CATIA CATIAA级曲面检查规范说明
CATIA A级曲面基本设计
CATIA A级曲面基本设计示意图一、A级曲面基本设计意图:A级曲面通常是围绕造型师的设计意图,为了实现所需要的三维数字模型,来验证造型要求是否成立。
为了弥补手工模型制作缺陷,所以使用当今最先进的计算机辅助设计工具,进行数字化高精度处理,可直接定义所需的设计参数,可直接在计算机进行光顺品质检查。
所谓的A级曲面通常是指有规律性曲面,它可以定义单个曲面,也可以定义整体曲面的完整性,A级曲面严格定义就是完美表达形体,精度要求非常高。
二、A级曲面评价原则A级曲面: 所谓的A级曲面通常是指有规律性曲面,它可以定义单个曲面,也可以定义整体曲面的完整性,A级曲面严格定义就是完美表达形体,精度要求非常高。
对于单一A级曲面,其控制顶点排列必须有规律,最高阶数通常在5~6阶,最高一般不超过8阶。
曲面边界延伸后一般不会出现卷曲自交现象。
总之单一曲面要简单漂亮,曲率一般单凸,斑马纹一般均匀分布,并有规律性变化。
对于整体A级曲面,所有曲面控制顶点一般排列整齐,相关特征流动方向均匀一致,对于汽车高可见区零件及仪表板表面,门内饰板上部等,曲面的质量达到95%以上的大的特征面达到2阶曲率连续或2阶曲率以上连续, 5%的局部少可见区小面或过渡圆角达到1阶连续或1阶曲率以上连续. 特征面在分块线(分缝线)处在高可见区要2阶或以上曲率连续,少可见区或不特别重要的零件分块线(缝隙处)区可小区域1阶曲率连续(如果是造型因素不连续也可以例外)。
特征性不连续属正常造型设计可以不连续,对于大曲面特征最好采用单一特征曲面,个别不能用一个面而必须用两个特征面拼接的高可见区大面,要2阶或2阶以上的连续,以使曲面质量达到较高水平。
三、A级曲面光顺基本要求外表面所有区域及内饰的高可见区表面都属于A级曲面。
A面中95%大面和明显区域特征面间拼接处位置偏差小于0.005mm, 角度偏差小于0.05度,且必须为单片面(v和u 方向均为单patch 面),阶数小于等于6阶,个别不超过8阶。
汽车A级曲面评估标准
汽车A级曲面评估标准1 范围本标准规定了车身外形曲面Class A的一些基本的质量和检验要求。
本标准适用于汽车A级曲面的评估。
2 规范性引用文件下列文件中的条款通过本标准的引用而成为本标准的条款。
凡是注日期的引用文件,其随后所有的修改单(不包括勘误的内容)或修订版均不适用于本标准,然而,鼓励根据本标准达成协议的各方研究是否可使用这些文件的最新版本。
凡是不注日期的引用文件,其最新版本适用于本标准。
3 术语3.1 A Class 曲面:达到G2, G3连续,即2阶或3阶连续。
面与面之间曲率连续。
(见图一)3.2 B Class 曲面:达到G1连续,即1阶连续。
面与面之间相切连续;曲率不连续;点连续;(见图二)3.3 C Class 曲面:达到G0连续,即0阶连续。
面与面之间点连续;曲率不连续,相切不连续。
4 职责本标准规定的车身外形曲面Class A的一些基本的质量和检验要求,由其设计部门负责。
5 内容5.1技术要求:面的质量要求最终是精细的光学质量要求,以达到良好的视觉效果。
用户可以在丰富的灯光条件下获得好的外表效果,这就说明这个数据模型是高质量的。
为了达到这个目的通常使用一些灯光来检查面的连续性和表面的张力。
在CATIA软件中有一些检测的方法如:斑马线,反射线等都可以作为数据检测的方法。
5.2数据质量要求:5.2.1 面的分块:a 面应该具有一定的造型效果。
b 面的分块应该将主模型作为一个整体来考虑,而不是由一些小块组合起来变成整体。
被分块的面以面的边界为边界,整体的思想可保证整个面的和谐统一。
建议采用尽可能少的面片,面片采用贝塞尔(BEZIER)曲面(见图三),曲面使用单段面和低阶面。
不要采用非均匀有理样条(NURBS)曲面(见图四)。
5.2.2 为了指导正确的完成数据,要避免下面的情况:a 在属于模型的元素之间不合理的分块b 出现重面;c 存在一些不属于模型的元素,不能被剪切;d 存在三角面和单独的面(见图五);e 过多的使用了延伸面或是超出边界过多;f 偶然出现面的参数不能调整;g 面的边界线对应面的轮廓线5.2.3 半径和过渡面:1用数字化方法创建过渡面时,尽可能避免在一些过渡面上使用出现呆板的曲率变化或是定曲率的方式,这些呆板的面仅限于在一些不重要的或是不显眼的地方。
A面检查标准经典总结
A级曲面全面介绍a-class包括多方面评测标准,比如说反射是不是好看、顺眼等等。
当然,G2可以说是一个基本要求,因为g2以上才有光顺的反射效果。
但是,即使G3了,也未必是a-class,也就是说有时虽然连续,但是面之间出现褶皱,此时就不是a-class通俗一点说,class-A就必须是G2以上连接。
G3连续的面不一定是CLASS-A曲面。
汽车业界对于a class要求也有不同的标准,GM要求比TOYOTA ,BMW等等要低一些,也就是说gap和angle 要求要松一些。
关于A-class surfaces,涉及曲面的类型的二个基本观点是位置和质量。
位置——所有消费者可见的表面按A-Surface考虑。
汽车的console(副仪表台)属于A-surf,内部结构件则是B-surf。
质量——涉及曲面拓扑关系、位置、切线、曲面边界处的曲率和曲面内部的patch结构。
有一些意见认为“点连续”是C类,切线连续是B类,曲率连续是A类。
而我想更加适当地定义为C0、C1和C2,对应于B样条曲线方程和它的1阶导数(相切=C1)和它2阶导数(曲率=C2)。
因此一个A-surf有可能是曲率不连续的,如果那是设计的意图,甚至有可能切线不连续,如果设计意图是一处折痕或锐边,(而通常注塑或冲压不能有锐边,因此A-suuf一定是切线连续(C1)的)。
第二种思想以汽车公司和白车身制造方面的经验为基础,做出对A-surf更深刻的理解。
他们按独立分类做出了同样的定义。
物理定义:A-surf是那些在各自的边界上保持曲率连续的曲面。
曲率连续意味着在任何曲面上的任一"点"中沿着边界有同样的曲率半径。
曲面是挺难做到这一点的切向连续仅是方向的连续而没有半径连续,比如说倒角。
点连续仅仅保证没有缝隙,完全接触。
事实上,切连续的点连续能满足大部分基础工业(航空和航天、造船业、BIW等)。
基于这些应用,通常并无曲率连续的需要。
A-surf首先用于汽车,并在消费类产品中渐增(牙刷,Palm,手机,洗机机、卫生设备等)。
A级曲面全面介绍
A级曲面全面介绍(转贴)在整个汽车开发的流程中,有一工程段称为Class A Engineering,重点是在确定曲面的质量可以符合A级曲面的要求。
所谓A级曲面的定义,是必须满足相邻曲面间之间隙在0.005mm 以下(有些汽车厂甚至要求到0.001mm),切率改变( tangency Change ) 在0.16度以下,曲率改变(curvature change) 在0.005 度以下,符合这样的标准才能确保钣件的环境反射不会有问题。
a-class包括多方面评测标准,比如说反射是不是好看、顺眼等等。
当然,G2可以说是一个基本要求,因为g2以上才有光顺的反射效果。
但是,即使G3了,也未必是a-class,也就是说有时虽然连续,但是面之间出现褶皱,此时就不是a-class通俗一点说,class-A就必须是G2以上连接。
G3连续的面不一定是CLASS-A曲面。
汽车业界对于a class要求也有不同的标准,GM要求比TOYOTA,BMW等等要低一些,也就是说gap和angle要求要松一些。
关于A-class surfaces,涉及曲面的类型的二个基本观点是位置和质量。
位置——所有消费者可见的表面按A-Surface考虑。
汽车的console(副仪表台)属于A-surf,内部结构件则是B-surf。
质量——涉及曲面拓扑关系、位置、切线、曲面边界处的曲率和曲面内部的patch结构。
有一些意见认为“点连续”是C类,切线连续是B类,曲率连续是A类。
而我想更加适当地定义为C0、C1和C2,对应于B样条曲线方程和它的1阶导数(相切=C1)和它2阶导数(曲率=C2)。
因此一个A-surf有可能是曲率不连续的,如果那是设计的意图,甚至有可能切线不连续,如果设计意图是一处折痕或锐边,(而通常注塑或冲压不能有锐边,因此A-suuf一定是切线连续(C1)的)。
第二种思想以汽车公司和白车身制造方面的经验为基础,做出对A-surf更深刻的理解。
Catia_A级曲面设计
CLASS ‘A’ SURFACING‘A'Class surfacing and its importance:A class surfaces are those aesthetic/free form surfaces,which are visible to us(interior/exterior),having an optimalaesthetic shape and high surface quality.Mathematically class A surface are those surfaces which arecurvature continuous while providing the simplest mathematical representation needed for the desiredshape/form and does not have any undesirable waviness.Curvature continuity:It is the continuity between thesurfaces sharing the same boundary.Curvature continuitymeans that at each point of each surface along the commonboundary has the same radius of curvature.Why Class A is needed:We all understand that today products are not only designed considering the functionality but special consideration aregiven to its form/aesthetics which can bring a desire in onesmind to own that product.Which is only possible with high-class finish and good forms.This is the reason why in designindustries Class A surface are given more importance.UNDERSTANDINGUnderstanding for Class A surfaces:1. The fillets -Generally for Class A, the requirement is curvature continuous and Uniform flow of flow lines from fillet to parent surface value of 0.005 or better (Position 0.001mm and tangency to about 0.016 degrees).2. The flow of the highlight lines -The lines should form a uniform family of lines. Gradually widening or narrowing but in general never pinching in and out.3. The control points should form a very ordered structure -again varying in Angle from one Row to the next in a gradual manner (this will yield the good Highlights required).4. For a Class A model the fillet boundary should be edited and moved to form a Gentle line -and then re-matched into the base surface.5. Matched iso-params in U & V direction are also a good representation of class A.6. The degree (order) of the Bezier fillets should generally be about 6 (also for arc Radius direction) sometimes you may have to go higher.7. Also you have to take care of Draft angle, symmetry, gaps and matching of surfaces Created with parent or reference surfaces.8. Curvature cross-section needles across the part -we make sure the rate of Change of curvature (or the flow of the capping line across the top of the part) is Very gentle and well behaved.The physical meaning:Class A refers to those surfaces, which are CURVATURE continuous to each other at their respective boundaries. Curvature continuity means that at each "point" of each surface along the common boundary has the same radius of curvature.This is different to surfaces having;Tangent continuity -which is directional continuity without radius continuity -like fillets.Point continuity -only touching without directional (tangent) or curvature equivalence.In fact, tangent and point continuity is the entire basis most industries (aerospace, shipbuilding, BIW etc ). For these applications, there is generally no need for curvature.By definition:Class A surface refers to those surfaces which are VISIBLE and abide to the physical meaning, in a product. This classification is primarily used in the automotive and increasingly in consumer goods (toothbrushes, PalmPC's, mobile phones, washing machines, toilet lids etc). It is a requirement where aesthetics has a significant contribution. For this reason the exterior of automobiles are deemed Class-A. BIW is NOT Class-A. The exterior of you sexy toothbrush is Class-A, the interior with ribs and inserts etc is NOT Class-A. QUESTION:What is Body_in_white?What is class A surface?Are the interior trim (A,B,C pillar, dash board, center console, handles) of a car using class A surface? Anybody using the basic design bundle of UG for class A surfacing? UG\Shape Studio?How does it compare with Catia?Ans:1A class A surface is anything that you the customer sees. i.e. exterior panels and interior surfaces.A ClassB surface is something that is not always visible i.e. the underside of a fascia that you would have to bend down to see.A Class C surface is the back side of a part of a surface that is permanently covered by another part.BIW is stuff like the body side etc..Ans:2Actually 'body in white' is the term used to describe the whole vehicle body after it has been welded/bolted together before it is painted or any parts are attached on the fit up line.Ans:3We also use it to mean after it has been painted -I always assumed that the white bit refers to primer. Next step is to fit the windscreen and backlight, when it becomes the glazed body in white, or BIW+G.ANS: 4BIW -Some surfaces are Class A, i.e. body side, roof, sill appliqué.I heard some time ago from a old designer that the term BIW comes from when cars were built from wood, they were painted white as it gives the frame a uniform color so imperfections were easily visible.Ans:5BIW meaning Body In White is so called due to its appearance after the application of the primer to the entirely Body panel assembled vehicle just before going into the painting process.Usually the primer is white or silver grey which gives the so called name.ANS: 6Catia is mostly used for BIW design (Ford switching to catia, and Toyota). Is this because itcould easily create quintic surfaces? With UG with Design bundle only, most of the surfaces created are cubic.