SLA优选方向的光栅扫描方式研究与实现
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摘要
SLA技术使用激光束进行截面区域加工,扫描系统需要作大量的扫描,所以扫描路径的选择就显得尤为重要。高效精确的扫描路径在减小翘曲变形,提高成形件精度和强度以及设备的制造效率,延长激光-振镜的使用寿命等方面有着重要的作用。
本文详细分析了当前SLA系统中常用激光扫描路径的特点。针对快速成形系统中光栅式扫描在切片轮廓边界处逆转换向产生延时,振镜偏转额外消耗时间,提出了一种优选方向的光栅扫描方式,寻求扫描线与轮廓相交次数最少的方向进行扫描。这种扫描方式在保持原有成形精度基础上,能大幅度提高激光扫描效率,缩短成形时间,延长激光器使用寿命。
但对任意多边形轮廓,要获得扫描线与轮廓相交次数最少的扫描方向,如果直接运用直线与多边形求交,计算量非常大。凸多边形与一条直线相交只有两个交点,那么一系列均匀间隔的平行直线与凸多边形求交,算法简单易实现。为此本文设计了将任意多边形等效变形为凸多边形的两种算法,不改变直线与多边形相交次数。
文中对这种扫描方式的实现策略和方法进行了深入地分析和研究,运用二维图形变换实现了任意方向扫描路径数据的生成问题,将优选方向的光栅扫描方式集成到华中科技大学研发的HRPL系列快速成形系统中。
通过强度、精度测试实验及效率对比实验,可以得出结论:本文开发的扫描方式在抗弯曲、抗拉伸强度与普通的平行X、Y方向的光栅扫描方式几乎一样,由于同属于光栅扫描,其精度效果属于同级别。而在成形效率上,对于截面长宽不等的情况有所提高,截面长宽尺寸或分组区域内长宽尺寸相差大的情况下效果相当明显。
Laser is used to sinter the stereo lithography (SLA) parts. The scanning system needs to do plenty of scan, so scan method is very important to SLA process. Efficient scan method can minimize the parts’shrinkage, increase the precision and strength of the SLA parts, improve the fabrication productivity of the SLA machine, and increase of the laser-galvanometer’s service life.
The character of the scan method currently used in SLA process is investigated in this dissertation. The number of switch-backs at the contour in the path is a major contributor to scanning time. We develop algorithms to pick the direction in which a zigzag path on a polygon will have the minimum number of switch-backs. These algorithms are adopted to generate a new scan method that selects the optimal direction for zigzag path based on section information. This new method can assure the strength of the parts, increase scanning efficiency, shorten fabrication time, increase of the laser service life.
For general polygon, it’s too complicate to find the optimal direction. But for convex polygon, the problem is reduced. Therefore, two algorithms were proposed to convert an arbitrary polygon into a convex polygon with the same switch-backs.
The path generation strategy was studied and the two-dimensional graphics trans-formation theory was used to produce final path data. The optimal direction scanning method was integrated to HRPL series system, which is developed by the Rapid Manufacturing Center of Huazhong University of Science and Technology.
The results of the experiment indicate that the fabrication efficiency of SLA parts fabricated with the optimal direction scan method is improved and they have the same strength and precision effect as with other raster scan methods. The method show great effect dealing with polygons with slim characters.
本文详细分析了当前SLA系统中常用激光扫描路径的特点。针对快速成形系统中光栅式扫描在切片轮廓边界处逆转换向产生延时,振镜偏转额外消耗时间,提出了一种优选方向的光栅扫描方式,寻求扫描线与轮廓相交次数最少的方向进行扫描。这种扫描方式在保持原有成形精度基础上,能大幅度提高激光扫描效率,缩短成形时间,延长激光器使用寿命。
但对任意多边形轮廓,要获得扫描线与轮廓相交次数最少的扫描方向,如果直接运用直线与多边形求交,计算量非常大。凸多边形与一条直线相交只有两个交点,那么一系列均匀间隔的平行直线与凸多边形求交,算法简单易实现。为此本文设计了将任意多边形等效变形为凸多边形的两种算法,不改变直线与多边形相交次数。
文中对这种扫描方式的实现策略和方法进行了深入地分析和研究,运用二维图形变换实现了任意方向扫描路径数据的生成问题,将优选方向的光栅扫描方式集成到华中科技大学研发的HRPL系列快速成形系统中。
通过强度、精度测试实验及效率对比实验,可以得出结论:本文开发的扫描方式在抗弯曲、抗拉伸强度与普通的平行X、Y方向的光栅扫描方式几乎一样,由于同属于光栅扫描,其精度效果属于同级别。而在成形效率上,对于截面长宽不等的情况有所提高,截面长宽尺寸或分组区域内长宽尺寸相差大的情况下效果相当明显。
Laser is used to sinter the stereo lithography (SLA) parts. The scanning system needs to do plenty of scan, so scan method is very important to SLA process. Efficient scan method can minimize the parts’shrinkage, increase the precision and strength of the SLA parts, improve the fabrication productivity of the SLA machine, and increase of the laser-galvanometer’s service life.
