CATIA汽车摩托车企业设计人员内部培训资料CATIAA级曲面检查规范说明OK

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。

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 (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 (9)4.3曲率梳连续性检查 (10)4.4两零件搭接关系检查 (12)4.5 A级曲面的间距离检查 (12)4.6 曲面“阶”数检 (13)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.A级曲面介绍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.A级曲面标准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。

1.机构运动的目的及意义机构运动仿真分析报告有别于干涉检查报告，其具体内容包括下列项目：运动仿真动画驱动参数说明分析项目◆运动状态曲线◆运动件包络空间，运动轨迹等进入CATIA，点击新建，选择新建文件类型为“新建装配文件名称（如“Side_Stand_KIN称的装配文件。

先使用插入命令，在弹出的文件选择对话框内选择需要装配的零件，点击打开完成零件的调入（若文件，需要对调入的零件使用DMU漫游器模块中选择组命令，修改组名称，点击确定在CATIA结构树中生成组（本例中组名为Side_Stand”）。

制作组的目的是将需要考察的零件打包整体考虑，如需要考察一个运动零件在运动过程与其周边所有零件最小距离，就需将该运动件周边零件全部放到使用CATIA DMU 机构分析模块进行驱动、运动副及固定件的创建，最终完成整个机构的运动创建。

创建完成后，就可以进行整个机构的运动仿真及相关运线方向的平移；，释放三个自由度，沿着曲面Step.2 创建机构运动副。

该步骤机构运动的难点，机构创建命令为手段，逐步创建整个机构所含有的所有运动副。

每个运动副都是整个机构运动的基础，创建时，可以根据零件的机械结构判断其运动副的种类，并使用动副添加。

这里可以通过自由度对机构运动副进行相关的判断。

结合整个机构利用CATIA提供的运动副，将整个机构的运动副全部创建完成。

3.1.2 固定件的创建对于整个运动机构来说，必然存在一个固定的零件，该零件作为整个运动在机构运动副、驱动及固定件全部创建完成后，系统会自动弹出一个对话框，提示该机构可以仿真了。

这样，就做完了整个机构的运动仿真。

若没有提示该对话框，表示创建的运动机构有问题。

这时可以根据自由度选项的下拉菜单里选择相应的机构；选项里是第一个驱动命令数值的界限，Step.6点击Analysis...按钮可以添加运动分析项目，比如距离、干涉检查等；按钮，展开对话框；直接模拟，用鼠标直接拖着驱动副上的绿色箭头线移动；On request选项，下面的播放器按钮就会变亮，可以设置固Number Of Steps）来进行仿真运动。

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.。

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。

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4规范内容 ............................... 错误!未定义书签。

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A级曲面的间距离检查................. 错误!未定义书签。

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。

1.干涉检查的目的及意义3. 干涉检查有目的性，便于应用。

4. 对于已应用的干涉可以进行快速的查找。

DMU 审查创建工具条下的审查命令。

创建一个审查文件包，用来存放需要检查的各个子总成。

由于每个干涉结果只能在指定的审查文件包中存放，固该文件包需要针对与每个需要检查的总成单独创建。

分别用来存放每个单独总成下子总成的组。

且最终审查文件包的级次与CATIA结构树的级次一一对应，这样便于干涉检查的结果的保存和查找。

在审查文件包创建完成后，在结构树中双击文件夹，即可激活该审查文查文件包下。

Step.3 创建各个一级总成所对应的组。

确认无误后点击确定。

在结构树中生成一个组。

并通过属性修改其名称为：51000000-MQ05010-0.1，使之与结构树中一级总成名称唯依照此方法，创建所有一级总成的组。

并在属性中对其进名称这样，就完成了整个样机的一级总成数据组织。

今后在应用的时，只需要点击组即可完成每个单独总成的选取。

便于操作。

各系统中数据的组织在完成了整车数据组织之后，为了将各个系统的检查结果表述清晰，需要继续创建各系统的审查文件包及系统内子总成的组。

实施步骤如下：Step.1 先通过鼠标右键在级审查文件包的扩展菜单中关闭该文件包。

这样，就可以跳出该文件包，在点击创建审查文件包命令在结构树根目录下创建新的审查文件包，并命名为一级总成名称。

用来存放该总成下子总成的组。

Step.3 创建一级总成下子总成的组。

并将其放置在该一级总成的审查文件包下。

Step.4 依次创建所有一级总成所对应的审查文件包及其内部子总成所对应的组。

这样，就完成了第一版数据整机数据的组织。

其组织形式与BOM级次相对应，能够快速的实现零件查找及应用。

为后期的干涉检查做好的准备，也使得干涉检查能够快速系统的完成。

2.3 更新数据组织对于第一版数据以后的数据，进行后期更新数据组织。

由于后期数据更新是及时的更新，即以没有完整的样车数据。

这样，就无需在进行整机的数据组织，只要完成更新零件，及更新零件周边零件的数据组织即可。

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。