-------------------------------------------------------------------ANS: 7A class surface means -it is not just seen surface and unseen surface In normal no technical words,A class surface meansIt is smooth looking reflective surface with no distortion of light highlights, which moves in a smooth uniform designer intended formations.when you create -car body panel, due to their complex shapes it not possible to create the surface with one single face /patch so you make multiple face/patch ( surface is a group of face/patch added together.)when these things are added, at the boundary of joining you need to have connectivity and continuation of minimum order two.for exampleIn case one, at the connecting boundary of two patches you have common boundary but it is sharp corner. this does not qualify as A class surface.In case two -at the connecting boundary of two patches have common boundary and no sharp corner -but you have tangent continuity, this also does not qualify as A class surface.In case two -at the connecting boundary of two patches have common boundary and no sharp corner -you have tangent continuity and curvature continuity this does qualify as A class surface. ( sine curve is good example for curvature continuity. but you can not call it a A class surface )reason is very simple the real requirement of aesthetic and good looking and designer intended shape is not there.ANS:8For obtaining Class-A surfaces,CATIA is more commonly used due to its inherent ability to model very high quality surfaces in general.But,any engineering software(CATIA,UG,IDEAS,Pro-E,etc)cannot develop a Class-A surface.This being due to engineering calculations involved in any surface generated by such softwares.For pure Class-A surfaces you would need styling softwares like Alias,Studio,etc.The use of any software would depend on the level of expectations placed on you.If your projects need only the modeling of the trim,generic engg softwares will do,but if you intend to go down right from styling,you would need Studio,etc.-------------------------------------------------------------------ANS:9IHO,Catia V4has added a tool called Blend surf that is able to obtain virtual curvature continuity.Previously, even styling was comfortable with models-and hence tools-defining fillets with conics,and many OEMs still accept this for Class-A surfaces.Catia V5has GUI interfaces to impose curvature continuity the same way that Alias-Wave front Studio Tools(Auto Studio)does.They are both based on piece-wise polynomial equations,for what its worth.While a conic fillet is not technically curvature continuous,there are many vehicles,including luxury models,that have utilized them for Class-A surfaces and downstream-parts.Considering the tolerances in creating molds and dies and then producing parts from them....a sheet metal panel is not a math model.-------------------------------------------------------------------ANS:10It is true that it is tough to make good curvature continuous surface in UG,but not impossible.Remember one thing A-class doesn't mean just curvature continuity.and smooth reflections on CAD surface.it is lot more than that.Imagine.what happens to your A class surface in case pressed sheet metal body panel. and molded plastic components.They have to retain there intended smoothness and other characteristics to remain A class.to achieve this lot of other things has to be taken care while designing A class surfaces.For example:1-Line features on body side external panel and feature on hood panel which is very common,are to be designed to avoid skidding while they are pressed.like wise2-Flange width and other things are to be taken care while designing fenders wheel arch area for avoiding bulging effect and skidding effect.3-Fuel lid opening area,plunged flange for bulge effect.4-Panel stretching needs to be taken care.Lot many other things go in designing A class sheet metal panels for door,roof etc.5-In case of plastic,sink marks and other things.ANS:11In Europe a'A'class surface is generally taken to be the visible side of any component/assembly-a'B' class surface generally relates to the opposite(or inside)face of an'A'surface-i.e.the surface which defines the thickness of the part,and is where the mounting and reinforcing detail tends to be located.'B' class surfaces can also be referred to as'engineering surfaces.I have not personally heard of any surface being referred to as a'C'type.Catia,while it is ok for surfacing tends to be more used for generating engineering surface detail and solid models-software packages like ICEMSURF tend to be more used for generating visual quality surfaces.-------------------------------------------------------------------ANS:12True A-class surfacing-especially on vehicle exteriors goes further than G2or"curvature"continuity.G3is often sought on the more major block surfaces.G3deals with curvature"acceleration",i.e.the rate of change of curvature across a boundary.G2means as has been described before that the curvature value is the same across a boundary.G3means that the surface curvature leading to the boundary is changing shape at the same rate.Its like driving a car round a bend,you start off straight then gently add steering lock to the point where you need no more,then you gently wind off the steering until you're straight again.If you look at the curve your car made,this would be G3.A-Class and B-class would refer to surface quality required for the component which is different to A-side and B-side which refers to which is the visible/non visible part of a component.ICEM surf is considered the best tool for speedy A-class surfacing due to the sophistication of its real-time diagnostics.The consequence:The consequence of these surfaces apart from visually and physically aesthetic shapes is the way they reflect the real world. What would one expect to see across the boundary of pairs of point continuity, tangent continuity and curvature continuity surfaces when reflecting a straight and dry tree stump in the desert????Point Continuity (also known as G0 continuity) -will produce a reflection on one surface, then at the boundary disappear and re-appear at a location slightly different on the other surface. The same reflective phenomenon will show when there is a gap between the surfaces (the line markers on a road reflecting across the gap between the doors of a car).Tangent Continuity (also known as G1 continuity) -will produce a reflection on one surface, then at the boundary have a kink and continue. Unlike Point continuity the reflection (repeat REFLECTION) is continuous but has a tangent discontinuity in it. In analogy, it is "like" a greater than symbol.Curvature Continuity (also known as G2 continuity, Alias can do G3!) -this will produce the unbroken and smooth reflection across the boundary.To achieve the same Class 'A' surfaces that automotive manufacturers demand, consumer product manufacturers have availed themselves of the same advanced surface modeling tools. What is a Class 'A' surface? The simple answer is that it is a perfectly