The character of the scan method currently used in SLA process is investigated in this dissertation. The number of switch-backs at the contour in the path is a major contributor to scanning time. We develop algorithms to pick the direction in which a zigzag path on a polygon will have the minimum number of switch-backs. These algorithms are adopted to generate a new scan method that selects the optimal direction for zigzag path based on section information. This new method can assure the strength of the parts, increase scanning efficiency, shorten fabrication time, increase of the laser service life.
For general polygon, it’s too complicate to find the optimal direction. But for convex polygon, the problem is reduced. Therefore, two algorithms were proposed to convert an arbitrary polygon into a convex polygon with the same switch-backs.
The path generation strategy was studied and the two-dimensional graphics trans-formation theory was used to produce final path data. The optimal direction scanning method was integrated to HRPL series system, which is developed by the Rapid Manufacturing Center of Huazhong University of Science and Technology.
The results of the experiment indicate that the fabrication efficiency of SLA parts fabricated with the optimal direction scan method is improved and they have the same strength and precision effect as with other raster scan methods. The method show great effect dealing with polygons with slim characters.
引文
[1]黄树槐,肖跃加,莫健华等.快速成型技术的展望.中国机械工程, 2000, 11(1-2): 195 ~ 200
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[3]朱林泉,白培康,朱水淼.快速成型与快速制造技术.国防工业出版社, 2003. 105 ~ 109.
[4]金天拾.粉末激光烧结技术在波音公司的成功应用.航空制造技术, 2005, (10): 60~63
[5]金杰,张安阳.快速成型技术及其应用.浙江工业大学学报, 2005, 33(5): 592 ~ 595
[6]颜永年,齐海波.快速制造的内涵与应用.航空制造技术. 2004, (5): 26 ~ 29
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[8]王军杰,郭九生,洪军等.激光快速成形加工中扫描方式与成形精度的研究与实验.中国机械工程, 1998, 8(5): 54 ~ 55
[9] Xiangwei Wang. Calibration of shrinkage and beam offset in SLS process. Rapid Prototyping Journal, 1999, 5(3): 129 ~137
[10] Bai Junsheng. Influences of scanning paths on SLS part qualities. Progress in Rapid Prototyping Manufacturing and Rapid Tooling, ICRPM’98, Beijing, China, July: 116 ~120
[11] QU, X., B. STUCKER, Gibson. A three-dimensional surface offset method for STL-format models. in: International Conference on Manufacturing Automation(ICMA). 2002, 127 ~135
[12] Xiuzhi Qu, Brent Stucker. A 3D surface offset method for STL-format models. Rapid Prototyping Journal, 2003, 9(3): 133 ~ 141
[13] V. D. Holla, K. G. D. Shaatry, B. G. Prakash. Offset of curves on tessellated surfaces. Computer Aided Design, 2003, 35: 1099 ~ 1108
[14]史玉升,钟庆,陈学彬等.选择性激光烧结新型扫描方式的研究及实现.机械工程学报, 2002, 38(2): 35
[15]陈剑虹,马鹏举,田杰谟等.基于Voronoi图的快速成形扫描路径生成算法研究.机械科学与技术, 2003, 22(5): 728
[16] Renji Zhang, Guanghua Sui, Liang Guan, et al. Study on Scanning Process of Selective Laser Sintering. Progress in Rapid Prototyping Manufacturing and Rapid Tooling. ICRPM’98, Beijing, China, July: 72 ~ 78
[17]陈鸿,张志钢,程军. SLS快速成型工艺激光扫描路径策略研究.应用基础与工程科学学报, 2001, 9(2-3): 202 ~ 207
[18]陈学兵. HRPS-I激光烧结系统的研究与实现: [硕士学位论文].华中科技大学, 2000
[19]张人佶,单忠德,隋光华等.粉末材料的SLS工艺激光扫描过程研究.应用激光, 1999, 19(5): 299 ~ 302
[20]赵毅,李占利,卢秉恒.激光快速成形中激光扫描路径的快速生成算法.计算机辅助设计与图形学报, 1998, 10(3): 260 ~ 265
[21]李忠锋,王从军,黄树槐.基于拓扑信息的扫描路径生成算法.华中科技大学学报(自然科学版), 2003, 31(6): 7 ~ 8, 19
[22]谢存禧,李仲阳,邵明.基于机器人快速成形的截面填充与轨迹规划.机械设计与研究, 2000, 3: 30 ~ 32
[23] Srinivasan V. and Nackman R. Voronoi diagrams for multiply-connected polygon domains, IBM Journal of Research and Development, 1987, 31(3): 361 ~ 372
[24]蔡道生.选择性激光烧结工艺软件关键技术研究. [博士学位论文].华中科技大学. 2004
[25]江开勇,刘斌,李洪友.快速成形技术的研究现状及发展趋势.华侨大学学报(自然科学版), 2006, 27(1): 1 ~ 6
[26]胥光申,张锡强,金雄等.光固化快速成形精度影响因子的优化, 2006, 17(6): 559 ~562.
