- What does '/CLN' command do?
- What do you mean by 'cold start' and 'warm start'?
- Name any 5 licenses of CATIA?
- Name any 2 Translators in CATIA?
- How do you see more than one model simultaneously (in one screen)?
- What is the procedure and/or how do you 'renumber'?
- What is the difference between tangent continuity and curvature continuity?
- How do! you grab a picture from main window?
- What is the difference between AUXVIEW and AUXVIEW2?
- What is DETAIL?
- What do you (or how do you) do hatching in drafting?
- How do you draw centrelines of circle in draft?
- What are (/is) the tools used to capture 2D-3D models?
- How do you parameterize the geometry in your model?
- What is 'PARTEDITOR'?
- What is 'skin'? How so you create?
- Does (/will) geometry constraining in sketcher help in parameterizing?
- What is the command for creating thin walled solids?
- What is the difference between SURF1 and SURF2?
- Name any 3 methods of creating 3 points curve?
- What is the difference (/what does this command do) LIM2+SURF+extrapolate and SURF+GEO+ extrapolate?
- Give any 3 functions of FORMTOOL?
- How do you give skin command?
- What is 'LAW'?
- Name any 3 functions of LIM2?
- What is 'spine'?
- What is '/anadia'?
- What is the full form of NURBS?
- What does BLENDSURF do?
- Give any 2 (or what are the) functions of UTILITY?
- What is 'INTERFER'?
- If given die direction how will you check minimum draft angle in the SURF (surface) model?
- What checks will you perform between surfaces with common boundary?
- What is the differ! ence bet ween '*role' file and '*save' file?
- Can data be model history be exported between 2 different CAD systems?
- What is 'FTRCLASS' command?
- Which module is used for surfacing with history in CATIA?
- What is Class 'A' Surfaces?
A1_Q2-060804
1) /CLN- This is the Cat Clean command used to clean the model for any unwanted geometery and to pack the model to compress the size of the model.
2) COLD START means it will start the CATIA workwindow in the normal way, whereas WARM START means if your system closed abruptly, without saving, it will start from that particular file in which you were working, maybe with some loss of data.
3)ADD,FREE FORM DESIGN,SPA,SHIP DESIGN,AERO SPACE
4)IGES,VDAFS
6)We renumber with the command Identity
Identity-------> Renumber
7)Tangent Continuty is the surface will be tangent to the existing surface, whereas curvature continuty means surface will follow the curvature of the curve.
8)go to tools + screen grab and select the area.
9)AUXVIEW is used to create/modify the frames of different views, whereas AUXVIEW2 is used to create the views.
10) Detail function is used if you have a assembly to create, and there are some common parts in different locations, then you can create a detail and use it in the master workspace wherever needed.
11) For doing hatching go to PATTERN+SELECT+HATCHING then select the boundary of the required view till you get the symbol \"c\", then press \"YES\" twice.
12) For creating centerlines of circles in draft, first you can select POINT+LIMITS ! and select the circle; you will get the center point. And then select LINE+HORIZONTAL+Symmetrical; you will get the horizontal line; and then Select LINE+VERTICAL+Symmetrical, you will get the vertical line.
14) Auxview2+USE in the popup window; select Parameter Tab, and you can do the parameterization, whatever you want.
15)PARTEDITOR is the history of all the work you have done, and you can use the parteditor to change and update the solid.
16)For creating SKIN, first you need the faces; once you have faces then you can select LIMIT2+CREATE+SKIN and select the faces from which you want to create skin. Everytime you select the face it should be the adjacent face which you have selected earlier, and the! y will be merged together. Once all the faces are selected the! n press \"YES\" twice; the skin is created. Now you can use this SKIN to create the solid.
19)SURF1 is used for the planner curves, whereas SURF2 you can use for the intricate curves where you need the tangency constraints and curvature constraints.
1) Name any 3 methods of creating a 3 point curve?
Ans: 1) Functions Arc, Spline, Curve2+Circle+ThreePT
2) What is the difference (/what does this command do) LIM2+SURF+EXTRAPOLATE AND SURF+GEO+ EXTRAPOLATE?
Ans: 2) Lim2 w! ill extend an existing surface (a percentage of the original length) and attempt to maintain curvature. Use with care because the theoretical extension loses accuracy over distance. Surf+GeoExtra will create a surface extension that is linear and tangent to the existing surface at a given length (it also offers the option to concatenate the two surfaces). Isoparms may be distorted using this process.
3) Give any 3 functions of FORMTOOL?