smooth surface with no anomalies, in which all adjoining surfaces have curvature continuity. This means that where two surfaces meet, the graduation of one into the other is achieved without discernible abrupt transitions. The techniques used to create Class 'A' surfaces typically reside in top level surface modeling software developed for the motor industry, rather than mid-range mechanical CAD packages that have evolved from 3D solid modeling for mechanical assemblies.Analyzing A Class SurfaceHighlight plot :Highlight is the behavior of the form orShape of a surface when a light ornature reflects on it. This reflection oflight or nature gives you anunderstanding about the quality ofsurface. This reflection required shouldbe natural, streamline and withuniformityDesigner Fillets:If you take two adjoining2D lines,or a couple of tangential surfaces,the intersection between them can be turned into an arc(2D)or a fillet(3D),each of which is inserted with a constant radius.However the transition from each line or surface can often be too abrupt for the design.According to Mike Lang,Technical Director of VX,fillets should look simple-you shouldn't see a fillet line in a model.They should also be simple to create."Achieving tangent and curvature continuity in complex shapes on other systems is hard work.A reduction in the weight of a curve will allow it to retain its tangency,but sharpen the change in curvature. This can be seen most effectively by reducing the weight almost to zero.Fairings-the shape of the curve-can be influenced by energy,variation,jerk,bend or tension-each of which will produce a subtle difference in the mathematical fit through the curve.Echo Attributes:Part of the process of obtaining Class'A'surfaces is being able to see what's happening to the curve or the surface as it is being developed.Increasing the scale of the iso lines allows designers to pick up smaller imperfections in surfaces.Where blue iso lines lose their curve they change to white.The shifting colors of Gaussian shading are also particularly adept at detecting subtle blemishes.Echo Attributes also has numerous other modifiable elements,including the ability to apply colors to lines and surfaces,and to alter the transparency of the surface.Curvature plots on non-designer fillets show regular arcs,unlike designer fillets that show the weighting of the curve at each point."good design work relies on good wire frame technology.If you don't have basic curve geometry,you won't be able to produce a good surface”.Designers must always go through the routine of checking curves,especially if the design has come in from an outside source-perhaps containing older style Bezier curves with lots of points.The following describes the mathematics for the so called Bezier curve.It is attributed and named after a French engineer ,Pierre Bezier ,who used them for the body design of the Renault car in the 1970's.They have since obtained dominance in the typesetting industry.Consider N+1control points pk (k=0to N)in 3space.The Bezier parametric curve function is of the form.B (u)is a continuous function in 3space defining the curve with N discrete control points P k .u=0at the first control point (k=0)and u=1at the last control point (k=N).Notes:•The curve in general does not pass through any of the control points except the first and last. From the formula B (0) = P 0and B (1) = P N .•The curve is always contained within the convex hull of the control points, it never oscillates wildly away from the control points.•If there is only one control point P 0, i.e.: N=0 then B (u) = P 0for all u.•If there are only two control points P 0and P 1, i.e.: N=1 then the formula reduces to a line segment between the two control points.•the term shown below is called a blending function since it blends the control points to form the Bezier curve.Bezier Curves•The blending function is always a polynomial one degree less than the number of control points. Thus 3 control points results in a parabola, 4 control points a cubic curve etc.•Closed curves can be generated by making the last control point the same as the first control point. First order continuity can be achieved by ensuring the tangent between the first two points and the last two points are the same.•Adding multiple control points at a single position in space will add more weight to that point "pulling" the Bezier curve towards it.•As the number of control points increases it is necessary to have higher order polynomials and possibly higher factorials. It is common therefore to piece together small sections of Bezier curves to form a longer curve. This also helps control local conditions, normally changing the position of one control point will affect the whole curve. Of course since the curve starts and ends at the first and last control point it is easy to physically match the sections. It is also possible to match the first derivative since the tangent at the ends is along the line between the two points at the end.Second order continuity is generally not possible.•Except for the redundant cases of 2 control points (straight line), it is generally not possible to derive a Bezier curve that is parallel to another Bezier curve.A circle cannot be exactly represented with a Bezier curve.It isn't possible to create a Bezier curve that is parallel to another,except in the trivial cases of coincident parallel curves or straight line Bezier curves.Bezier curves have wide applications because they are easy to compute and very stable. There are similar formulations which are alsocalled Bezier curves which behave differently, in particular it ispossible to create a similar curve except that it passes through the control points. See also Spline curves.Examples: The pink lines show the control point polygon, the grey lines the Bezier curve.1.The degree of the curve is one less than the number of controlpoints, so it is a quadratic for 3 control points. It will always besymmetric for a symmetric control point arrangement.2.The curve always passes through the end points and is tangent tothe line between the last two and first two control points. Thispermits ready piecing of multiple Bezier curves together with first order continuity.3.The curve always lies within the convex hull of the control points.Thus the curve is always "well behaved" and does not oscillatingerratically.4.Closed curves are generated by specifying the first point the sameas the last point. If the tangents at the first and last points match then the curve will be closed with first order continuity.. Inaddition, the curve may be pulled towards a control point byspecifying it multiple times. 1 2 3 4The Bezier surface is formed as the Cartesian product of the blending functions of two orthogonal Bezier curves.Where P i,j is the i,jth control point. There are N i+1and N j+1control points in the i and j directions respectively. The corresponding properties of the Bezier curve apply to the Bezier surface. -The surface does not in general pass through the control points except for the corners of the control point grid. -The surface is contained within the convex hull of the control points. Along the edges of the grid patch the Bezier surface matches that of a Bezier curve through the control points along that edge.Closed surfaces can be formed by setting the last control point equal to the first. If the tangents also match between the first two and last two control points then the closed surface will have first order continuity. While a cylinder/cone can be formed from a Beziersurface, it is not possible to form a sphere.BEZIER SURFACEA little history of Surface Modeling A little historySurface modeling was developed in the automotive and aerospace industries in the late1970s to design and manufacture complex shapes.Nurbs--nonuniform rational B-splines--and cubic-surface formats appeared early and remain the primary spline and surface formatsused throughout the CAD industry.Nurbs