[27]胥光申,邓攀,赵万华等.高分辨率激光快速成形系统的开发与研究.机械工程学报, 2005, 41(2): 127 ~131
[28]胥光申,赵万华,卢秉恒.用高分辨率快速成形系统制作细微结构.机械工程学报, 2005, 41(9): 23 ~ 26
[29] Huang, Y. M., H. Y. Lan. CAD/CAE/CAM integration for increasing the accuracy of mask rapid prototyping system. Computers in Industry. 2005, 56(5): 442 ~ 456
[30] Sun W, Jiang J, Lin F. A processing algorithm for freeform fabrication of heterogeneous structures. Rapid Prototyping Journal. 2004, 10(5): 316 ~ 326
[31] GSI LUMONICS Corporation. PC-MARK MT Programmer’s Manual, 1997
[32] GSI LUMONICS HPLK User Manual, 2003
[33] Installation and Operation The RTC3 PC Interface Board for Real Time Control of Scan Heads and Lasers, 2005
[34]汪苏,徐海然,薛忠明. SLS快速成形技术中激光加工参数对制件性能的影响.中国机械工程, 2003, 14(17): 1460 ~1462
[35] Williams, J. D. and Deckard, C. R. Advances in modeling the effects of selected parameters on the SLS process. Rapid Prototyping Journal, 1998, 4(2): 90 ~100
[36] Tata K, Flynn D. A procedure to estimate builds time for stereo lithography machines. Prototype Express, 1996, (7): 22 ~ 31
[37] Joel E, Mcclurkin D, Rosen W. Build time estimation for stereo lithography[EB/OL].http://Mrpmi.marc.gatech.edu/Bte.html
[38] Chen C, Sullivan P. Predicting total build time and the resultant cure depth of the 3D stereo lithography process. Rapid Prototyping Journal, 1996, 2(4): 27 ~ 40
[39]吴懋亮,方明伦,胡庆夕.光固化快速成形制造时间的影响因素分析.机械设计与研究, 2004, 20(1): 43 ~ 44, 57
[40]周培德.计算几何—算法分析与设计.北京:清华大学出版社,南宁:广西科学技术出版社. 2000, 38 ~ 39
[41]李小林,朱力群,黄因慧.快速成形中的振镜扫描系统.电加工, 1998, 1(3): 36 ~ 37
[42]赵毅,卢秉恒.振镜扫描系统的枕形畸变校正算法.中国激光, 2003, 30(3): 216 ~ 218
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[2]颜永年,林峰,张人佶等.快速制造技术的最新进展及其发展趋势.电加工与模具, 2006,中国国际模展特辑(增刊): 12 ~ 21
[3]朱林泉,白培康,朱水淼.快速成型与快速制造技术.国防工业出版社, 2003. 105 ~ 109.
