Machining-features of the workplace are described by using of the object-oriented （O-O） technology. Geometrical machining-features are recognized in the given cut region by using the maximum membership priciple abou...Machining-features of the workplace are described by using of the object-oriented （O-O） technology. Geometrical machining-features are recognized in the given cut region by using the maximum membership priciple about the fuzzy set. Depending on the IF-THEN rule and the fuzzy matching method, the rough information of the machining-process for high-speed milling （HSM） is extracted based on the database of machining-process for HSM. The optimization model of machining-process scheme is established to obtain shorter cut time, lower cost or higher surface quality. It is helpful to form successful cases for HSM. NC programming for HSM is realized according to optimized machining-process data from HSM cases selected by the optimization model and the extracted information of machining-process.展开更多
Due to the unproductive and time consuming of the test cut, it is important to recognize all the possible errors before starting the process. This paper introduces a simulation program which can be used in an NC verti...Due to the unproductive and time consuming of the test cut, it is important to recognize all the possible errors before starting the process. This paper introduces a simulation program which can be used in an NC vertical milling machine. A unique method is used for simulating the cutting process and displaying the three dimensional images. This method not only simplifies greatly the treatment of the hidden line but also creates a “photograph effect” image. The program is written in Visual B.展开更多
The planning method of tool orientation in the five-axis NC machining is studied. The problem of the existing method is analyzed and a new method for generating the global smoothing tool orientation is proposed by int...The planning method of tool orientation in the five-axis NC machining is studied. The problem of the existing method is analyzed and a new method for generating the global smoothing tool orientation is proposed by introducing the key frame idea in the animation-making. According to the feature of the part, several key tool orientations are set without interference between the tool and the part. Then, these key tool orientations are inter- polated by the spline function. By mapping the surface parameter to the spline parameter, the spline function value is obtained and taken as the tool orientation when generating the CL file. The machining result shows that the proposed method realizes the global smoothing of the tool orientation and the continuity of the rotational speed and the rotational acceleration. It also avoids the shake of the machine tool and improves the machining quality.展开更多
The equipment used in various fields contains an increasing number of parts with curved surfaces of increasing size.Five-axis computer numerical control(CNC)milling is the main parts machining method,while dynamics an...The equipment used in various fields contains an increasing number of parts with curved surfaces of increasing size.Five-axis computer numerical control(CNC)milling is the main parts machining method,while dynamics analysis has always been a research hotspot.The cutting conditions determined by the cutter axis,tool path,and workpiece geometry are complex and changeable,which has made dynamics research a major challenge.For this reason,this paper introduces the innovative idea of applying dimension reduction and mapping to the five-axis machining of curved surfaces,and proposes an efficient dynamics analysis model.To simplify the research object,the cutter position points along the tool path were discretized into inclined plane five-axis machining.The cutter dip angle and feed deflection angle were used to define the spatial position relationship in five-axis machining.These were then taken as the new base variables to construct an abstract two-dimensional space and establish the mapping relationship between the cutter position point and space point sets to further simplify the dimensions of the research object.Based on the in-cut cutting edge solved by the space limitation method,the dynamics of the inclined plane five-axis machining unit were studied,and the results were uniformly stored in the abstract space to produce a database.Finally,the prediction of the milling force and vibration state along the tool path became a data extraction process that significantly improved efficiency.Two experiments were also conducted which proved the accuracy and efficiency of the proposed dynamics analysis model.This study has great potential for the online synchronization of intelligent machining of large surfaces.展开更多