Ans: 3) Filleting of skins, limiting of skins and offseting of skins.
4) How do you give the skin command?
Ans: 4) Too vague to answer.
5) ! What is "LAW"?
Ans: 5) Laws are used to add precise control to surfaces created with Surf2. Radius, Area, Angle and Parameter values can be specified.
6) Name any 3 functions of LIM2?
Ans: 6) Creation of faces and volumes. Also used for surface breaks and concatenates. Other uses as well.
7) What is "spine"?
Ans: 7) A Spine is the \"backbone\" or support for a Surf2 surface. It dictates the orientaion of a surface as it relates to generating curves.
8) What is "/anadia"?
Ans: 8) Anadia is an analysis tool that allows you to save and update specific analysis processes. Used mainly for surface analysis.
9) What is the full form of NURBS?
Ans: 9) Too vague to answer.
10) What does BLENDSURF do?
Ans: 10) Blensurf allows you to create curvature continous (class A) fillets relatively easily.
11) Give any 2 (or what are the) functions of UTILITY?
Ans: 11) Many Utility functions. Commonly used to import and export CATIA files. Also used to process IGES and STEP file formats.
12) What is "INTERFER"?
Ans: 12) Another analysis tool.
13) If given die direction, how will you check minimum draft angle in the SURF (surface) model?
Ans: 13) One way is to use the Tools pull down menu and select Analyze+Draft (you must also indicate a direction and which elements to be analyzed). Moldpart can also do this along with many other cool bells and whistles (it helps you design the draft surfaces). There are other ways to check drafts as w! ell.
14) What checks do you perform between surfaces with common boundaries?
Ans: 14) Continuity of connection, tangency and curvature mainly.
15) What is the difference between a "*role" file and a "*save" file?
Ans: 15) These are files created by CATIA in order to maintain a temporary version of the files in use. If CATIA were to crash, a warm start would try to access these files to re-establish your CATIA session.
16) Can data model history be exported between 2 different CAD systems?
Ans: ! ; & #160;16) It depends on which two systems are being used. V4 models, unless you are sending them to V5, usually have their history stripped from the model.
17) What is the "FTRCLASS" command?
Ans: 17) Used to create solid features that can be stored and accessed from a library. Used in conjunction with the Param3D function.
18) Which module is used for surfacing with history in CATIA?
Ans: 18) Sorry on this one. I can't remember the designation as I use AL3 (basically, everything).
19) What are Class "A" Surfaces?
Ans: 19) Surfaces that when connected have tangent and curvature continuous properties with their adjoining surfaces. Example: the curvature value along the boundary of Surface A matches the curvature value of the adjacent boundary of Surface B. This is the simplest explanation.
20) What is a "Layer"? What is the use of it? And how do you create Layers?
Ans: 20) Think of layers as transparencies on an overhead projector (in the old days before Powerpoint). Different categories of objects can be assigned to various layers. Then you create Filters which instruct CATIA to display only those layers you wish to see at a given point in time.
J ust some Answers………………………. If it helps,
- Four arcs.
- CRV or Curves is that curve which is continous in curvature and tangency.
CCV or Composite curve is that curve which is a combination of more than one curve and is not continous in curvature and tangency.
- The hiearchy of making a complex solid design is: Freefirm Surface (Face, Surface, Skin)
|
&! #160; |
Closed volume
|
|
! &# 160; Solid
- Face --- *fac, Surface ---- *sur, Volume------ *vol, Skin--- *ski, Draw axis---- *axd, Dittos-----*dit, Curves----*crv.
- Volume element is the collection of the surfaces (faces, surfaces, skin) placed next to each other such that they form a closed space or volume.
- ALPHA-numeric winodow :- alt+
- A face bounded by lines and curves on a plane is known as planar face.
A face created from ! surface may or may not be planar depending upon the shape of surface.
- SURF1 function helps in creating simple individual building surface shapes. i.e they are of definite shape that can be represented by mathematical equations.
SURF2 function helps in creating complex shape using different conditions available. It can not be represented by mathematical equations.
- A functional surface is the surface of the solid.
- Surface element is represented in CATIA by * sur and the isoparametric curves(optional)
- surface model are created out of the surface by various methods like offset, ..........
S! olid mod els are created out of simple indivisual building blocks or regular shaped solids like PRISM, CYLINDER, CUBE, CONE, PYRAMIDS etc.