[4]金天拾.粉末激光烧结技术在波音公司的成功应用.航空制造技术, 2005, (10): 60~63
[5]金杰,张安阳.快速成型技术及其应用.浙江工业大学学报, 2005, 33(5): 592 ~ 595
[6]颜永年,齐海波.快速制造的内涵与应用.航空制造技术. 2004, (5): 26 ~ 29
[7]王运赣.快速成形系统.武汉:华中理工大学出版社, 1999
[8]王军杰,郭九生,洪军等.激光快速成形加工中扫描方式与成形精度的研究与实验.中国机械工程, 1998, 8(5): 54 ~ 55
[9] Xiangwei Wang. Calibration of shrinkage and beam offset in SLS process. Rapid Prototyping Journal, 1999, 5(3): 129 ~137
[10] Bai Junsheng. Influences of scanning paths on SLS part qualities. Progress in Rapid Prototyping Manufacturing and Rapid Tooling, ICRPM’98, Beijing, China, July: 116 ~120
[11] QU, X., B. STUCKER, Gibson. A three-dimensional surface offset method for STL-format models. in: International Conference on Manufacturing Automation(ICMA). 2002, 127 ~135
[12] Xiuzhi Qu, Brent Stucker. A 3D surface offset method for STL-format models. Rapid Prototyping Journal, 2003, 9(3): 133 ~ 141
[13] V. D. Holla, K. G. D. Shaatry, B. G. Prakash. Offset of curves on tessellated surfaces. Computer Aided Design, 2003, 35: 1099 ~ 1108
[14]史玉升,钟庆,陈学彬等.选择性激光烧结新型扫描方式的研究及实现.机械工程学报, 2002, 38(2): 35
[15]陈剑虹,马鹏举,田杰谟等.基于Voronoi图的快速成形扫描路径生成算法研究.机械科学与技术, 2003, 22(5): 728
[16] Renji Zhang, Guanghua Sui, Liang Guan, et al. Study on Scanning Process of Selective Laser Sintering. Progress in Rapid Prototyping Manufacturing and Rapid Tooling. ICRPM’98, Beijing, China, July: 72 ~ 78
[17]陈鸿,张志钢,程军. SLS快速成型工艺激光扫描路径策略研究.应用基础与工程科学学报, 2001, 9(2-3): 202 ~ 207
[18]陈学兵. HRPS-I激光烧结系统的研究与实现: [硕士学位论文].华中科技大学, 2000
[19]张人佶,单忠德,隋光华等.粉末材料的SLS工艺激光扫描过程研究.应用激光, 1999, 19(5): 299 ~ 302
[20]赵毅,李占利,卢秉恒.激光快速成形中激光扫描路径的快速生成算法.计算机辅助设计与图形学报, 1998, 10(3): 260 ~ 265
[21]李忠锋,王从军,黄树槐.基于拓扑信息的扫描路径生成算法.华中科技大学学报(自然科学版), 2003, 31(6): 7 ~ 8, 19
[22]谢存禧,李仲阳,邵明.基于机器人快速成形的截面填充与轨迹规划.机械设计与研究, 2000, 3: 30 ~ 32
[23] Srinivasan V. and Nackman R. Voronoi diagrams for multiply-connected polygon domains, IBM Journal of Research and Development, 1987, 31(3): 361 ~ 372
[24]蔡道生.选择性激光烧结工艺软件关键技术研究. [博士学位论文].华中科技大学. 2004
[25]江开勇,刘斌,李洪友.快速成形技术的研究现状及发展趋势.华侨大学学报(自然科学版), 2006, 27(1): 1 ~ 6
[26]胥光申,张锡强,金雄等.光固化快速成形精度影响因子的优化, 2006, 17(6): 559 ~562.
[27]胥光申,邓攀,赵万华等.高分辨率激光快速成形系统的开发与研究.机械工程学报, 2005, 41(2): 127 ~131
[28]胥光申,赵万华,卢秉恒.用高分辨率快速成形系统制作细微结构.机械工程学报, 2005, 41(9): 23 ~ 26
[29] Huang, Y. M., H. Y. Lan. CAD/CAE/CAM integration for increasing the accuracy of mask rapid prototyping system. Computers in Industry. 2005, 56(5): 442 ~ 456
[30] Sun W, Jiang J, Lin F. A processing algorithm for freeform fabrication of heterogeneous structures. Rapid Prototyping Journal. 2004, 10(5): 316 ~ 326
[31] GSI LUMONICS Corporation. PC-MARK MT Programmer’s Manual, 1997
[32] GSI LUMONICS HPLK User Manual, 2003
[33] Installation and Operation The RTC3 PC Interface Board for Real Time Control of Scan Heads and Lasers, 2005
[34]汪苏,徐海然,薛忠明. SLS快速成形技术中激光加工参数对制件性能的影响.中国机械工程, 2003, 14(17): 1460 ~1462
[35] Williams, J. D. and Deckard, C. R. Advances in modeling the effects of selected parameters on the SLS process. Rapid Prototyping Journal, 1998, 4(2): 90 ~100
[36] Tata K, Flynn D. A procedure to estimate builds time for stereo lithography machines. Prototype Express, 1996, (7): 22 ~ 31
[37] Joel E, Mcclurkin D, Rosen W. Build time estimation for stereo lithography[EB/OL].http://Mrpmi.marc.gatech.edu/Bte.html
[38] Chen C, Sullivan P. Predicting total build time and the resultant cure depth of the 3D stereo lithography process. Rapid Prototyping Journal, 1996, 2(4): 27 ~ 40
[39]吴懋亮,方明伦,胡庆夕.光固化快速成形制造时间的影响因素分析.机械设计与研究, 2004, 20(1): 43 ~ 44, 57
[40]周培德.计算几何—算法分析与设计.北京:清华大学出版社,南宁:广西科学技术出版社. 2000, 38 ~ 39
[41]李小林,朱力群,黄因慧.快速成形中的振镜扫描系统.电加工, 1998, 1(3): 36 ~ 37
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