Tool path generated by space-filling curve always turns frequently causing trembling to machine,reducing toollife and affecting workpiece quality. Length and generation time of tool paths are both relatively long. In ...Tool path generated by space-filling curve always turns frequently causing trembling to machine,reducing toollife and affecting workpiece quality. Length and generation time of tool paths are both relatively long. In order to solve these problems,a toolpath generation method of NC milling based on space-filling curve is proposed. First,T-spline surface is regarded as the modeling surface,the grid,which is based on the limited scallop-height,can be got in the parameter space,and the influence value of grid node is determined. Second,a box is defined and planned,and the tool paths are got preliminarily,which is based on minimal spanning tree; Finally,based on an improved chamfering algorithm,the whole tool paths are got. A simulation system is developed for computer simulation,and an experiment is carried out to verify the method. The results of simulation and experiment show that the method is effective and feasible,and length and time of the tool paths are reduced.展开更多
The methods for reducing interface aperture inconsistency are studied in NC orbital milling(NCOM)of CFRP/Ti6Al4V laminates with coarse pitch.Comparative experiments show burr,aperture inconsistency and error are typic...The methods for reducing interface aperture inconsistency are studied in NC orbital milling(NCOM)of CFRP/Ti6Al4V laminates with coarse pitch.Comparative experiments show burr,aperture inconsistency and error are typical interface defects.Meanwhile,aperture inconsistency and error are more serious than burr in NCOM with coarse pitch.As one of the major causes of interface defects,axial force and radial force are intensively studied.Based upon the machining principle of orbital milling(OM)and the actual hole-making condition in laminated structures,NCOM experiments with coarse pitch are conducted on CFRP/Ti6Al4V laminates under different cutting conditions.Then,the effects of interlayer clamping,minimal quantity lubrication(MQL),twice milling instead of reaming,and interlayer speed change on interface aperture are analyzed.Research shows that interlayer clamping,interlayer speed change and MQL can effectively reduce out-of-tolerance of interface aperture.When making holes of different diameters with one cutter,axial feed has a greater effect on interface aperture precision than tangential feed.When making holes of the same diameter with different cutters,small diameter cutter will reduce interface aperture precision in a single processing.But the method of“twice milling instead of reaming”can improve the aperture precision effectively.展开更多
How to generate rake faces of nonconventional milling cutters (NCMC) with constant spiral angled and normal rake angled edges on NC machine tools is presented by use of a blunt cup grinder or a cup milling cutter. Mot...How to generate rake faces of nonconventional milling cutters (NCMC) with constant spiral angled and normal rake angled edges on NC machine tools is presented by use of a blunt cup grinder or a cup milling cutter. Motion functions of the NC machining system are mathematically deduced and exam- ed by a experiment. The research will provide theoretical and practical guidance for machining noncon- ventional tools on NC machine tools.展开更多
A mirror milling system(MMS)comprises two face-to-face five-axis machine tools,one for the cutting spindle and the other for the support tool.Since it is essential to maintain the cutter and support coaxial during the...A mirror milling system(MMS)comprises two face-to-face five-axis machine tools,one for the cutting spindle and the other for the support tool.Since it is essential to maintain the cutter and support coaxial during the cutting process,synchronous motion accuracy is the key index of the MMS.This paper proposed a novel method for measuring and estimating the synchronous motion accuracy of the dual five-axis machine tools.The method simultaneously detects errors in the tool center point(TCP)and tool axis direction(TAD)during synchronous motion.To implement the suggested method,a measurement device,with five high-precision displacement sensors was developed.A kinematic model was then developed to estimate the synchronous motion accuracy from the displacement sensor output.The screw theory was used to obtain the analytical expression of the inverse kinematic model,and the synchronous motion error was compensated and adjusted based on the inverse kinematic model of the dual five-axis machine tools.TCP and TAD quasi-static errors,such as geometric and backlash errors,were first compensated.By adjusting the servo parameters,the dynamic TCP and TAD errors,such as gain mismatch and reversal spike,were also reduced.The proposed method and device were tested in a large MMS,and the measured quasi-static and dynamic errors were all reduced when the compensation and adjustment method was used.Monte Carlo simulations were also used to estimate the uncertainty of the proposed scheme.展开更多