and cubics are supported byIGES(Initial Graphics Exchange Specification),a neutral file format for exchanging data between CAD systems.Nurbs and cubic formats are represented in a computer by polynomial equations generated by a CAD system,and onscreen through thelocation and shape of curves and surfaces.For example,the equationof a line,a first-degree polynomial,has this formY=ax+bThe equation for a parabola,a second-degree polynomial,has the formY=ax2+bx+cAnd the equation of a cubic spline,a third-degree polynomial,looks likeY=ax3+bx2+cx+dThe more terms in the polynomial equation,the more"shape"thecurve or surface has.The data structure of a Nurbs curve or surface is comprised of points, weights,and parameter values that define a control net which istangent to the curve or surface.The control net on a Nurbs surface is a rectangular grid of connected straight-line elements which define thetangency of the surface at positions along the control net.The points inthe database which describe the control net are not actually on the surface,they are at the vertices of the control net.Weights in theNurbs data structure determine the amount of surface deflectiontoward or away from its control point.Cubic data structures use third-degree polynomials that describe pointsactually on the curve or surface.Therefore,the Nurbs control net is an abstraction of the underlying surface,whereas the cubic equation is the surface.Nurbs and cubic formats each have advantages and disadvantages.Nurbs equations model more complex shapes by increasing the degree of the exponents in the polynomial,thus increasing the memory required to store and evaluate the equation.Cubic equations,on the other hand,require less storage and can capture complex shapes by adding more cubic segments to the spline or surface.Nurbs and cubic equations are said to be"piecewise"and"parametric,"which means the curve or surface is a sequence of connected segments that use parametric u and v values ranging from0to1or0to n(number of segments)to calculate points along the curve or surface.Nurbs and cubic formats each have advantages and disadvantages.Nurbs equations model more complex shapes by increasing the degree of the exponents in the polynomial,thus increasing the memory required to store and evaluate the equation.Cubic equations,on the other hand,require less storage and can capture complex shapes by adding more cubic segments to the spline or surface.Nurbs and cubic equations are said to be"piecewise"and"parametric,"which means the curve or surface is a sequence of connected segments that use parametric u and v values ranging from0to1or0to n(number of segments)to calculate points along the curve or surface.Ultimately,a good CAD system shields users from having to know too much about the mathematics that represent the underlying surfaces.In addition,surface modelers should:Provide enough tools to completely define any feature on the part using surfaces.Have many functions for defining the different shapes of surfaces including ruled,revolved,lofted,extruded, swept,offset,filleted,blended,planar boundary,and drafted.Each of these functions have further variations. For example,offset surfaces should allow for constant or tapered offsets.Draft-surface functions should let users input curves to define the draft surface,or allow using curves on a surface whereby the draft angle is referenced off a surface-normal vector at points along the curve.The lofted surface should allow for the input of cross-section curves or for the input of curves both along and across the surface.Support functions such as surface trimming,extending,intersecting,projecting,polygon tessellation,IGES translation,coordinate-system transformations,and editing.Allow extracting surface data such as flow curves,vectors,and planes,among other functions.Have a set of tools for defining points,planes,vectors,and splines used with surface modeling.Most surface creation functions need user inputs to define surfaces.Two useful surface-modeling functions are the controlled sweep and the draft surface.A controlled sweep forces a profile curve to remain perpendicular to the sweep path by using a control surface.Without a control surface in the construction of a swept surface,the profile curve typically wants to lay down or spin around the sweep path.A properly defined control surface solves the problem.A draft surface is similar to a controlled sweep in that it uses curves lying on one surface to create another.The resultant draft surface passes through the input curve and is composed of straight-line elements radiating from the reference surface at an angle to the surface normal vectors taken at points along the input curve.A draft-surface function can build one surface perpendicular to another,along a curve.A Comparison Between Solid-Surface Modeling:While surface modelers excel at defining complex shapes,solid modeling is good at quickly building primitive geometry.Primitive geometry consists of basic surfaces such as planes,cylinders,cones, spheres,and tori.Surface modeling is not as fast at creating simple part geometry,but if your solid modeler can't easily model a feature,such as a fillet,surface modeling can almost always finish the part. And for every solid-modeling function there is a counterpart in surface modeling.Nurbs surfaces can be incorporated into an existing solid model by"stitching"the Nurbs surface to the solid model.Some parts can be completely defined by a solid modeler as a collection of primitive surfaces,while other parts require Nurbs surfaces to fully define the geometry.Most parts manufactured with tooling require some kind of Nurbs surface to support production.Reverse engineering is heavily dependent on Nurbs surfaces to capture digitized points into surfaces.In addition,Nurbs-surface files generated over the last20years are circulating in IGES format between vendors and subcontractors.These files support the design of parts in one system and manufacturing in another.Solid modeling will not replace Nurbs-surface modeling because the two work hand in hand to complete part geometry.TYPES OF CONTINUTYContinuity is a measure of how well two curves or surfaces "flow" into each other.•POSITION (G0)This type of continuity between curves implies that the endpoints of the curves have the same X,Y, and Z position in the world space. This is the minimum requirement for obtaining G0.•TANGENT (G1)This type of continuity between curves implies that the tangent CVs must be on one line.•CURVATURE (G2)This continuity type impacts the third CV of the curve. All three CVs have to be considered in order to maintain a smooth curvature comb.If a curvature comb does not have a smooth transitional line. In order to improve the curvature comb, manually modify the position of the three CVs that constitute the G2continuity.。
何谓A级曲面的评定标准
何謂A級曲面的評定標準汽車外形設計對曲面的評定標準分為A、B、C3級。
A級要求最高,反射評定不可以出現變異,對於車身來說,一般指車身外表可見件及內飾可見件,如頂蓋,發動機罩外板,葉子板、保險桿及內飾儀錶板等部件。
B級是指地板等大型不可見件。
C級主要是結構撐件,如支架等。
關於A-class surfaces,涉及曲面的類型的二個基本觀點是位置和質量。
.位置—所有消費者可見的表面按A-Surface考慮。
汽車的console(副儀錶台)屬於A-surf,內部結構件則是B-surf。
.質量—涉及曲面拓撲關係、位置、切線、曲面邊界處的曲率和曲面內部的patch 結構。
有一些意見認為“點連續”是C類,切線連續是B類,曲率連續是A類。
而我想更加適當地定義為C0、C1和C2,對應於B樣條曲線方程和它的1階導數(相切=C1)和它2階導數(曲率=C2)。
因此一個A-surf有可能是曲率不連續的,如果那是設計的意圖,甚至有可能切線不連續,如果設計意圖是一處折痕或銳邊,(而通常射出或沖壓不能有銳邊,因此A-surf一定是切線連續(C1)的)。
第二種思維以汽車公司和白車身製造方面的經驗為基礎,做出對A-surf更深刻的理解。
他們按獨立分類做出了同樣的定義。
1.物理定義:A-surf是那些在各自的邊界上保持曲率連續的曲面。
曲率連續意味著在任何曲面上的任一"點"中沿著邊界有同樣的曲率半徑。
曲面是挺難做到這一點的,切線連續僅是方向的連續而沒有半徑連續,比如說倒角。
點連續僅僅保證沒有縫隙,完全接觸。
事實上,切線連續的點連續能滿足大部分基礎工業(航空和航太、造船業、BIW等)。
基於這些應用,通常並無曲率連續的需要。
2.根據定義:A-surf是那些在產品中可見的有特定物理意義的曲面。
A-surf首先用於汽車,並在消費類產品中漸增(牙刷,PDA,手機,洗衣機......等)。
同時它也是美學的需要,在真實世界裡,曲率連續是無處不在的,是主旋律.點連續(也稱為G0連續)在每個表面上生產一次反射,反射線成間斷分佈。
catia的汽车a级曲面质量评价方法
当它在CATIA的汽车设计中到A级表面时,我们把质量评价带到一个全新的水平!图片:表面连续性就像一个老练的探戈双人舞的完全平滑的舞步,在眼前没有尴尬的缺口或错步。
公平就是要确保这些表面的对称性和眼球捕捉性和完美的霜冻蛋糕一样,曲线那么统一,甚至可以做一个数学家。
准确性呢?这就像确保我们的虚拟表面模型像GPS制导导弹击中它的目标一样伙计们,我们说的是精确度系好安全带,因为这是一个疯狂的穿越世界的汽车设计你不会想错过的!
