In milling around sharp corners, residual materials are left at sharp corners when the stepover is extremely long in the contour-parallel tool path. Milling force at the sharp corner rises momentarily due to the incre...In milling around sharp corners, residual materials are left at sharp corners when the stepover is extremely long in the contour-parallel tool path. Milling force at the sharp corner rises momentarily due to the increase of the cutter contact length, thus shortening the tool life and leading to machine chatter, even cutter breakage. Then a tool path improvement method by inserting biarc transition segments in the contour-parallel tool path is proposed for milling the pocket. Using the method, the cutter moves along the biarc transition tool path. And the corner material is removed. The improved tool path is continuous for clearing residual materials at the sharp corner. Finally, the machining experiment validates the proposed method.展开更多
The CAD model of molar prosthesis is usually stored in standard templete library （STIr） format. A new topological structure is given based on STL format and the vertex-based entity offset algorithm is presented to r...The CAD model of molar prosthesis is usually stored in standard templete library （STIr） format. A new topological structure is given based on STL format and the vertex-based entity offset algorithm is presented to realize the rapid generation of roughing/finishing tool path for molar prosthesis. Simulation results show that the proposed algorithm prossesses characteristics of excellent stabilization, fast calculation speed and high machining accuracy.展开更多
The current research of the 5-axis tool positioning algorithm mainly focuses on searching the local optimal tool position without gouging and interference at a cutter contact（CC） point,while not considering the smoo...The current research of the 5-axis tool positioning algorithm mainly focuses on searching the local optimal tool position without gouging and interference at a cutter contact（CC） point,while not considering the smoothness and continuity of a whole tool path.When the surface curvature varies significantly,a local abrupt change of tool paths will happen.The abrupt change has a great influence on surface machining quality.In order to keep generated tool paths smooth and continuous,a five-axis tool positioning algorithm based on smooth tool paths is presented.Firstly,the inclination angle,the tilt angle and offset distance of the tool at a CC point are used as design variables,and the machining strip width is used as an objective function,an optimization model of a local tool positioning algorithm is thus established.Then,a vector equation of tool path is derived by using the above optimization model.By analyzing the equation,the main factors affecting the tool path quality are obtained.Finally,a new tool position optimization model is established,and the detailed process of tool position optimization is also given.An experiment is conducted to machine an aircraft turbine blade by using the proposed algorithm on a 5-axis blade grinding machine,and the machined blade surface is measured with a coordinate measuring machine（CMM）.Experimental and measured results show that the proposed algorithm can ensure tool paths are smooth and continuous,improve the tool path quality,avoid the local abrupt change of tool paths,and enhance machining quality and machining efficiency of sculptured surfaces.展开更多
Based on the object oriented data structure of Voronoi diagram, the algorithm of the trimmed offset generating and the optimal too l path planning of the pocket machining for multiply connected polygonal domains are ...Based on the object oriented data structure of Voronoi diagram, the algorithm of the trimmed offset generating and the optimal too l path planning of the pocket machining for multiply connected polygonal domains are studied. The intersection state transition rule is improved in this algorithm. The intersection is between the trimmed offsets and Voronoi polygon. On this basis, the trimmed offset generating and the optimal tool path planning are mad e with three stacks(I stack, C stack and P stack)in different monotonous pouches of Voronoi diagram. At the same time, a merging method of Voronoi diagram an d offsets generating for multiply connected polygonal domains is also presented. The above algorithms have been implemented in NC machining successfully, and the efficiency is fully verified.展开更多
Structure design and fabricating methods of three-dimensional （3D） artificial spherical compound eyes have been researched by many scholars. Micro-nano optical manufacturing is mostly used to process 3D artificial c...Structure design and fabricating methods of three-dimensional （3D） artificial spherical compound eyes have been researched by many scholars. Micro-nano optical manufacturing is mostly used to process 3D artificial compound eyes. However, spherical optical compound eyes are less at optical performance than the eyes of insects, and it is difficult to further improve the imaging quality of compound eyes by means of micro-nano optical manufacturing. In this research, nonhomogeneous aspheric compound eyes （ACEs） are designed and fabricated. The nonhomogeneous aspheric structure is applied to calibrate the spherical aberration. Micro milling with advantages in processing three-dimensional micro structures is adopted to manufacture ACEs. In order to obtain ACEs with high imaging quality, the tool paths are optimized by analyzing the influence factors consisting of interpolation allowable error, scallop height and tool path pattern. In the experiments, two kinds of ACEs are manufactured by micro-milling with different too path patterns and cutting parameter on the miniature precision five-axis milling machine tool. The experimental results indicate that the ACEs of high surface quality can be achieved by circularly milling small micro-lens individually with changeable cutting depth. A prototype of the aspheric compound eye （ACE） with surface roughness （Ra） below 0.12 p.m is obtained with good imaging performance. This research ameliorates the imaging quality of 3D artificial compound eyes, and the proposed method of micro-milling can improve surface processing quality of compound eyes.展开更多