The cutting force prediction is essential to optimize the process parameters of machining such as feed rate optimization, etc. Due to the significant influences of the runout effect on cutting force variation in milli...The cutting force prediction is essential to optimize the process parameters of machining such as feed rate optimization, etc. Due to the significant influences of the runout effect on cutting force variation in milling process, it is necessary to incorporate the cutter runout parameters into the prediction model of cutting forces. However, the determination of cutter runout parameters is still a challenge task until now. In this paper, cutting process geometry models, such as uncut chip thickness and pitch angle, are established based on the true trajectory of the cutting edge considering the cutter runout effect. A new algorithm is then presented to compute the cutter runout parameters for flat-end mill utilizing the sampled data of cutting forces and derived process geometry parameters. Further, three-axis and five-axis milling experiments were conducted on a machining centre, and resulting cutting forces were sampled by a three-component dynamometer. After computing the corresponding cutter runout parameters, cutter forces are simulated embracing the cutter runout parameters obtained from the proposed algorithm. The predicted cutting forces show good agreements with the sampled data both in magnitude and shape, which validates the feasibility and effectivity of the proposed new algorithm of determining cutter runout parameters and the new way to accurately predict cutting forces. The proposed method for computing the cutter runout parameters provides the significant references for the cutting force prediction in the cutting process.展开更多
Presents the division of non developable ruled surface into divided small areas and flank milling in these divided areas to improve machining efficiency and machined surface quality by controlling the machining error ...Presents the division of non developable ruled surface into divided small areas and flank milling in these divided areas to improve machining efficiency and machined surface quality by controlling the machining error for each area, and the algorithms developed for generation of tool path and calculation of errors, and concludes from computer simulation results that the algorithms are correct.展开更多
This paper presents an advanced octree(AO-rep) model and an implicit formula of a generalized cutter model for five-axis milling simulation.First,the main ideal of the AO-rep model is building a hierarchical structure...This paper presents an advanced octree(AO-rep) model and an implicit formula of a generalized cutter model for five-axis milling simulation.First,the main ideal of the AO-rep model is building a hierarchical structure and representing solid volumes.The AO-rep model utilizes an octree to cull unrelated voxels,and generates a small-scale voxel model in grey octants when a cutter intersects these octants.Using a simplified intersection computation between a cube and triangles in E^3,an STL model can be converted into its AO-rep model at a preprocessing stage.Second,the authors formulate an implicit function of a generalized cutter in moving cutter frame,and determine the function in fixed workpiece frame using the theory of a rigid body motion.Finally,the authors make a simulation of machining an impeller.The result shows that the proposed approach has a high performance of time and space.展开更多
文摘Machining-features of the workplace are described by using of the object-oriented （O-O） technology. Geometrical machining-features are recognized in the given cut region by using the maximum membership priciple about the fuzzy set. Depending on the IF-THEN rule and the fuzzy matching method, the rough information of the machining-process for high-speed milling （HSM） is extracted based on the database of machining-process for HSM. The optimization model of machining-process scheme is established to obtain shorter cut time, lower cost or higher surface quality. It is helpful to form successful cases for HSM. NC programming for HSM is realized according to optimized machining-process data from HSM cases selected by the optimization model and the extracted information of machining-process.
文摘Due to the unproductive and time consuming of the test cut, it is important to recognize all the possible errors before starting the process. This paper introduces a simulation program which can be used in an NC vertical milling machine. A unique method is used for simulating the cutting process and displaying the three dimensional images. This method not only simplifies greatly the treatment of the hidden line but also creates a “photograph effect” image. The program is written in Visual B.
文摘The planning method of tool orientation in the five-axis NC machining is studied. The problem of the existing method is analyzed and a new method for generating the global smoothing tool orientation is proposed by introducing the key frame idea in the animation-making. According to the feature of the part, several key tool orientations are set without interference between the tool and the part. Then, these key tool orientations are inter- polated by the spline function. By mapping the surface parameter to the spline parameter, the spline function value is obtained and taken as the tool orientation when generating the CL file. The machining result shows that the proposed method realizes the global smoothing of the tool orientation and the continuity of the rotational speed and the rotational acceleration. It also avoids the shake of the machine tool and improves the machining quality.