CATIA为评估表面质量提供了一些非常强大的工具。
有一个工具让设计者通过观察整个事物的曲率值来检查一个表面的光滑性和连续性。
还有另一种工具可以模拟光线如何从表面反射出来来发现任何缺陷。
还有一种工具用参考几何图案将设计好的表面涂抹,并确保其准确度达到所需的水平。
这些工具帮助设计者系统地提高CATIA中A级表面的质量。
除了使用自动化分析工具外,汽车设计中A级表面的质量评价过程需要由老练的设计者进行人工检查和验证。
通过从各种角度进行仔细审查,设计人员认真审查表面,以发现任何可能仅通过自动化分析而逃避发现的不完善或不合规定之处。
他们的专门知识使他们能够对表面的公正性和视觉吸引力进行主观评估。
通过利用先进的分析工具和人力专长的趋同,CATIA保证遵守汽车设计中的最高质量标准,从而产生不仅视觉震撼而且具有空气动力效率的车辆。
CATIA_a级曲面光顺原则介绍
A级曲面光顺原则1.所有特征都必须具有可扩展性和可编辑性。
2.所有特征都必须分解成单凸或单凹特征。
3.所有特征面的光顺保证2阶导数以上连续。
4.所有特征线(面)函数必须小于6阶。
5.所有特征间的连接要2阶导数以上连续(曲率连续)6.所有特征间的连接偏差小于0.0001。
7.一块大面上多特征拼接的,建模默认误差小于0.0001,角度误差小于0.01度。
8.单一特征面的建模默认误差小于0.00001,角度误差小于0.001度9.造型决定的不同特征形状可不要求曲率连续或相切连续。
10.在不能保证大特征面如上质量情况下,宁可牺牲边界线或缝线或特征连接,特征的连续保证相切连续(角度误差小于0.1度)。
11.不明显的局部特征过渡区(如A柱下端与翼子板过渡区),允许曲率不连续,但要保证相切连续。
12.外观特征筋线倒角R2~R5 仪表板边界相交倒角R5~R10 13.顶盖、发动机盖、行李箱盖,与侧围做大面相交,然后以交线为中心,依据点云特征,进行曲率或相切连续。
14.大于R10的倒角,要考虑搭桥,保证曲率连续。
15.为获得A级曲面、允许与点云误差±5mm。
16.零件边界线必须光顺。
17.一块大面如果在两头曲率变化太大(相差2倍以上)必须分开特征,然后与主曲面拼接,拼接精度偏差小于0.0001,角度偏差小于0.01度)。
18.不可以用多个特征断面,用扫面(sweep)的方法,但可用单特征面(曲率变化不超过2倍)多个断面扫面。
19.不可用多个边界约束的小面拼接零件。
A级面介绍:我们对A级曲面是这样理解的1.轮廓曲面--通常都是A级曲面,这样的曲面通常都要求曲率连续,沿着曲面和相邻的曲面有几乎相同的曲率半径(相差0.05或更小,位置偏差0.001mm或角度相差0.016度。
)2、A级曲面用高光等高线检测时显亮的曲线--这些曲线应该有一个共同的曲率特征,等高线连续且过度均匀、逐渐的发散或收缩,而不是一下子汇集消失到一点3、A级曲面上的控制点也应该按一定的规律分布,一行控制点与另一行相邻的控制点的角度变化应该有一定的规律可循,这是画高质量的曲线所必需的4、A级曲面模型的曲面的边界线又该可以被编辑、移动以生成另外一个曲线,同时这个新生成的曲线可以重新加入曲面来控制区面。
汽车设计-A级曲面(A-Class Surface)模型设计质量规范模板
XX公司企业规范编号xxxx-xxxx汽车设计-A级曲面(A-Class Surface)模型设计质量规范模板A级曲面模型设计质量规范1 范围本规范规定了使用计算机软件(Alias或CATIA V5)构建A-Class Surface曲面数字模型所遵循的质量技术要求。
2 术语和定义下列术语和定义适用于本规范。
曲面Surface数学点的集合,它是在平面(R2)的一个连通子集上定义的连续函数图像。
A级曲面A-Class Surface造型外表面数字模型的一种,满足特定的技术质量要求,用于表示最终冻结的造型外表面。
曲面连续性Surface Continuity在使用多个小块曲面构建大的曲面时,在两个和两个以上曲面进行拼接边界处存在的几何位置关系。
一般用到的有位置连续(G0)、相切连续(G1)、曲率连续(G2)、曲率变化率连续(G3)。
曲线阶数曲线数学表达多项式的最高次幂就是曲线的阶数(Degree),等于该曲线控制点数(Order)减一。
曲线控制点(CV)与控制边(Hull)曲线的直观表达一般用控制点来表示的,两个相邻控制点的连线就是控制边(Hull)。
如图1所示。
曲线Span用来描述曲线特定位置分段数字信息,可以简单的理解为曲线的段。
曲线可以是单段(1 Span)多次的,也可以是多段(N Spans)多次的。
如图1所示,图1中的曲线就是多段(N Spans)多次。
图1 曲线基本信息图曲面块Patch在使用曲线构建曲面过程中,形成曲面的U、V方向上曲线的Span数的乘积就是曲面的Patch数,也相应把曲面分成若干个曲面块(Patch)。
如图2所示。
图2 曲面基本信息图3 A-Class Surface曲面数字模型质量要求3.1公差要求3.1.1曲线间隙:=0mm。
3.1.2曲面间隙:≤0.003mm;3.1.3曲面相切角度偏差:≤0.1Grad(圆角处:≤0.5Grad)。
3.1.4没有边长小于1mm的微小曲面。
A级曲面1
汽车A级曲面-A级曲面设计软件比较-ICEM Surf/Alias/UG/Imageware/CA TIA 在整个汽车开发的流程中,有一工程阶段称为Class-A Engineering:重点是在确定曲面的品质可以符合A级曲面的要求。
所谓A级曲面的定义:是必须满足相邻曲面间间隙(Gap)在0.005mm 以下(有些汽车厂甚至要求到0.001mm),切率改变( Tangency Change ) 在0.16度以下,曲率改变(Curvature change) 在0.005 度以下,符合这样的标准才能确保钣金件的环境反射不会有问题。
Class-A包括多方面评测标准,比如说反射是不是好看、顺眼等等。
当然,G2可以说是一个基本要求,因为G2以上才有光顺的反射效果。
但是,即使G3了,也未必是Class-A,也就是说有时虽然连续,但是面之间出现褶皱,此时就不是Class-A,通俗一点说:Class-A 必须是G2以上连接,但G3连续的面不一定是Class-A曲面。
汽车业也有这种简单的分类法:A面指的是车身外表面及白车身;B面指的是不重要表面,比如内饰表面等;C面指的是不可见表面。
但是现在随着现代美学的发展及舒适性要求的日益提高,对汽车内饰件也提到了Class-A的要求。
不同汽车厂商对于Class-A的要求也不尽相同,GM要求比TOYOTA、BMW等要求低一些,也就是说Gap和Angle 要求要松一些。
目前国内的A级曲面的生成软件中,比较流行的有Alias、ICEM Surf、UG、Imageware/Surfacer、CA TIA V5 等。
同时每个软件有配套的数据展示软件,即虚拟现实展示软件(渲染)。
1)Alias:大多数设计公司和整车企业采用Autodesk Alias软件作为A级曲面生成工具。
它主要的优点是生成曲面的速度快,在软件中可以根据造型的意图进行快速修改,进行曲面的检测和验收,还能提供很漂亮的造型展示。