- Smoothness of surface can be checked by TOOL+ANALYSE+CURVATURE.
three colour comes up on the surface GREEN------>smooth surface. BLUE & RED ----->not smooth surface indicating depression at that region
- Connect---> It is the surface fillet created between the two surfaces(face, skin, or surface)
Corner---> It is the surface fillet created at the corner created by three surface (face, skin or surface) meeting each other.
- Surfaces---> It is a support which include used portions to be machined as faces.
Faces---> They are the planes or surfaces bound by lines and curves
Skins----> It is the collecton of freeform surfaces (face, or surface) which are placed next to each other.
- SPINE - indicates the direction of surface formation.
- LAW is the function used to define a condition for creating a surface.
LAW is a defined values along a curve or surface for the surfaces to be formed under different operations.
The different types of LAW's a! re:-
1)! 0; Radius law- to draw variable fillet.
2) Area law - to define area of the surface element.
3) Angle law - to draw variable angle while sweeping a contour over a spine.
4) Param - To define parameters.
- The CONNECT & CORNER under SURF1 functions are used for filleting surfaces.
CONNECT is used for filleting at a command edge of surfaces.
see fig. page9
CORNER is used for filleting at a common vertex of the surfaces.
see fig. page9
- Master Workspace is the default workspace which is displayed when CATIA is started. The main design and modelling is carried out in this space.
A master Workspace is the space in which the main modelling is done or the initial workspace when CATIA is started.
Additional workspace can be created by clicking WSP icon in the tool pallete and giving user defined names. This can also be defined workspace under DETAIL function.
Additional workspace can be created by following this methods
DETAIL+CREATE+W.SP! ACE
&! #160; 60; followed by keying some name.
We can switch to the additional workspace on the master workspace by following methods:
i) Click on workspace present on tool bar
ii) enter to get the list of workspace available
iii) Select the workspace required
iv) close the workspace list box.
- whenever a particular body occures in the modelling several time, instead of creating each time, it is better to create in DETAIL workspace and copy it into the master workspace to wherever necessary.
There are two way of doing it:-
i) DITTO---> It copies the detail to the master workspace. The changes made on this solid in DETAIL workspace is reflected on the master workspace i.e those solids are associated.
ii) COPY---> Here the change made in the DETAIL workspace is not reflected on the master workspace. i.e they are isolated from each other.
[ The DITTO under detail function, the modification made on DITTO is reflected in the main model where it is used, but in the case of copy under DETAIL function only the DITTO is changed for corresponding modification and not the DITTO copied in the main model.]
- Extens! ion of assembly file - .asm
- Different constraints in assembly:
The constraints available are:-
i) Axis coincident constraint.
ii) Surface contact constraint.
iii) Surface offset constraint.
iv) Angular constraint.
v) Snap constraint.
i) The changes made are automatically |
updated |
|
ii) The views shows the hidden lines
i) It needs updation.
| ii) The views does not show the hidden lines.
- When AUXVIEW2+DROP [command is given for a view, it loses all its links with the parent model and in future cases, whenever any modification done on the parent model cannot be updated on the earlier dropped views)command is used on any view, it get completly isolated from the solid model in the space mode.
No command works on it except the delete function
- SURF1 function is used for creating canonic surfaces or simple surfaces.
eg:- Ruled surfaces, Cylindrical surfaces, Spherical surfaces etc...
SURF2 function is used to create complex freedorm surfaces.
- A! functional surface is a surface extracted from a solid to manipulate the model.
- Surface element in CATIA is represented by isoparams along and across the boundary of the surface element.
- Surfaces are closed boundary elements with out any holes in between.
Faces are superform of surfaces which may or maynot have holes inside it.
Skin is a combination of adjacent faces.
- The smoothness of a surface is checked by analysing the curvature and tangent continous of the surface. The curvature & tangency of surface analysed will have the following options.
1)the boundries between sur! face are not joined, then the surface are not tangent continous.
2)
- Surface degree is the measured along and across the surface element. i.e along 'u' and 'v' directions.
the surface degree denotes the oscillations and smoothss of the inside surface curves.
- Featured based design is the design based on the company's customisation of product feature and [arameters.
- SOLIDM - SOLID MOCK-UP:- This is an approsimate solid and was used in the earlier version of CATIA.
- SOLIDE - EXACT SOLID:- As the name indicates, the solid formed are exact fulfill! ing all the conditions defined by the user.
- A constraint element in CATIA is one in which the parameters of the element cannot be changed.
- Local function window is an window consisting of the follwing sub. functions
1)STD - This is used to check the visualisation of the partmodel by checking on/off for the sections
2)2D - Settings for draw mode & space 2D
3)3D - Settings for space 3D mode
4)COL - Setting the colour of the background.