基金Supported by National Natural Science Foundation of China(Grant Nos.52005078,U1908231,52075076).
文摘The equipment used in various fields contains an increasing number of parts with curved surfaces of increasing size.Five-axis computer numerical control(CNC)milling is the main parts machining method,while dynamics analysis has always been a research hotspot.The cutting conditions determined by the cutter axis,tool path,and workpiece geometry are complex and changeable,which has made dynamics research a major challenge.For this reason,this paper introduces the innovative idea of applying dimension reduction and mapping to the five-axis machining of curved surfaces,and proposes an efficient dynamics analysis model.To simplify the research object,the cutter position points along the tool path were discretized into inclined plane five-axis machining.The cutter dip angle and feed deflection angle were used to define the spatial position relationship in five-axis machining.These were then taken as the new base variables to construct an abstract two-dimensional space and establish the mapping relationship between the cutter position point and space point sets to further simplify the dimensions of the research object.Based on the in-cut cutting edge solved by the space limitation method,the dynamics of the inclined plane five-axis machining unit were studied,and the results were uniformly stored in the abstract space to produce a database.Finally,the prediction of the milling force and vibration state along the tool path became a data extraction process that significantly improved efficiency.Two experiments were also conducted which proved the accuracy and efficiency of the proposed dynamics analysis model.This study has great potential for the online synchronization of intelligent machining of large surfaces.
基金Supported by the National Natural Science Foundation of China(No.51575143)
文摘Tool path generated by space-filling curve always turns frequently causing trembling to machine,reducing toollife and affecting workpiece quality. Length and generation time of tool paths are both relatively long. In order to solve these problems,a toolpath generation method of NC milling based on space-filling curve is proposed. First,T-spline surface is regarded as the modeling surface,the grid,which is based on the limited scallop-height,can be got in the parameter space,and the influence value of grid node is determined. Second,a box is defined and planned,and the tool paths are got preliminarily,which is based on minimal spanning tree; Finally,based on an improved chamfering algorithm,the whole tool paths are got. A simulation system is developed for computer simulation,and an experiment is carried out to verify the method. The results of simulation and experiment show that the method is effective and feasible,and length and time of the tool paths are reduced.
基金Natural Science Research in Jiangsu Province(No.17KJB460008)the 333 Project Research Funding Project in Jiangsu Province(No.BRA2018310)the Innovation Project of Jiangsu Province.
文摘The methods for reducing interface aperture inconsistency are studied in NC orbital milling(NCOM)of CFRP/Ti6Al4V laminates with coarse pitch.Comparative experiments show burr,aperture inconsistency and error are typical interface defects.Meanwhile,aperture inconsistency and error are more serious than burr in NCOM with coarse pitch.As one of the major causes of interface defects,axial force and radial force are intensively studied.Based upon the machining principle of orbital milling(OM)and the actual hole-making condition in laminated structures,NCOM experiments with coarse pitch are conducted on CFRP/Ti6Al4V laminates under different cutting conditions.Then,the effects of interlayer clamping,minimal quantity lubrication(MQL),twice milling instead of reaming,and interlayer speed change on interface aperture are analyzed.Research shows that interlayer clamping,interlayer speed change and MQL can effectively reduce out-of-tolerance of interface aperture.When making holes of different diameters with one cutter,axial feed has a greater effect on interface aperture precision than tangential feed.When making holes of the same diameter with different cutters,small diameter cutter will reduce interface aperture precision in a single processing.But the method of“twice milling instead of reaming”can improve the aperture precision effectively.
文摘How to generate rake faces of nonconventional milling cutters (NCMC) with constant spiral angled and normal rake angled edges on NC machine tools is presented by use of a blunt cup grinder or a cup milling cutter. Motion functions of the NC machining system are mathematically deduced and exam- ed by a experiment. The research will provide theoretical and practical guidance for machining noncon- ventional tools on NC machine tools.