CATIA中A级曲面应用全面介绍精华篇
A级曲面没有十分严格的数学描述也没有十分严格的概念定义。
在汽车行业,所谓A级曲面的定义,是必须满足相邻曲面间的间隙在 0.005mm 以下(有些汽车厂甚至要求到 0.001mm),切率改变 ( Tangency Change ) 在0.16度以下,曲率改变 (Curvature Change) 在0.005 度以下,符合这样的标准才能确保钣件的环境反射不会有问题。
CLASS-A包括多方面评测标准,比如说反射是不是好看、顺眼等等。
当然,G2可以说是一个基本要求,因为G2以上才有光顺的反射效果。
但是,即使G3了,也未必是A级曲面,也就是说有时虽然连续,但是面之间出现褶皱,此时就不是A级曲面了。
通俗一点说,CLASS-A就必须是G2以上连接。
汽车业界对于A级曲面要求也有不同的标准,GM要求比TOYOTA ,BMW等要低一些,也就是说Gap和Angle要求要松一些。
关于A级曲面,涉及曲面类型的二个基本观点是位置和质量。
位置,所有消费者可见的表面按A-Surf考虑,汽车的Console(副仪表台)属于A-Surf,内部结构件则是B-surf;质量,涉及曲面拓扑关系、位置、切线、曲面边界处的曲率和曲面内部的Patch结构。
在老的汽车业有这样一种分类法:A面,车身外表面,白车身;B面,不重要表面,比如内饰表面;C面,不可见表面。
这其实就是A级曲面的基础。
但是现在随着美学和舒适性的要求曰益提高,对汽车内饰件也提到了A-CLASS的要求。
因而分类随之简化,A面,可见(甚至是可触摸)表面;B面,不可见表面。
关于曲面质量的连续理论,有一些意见认为“点连续”是C类,切线连续是B类,曲率连续是A类。
而我想更加适当地定义为C0、C1和C2,对应于B样条曲线方程和它的1阶导数(相切=C1)和它2阶导数(曲率=C2)。
因此一个A-surf有可能是曲率不连续的,如果那是设计的意图,甚至有可能切线不连续,例如设计意图是一处折痕或锐边。
A面质量检查
A 级曲面验收方法.检查A 面的质量,具体方法是在catia 的Free Style/ insert /shape analysis 模块中实现。
1. 曲面形状分析1.1 斑马纹检查(等照度线分析)映射类型(Mapping Type):“圆柱模式 (Cylindrical mode)”:显示圆柱映射分析。
“球面模式(Spherical mode)”:显示球面映射分析。
我们一般情况下选择圆柱模式,斑马纹效果才能更明显。
全局 (Gl obal ):允许分析整个零件。
要分析整个零件时建议使用此选项。
取消选中此选项可进行逐元素分析,如果是单个面您用可以不选此项。
指南针 (Compass):将指南针翻转到模型中,使您可以在 3D 几何图形中移动指南针以定义光源方向。
条纹参数 (Zebra parameters):条纹数目 (Number of stripes):设置条纹的数目。
条纹宽度 (Width of stripes):设置条纹的宽度。
颜色转换 (Color transition):设置条纹颜色转换。
您把条纹相关参数调到合适的值。
如果斑马纹很光顺,而且圆滑过渡,表示该A 面质量可以通过验收。
如图1。
1.2 曲面间的连续检查a ) 好b ) 不好 图1 斑马纹检查如果曲面间的距离(distance)偏差大于0.001或相切连续偏差大于0.01度或曲率连续大于0.005都达不到要求.如果想知道偏差具体的分布可以点Full 图标后在显视(Display)中选择如图所示即可.1.3截面曲率分析如果曲面的U 、V向与基准坐标系大致相同,可以选择默认的方向;如果曲面的U 、V向与基准坐标系相差较大可选择后选择一条合适的线。
如果截面曲率,而且圆滑过渡,表示该A 级曲面质量可以通过验收(如果是主面还要求其方向相同)。
如图2。
1.4 在曲面上映射环境选择一张合适的环境图片映射到外表面上,检查映射的质量。
如果数模的质量好,应能看见类似镜子的作用。
CATIA汽车摩托车企业设计人员内部培训CATI级曲面检查规范说明OK
重庆南方摩托车技术研发有限公司CATIAA级曲面检查规范北京迅利创成科技有限公司日期:2011年12月7日目录1.规范描述 (1)2.A级曲面介绍 (2)2.1定义 (2)2.2特征 (2)3.A级曲面标准 (3)3.1设置建模精度 (3)3.2曲面间的间隙/重叠 (3)3.3曲面间的连续性 (3)3.4光顺性要求 (4)3.5脱模 (4)3.6配合间隙 (4)3.7输出格式 (4)4规范内容 (5)4.1高光连续性检查 (5)4.2 连续性检查 (7)4.3曲率梳连续性检查 (7)4.4两零件搭接关系检查 (8)4.5 A级曲面的间距离检查 (8)4.6 曲面“阶”数检 (9)1.规范描述A级曲面检查是为了规范使用CATIA对外委数模和本公司设计的高质量模型表面的检查,检查的目的是检验模型的质量是否符合A级曲面的标准、要求。
本规范对A级曲面检查的标准进行了初步的定义,并对采用CATIA V5进行A级曲面检查的具体功能和操作进行了详细的说明。
2.1定义A级曲面是那些在各自的边界上保持曲率连续的曲面,曲率连续意味着在任何曲面上的任一“点”中沿着边界有同样的曲率半径。
A级曲面广泛应用于汽车行业的外观件和内饰件。
同样的,针对摩托车行业,所有的摩托车覆盖件原则上都应当遵循A级曲面的质量要求。
摩托车覆盖件A面造型汽车车身外表面A 面造型2.2特征同一般的零件结构曲面不同,A级曲面通常具有如下的一些特征:一般CLASS A的阶次与控制点数目都不多,一般曲面UV方向大概为6个控制点;单独一个CLASS A曲面在UV方向都保证曲率的连续性及变化趋势的一致;CLASS A曲面之间的连接需要满足曲率连续(G2),在部分特殊曲面可以用切连续来保证(G1),绝对禁止仅仅是点连续(G0);使用多种数学检验方法来检验CLASS A曲面,不应该出现视觉上的明显瑕疵。
3.1设置建模精度覆盖件建模精度的要求标准为0.005mm,即当覆盖件精度值大于0.005mm时,不满足我们的A级曲面建模的标准,只有当覆盖件建模精度值小于或等于0.005mm时,才满足A级曲面的建模要求。
CATIA中A级曲面应用全面介绍精华篇
A级曲面没有十分严格的数学描述也没有十分严格的概念定义。
在汽车行业,所谓A级曲面的定义,是必须满足相邻曲面间的间隙在 0.005mm 以下(有些汽车厂甚至要求到 0.001mm),切率改变 ( Tangency Change ) 在0.16度以下,曲率改变 (Curvature Change) 在0.005 度以下,符合这样的标准才能确保钣件的环境反射不会有问题。
CLASS-A包括多方面评测标准,比如说反射是不是好看、顺眼等等。
当然,G2可以说是一个基本要求,因为G2以上才有光顺的反射效果。
但是,即使G3了,也未必是A级曲面,也就是说有时虽然连续,但是面之间出现褶皱,此时就不是A级曲面了。
通俗一点说,CLASS-A就必须是G2以上连接。
