一种基于选择性激光烧结的分层切片方法 A slicing method based on selective laser sintering

技术领域 Technical Field

[0001] 本发明涉及快速成型研究领域，特别是涉及一种基于选择性激光烧结的分层切片方法。 [0001] The present invention relates to the field of rapid prototyping studies, particularly those involving slicing method based on selective laser sintering.

背景技术 Background

[0002] 快速成型技术又称快速原型制造技术，是一种将零部件的几何形状、结构等信息建立数字化描述模型，然后将这些信息输出到计算机控制的机电集成制造系统，通过逐点、逐线、逐面进行材料的三维堆砌成型，从而达到快速、准确地制造实际零部件的现代化方法。 [0002] The rapid prototyping technology, also known as rapid prototyping technology, is a part of the geometry, structure, description and other information to build digital models, and then outputs the information to the mechanical and electrical integration of computer-controlled manufacturing systems, point by point, by Line-by-side were piled forming a three-dimensional material, so as to achieve rapid and accurate method for the manufacture of modern practical parts. 由于快速成型是按照一层层截面轮廓来进行加工的，因此，在加工前必须用分层切片软件将三维模型沿着成型的高度方向，每隔一定的厚度进行分层切片处理，以便提取截面的轮廓。 Since rapid prototyping is a cross-sectional contour layers according to the process, therefore, it must be processed before slicing software molded three-dimensional model along the height direction, slicing processing performed every certain thickness, in order to extract cross-section profile.

[0003] 根据快速成型原理，以激光成形加工为例，激光扫描线按层片图形对粉末材料进行扫描烧结，形成以该图形为截面的柱形层片，而该柱形层片与两相邻切平面之间的实际三维实体的层片形状是有差别的。 [0003] According to the principle of rapid prototyping, laser forming, for example, laser scan lines plies graphics scan sintering the powder material, to form a cylindrical section of the graph for the layers, and the cylindrical ply and two-phase o realistic three-dimensional planar entities ply shape is a difference. 当分层厚度过大时，一些位于两个切平面之间的三维实体上的点、线、面的特征将失去，成型精度降低。 When the layer thickness is too large, some at point D between entities on both flat cut, line and surface features would be lost, reducing the molding accuracy. 同时对轮廓表面为倾斜面的部分进行分层时，随着分层厚度的增加，台阶误差随之加大，将严重影响工件的表面质量。 Contour surface at the same time as part of the inclined surface of stratified, with increasing layer thickness, steps will increase the error, it will seriously affect the quality of the workpiece surface. 如果分层厚度取的太小，虽然可以提高成型精度，但加工效率将受影响。 If the layer thickness is too small to take, although the molding accuracy can be improved, but the processing efficiency will be affected. 因此分层厚度的选取应在考虑如何较好地保留三维实体上细微特征、满足表面质量要求的前提下，要尽可能采用较大层厚。 Select the layer thickness should therefore consider how better to preserve the three-dimensional solid fine features, to meet the requirements of surface quality under the premise, as far as possible the use of larger thickness. 对于一个成型系统，在对特定的成型材料进行烧结时，层厚的选取有一个最大烧结厚度(由材料的性质和激光功率、扫描速度等决定)和最小烧结厚度(由材料的粒度决定)的限制。 For a molding system, in particular when the molding material is sintered, there is a selection of the maximum thickness sintered thickness (determined by the nature and the laser power, scanning speed of the material, etc.) and the minimum thickness of the sintered (particle size decided by the material) of the limit.

[0004]目前现有的各种快速成型机都带有分层切片软件，其切片厚度通常都为定值。 [0004] The currently available are presented with a variety of rapid prototyping machine slicing software, which is usually slice thickness is constant. 也就是说，不论工件在不同高度的形状复杂程度的差别，都按照相同的层厚进行切片处理。 That is, regardless of the shape of the workpiece in the degree of difference between the different levels of complexity, both in the same slice thickness processing. 这种方法比较简单易实现，但是，当选定的层厚比较大时，容易造成成型件较大的误差，当选定的层厚较小时，成型件的精度高了，但是成型的时间就长了，成型效率变低。 This method is relatively simple and easy to achieve, however, when the selected layer thickness is relatively large, molded parts likely to cause large errors when the selected layer thickness is small, high precision molded parts, but the forming time long, forming efficiency becomes lower.

