements.The connection between the intensity of heat sources as well as heat partitions into the tool,work piece and chip is yet not fully understood.Thus heat flows and other thermal conditions in the cutting zone cannot be predicted satisfactory,though they influence the chip formation mechanics,the surface integrity,respectively functionality of the machined work piece as well as the tool wear and lifetime.Because of this deficit the ecological and economical design of the manufacturing process is still limited and often not knowledge based.The proposed paper presents a methodology in order to measure and predict heat flows respectively affiliated temperatures during cutting nickel-base super alloy(Inconel 718).The heat flows in the cutting zone are determined by infrared thermography and a further energy balance by post processing the thermal images.A FE-model for chip formation simulation,which is based on CEL(Coupled-Eulerian-Lagrange)formulation,was used to calculate the heat flows.Finally,the results of the simulation and the experiments were compared.展开更多
The thermal conditions like the temperature distribution and the heat fluxes during metal cutting have a major influence on the machinability, the tool lifetime, the metallurgical structure and thus the functionality ...The thermal conditions like the temperature distribution and the heat fluxes during metal cutting have a major influence on the machinability, the tool lifetime, the metallurgical structure and thus the functionality of the work piece. This in particular applies for manufacturing processes like milling, drilling and turning for high-value turbomachinery components like impellers, combustion engines and compressors of the aerospace and automotive industry as well as energy generation, which play a major role in modern societies. However, numerous analytical and experimental efforts have been conducted in order to understand the thermal conditions in metal cutting, yet many questions still prevail. Most models are based on a stationary point of view and do not include time dependent effects like in intensity and distribution varying heat sources, varying engagement conditions and progressive tool wear. In order to cover such transient physics an analytical approach based on Green＇s functions for the solution of the partial differential equations of unsteady heat conduction in solids is used to model entire transient temperature fields. The validation of the model is carried out in orthogonal cutting experiments not only punctually but also for entire temperature fields. For these experiments an integrated measurement of prevailing cutting force and temperature fields in the tool and the chip by means of high-speed thermography were applied. The thermal images were analyzed with regard to thermodynamic energy balancing in order to derive the heat partition between tool, chips and workpiece. The thus calculated heat flow into the tool was subsequently used in order to analytically model the transient volumetric temperature fields in the tool. The described methodology enables the modeling of the transient thermal state in the cutting zone and particular in the tool, which is directly linked to phenomena like tool wear and workpiece surface modifications.展开更多
For precision machining, the hard turning process is becoming an important alternative to some of the existing grinding processes. This paper presents an analytical model for predicting cutting forces in hard turning ...For precision machining, the hard turning process is becoming an important alternative to some of the existing grinding processes. This paper presents an analytical model for predicting cutting forces in hard turning of 51CRV4 with hardness of 68 HRC. The cutting tool used is made from cubic boron nitride （CBN） with a wiper cutting edge. Formulas for differential chip loads are derived for three different situations, depending on the radial depth of cut. The cutting forces are determined by integrating the differential cutting forces over the tool-workpiece engagement domain. For validation, cutting forces predicted by the model were compared with experimental measurements, and most of the results agree quite well.展开更多
The experimental determination of stability lobediagrams （SLDs） in milling can be realized by eithercontinuously varying the spindle speed or by varying thedepth of cut. In this paper, a method for combining boththe...The experimental determination of stability lobediagrams （SLDs） in milling can be realized by eithercontinuously varying the spindle speed or by varying thedepth of cut. In this paper, a method for combining boththese methods along with an online chatter detectionalgorithm is proposed for efficient determination of SLDs.To accomplish this, communication between the machinecontrol and chatter detection algorithm is established, andthe machine axes are controlled to change the spindle speedor depth of cut. The efficiency of the proposed method isanalyzed in this paper.展开更多
The measurement of boreholes with diameters smaller than 500 μm is a demanding task that cannot be performed using state-of-the-art production metrology. In this letter, a miniaturized fiber probe with a diameter of...The measurement of boreholes with diameters smaller than 500 μm is a demanding task that cannot be performed using state-of-the-art production metrology. In this letter, a miniaturized fiber probe with a diameter of 80μm is presented. A probe is used for low-coherence interferometry to conduct highly precise measurements of form deviations of small boreholes. Measurements conducted in nozzles are also presented. The results prove the potential of the fiber-optical sensor for quality inspection of high-precision parts, such as injection nozzles, for common-rail diesel engines.展开更多
文摘This paper focuses on model development for computer analysis of the thermal behavior of an externally driven spindle. The aim of the developed model is to enable efficient quantitative estimation of the thermal characteristics of the main spindle unit in an early stage of the development process. The presented work includes an experimental validation of the simulation model using a custom-built test rig. Specifically, the effects of the heat generated in the bearings and the heat flux from the bearing to the adjacent spindle system elements are investigated. Simulation and experimental results are compared and demonstrate good accordance. The proposed model is a useful, efficient and validated tool for quantitative simulation of thermal behavior of a main spindle system.