Sheet metal dieless forming is a new metal forming technology. Thistechnology adopts the principle of rapid prototyping technology, so it can form sheet metal partswithout traditional die and moulds. According to the ...Sheet metal dieless forming is a new metal forming technology. Thistechnology adopts the principle of rapid prototyping technology, so it can form sheet metal partswithout traditional die and moulds. According to the characteristic of sheet metal dieless formingtechnology a new way of tool path generation based on the STL file for sheet metal dieless formingis proposed.展开更多
A global energy fairing method,applied to automated fiber placement(AFP)tool path,was proposed.The main purpose was to improve the adaptability of AFP path towards part with sharp curvature variation as well as produc...A global energy fairing method,applied to automated fiber placement(AFP)tool path,was proposed.The main purpose was to improve the adaptability of AFP path towards part with sharp curvature variation as well as product quality.The relation between path geometric property and manufacturing property was discussed and a series of experiments were carried out.Based on cubic B-Spline global fairing method,the AFP tool path was faired which decreased the tool path curvature and curvature changing rate.Compared with initial ones,the path faired by the proposed method was relatively flat and smooth,which contributed to layup efficiency and reducing bulking defects.The method was demonstrated potentials in application for AFP manufacturing,especially for aeronautic and aerospace industry practice.展开更多
This paper presents a new approach for designing the tool paths in the machining of sculptured surfaces for computer nu- merical controlled end milling. In the proposed method, the tool paths are determined so that th...This paper presents a new approach for designing the tool paths in the machining of sculptured surfaces for computer nu- merical controlled end milling. In the proposed method, the tool paths are determined so that the scallop height formed by two adja- cent machining paths is maintained constant across the machined surface. Unlike previous work on iso-scallop height milling, the present work considers the true 3D configuration of the milling procedure and can be used to generate better results, which is shown by examoles.展开更多
With the increasing market demand for optical complex surface parts,the application of multi-axis ultraprecision single-point diamond turning is increasing.A tool path generation method is very important to decrease m...With the increasing market demand for optical complex surface parts,the application of multi-axis ultraprecision single-point diamond turning is increasing.A tool path generation method is very important to decrease manufacturing time,enhance surface quality,and reduce cost.Compared with the tool path generation of the traditional multi-axis milling,that of the ultra-precision single-point diamond turning requires higher calculation accuracy and efficiency.This paper reviews the tool path generation of ultra-precision diamond turning,considering several key issues:cutter location(CL)points calculation,the topological form of tool path,interpolation mode,and G code optimization.展开更多
Diamond turning based on a fast tool servo(FTS)is widely used in freeform optics fabrication due to its high accuracy and machining efficiency.As a new trend,recently developed high-frequency and long-stroke FTS units...Diamond turning based on a fast tool servo(FTS)is widely used in freeform optics fabrication due to its high accuracy and machining efficiency.As a new trend,recently developed high-frequency and long-stroke FTS units are independently driven by a separate control system from the machine tool controller.However,the tool path generation strategy for the independently controlled FTS is far from complete.This study aims to establish methods for optimizing tool path for the independent control FTS to reduce form errors in a single step of machining.Different from the conventional integrated FTS control system,where control points are distributed in a spiral pattern,in this study,the tool path for the independent FTS controller is generated by the ring method and the mesh method,respectively.The machined surface profile is predicted by simulation and the parameters for the control point generation are optimized by minimizing the deviation between the predicted and the designed surfaces.To demonstrate the feasibility of the proposed tool path generation strategies,cutting tests of a two-dimensional sinewave and a micro-lens array were conducted and the results were compared.As a result,after tool path optimization,the peak-to-valley form error of the machined surface was reduced from 429 nm to 56 nm for the two-dimensional sinewave by using the ring method,and from 191 nm to 103 nm for the micro-lens array by using the mesh method,respectively.展开更多
Facing the challenges of a shorter product design a nd manufacturing lead-time, many mold companies are using 3-D CAD/CAM software s ystems in design and manufacturing. A new product file is often issued to the mo ld ...Facing the challenges of a shorter product design a nd manufacturing lead-time, many mold companies are using 3-D CAD/CAM software s ystems in design and manufacturing. A new product file is often issued to the mo ld design department before it is completely finalized and the design may have t o be iterated many times during the mold design and making processes. In practic e, if a mold has been modified, all the tool paths that cover the modified regio n must be re-generated, no matter how small the modified region may be. With th e available tool path generation systems, if a tool path needs to be re-generat ed, all the cutter location (CL) points must be re-calculated, and none of the original CL points can be re-used. It would require as much time to re-gen erate the modified tool path as in the original case. On the other hand, the mod ified region is usually quite small compared with the entire mold. The complete