发明内容 DISCLOSURE

[0005] 发明目的:本发明旨在提供一种运算量少、计算时间短、计算效率高的自适应性的有效分层切片方法，该方法根据成型件的表面特征，可以自动调节切片的厚度，能够显著提高制件表面质量和几何精确度。 [0005] The object of the invention: The present invention aims to provide an arithmetic less computing time is short, computationally efficient and effective adaptive slicing method according to the surface characteristics of the molded article, it can automatically adjust the thickness of slices can significantly improve workpiece surface quality and geometric accuracy.

[0006] 技术方案:一种基于选择性激光烧结的分层切片方法，其特征在于，包括以下步骤: [0006] Technical Solution: slicing method based on selective laser sintering, characterized in that it comprises the following steps:

[0007] (I)读取待加工零件的STL文件； [0007] (I) read parts of STL files to be processed;

[0008] (2)确定分层方向、分层厚度的最大最小值、台阶误差的最大值以及表面粗糙度的最大值； [0008] (2) to determine the direction of layering, layer thickness of maximum and minimum, maximum level error and surface roughness of the maximum;

[0009] (3)将STL模型里的三角面片在分层方向上进行第一层切片；[0010] (4)根据层平面轮廓多边形的各条边以及与其相关的各三角面片，计算出下一层满足精度要求的最小分层厚度； [0009] (3) The STL model in the triangular patches in the direction of the first layer layered slice; [0010] (4) The respective sides of the layer plane contour polygons and its relevance to the triangular patches, computing lower level to meet the minimum layer thickness accuracy requirements;

[0011] (5)根据每层层厚对该层切片的交点集合组进行排序处理得到该切平面的轮廓线。 [0011] (5) of the sorting process to obtain the contour of the cut plane of the layer thickness of each layer slice of the intersection set group.

[0012] 所述步骤(4)中，计算下一层满足精度要求的最小分层厚度的具体步骤为: [0012] The step (4), the calculation of the next layer of concrete steps to meet the accuracy requirements of the minimum layer thickness is:

[0013] 设STL模型的三角面片在分层方向上的最大和最小坐标值分别为Zmax和Zmin,允许的台阶误差最大值为Smax，表面粗糙度极值为Rb，每层的最大烧结厚度和最小烧结厚度分别为h_和Iw [0013] The set of triangular facets STL model maximum and minimum coordinate values ​​in the direction of stratification were Zmax and Zmin, the maximum allowable level of error Smax, the surface roughness of the extreme value of Rb, the maximum sintering thickness of each layer and the minimum thickness was h_ sintering and Iw

[0014] 假设在层高为Z的层面，一个三角面片F与切平面S相交，其交线的两个端点坐标为P1U1, Y1, Z1)和P2 (x2, y2, Z1),其交线的中点PQ(xQ，y0, z0)的坐标可以通过下列算式求得: [0014] Assuming storey level Z, and a triangular facet F and S tangent plane intersects the intersecting line coordinates of the two endpoints of P1U1, Y1, Z1) and P2 (x2, y2, Z1), which pay the midpoint of the line PQ (xQ, y0, z0) coordinates can be determined by the following formula:

[0015] X0 = (x1+x2)/2 ； [0015] X0 = (x1 + x2) / 2;

[0016] J0 = /2 ； [0016] J0 = / 2;

[0017] Z0 = Z1 = Z2 = z ； [0017] Z0 = Z1 = Z2 = z;

[0018] 以除P1P2之外任意一点P。 [0018] In addition to the P1P2 any point P. 作一投影面M，该平面与P1P2垂直，经过P。 As a projection surface M, the plane perpendicular P1P2 through P. 点，由此可得该平面的点法式方程: Points, which can get the point of the French plane equation:

[0019] (X2-X1) (X-X0) + (y2~yi) (y-y0) = O ； [0019] (X2-X1) (X-X0) + (y2 ~ yi) (y-y0) = O;

[0020] 由可允许的最大台阶误差δ max可得该三角面片F允许的最大分层厚度: [0020] by the allowable maximum level error δ max available the triangular facet F maximum allowable layer thickness:

_] htmaxl = δ max/cos θ ； _] Htmaxl = δ max / cos θ;

[0022] 其中θ为三角面片F与切片面S的夹角； [0022] where θ is triangular facet F and S slice plane angle;