基金Supported by the DAAD (German Academic Exchange Service)
文摘With hard turning, which is an attractive alternative to existing grinding processes, surface quality is of great importance. Signal processing techniques were used to relate workpiece surface topography to the dynamic behavior of the machine tool. Spatial domain frequency analyses based on fast Fourier transform were used to analyze the tool behavior. Wavelet reconstruction was used for profile filtering. The results show that machine vibration remarkably affects the surface topography at small feed rates, but has negligible effect at high feed rates. The analyses also show how to control the surface quality during hard turning.
文摘Today＇s production systems are demanded to exhibit an increased flexibility and mutability in order to deal with dynamically changing conditions, objectives and an increasing number of product variants within industrial turbulent environments. Flexible automated systems are requested in order to improve dynamic production efficiency, e.g. robot-based hardware and PC-based controllers, but these usually induce a significantly higher production complexity, whereby the efforts for planning and programming, but also setups and reconfiguration, expand. In this paper a definition and some concepts of self-optimizing assembly systems are presented to describe possible ways to reduce the planning efforts in complex production systems. The concept of self-optimization in assembly systems will be derived from a theoretical approach and will be transferred to a specific application scenario---the automated assembly of a miniaturized solid state laser--where the challenges of unpredictable influences from e.g. component tolerances can be overcome by the help of self-optimization.
文摘Cutting super alloy is a highly sensitive manufacturing process regarding the complex thermo-mechanical interactions in the cutting zone,which finally determine the capability of the process in order to reach economic requirements.The connection between the intensity of heat sources as well as heat partitions into the tool,work piece and chip is yet not fully understood.Thus heat flows and other thermal conditions in the cutting zone cannot be predicted satisfactory,though they influence the chip formation mechanics,the surface integrity,respectively functionality of the machined work piece as well as the tool wear and lifetime.Because of this deficit the ecological and economical design of the manufacturing process is still limited and often not knowledge based.The proposed paper presents a methodology in order to measure and predict heat flows respectively affiliated temperatures during cutting nickel-base super alloy(Inconel 718).The heat flows in the cutting zone are determined by infrared thermography and a further energy balance by post processing the thermal images.A FE-model for chip formation simulation,which is based on CEL(Coupled-Eulerian-Lagrange)formulation,was used to calculate the heat flows.Finally,the results of the simulation and the experiments were compared.
文摘The thermal conditions like the temperature distribution and the heat fluxes during metal cutting have a major influence on the machinability, the tool lifetime, the metallurgical structure and thus the functionality of the work piece. This in particular applies for manufacturing processes like milling, drilling and turning for high-value turbomachinery components like impellers, combustion engines and compressors of the aerospace and automotive industry as well as energy generation, which play a major role in modern societies. However, numerous analytical and experimental efforts have been conducted in order to understand the thermal conditions in metal cutting, yet many questions still prevail. Most models are based on a stationary point of view and do not include time dependent effects like in intensity and distribution varying heat sources, varying engagement conditions and progressive tool wear. In order to cover such transient physics an analytical approach based on Green＇s functions for the solution of the partial differential equations of unsteady heat conduction in solids is used to model entire transient temperature fields. The validation of the model is carried out in orthogonal cutting experiments not only punctually but also for entire temperature fields. For these experiments an integrated measurement of prevailing cutting force and temperature fields in the tool and the chip by means of high-speed thermography were applied. The thermal images were analyzed with regard to thermodynamic energy balancing in order to derive the heat partition between tool, chips and workpiece. The thus calculated heat flow into the tool was subsequently used in order to analytically model the transient volumetric temperature fields in the tool. The described methodology enables the modeling of the transient thermal state in the cutting zone and particular in the tool, which is directly linked to phenomena like tool wear and workpiece surface modifications.
基金Supported by the DAAD (German Academic Exchange Service) on its exchange student program
文摘For precision machining, the hard turning process is becoming an important alternative to some of the existing grinding processes. This paper presents an analytical model for predicting cutting forces in hard turning of 51CRV4 with hardness of 68 HRC. The cutting tool used is made from cubic boron nitride （CBN） with a wiper cutting edge. Formulas for differential chip loads are derived for three different situations, depending on the radial depth of cut. The cutting forces are determined by integrating the differential cutting forces over the tool-workpiece engagement domain. For validation, cutting forces predicted by the model were compared with experimental measurements, and most of the results agree quite well.
文摘The experimental determination of stability lobediagrams （SLDs） in milling can be realized by eithercontinuously varying the spindle speed or by varying thedepth of cut. In this paper, a method for combining boththese methods along with an online chatter detectionalgorithm is proposed for efficient determination of SLDs.To accomplish this, communication between the machinecontrol and chatter detection algorithm is established, andthe machine axes are controlled to change the spindle speedor depth of cut. The efficiency of the proposed method isanalyzed in this paper.
基金the financial support of the German Ministry of Education and Science BMBF for the Project ‘Mikrofiz’ under Grant No. FKZ13N9495
文摘The measurement of boreholes with diameters smaller than 500 μm is a demanding task that cannot be performed using state-of-the-art production metrology. In this letter, a miniaturized fiber probe with a diameter of 80μm is presented. A probe is used for low-coherence interferometry to conduct highly precise measurements of form deviations of small boreholes. Measurements conducted in nozzles are also presented. The results prove the potential of the fiber-optical sensor for quality inspection of high-precision parts, such as injection nozzles, for common-rail diesel engines.