re-generation process is therefore highly unproductive and time-consuming. This paper proposes an efficient tool path re-generation approach for 3-axis d ie and mold machining. It is assumed in this research that a gouge-free too l path has been generated for the original mold and the same ball end-mill is to be used to generate the tool path for the modified mold. It is shown in th is work that if the boundary of the modified region is interference-free, the a ffected CL points are enclosed by a set of CL points which correspond to the poi nts on the boundary of the modified region. An efficient tool path re-generatio n algorithm was developed in this research. With this algorithm, a closed CL cur ve is first generated from the boundary of the affected region. The CL points fo r the original mold are then analyzed by comparing the x and y values with the b oundary of the affected CL points. If the CL points are not affected by the modi fication, they are output to the new CL file directly. Otherwise, they are remov ed and replaced by the new CL points. The algorithm has been tested using severa l industrial parts, and results show that it is efficient, robust, and the re-g enerated tool path is gouge-free and smooth.展开更多
An enveloping theory based method for the determination of path interval in three axis NC machining of free form surface is presented, and a practical algorithm and the measures for improving the calculating efficien...An enveloping theory based method for the determination of path interval in three axis NC machining of free form surface is presented, and a practical algorithm and the measures for improving the calculating efficiency of the algorithm are given. Not only the given algorithm can be used for ball end cutter, flat end cutter, torus cutter and drum cutter, but also the proposed method can be extended to arbitrary milling cutters. Thus, the problem how to strictly calculate path interval in the occasion of three axis NC machining of free form surfaces with non ball end cutters has been resolved effectively. On this basis, the factors that affect path interval are analyzed, and the methods for optimizing tool path are explored.展开更多
This paper presents a strategy to generate interference-free tool paths for machining sculptured surfaces. The strategy proposed here is first to determine the tool path topology. The values of the step length and the...This paper presents a strategy to generate interference-free tool paths for machining sculptured surfaces. The strategy proposed here is first to determine the tool path topology. The values of the step length and the path interval are then calculated based on the machining tolerance requirements. After detecting and eliminating the tool interference, the interference-free tool path is generated. The effectiveness of the developed algorithm is demonstrated through simulation and actual cutting tests.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
Ruled surfaces found in engineering parts are often blended with a constraint surface,like the blade surface and hub surface of a centrifugal impeller.It is significant to accurately machine these ruled surfaces in fl...Ruled surfaces found in engineering parts are often blended with a constraint surface,like the blade surface and hub surface of a centrifugal impeller.It is significant to accurately machine these ruled surfaces in flank milling with interference-free and fairing tool path,while current models in fulfilling these goals are complex and rare.In this paper,a tool path planning method with optimal cutter locations(CLs)is proposed for 5-axis flank milling of ruled surfaces under multiple geometric constraints.To be specific,a concise three-point contact tool positioning model is firstly developed for a cylindrical cutter.Different tool orientations arise when varying the three contact positions and a tool orientation pool with acceptable cutter-surface deviation is constructed using a meta-heuristic algorithm.Fairing angular curves are derived from candidates in this pool,and then curve registration for cutter tip point on each determined tool axis is performed in respect of interference avoidance and geometric smoothness.On this basis,an adaptive interval determination model is developed for deviation control of interpolated cutter locations.This model is designed to be independent of the CL optimization process so that multiple CLs can be planned simultaneously with parallel computing technique.Finally,tests are performed on representative surfaces and the results show the method has advantages over previous meta-heuristic tool path planning approaches in both machining accuracy and computation time,and receives the best comprehensive performance compared to other multi-constrained methods when machining an impeller.展开更多
Tool path smoothing of linear commands is important to guarantee the high-order motion continuity of multi-axis motion control systems.The existing local tool path smoothing methods mainly construct symmetrical spline...Tool path smoothing of linear commands is important to guarantee the high-order motion continuity of multi-axis motion control systems.The existing local tool path smoothing methods mainly construct symmetrical splines at transition corners of linear segments.When the linear segments are short,the symmetrical splines must be shrunk to avoid overlapping,which gives rise to relatively high curvature and low machining efficiency.This paper proposes a tool-path smoothing algorithm for serial industrial robots with 6 rotary(6R)joints by constructing asymmetrical Pythagorean-hodograph(PH)splines.Firstly,symmetrical PH splines are initially constructed at transition corners to realize the third-order differential continuity of tool path position and tool orientation.Tool tip position smoothing errors are constrained by directly evaluating the control polygon length of spline according to the error tolerance in the workpiece coordinate system,while the tool orientation smoothing errors are constrained by adjusting control polygon length after converting tool orientation error to Euler angles using Jacobian matrix.Then asymmetrical splines are constructed by dealing with the spline overlapping problem,while guarantying the fully utilization of error tolerance to reduce spline curvature.The position and orientation are synchronized to the arc-length of the tool tip position to ensure the continuity of acceleration and jerk commands.The control points and arc-length of the constructed asymmetrical splines can all be solved analytically,which makes it suitable for on-line tool path smoothing.Experiments demonstrate that the proposed method achieves higher motion efficiency and lower tracking error than the existing symmetrical and asymmetrical tool path smoothing methods,which validates the advantages of the proposed method in high speed machining.展开更多