[0023] 由可允许的表面粗糙度的最大值Rb可得三角面片F允许的最大分层厚度: [0023] by the allowable maximum surface roughness Rb available triangular facet F maximum allowable layer thickness:

[0024] htmax2 = (Rb+2.04067-0.22 α +0.001368 α 2) /0.06722 ； [0024] htmax2 = (Rb + 2.04067-0.22 α +0.001368 α 2) /0.06722;

[0025] 其中α为三角面片F与切平面法S向量的夹角； [0025] where α is the angle between the triangular facet F and S vector tangent plane method;

[0026] 计算M平面与三角面片F的上交点P3 (x3, y3, z3)，交点距切平面S的距离为: [0026] calculate M plane and triangular facet F is handed point P3 (x3, y3, z3), cross-cut from the pitch plane S is:

[0027] htmax3 = Z3-Z ； [0027] htmax3 = Z3-Z;

[0028]取 ht = min {htmaxl, htmax2, htmax3}， [0028] to take ht = min {htmaxl, htmax2, htmax3},

[0029] 若ht > hmin，则利用三维实体的点、面、边拓扑关系找到与三角面片F相邻的三角面片，并继续计算相邻三角面片的分层厚度，并与hmin和hmax相比较，若所有ht都在hmin和hmax之间，则取htmin为下一层切片的厚度； [0029] If ht> hmin, the use of point of three-dimensional solid, surface, edge topology found with triangular facets F adjacent triangular patches, and continue to calculate the adjacent triangular facets of layer thickness, and with hmin and hmax compared to if all ht are between hmin and hmax, then take the next layer htmin slice thickness;

[0030] 若ht≤hmin，则停止计算，取hmin为下一层切片的厚度； [0030] If ht≤hmin, then stop counting, taking hmin for the next layer thickness of the slice;

[0031] 若遍历该层所有相交三角面片，得到的ht均大于等于hmax，则取hmax为下一层切片的厚度。 [0031] If the layer traverse all intersecting triangular facets, resulting ht were more than equal to hmax, hmax is taken for the thickness of the lower layer slice.

[0032] 所述步骤(5)中根据每层层厚对该层切片的交点集合组进行排序处理得到该切平面的轮廓线的具体步骤为:由步骤(4)得到下一层层厚，找到一个与下一层切平面相交的三角面片FcJA, B, C}，求得相交的两个交点，根据拓扑关系找到与三角面片Ftl相邻的三角面片F1，并求得下一个交点，依次遍历该层所有相交三角面片直至到达第一个三角面片F。 [0032] The step (5) slice thickness of the layer based on the intersection of each set of group sorting process outline concrete steps to give the cut plane is: the step (4) to give the next layer thick, find a cut and the next layer plane intersecting triangular patches FcJA, B, C}, obtained by the intersection of the intersection of the two, according to the topology found with triangular facets Ftl adjacent triangular facets F1, and determined next intersection, turn to traverse all the layer until you reach the intersection of triangular facets first triangular facets F. 结束，得到该层切片的轮廓线。 The end to give the layer slice contour.

[0033] 有益效果:本发明在确定下一层的分层厚度时，不需要多次的试切过程，只需要利用当前层片多边形截面轮廓上各边的顶点坐标，以及与各边相关的三角面片对应关系和三维实体的点、面、边的拓扑信息，就可以直接计算出下一层满足分层精度要求(台阶误差和表面粗糙度)的分层厚度，简化了计算，提高了计算效率。 [0033] beneficial effects: the invention is determined by layer thickness of the next layer, the trial cutting process does not require many times, only need to use the current layer slice polygon vertex coordinates of each side of the cross-sectional profile, and associated with each edge triangular patches corresponding point relation and three-dimensional solid, surface, edge topology information, you can directly calculate the next level to meet the accuracy requirements stratification (step error and surface roughness) of the layer thickness, it simplifies the calculation and improve computational efficiency. 通过自适应调整切片的厚度来控制成型的速度和精度，从而可以有效的提高生产效率和生产质量，尤其是针对结构比较复杂的成型件，在保证成型速度的前提下，工件的精度得到了很大的提高。 By adjusting the thickness of the slice adaptive to control the speed and precision molding, which can effectively improve production efficiency and production quality, especially for complex structure of molded parts, under the premise of forming speed to ensure the accuracy of the workpiece has been very greatly improved.