5OFF - To come out of local function window.
1. ! 60; What is the difference between point/int ! lim-on a nd lim-off?
lim-on: Creates the point by intersection & Projection can be done
with in the limits of the Selected elements.
Lim-off: Creates the point by intersection & Projection can be done
Outside the limits of the Selected elements.
2. What is the difference between surf1/geo extra and limit2/extrapol?
Geo-extra: extrapolates a new surface which is in the form of ruled
Surface.
Extrapolate: creates non-ruled surface thus changing original surface
Definition.
3. &#! 160;What is the use of formtool function?
Used to:
a. to connect skin(or face) elements - connect
b. to relimit skin(or face) elements - relimit
c. to break skin(or face) elements - break
4. What is the difference between face, surface and skin?
a. Faces are infinitely thin elements that represent the bounded exterior
defn. of a part. Faces can be planar or built on existing surfaces.
b. Skin are infinitely thin elements that are incorporate or group a series
of faces together to completely define a feature of part.
c. S! urfaces are infinitely thin elements that are used to define a! bounded
contour in space. Surface is parent.
5. What is hlr and nhr explain?
Hidden line removal
No hidden line removal
Purpose : Visualisation of solids in different modes.
6. What is the difference between isolate and separate?
Isolate: Deletes logical links between elements.
Separate: Separates lines , curves & faces from their links with other
elements ex: A curve is considered as separate when it is linked
to only one surface.
7. Is it possible to change pattern as required to exis! ting pattern?
Yes
8. What is the difference between parametric and nonparametric modeling?
a. Relational model is parametric. i.e. one to one relation.
If any change in dimension that may reflects on other dimensions.
b. Developing a solid by using surface, face, solid primitives etc.,
There is no one to one relation.
9. Which is the better to split the solid a) surface b) plane c) face?
Plane
10. What is the difference between spine and spline?
a. Spine: Creates a ! curve passing thro' point on a plane & normal to
! &# 160; one or more other planes.
b. Spline: Creates a curve passing thro' several points having tangential
& curvature contuinuity.
11. How you will delete the surface if the face is created by surface?
First erase face & then surface.
12. What are master w/s and detail w/s?
Master w/s: Model w/s
Detail w/s: We can have any no. of detail w/s, that can be called in
model w/s.
13. What is difference between curve1 project and combine?
Project: Perpendicular projecti! on of a curve on to plane, surface, face
etc,.
Combine: Unspecific projection of a curve on to plane, surface, face etc,.
14. Is it possible to split by using sewing operation
Yes
15. Diff. b/w surf1 connect & surf2 fillet
Connect: Creates a fillet surface that connects two existing surfaces,
Planes, or planar faces.
Fillet: Creates a fillet surface that connects two existing surfaces,
Planes, or planar faces using spine.
16. What is functional surface
A FSUR is an element that defines a fac! e on a solid. The displayed in
&! #160; 60;non-hidden mode.
17. Purpose of IUA
IUA: Interactive users application, used to customize the CATIA users
command.
18. How you will convert ccv into crv
Using limit1 è Appr ccv
i.e., Approximate compound curve or composite curve.
20. How you are setting attribute to a particular file
Standardization of model file by Permanent setting of layers, graphics
etc,.
as per Company standards for their project.
21. Is it possible to do shell operation to sphere
&#! 160; Yes
22. Difference between surf1+cylinder & surf1+depth
Cylinder: Extending a curve thro' space in a linear direction with
given length.Surface created length is equal to PAI * D.
Depth: Extending a curve thro' space in linear direction with given length.
23. How many types of environment is available to start Catia
a. From desktop [motif]
b. From console [dterm]
24. Mention different starting modes in catia. explain each briefly?
Normal, Cold, quick, warm start respectively
25. ! ; what does Adjust function is used for?
26. what are functions used to make "balloon with leader"?
27. what is difference b/w surf1+concanten+crv & surf1+concanten+ccv?
28. what is difference b/w solide+intersect/subtract+trim all/trim elem 1/no
trim?
29. what is difference b/w limit2+break & surf2+divide ?
30. Mention 5 primitives solids in solide function ?
31. Give two eg. for feature based primitive & contour based primitives ?
32. what is use of Markup function ?
33. what is required for to find massproperties of a surface model? And what
is used for finding the massprope! rty.
34. Difference between sewing and split
35. what is the difference b/w tranfor+affinity & tranfor+scaling ?