Feedrate scheduling in computer numerical control(CNC)machining is of great importance to fully develop the capabilities of machine tools while maintaining the motion stability of each actuator.Smooth and time-optimal...Feedrate scheduling in computer numerical control(CNC)machining is of great importance to fully develop the capabilities of machine tools while maintaining the motion stability of each actuator.Smooth and time-optimal feedrate scheduling plays a critical role in improving the machining efficiency and precision of complex surfaces considering the irregular curvature characteristics of tool paths and the limited drive capacities of machine tools.This study develops a general feedrate scheduling method for non-uniform rational B-splines(NURBS)tool paths in CNC machining aiming at minimizing the total machining time without sacrificing the smoothness of feed motion.The feedrate profile is represented by a B-spline curve to flexibly adapt to the frequent acceleration and deceleration requirements of machining along complex tool paths.The time-optimal B-spline feedrate is produced by continuously increasing the control points sequentially from zero positions in the bidirectional scanning and sampling processes.The required number of knots for the time-optimal B-spline feedrate can be determined using a progressive knot insertion method.To improve the computational efficiency,the B-spline feedrate profile is divided into a series of independent segments and the computation in each segment can be performed concurrently.The proposed feedrate scheduling method is capable of dealing with not only the geometry constraints but also high-order drive constraints for any complex tool path with little computational overhead.Simulations and machining experiments are conducted to verify the effectiveness and superiorities of the proposed method.展开更多
The problem of finished surface being not first-order continuous commonly exists in machining sculptured surfaces with a torus cutter and some other types of cutters. To solve this problem, a dual drive curve tool pat...The problem of finished surface being not first-order continuous commonly exists in machining sculptured surfaces with a torus cutter and some other types of cutters. To solve this problem, a dual drive curve tool path planning method is proposed in this article. First, the maximum machining strip width of a whole tool path can be obtained through optimizing each tool position with multi-point machining （MPM） method. Second, two drive curves are then determined according to the obtained maximum machining strip width. Finally, the tool is positioned once more along the dual drive curve under the condition of tool path smoothness. A computer simulation and cutting experiments are carried out to testify the performance of the new method. The machined surface is measured with a coordinate measuring machine （CMM） to examine the machining quality. The results obtained show that this method can effectively eliminate sharp scallops between adjacent tool paths, keep tool paths smooth, and improve the surface machining quality as well as machining efficiency.展开更多
Machining quality of clean-up region has a strong influence on the performances of the impeller. In order to plan clean-up tool paths rapidly and obtain good finish surface quality, an efficient and robust tool path g...Machining quality of clean-up region has a strong influence on the performances of the impeller. In order to plan clean-up tool paths rapidly and obtain good finish surface quality, an efficient and robust tool path generation method is presented, which employs an approach based on point-searching. The clean-up machining mentioned in this paper is pencil-cut and multilayer fillet-cut for a free-form model with a ball-end cutter. For pencil-cut, the cutter center position can be determined via judging whether it satisfies the distance requirement. After the searching direction and the tracing direction have been determined, by employing the point-searching algorithm with the idea of dichotomy, all the cutter contact （CC） points and cutter location （CL） points can be found and the clean-up boundaries can also be defined rapidly. Then the tool path is generated. Based on the main concept of pencil-cut, a multilayer fillet-cut method is proposed, which utilizes a ball-end cutter with its radius less than the design radius of clean-up region. Using a sequence of intermediate virtual cutters to divide the clean-up region into several layers and given a cusp-height tolerance for the final layer, then the tool paths for all layers are calculated. Finally, computer implementation is also presented in this paper, and the result shows that the proposed method is feasible.展开更多
文摘In milling around sharp corners, residual materials are left at sharp corners when the stepover is extremely long in the contour-parallel tool path. Milling force at the sharp corner rises momentarily due to the increase of the cutter contact length, thus shortening the tool life and leading to machine chatter, even cutter breakage. Then a tool path improvement method by inserting biarc transition segments in the contour-parallel tool path is proposed for milling the pocket. Using the method, the cutter moves along the biarc transition tool path. And the corner material is removed. The improved tool path is continuous for clearing residual materials at the sharp corner. Finally, the machining experiment validates the proposed method.