附图说明 Brief Description

[0034] 图1是本发明的流程示意图； [0034] FIG. 1 is a schematic flow diagram of the present invention;

[0035] 图2是本发明的零件三角面片模型结构图； [0035] FIG. 2 is a part triangular patch model configuration diagram of the present invention;

[0036] 图3是本发明的通过自适应分层切片之后的层厚示意图； [0036] FIG. 3 is an adaptive slicing through the thickness of the schematic diagram of the present invention after;

[0037] 图4是本发明的层厚的二维示意图。 [0037] FIG. 4 is a schematic diagram of a two-dimensional layer thickness of the present invention.

具体实施方式 DETAILED DESCRIPTION

[0038] 如图1、2、3、4所示，一种基于选择性激光烧结的分层切片方法，包括以下步骤: [0038] As shown in Figure 1, 2, a slicing method is based on selective laser sintering, comprising the steps of:

[0039] (I)读取由CAD待加工零件图生成的STL文件； [0039] (I) to be read by the CAD processing part drawings generated STL files;

[0040] (2)确定分层方向、分层厚度的最大最小值、台阶误差的最大值以及表面粗糙度的最大值； [0040] (2) to determine the direction of layering, layer thickness of maximum and minimum, maximum level error and surface roughness of the maximum;

[0041] (3)将STL模型里的三角面片在分层方向上进行第一层切片； [0041] (3) The STL model in the triangular patches in the direction of the first layer layered slice;

[0042] (4)根据层平面轮廓多边形的各条边以及与其相关的各三角面片，计算出下一层满足精度要求的最小分层厚度，具体步骤为: [0042] (4) The respective sides of the layer plane contour polygons and its associated triangular patches each calculated layer thickness of the next layer to meet the minimum accuracy requirements, the specific steps:

[0043] 设STL模型的三角面片在分层方向上的最大和最小坐标值分别为Zmax和Zmin,允许的台阶误差最大值为Smax，表面粗糙度极值为Rb，每层的最大烧结厚度和最小烧结厚度分别为h_和Iw [0043] set of triangular facets STL model maximum and minimum coordinate values ​​in the direction of stratification were Zmax and Zmin, the maximum allowable level of error Smax, the surface roughness of the extreme value of Rb, the maximum sintering thickness of each layer and the minimum thickness was h_ sintering and Iw

[0044] 假设在层高为Z的层面，一个三角面片F与切平面S相交，其交线的两个端点坐标为P1U1, Y1, Z1)和P2 (x2, y2, Z1),其交线的中点PQ(xQ，y0, z0)的坐标可以通过下列算式求得: [0044] Assuming storey level Z, and a triangular facet F and S tangent plane intersects the intersecting line coordinates of the two endpoints of P1U1, Y1, Z1) and P2 (x2, y2, Z1), which pay the midpoint of the line PQ (xQ, y0, z0) coordinates can be determined by the following formula:

[0045] X0 = (x1+x2)/2 ； [0045] X0 = (x1 + x2) / 2;

[0046] J0 = /2 ； [0046] J0 = / 2;

[0047] Z0 = Z1 = Z2 = z ； [0047] Z0 = Z1 = Z2 = z;

[0048] 以除P1P2之外任意一点P。 [0048] In addition to the P1P2 any point P. 作一投影面M，该平面与P1P2垂直，经过P。 As a projection surface M, the plane perpendicular P1P2 through P. 点，由此可得该平面的点法式方程: Points, which can get the point of the French plane equation:

[0049] (X2-X1) (x-x0) + (y2~yi) (y-y0) = O ； [0049] (X2-X1) (x-x0) + (y2 ~ yi) (y-y0) = O;

[0050] 由可允许的最大台阶误差δ max可得该三角面片F允许的最大分层厚度: [0050] by the allowable maximum level error δ max available the triangular facet F maximum allowable layer thickness:

[0051] htmaxl = 5 max/cOS θ ; [0051] htmaxl = 5 max / cOS θ;

[0052] 其中Θ为三角面片F与切片面S的夹角； [0052] where Θ is triangular facet F and S slice plane angle;

[0053] 由可允许的表面粗糙度的最大值Rb可得三角面片F允许的最大分层厚度: [0053] by the allowable maximum surface roughness Rb available triangular facet F maximum allowable layer thickness:

[0054] htmax2 = (Rb+2.04067-0.22 α +0.001368 α 2) /0.06722 ； [0054] htmax2 = (Rb + 2.04067-0.22 α +0.001368 α 2) /0.06722;