汽车业界对于A级曲面要求也有不同的标准,GM要求比TOYOTA ,BMW等要低一些,也就是说Gap和Angle要求要松一些。
关于A级曲面,涉及曲面类型的二个基本观点是位置和质量。
位置,所有消费者可见的表面按A-Surf考虑,汽车的Console(副仪表台)属于A-Surf,内部结构件则是B-surf;质量,涉及曲面拓扑关系、位置、切线、曲面边界处的曲率和曲面内部的Patch结构。
在老的汽车业有这样一种分类法:A面,车身外表面,白车身;B面,不重要表面,比如内饰表面;C面,不可见表面。
这其实就是A级曲面的基础。
但是现在随着美学和舒适性的要求曰益提高,对汽车内饰件也提到了A-CLASS的要求。
因而分类随之简化,A面,可见(甚至是可触摸)表面;B面,不可见表面。
关于曲面质量的连续理论,有一些意见认为“点连续”是C类,切线连续是B类,曲率连续是A类。
而我想更加适当地定义为C0、C1和C2,对应于B样条曲线方程和它的1阶导数(相切=C1)和它2阶导数(曲率=C2)。
因此一个A-surf有可能是曲率不连续的,如果那是设计的意图,甚至有可能切线不连续,例如设计意图是一处折痕或锐边。
A级曲面验收方法
a) 好
1.2 曲面间的连续检查
图 1 斑马纹检查
b) 不好
如果曲面间的距离(distance)偏差大于 0.001 或相切连续偏差 大于 0.01 度或曲率连续大于 0.005 都达不到要求. 如果想知道偏差具体的分布可以点 Full 图标后在显视 (Display)中选择如图所示即可.
1.3 截面曲率分析
以上的检测方法应该足够了,如果还有一些其它的要求我们还可以用 Free
Style/ insert /shape analysis 中的反射线(Reflection Line)、变形线(Inflection line) 和
ACA 高光(ACA Highline).
析。 “球面模式 (Spherical mode)”:显示球面映射分析。
我们一般情况下选择圆柱模式,斑马纹效果才能更明显。 全局 (Global):允许分析整个零件。要分析整个零件时建议使用此选
项。取消选中此选项可进行逐元素分析,如果是单个面您用可以不选此项。 指南针 (Compass):将指南针翻转到模型中,使您可以在 3D 几何图
A 级曲面上的控制点也应该按一定的规律分布,一行
控制点与另一行相邻的控制点的角度变化应该有一
定的规律可循。 A 级曲面的特征网格线必须均匀合
理的分布,最好在某一投影面上以矩形方式分布。
A 级曲面的特征网格控制点上表示曲面曲率方向
的箭头指向一致。在选项(Options)中选择
来检
查控制曲面曲率的方向.
A 级曲面验收方法.
检查 A 面的质量,具体方法是在 catia 的 Free Style/ insert /shape analysis 模 块中实现。 1. 曲面形状分析 1.1 斑马纹检查(等照度线分析)
CATIA-轿车外形A级曲面设计
家用小型轿车外形A 级曲面设计1轿车外形A 级曲面模型建立1 云点预处理及Mesh 面的建立此次毕业设计,云点的测量是由老师完成的,我只完成模型建立和二维图制作,主要应用CATIA V5软件,在界面内,用命令导入需处理的云点,如图1-1所示:图1-1 由于云点坐标系与车身坐标系不一致,需用命令对其进行调整,如图1-2所示:图1-2 先将云点用(Filter )进行过滤,参数值设为0.11。
然家用小型轿车外形A 级曲面设计2 后对云点用命令,生成Mesh 面,如图1-3所示:图1-32 顶盖、发动机罩及行李箱盖A 级曲面设计由于整车是一个对称体,所以只需做一半的车身曲面,另一半靠对称完成。
我们在做中间曲面时,就必须保证这些曲面关于ZX 平面对称后两块曲面之间无缝、无重叠,无棱角,并且具有较好的光顺性。
因此,在做顶盖、发动机罩及行李箱盖曲面时,就需注意上述要求,下面介绍两种常用的方法:1 由云点生成线,再由线组成一封闭体,在界面,用命令生成面。
这样作出的曲面比较容易保证光顺性,但此曲面与云点的误差较大,所以这就要求画出的线与云点所在的面结合很好。
2 由云点生成线,再由线组成一封闭体,在界面,用命令截取封闭体内的部分云点,再用命令生成面。
这样作出的曲面与云点的误差较小,但曲面的光顺性不易保证。
这就要求用命令生成面时,结合系数不能选的太小。
下面我将用上述两种方法完成顶盖、发动机罩及行李箱盖A 级曲面的制作。
2.1 应用第一种方法完成顶盖A 级曲面设计 首先,在界面,用命令,在ZX 平面上截出一组此平面上的点,如图2-1所示。
在图中看出由ZX 平面截出的是一条线,其实它是由很多的点组成,家用小型轿车外形A 级曲面设计3 并不是线,我们可通过(Cloud Display Options )命令将这些点稀释,就可看清这条“线”其实是点,如图2-2所示。
图2-1图2-2 用(3D Curve )画出一条光顺曲线,如图2-3所示:家用小型轿车外形A 级曲面设计4图2-3 通过(Curvature Analysis )分析曲线的光顺性,如图2-4所示。
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重庆南方摩托车技术研发有限公司CATIA A 级曲面检查规范北京迅利创成科技有限公司日期:2011年12月7日目录1.规范描述............................... 错误!未定义书签。
级曲面介绍............................... 错误!未定义书签。
定义................................. 错误!未定义书签。
特征................................. 错误!未定义书签。
级曲面标准............................... 错误!未定义书签。
设置建模精度......................... 错误!未定义书签。
曲面间的间隙/重叠.................... 错误!未定义书签。
曲面间的连续性....................... 错误!未定义书签。
光顺性要求........................... 错误!未定义书签。
脱模................................. 错误!未定义书签。
配合间隙............................. 错误!未定义书签。
输出格式............................. 错误!未定义书签。
4规范内容 ............................... 错误!未定义书签。
高光连续性检查....................... 错误!未定义书签。
连续性检查.......................... 错误!未定义书签。
曲率梳连续性检查..................... 错误!未定义书签。
两零件搭接关系检查................... 错误!未定义书签。
A级曲面的间距离检查................. 错误!未定义书签。