文摘The CAD model of molar prosthesis is usually stored in standard templete library （STIr） format. A new topological structure is given based on STL format and the vertex-based entity offset algorithm is presented to realize the rapid generation of roughing/finishing tool path for molar prosthesis. Simulation results show that the proposed algorithm prossesses characteristics of excellent stabilization, fast calculation speed and high machining accuracy.
基金supported by National Natural Science Foundation of China (Grant No. 50875012)National Hi-tech Research and Development Program of China (863 Program, Grant No. 2008AA04Z124)+1 种基金National Science and Technology Major Project of China (Grant No. 2009ZX04001-141)Joint Construction Project of Beijing Municipal Commission of Education of China
文摘The current research of the 5-axis tool positioning algorithm mainly focuses on searching the local optimal tool position without gouging and interference at a cutter contact（CC） point,while not considering the smoothness and continuity of a whole tool path.When the surface curvature varies significantly,a local abrupt change of tool paths will happen.The abrupt change has a great influence on surface machining quality.In order to keep generated tool paths smooth and continuous,a five-axis tool positioning algorithm based on smooth tool paths is presented.Firstly,the inclination angle,the tilt angle and offset distance of the tool at a CC point are used as design variables,and the machining strip width is used as an objective function,an optimization model of a local tool positioning algorithm is thus established.Then,a vector equation of tool path is derived by using the above optimization model.By analyzing the equation,the main factors affecting the tool path quality are obtained.Finally,a new tool position optimization model is established,and the detailed process of tool position optimization is also given.An experiment is conducted to machine an aircraft turbine blade by using the proposed algorithm on a 5-axis blade grinding machine,and the machined blade surface is measured with a coordinate measuring machine（CMM）.Experimental and measured results show that the proposed algorithm can ensure tool paths are smooth and continuous,improve the tool path quality,avoid the local abrupt change of tool paths,and enhance machining quality and machining efficiency of sculptured surfaces.
文摘Based on the object oriented data structure of Voronoi diagram, the algorithm of the trimmed offset generating and the optimal too l path planning of the pocket machining for multiply connected polygonal domains are studied. The intersection state transition rule is improved in this algorithm. The intersection is between the trimmed offsets and Voronoi polygon. On this basis, the trimmed offset generating and the optimal tool path planning are mad e with three stacks(I stack, C stack and P stack)in different monotonous pouches of Voronoi diagram. At the same time, a merging method of Voronoi diagram an d offsets generating for multiply connected polygonal domains is also presented. The above algorithms have been implemented in NC machining successfully, and the efficiency is fully verified.
基金Supported by National Natural Science Foundation of China(Grant No.50935003)National Numerical Control Major Projects of China(Grant No.2013ZX04001000215)
文摘Structure design and fabricating methods of three-dimensional （3D） artificial spherical compound eyes have been researched by many scholars. Micro-nano optical manufacturing is mostly used to process 3D artificial compound eyes. However, spherical optical compound eyes are less at optical performance than the eyes of insects, and it is difficult to further improve the imaging quality of compound eyes by means of micro-nano optical manufacturing. In this research, nonhomogeneous aspheric compound eyes （ACEs） are designed and fabricated. The nonhomogeneous aspheric structure is applied to calibrate the spherical aberration. Micro milling with advantages in processing three-dimensional micro structures is adopted to manufacture ACEs. In order to obtain ACEs with high imaging quality, the tool paths are optimized by analyzing the influence factors consisting of interpolation allowable error, scallop height and tool path pattern. In the experiments, two kinds of ACEs are manufactured by micro-milling with different too path patterns and cutting parameter on the miniature precision five-axis milling machine tool. The experimental results indicate that the ACEs of high surface quality can be achieved by circularly milling small micro-lens individually with changeable cutting depth. A prototype of the aspheric compound eye （ACE） with surface roughness （Ra） below 0.12 p.m is obtained with good imaging performance. This research ameliorates the imaging quality of 3D artificial compound eyes, and the proposed method of micro-milling can improve surface processing quality of compound eyes.