[0055] 其中α为三角面片F与切平面法S向量的夹角； [0055] where α is the angle between the triangular facet F and S vector tangent plane method;

[0056] 计算M平面与三角面片F的上交点P3 (x3，y3, Z3)，交点距切平面S的距离为: [0056] calculate M plane and triangular facet F is handed point P3 (x3, y3, Z3), cross-cut from the pitch plane S is:

[0057] Iitmax3 = Z3-Z ； [0057] Iitmax3 = Z3-Z;

[0058]取 ht = min {htmaxl, htmax2, htmax3}， [0058] to take ht = min {htmaxl, htmax2, htmax3},

[0059] 若ht > hmin，则利用三维实体的点、面、边拓扑关系找到与三角面片F相邻的三角面片，并继续计算相邻三角面片的分层厚度，并与hmin和hmax相比较，若所有ht都在hmin和hmax之间，则取htmin为下一层切片的厚度； [0059] If ht> hmin, the use of point of three-dimensional solid, surface, edge topology found with triangular facets F adjacent triangular patches, and continue to calculate the adjacent triangular facets of layer thickness, and with hmin and hmax compared to if all ht are between hmin and hmax, then take the next layer htmin slice thickness;

[0060] 若ht≤hmin，则停止计算，取hmin为下一层切片的厚度； [0060] If ht≤hmin, then stop counting, taking hmin for the next layer thickness of the slice;

[0061] 若遍历该层所有相交三角面片，得到的ht均大于等于hmax，则取hmax为下一层切片的厚度。 [0061] If the layer traverse all intersecting triangular facets, resulting ht were more than equal to hmax, hmax is taken for the thickness of the lower layer slice.

[0062] (5)根据每层层厚对该层切片的交点集合组进行排序处理得到该切平面的轮廓线，具体步骤为:由步骤(4)得到下一层层厚，找到一个与下一层切平面相交的三角面片F0{A, B, C}，求得相交的两个交点，根据拓扑关系找到与三角面片Ftl相邻的三角面片F1,并求得下一个交点，依次遍历该层所有相交三角面片直至到达第一个三角面片Ftl结束，得到该层切片的轮廓线。 [0062] (5) The thickness of the layer of each slice group set intersection sorting process to obtain the contour of the cut plane, the specific steps: from step (4) to give the next layer thick, find a lower one tangent plane intersecting triangular facets F0 {A, B, C}, obtained by the intersection of two intersecting, find and triangular facets Ftl adjacent triangular facets F1 according to the topological relations, and seek the next intersection, all intersecting successively traverse the layer triangular facets until reaching the first triangular facets Ftl end to give the layer slice contour.

[0063] 本发明根据成型件的表面特征，可以自动调节切片的厚度，具有运算量少、计算时间短、计算效率高的优点，并且能够显著提高制件表面质量和几何精确度。 [0063] The present invention is based on the surface characteristics of the molded article, it can automatically adjust the thickness of slices, with the operation amount, the calculation time is short, the advantages of high efficiency calculations, and can significantly improve workpiece surface quality and geometric accuracy. 在确定下一层的分层厚度时，不需要多次的试切过程，只需要利用当前层片多边形截面轮廓上各边的顶点坐标，以及与各边相关的三角面片对应关系和三维实体的点、面、边的拓扑信息，就可以直接计算出下一层满足分层精度要求(台阶误差和表面粗糙度)的分层厚度，简化了计算，提高了计算效率。 In determining the layer thickness of the next layer, the trial cutting process does not require many times, only need to use the current layer slice polygon vertex coordinates of each side of the profile, as well as triangular patches and related correspondence between each side and three-dimensional solid The point, face, edge topology information, we can directly calculate the next level to meet the accuracy requirements stratification (step error and surface roughness) of the layer thickness, simplify computing, computational efficiency. 通过自适应调整切片的厚度来控制成型的速度和精度，从而可以有效的提高生产效率和生产质量，尤其是针对结构比较复杂的成型件，在保证成型速度的前提下，工件的精度得到了很大的提高。 By adjusting the thickness of the slice adaptive to control the speed and precision molding, which can effectively improve production efficiency and production quality, especially for complex structure of molded parts, under the premise of forming speed to ensure the accuracy of the workpiece has been very greatly improved.