曲面“阶”数检...................... 错误!未定义书签。
1.规范描述A级曲面检查是为了规范使用CATIA对外委数模和本公司设计的高质量模型表面的检查,检查的目的是检验模型的质量是否符合A级曲面的标准、要求。
本规范对A级曲面检查的标准进行了初步的定义,并对采用CATIA V5进行A级曲面检查的具体功能和操作进行了详细的说明。
级曲面介绍定义A级曲面是那些在各自的边界上保持曲率连续的曲面,曲率连续意味着在任何曲面上的任一“点”中沿着边界有同样的曲率半径。
A级曲面广泛应用于汽车行业的外观件和内饰件。
同样的,针对摩托车行业,所有的摩托车覆盖件原则上都应当遵循A级曲面的质量要求。
摩托车覆盖件A面造型汽车车身外表面A面造型特征同一般的零件结构曲面不同,A级曲面通常具有如下的一些特征:一般CLASS A的阶次与控制点数目都不多,一般曲面UV方向大概为6个控制点;单独一个CLASS A曲面在UV方向都保证曲率的连续性及变化趋势的一致;CLASS A曲面之间的连接需要满足曲率连续(G2),在部分特殊曲面可以用切连续来保证(G1),绝对禁止仅仅是点连续(G0);使用多种数学检验方法来检验CLASS A曲面,不应该出现视觉上的明显瑕疵。
级曲面标准设置建模精度覆盖件建模精度的要求标准为,即当覆盖件精度值大于时,不满足我们的A 级曲面建模的标准,只有当覆盖件建模精度值小于或等于时,才满足A级曲面的建模要求。
曲面间的间隙/重叠覆盖件曲面间的间隙/重叠精度的要求标准为<=,即当曲面间的间隙/重叠精度值大于时,不满足我们的A级曲面设计的标准,只有当曲面间的间隙/重叠的精度值小于或等于时,才满足A级曲面的设计要求。
曲面间隙/重叠检查曲面间的连续性覆盖件的连续性包括质量要求一般和高质量两种:质量要求一般的要满足曲率(G2)连续,这种连续方式的精度标准为<=;高质量的要求满足曲率的变化率(G3)连续,这种连续方式的精度标准为<=。
曲面间连续性(G2)曲面间连续性(G3)光顺性要求(Highlight analysis)此要求要保障曲面高光走向流畅;斑马线:此要求要保证斑马线均匀无突变;曲率疏:要求要保曲面连续无突变。
斑马线检查曲率梳检查脱模按定义的脱模方向与脱模角度考虑,产品应该满足脱模角度要求。
配合间隙根据DTS以及工程要素条件,产品应该满足配合要求。
输出格式根据客户或终端应用对输出数据要求,进行输出数据。
4规范内容高光连续性检查对于曲面高光连续性检查,我们采用以下办法:对曲面打上高光或阴影,通过不断移动光源或移动曲面,观察面上高光或阴影是否有不正常的跳动、波浪、扭曲或者不连贯。
A级曲面在高光下,表面光带是连贯、流畅的,没有不正常的跳动、波浪、扭曲。
A、使用“视图/照明”命令,并调整光源位置和光源强度,来观察数模表面,是否有不连续。
具体操作步骤如下:Step1:在FreeStyle模块中的Shape Analysis工具条下选择“Light Source Manipulation”命令,生成对话框如下图所示:Step2:在以上对话框中选择其中一种光源模式后,再选择要进行光照的曲面,效果如下图所示:Step3:通过转动处箭头来控制点光源的位置,不同位置的点光源光线打到曲面上的明暗程度来观测曲面的优劣。
通过“Light Source Manipulation”来分析曲面质量的不同效果例子如下:B、使用FreeStyle模块中的“环境分析”命令来检查表面的连续性。
具体操作步骤如下:Step1:在FreeStyle模块中的Shape Analysis工具条下选择“环境分析”命令,生成对话框如下图所示:Step2:在以上对话框中选择其中一种图像(或在处加载自定义图片)后,再选择要进行环境分析的曲面,效果如下图所示:Step3:通过调节处的滑块来控制图像映射到曲面的强弱程度,效果如下图:通过“环境分析”来检测曲面质量的不同效果例子如下:C、使用FreeStyle模块中的“光栅分析”命令,看斑马线变化是否均匀且没有出现突变和抖动,无明显拐点等。
具体操作步骤如下:Step1:在FreeStyle模块中的Shape Analysis工具条下选择“光栅分析”命令,生成对话框如下图所示:Step2:在以上对话框中选择其中一种照射模式后,再选择要进行光照的曲面,效果如下图所示:Step3:通过调节处的滑块来分别控制斑马线在曲面的尺寸大小、黑白线条的比例以及斑马线的明暗程度,效果如下图:通过“光栅分析”来检测曲面质量的不同效果的例子如下所示:连续性检查使用“视图”中的“带边着色但不光顺”命令,检查数模的切矢连续性。
连续性不好的模型带有黑边,好的则没有。
使用FreeStyle模块中的Shape Analysis工具条中的“连接检查分析”具体的操作步骤如下:Step1:点击命令,生成对话框如下图所示: Step2:在对话框位置处选择要进行连接性检查分析的通过Ctrl点选的两个曲面,如下图所示:曲率梳连续性检查对于曲面的曲率梳连续性的检查,我们利用动态截面工具,将曲率梳打开,对面的X、Y和Z方向进行移动和扫描,观察曲率梳的变化,发现不合理的变形和多次尖点。
具体操作步骤如下:Step1:在FreeStyle模块中的Shape Analysis工具条下选择“曲率梳分析”命令,生成对话框如下图所示:Step2:曲率梳分析包括曲率、半径两种类型(如图一),两者互为反比例函数,选择其中一种类型(如曲率)后,再选则要进行曲率梳分析的曲面,点击确定后,会在曲面的边缘处产生梳状的分析结果(如图二)。
Step3:将梳状分析结果中曲率方向不一致等不合理处通过“控制点”命令进行重新调整。
两零件搭接关系检查两个零件有搭接关系时,应保证两零件间曲率连续。
A级曲面的间距离检查使用FreeStyle模块中的“距离分析”命令,测量A级曲面与点云间的距离,最大距离应满足误差要求。
具体操作步骤如下:Step1:在FreeStyle模块中的Shape Analysis工具条下选择“距离分析”命令,生成对话框如下图所示:Step2:在对话框位置处选择第一个要进行距离分析的曲面,如下图所示:Step3:在对话框位置处选择第二个要进行距离分析的曲面,如下图所示:Step4:在距离产生间隙位置处会出现如上图的信息时,应对此边界处进行调整,如果没有产生距离间隙,处于合理状态的,点击确定即可。
曲面“阶”数检使用FreeStyle模块中的“控制点”命令,选取曲面。
曲面的“阶”数通常不能大于6,局部复杂的曲面应不大于8。
并且“控制点”的排列应平顺有序。
具体操作步骤如下:Step1:在FreeStyle模块中的Shape Modification工具条下选择“控制点”命令,生成对话框如下图所示:Step2:在处选择要进行调整的曲面,如下图所示:通过对Nu以及Nv进行右键编辑来控制曲面的阶数。
Step3:在处选择要进行调整的支撑面方向,再选中要调整的网格点进行调整。
Step4:通过中的来观察曲面上所有网格点的曲率的方向是否一致;如果网格点处的曲率不完全一致,则反复在曲率方向不一致的网格处进行微调。
如下图:通过“控制点”来调整曲面的曲率方向一致性的不同效果的例子如下所示:。