基金This project is supported by National Natural Science Foundation of China(No.50175034).
文摘Sheet metal dieless forming is a new metal forming technology. Thistechnology adopts the principle of rapid prototyping technology, so it can form sheet metal partswithout traditional die and moulds. According to the characteristic of sheet metal dieless formingtechnology a new way of tool path generation based on the STL file for sheet metal dieless formingis proposed.
基金supported by the Major Science and Technology Projects of China (No.2016ZX04002-001-07)Basic Scientific Research Fund(56XAA15057)
文摘A global energy fairing method,applied to automated fiber placement(AFP)tool path,was proposed.The main purpose was to improve the adaptability of AFP path towards part with sharp curvature variation as well as product quality.The relation between path geometric property and manufacturing property was discussed and a series of experiments were carried out.Based on cubic B-Spline global fairing method,the AFP tool path was faired which decreased the tool path curvature and curvature changing rate.Compared with initial ones,the path faired by the proposed method was relatively flat and smooth,which contributed to layup efficiency and reducing bulking defects.The method was demonstrated potentials in application for AFP manufacturing,especially for aeronautic and aerospace industry practice.
基金Partially supported by a grant from NSFC (60821002)
文摘This paper presents a new approach for designing the tool paths in the machining of sculptured surfaces for computer nu- merical controlled end milling. In the proposed method, the tool paths are determined so that the scallop height formed by two adja- cent machining paths is maintained constant across the machined surface. Unlike previous work on iso-scallop height milling, the present work considers the true 3D configuration of the milling procedure and can be used to generate better results, which is shown by examoles.
基金supports of the Funds for the National Natural Science Foundation of China [grant numbers 51575386,51275344]
文摘With the increasing market demand for optical complex surface parts,the application of multi-axis ultraprecision single-point diamond turning is increasing.A tool path generation method is very important to decrease manufacturing time,enhance surface quality,and reduce cost.Compared with the tool path generation of the traditional multi-axis milling,that of the ultra-precision single-point diamond turning requires higher calculation accuracy and efficiency.This paper reviews the tool path generation of ultra-precision diamond turning,considering several key issues:cutter location(CL)points calculation,the topological form of tool path,interpolation mode,and G code optimization.
基金supported by Japan Society for the Promotion of Science,Grant-in-Aid for Scientific Research(B),Project Number 21H01230.
文摘Diamond turning based on a fast tool servo(FTS)is widely used in freeform optics fabrication due to its high accuracy and machining efficiency.As a new trend,recently developed high-frequency and long-stroke FTS units are independently driven by a separate control system from the machine tool controller.However,the tool path generation strategy for the independently controlled FTS is far from complete.This study aims to establish methods for optimizing tool path for the independent control FTS to reduce form errors in a single step of machining.Different from the conventional integrated FTS control system,where control points are distributed in a spiral pattern,in this study,the tool path for the independent FTS controller is generated by the ring method and the mesh method,respectively.The machined surface profile is predicted by simulation and the parameters for the control point generation are optimized by minimizing the deviation between the predicted and the designed surfaces.To demonstrate the feasibility of the proposed tool path generation strategies,cutting tests of a two-dimensional sinewave and a micro-lens array were conducted and the results were compared.As a result,after tool path optimization,the peak-to-valley form error of the machined surface was reduced from 429 nm to 56 nm for the two-dimensional sinewave by using the ring method,and from 191 nm to 103 nm for the micro-lens array by using the mesh method,respectively.