基金supported by the National Natural Science Foundation of China(Grant No.51875357)the State Key Program of National Natural Science Foundation of China(Grant No.U21B2081)the National Defense Science and Technology Excellence Youth Foundation(Grant No.2020-JCJQ-ZQ-079)。
文摘A mirror milling system(MMS)comprises two face-to-face five-axis machine tools,one for the cutting spindle and the other for the support tool.Since it is essential to maintain the cutter and support coaxial during the cutting process,synchronous motion accuracy is the key index of the MMS.This paper proposed a novel method for measuring and estimating the synchronous motion accuracy of the dual five-axis machine tools.The method simultaneously detects errors in the tool center point(TCP)and tool axis direction(TAD)during synchronous motion.To implement the suggested method,a measurement device,with five high-precision displacement sensors was developed.A kinematic model was then developed to estimate the synchronous motion accuracy from the displacement sensor output.The screw theory was used to obtain the analytical expression of the inverse kinematic model,and the synchronous motion error was compensated and adjusted based on the inverse kinematic model of the dual five-axis machine tools.TCP and TAD quasi-static errors,such as geometric and backlash errors,were first compensated.By adjusting the servo parameters,the dynamic TCP and TAD errors,such as gain mismatch and reversal spike,were also reduced.The proposed method and device were tested in a large MMS,and the measured quasi-static and dynamic errors were all reduced when the compensation and adjustment method was used.Monte Carlo simulations were also used to estimate the uncertainty of the proposed scheme.
基金supported by National Natural Science Foundation of China (Grant No. 51075054)National Basic Research Program of China (973 Program, Grant No. 2005CB724100)Program for New Century Excellent Talents in University of China (Grant No. NCET-08-081)
文摘The cutting force prediction is essential to optimize the process parameters of machining such as feed rate optimization, etc. Due to the significant influences of the runout effect on cutting force variation in milling process, it is necessary to incorporate the cutter runout parameters into the prediction model of cutting forces. However, the determination of cutter runout parameters is still a challenge task until now. In this paper, cutting process geometry models, such as uncut chip thickness and pitch angle, are established based on the true trajectory of the cutting edge considering the cutter runout effect. A new algorithm is then presented to compute the cutter runout parameters for flat-end mill utilizing the sampled data of cutting forces and derived process geometry parameters. Further, three-axis and five-axis milling experiments were conducted on a machining centre, and resulting cutting forces were sampled by a three-component dynamometer. After computing the corresponding cutter runout parameters, cutter forces are simulated embracing the cutter runout parameters obtained from the proposed algorithm. The predicted cutting forces show good agreements with the sampled data both in magnitude and shape, which validates the feasibility and effectivity of the proposed new algorithm of determining cutter runout parameters and the new way to accurately predict cutting forces. The proposed method for computing the cutter runout parameters provides the significant references for the cutting force prediction in the cutting process.
文摘Presents the division of non developable ruled surface into divided small areas and flank milling in these divided areas to improve machining efficiency and machined surface quality by controlling the machining error for each area, and the algorithms developed for generation of tool path and calculation of errors, and concludes from computer simulation results that the algorithms are correct.
基金supported by the National Science and Technology Major Project under Grant No.2012ZX01029001-002
文摘This paper presents an advanced octree(AO-rep) model and an implicit formula of a generalized cutter model for five-axis milling simulation.First,the main ideal of the AO-rep model is building a hierarchical structure and representing solid volumes.The AO-rep model utilizes an octree to cull unrelated voxels,and generates a small-scale voxel model in grey octants when a cutter intersects these octants.Using a simplified intersection computation between a cube and triangles in E^3,an STL model can be converted into its AO-rep model at a preprocessing stage.Second,the authors formulate an implicit function of a generalized cutter in moving cutter frame,and determine the function in fixed workpiece frame using the theory of a rigid body motion.Finally,the authors make a simulation of machining an impeller.The result shows that the proposed approach has a high performance of time and space.