文摘Facing the challenges of a shorter product design a nd manufacturing lead-time, many mold companies are using 3-D CAD/CAM software s ystems in design and manufacturing. A new product file is often issued to the mo ld design department before it is completely finalized and the design may have t o be iterated many times during the mold design and making processes. In practic e, if a mold has been modified, all the tool paths that cover the modified regio n must be re-generated, no matter how small the modified region may be. With th e available tool path generation systems, if a tool path needs to be re-generat ed, all the cutter location (CL) points must be re-calculated, and none of the original CL points can be re-used. It would require as much time to re-gen erate the modified tool path as in the original case. On the other hand, the mod ified region is usually quite small compared with the entire mold. The complete re-generation process is therefore highly unproductive and time-consuming. This paper proposes an efficient tool path re-generation approach for 3-axis d ie and mold machining. It is assumed in this research that a gouge-free too l path has been generated for the original mold and the same ball end-mill is to be used to generate the tool path for the modified mold. It is shown in th is work that if the boundary of the modified region is interference-free, the a ffected CL points are enclosed by a set of CL points which correspond to the poi nts on the boundary of the modified region. An efficient tool path re-generatio n algorithm was developed in this research. With this algorithm, a closed CL cur ve is first generated from the boundary of the affected region. The CL points fo r the original mold are then analyzed by comparing the x and y values with the b oundary of the affected CL points. If the CL points are not affected by the modi fication, they are output to the new CL file directly. Otherwise, they are remov ed and replaced by the new CL points. The algorithm has been tested using severa l industrial parts, and results show that it is efficient, robust, and the re-g enerated tool path is gouge-free and smooth.
文摘An enveloping theory based method for the determination of path interval in three axis NC machining of free form surface is presented, and a practical algorithm and the measures for improving the calculating efficiency of the algorithm are given. Not only the given algorithm can be used for ball end cutter, flat end cutter, torus cutter and drum cutter, but also the proposed method can be extended to arbitrary milling cutters. Thus, the problem how to strictly calculate path interval in the occasion of three axis NC machining of free form surfaces with non ball end cutters has been resolved effectively. On this basis, the factors that affect path interval are analyzed, and the methods for optimizing tool path are explored.
文摘This paper presents a strategy to generate interference-free tool paths for machining sculptured surfaces. The strategy proposed here is first to determine the tool path topology. The values of the step length and the path interval are then calculated based on the machining tolerance requirements. After detecting and eliminating the tool interference, the interference-free tool path is generated. The effectiveness of the developed algorithm is demonstrated through simulation and actual cutting tests.
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 Natural Science Foundation of China(Nos.U22A20202 and 52205516)the China Postdoctoral Science Foundation(No.2022 M720641)。
文摘Ruled surfaces found in engineering parts are often blended with a constraint surface,like the blade surface and hub surface of a centrifugal impeller.It is significant to accurately machine these ruled surfaces in flank milling with interference-free and fairing tool path,while current models in fulfilling these goals are complex and rare.In this paper,a tool path planning method with optimal cutter locations(CLs)is proposed for 5-axis flank milling of ruled surfaces under multiple geometric constraints.To be specific,a concise three-point contact tool positioning model is firstly developed for a cylindrical cutter.Different tool orientations arise when varying the three contact positions and a tool orientation pool with acceptable cutter-surface deviation is constructed using a meta-heuristic algorithm.Fairing angular curves are derived from candidates in this pool,and then curve registration for cutter tip point on each determined tool axis is performed in respect of interference avoidance and geometric smoothness.On this basis,an adaptive interval determination model is developed for deviation control of interpolated cutter locations.This model is designed to be independent of the CL optimization process so that multiple CLs can be planned simultaneously with parallel computing technique.Finally,tests are performed on representative surfaces and the results show the method has advantages over previous meta-heuristic tool path planning approaches in both machining accuracy and computation time,and receives the best comprehensive performance compared to other multi-constrained methods when machining an impeller.
基金supported by the Key Research and Development Plan(Grant No.2020YFB1710400)the National Natural Science Foundation of China(Grant No.52122512 and 52188102)the Natural Science Foundation of Hubei Province,China(Grant No.2021CFA075)。
文摘Tool path smoothing of linear commands is important to guarantee the high-order motion continuity of multi-axis motion control systems.The existing local tool path smoothing methods mainly construct symmetrical splines at transition corners of linear segments.When the linear segments are short,the symmetrical splines must be shrunk to avoid overlapping,which gives rise to relatively high curvature and low machining efficiency.This paper proposes a tool-path smoothing algorithm for serial industrial robots with 6 rotary(6R)joints by constructing asymmetrical Pythagorean-hodograph(PH)splines.Firstly,symmetrical PH splines are initially constructed at transition corners to realize the third-order differential continuity of tool path position and tool orientation.Tool tip position smoothing errors are constrained by directly evaluating the control polygon length of spline according to the error tolerance in the workpiece coordinate system,while the tool orientation smoothing errors are constrained by adjusting control polygon length after converting tool orientation error to Euler angles using Jacobian matrix.Then asymmetrical splines are constructed by dealing with the spline overlapping problem,while guarantying the fully utilization of error tolerance to reduce spline curvature.The position and orientation are synchronized to the arc-length of the tool tip position to ensure the continuity of acceleration and jerk commands.The control points and arc-length of the constructed asymmetrical splines can all be solved analytically,which makes it suitable for on-line tool path smoothing.Experiments demonstrate that the proposed method achieves higher motion efficiency and lower tracking error than the existing symmetrical and asymmetrical tool path smoothing methods,which validates the advantages of the proposed method in high speed machining.
基金The authors would like to thank the finical support from Scientific Research Projects of Jilin Provincial Department of Education(Grant No.JJKH20200104KJ)National Natural Science Foundation of China(Grant No.51975392).
文摘Feedrate scheduling in computer numerical control(CNC)machining is of great importance to fully develop the capabilities of machine tools while maintaining the motion stability of each actuator.Smooth and time-optimal feedrate scheduling plays a critical role in improving the machining efficiency and precision of complex surfaces considering the irregular curvature characteristics of tool paths and the limited drive capacities of machine tools.This study develops a general feedrate scheduling method for non-uniform rational B-splines(NURBS)tool paths in CNC machining aiming at minimizing the total machining time without sacrificing the smoothness of feed motion.The feedrate profile is represented by a B-spline curve to flexibly adapt to the frequent acceleration and deceleration requirements of machining along complex tool paths.The time-optimal B-spline feedrate is produced by continuously increasing the control points sequentially from zero positions in the bidirectional scanning and sampling processes.The required number of knots for the time-optimal B-spline feedrate can be determined using a progressive knot insertion method.To improve the computational efficiency,the B-spline feedrate profile is divided into a series of independent segments and the computation in each segment can be performed concurrently.The proposed feedrate scheduling method is capable of dealing with not only the geometry constraints but also high-order drive constraints for any complex tool path with little computational overhead.Simulations and machining experiments are conducted to verify the effectiveness and superiorities of the proposed method.
基金National Natural Science Foundation of China (50875012)National High-tech Research and Development Program (2008AA04Z124)+1 种基金National Science and Technology Major Project (2009ZX04001-141)Joint Construction Project of Beijing Municipal Commission of Education
文摘The problem of finished surface being not first-order continuous commonly exists in machining sculptured surfaces with a torus cutter and some other types of cutters. To solve this problem, a dual drive curve tool path planning method is proposed in this article. First, the maximum machining strip width of a whole tool path can be obtained through optimizing each tool position with multi-point machining （MPM） method. Second, two drive curves are then determined according to the obtained maximum machining strip width. Finally, the tool is positioned once more along the dual drive curve under the condition of tool path smoothness. A computer simulation and cutting experiments are carried out to testify the performance of the new method. The machined surface is measured with a coordinate measuring machine （CMM） to examine the machining quality. The results obtained show that this method can effectively eliminate sharp scallops between adjacent tool paths, keep tool paths smooth, and improve the surface machining quality as well as machining efficiency.
基金National Natural Science Foundation of China （51005183） National Science and Technology Major Project （2011X04016-031）
文摘Machining quality of clean-up region has a strong influence on the performances of the impeller. In order to plan clean-up tool paths rapidly and obtain good finish surface quality, an efficient and robust tool path generation method is presented, which employs an approach based on point-searching. The clean-up machining mentioned in this paper is pencil-cut and multilayer fillet-cut for a free-form model with a ball-end cutter. For pencil-cut, the cutter center position can be determined via judging whether it satisfies the distance requirement. After the searching direction and the tracing direction have been determined, by employing the point-searching algorithm with the idea of dichotomy, all the cutter contact （CC） points and cutter location （CL） points can be found and the clean-up boundaries can also be defined rapidly. Then the tool path is generated. Based on the main concept of pencil-cut, a multilayer fillet-cut method is proposed, which utilizes a ball-end cutter with its radius less than the design radius of clean-up region. Using a sequence of intermediate virtual cutters to divide the clean-up region into several layers and given a cusp-height tolerance for the final layer, then the tool paths for all layers are calculated. Finally, computer implementation is also presented in this paper, and the result shows that the proposed method is feasible.