36. what is parameter is asked for curve1+crv+crv ?
37. what is importance of tree in catia ?
1. What is the difference between ccv and crv?
2. What is difference between solid, surface and wireframe modeling?
3. What r the types of modelings?
4. What is the difference between solide and solidm?
5. What is the difference between surf1/geo extr and limit2/extra! pol?
6. ! ;What is the use of formtool function?
7. Using 3-points how many circles can create?
8. What is the use of adjust command?
9. Explain solide/operation/subtract & intersect/trim all: trim el1: no
trim?
10. What is the difference between face, surface and skin?
11. What are the solid primitives?
12. What is hlr and nhr explain?
13. What are the translators and explain?
14. What is the use of LAW function?
15. What is the use of layer function?
16. ! 0; What is the use of merge function?
17. What is the difference between isolate and separate?
18. Is it possible to change pattern as required to existing pattern?
19. What is the difference between parametric and nonparametric
(hybrid)modeling?
20. Which is the better to split the solid a) surface b) plane c) face?
21. What is the difference between spine and spline?
22. How you will delete the surface if the face is created by surface?
23. What is the difference between affinity and scaling?
24. What is CSG tree explain?
25. What a! re maste r w/s and detail w/s?
26. What are nurbs, B-ref, brazier curves?
27. What is difference between curve1 project and combine?
28. What is difference between curve1 project and reflect?
29. While creating solid model shell is first operation or fillet?
30. What are the types of starting modes?
31. What are the CATIA sessions?
32. Mention the ways to start the CATIA
33. Is it possible to split by using sewing operation
34. Is it possible to appr. Surface using isoparameter
35. Diff. B/w surf1 connect & surf2 fillet
36. What is functional surface
37. Difference between point projection and unspecific projection
38. Difference between curv2 mono and multi tangent
39. Purpose of iua
40. Catia element
41. Difference between sewing and split
42. How drawing will be extracted ---- aux2 or spc-drw2 [if related to
surface spc-drw]
43. Difference between line bisect and line median
44. How you will convert ccv into crv
45. Exp! and IGES ,DXF,CATIA,IUA,STEP
46. Catia file format
47. How you are setting attribute to a particular file
48. Difference between tangential continuity and curvature continuity
49. Necessity of using filters in layer
50. List out the command used for the surface modeling
51. What are different types of modules available with Catia package
52. Catia models requires at least ____co-ordinate axis system
53. What are different types of co-ordinate system
54. Which one is not a sub function of transfor in! space mode ---
(a)project (b) affinity (C)symmetry (d)scaling
55. Symbol is function of draw mode
56. Detail is function of draw & space mode
57. Is it possible to do shell operation to sphere
58. Difference between surf1+cylinder & surf1+depth
59. How many types of environment is available to start Catia
60. How many layers are present Catia
61. How many types of working space are there in Catia
62. How many operations can we done by using sewing command of solide
63! . What is the importance of pulling di! rection in case of sweep
64. Symbol can be defined in detail work space
65. Difference between limit1+appr ccv & curv2+approxm
66. Necessity of using filter in layer
67. What is the difference between point limit-on and off?
CLASS -A
Here is a further understanding of Class-A surfacing based on experiences with two automotive companies and whites goods manufacturers. They independently hav! e the same definition for the classification.
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 etc). For these applications, there is generally no need for curvature.
By ! definition:
Class ! A surfac e 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 etc 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.
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 continuos 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 ref! lection across the boundary.
60;
Please do not believe me! This is the real physical world. Look at your cars rounded hood reflecting lines on the road or trees. Look at ripples of water that are not turbulent, reflection is everywhere but all blend into each other, as there is also curvature continuity everywhere.
Still not convinced - For an analytical approach, you may simply prove this point using any rendering package (eg. CATIA V4 VST), Neon textures in 4D Navigator or DMU Navigator (V5), using the traditional CURVE1+REFLECT or /ANADIA in V4 CATIA and of course the neon-tray dynamic reflect curve facility in V5.
What about CATIA??
Traditionally CATIA has been used to create the "engineer! ing" side of most designs, rather then the exterior "aesthetic" shell (ie Class-A). These traditional yet awesome tools (like SURF2) are geared for this kind of engineering work. The best example being BIW in the automotive industry.
Functions like SURF2 and FORMTOOL carve up even the most difficult inner panel structures into reality. This is why, historically, CATIA took an early strangle hold (amongst other reasons like a great capacity in all aspects of DMU and integration across disciplines).
CATIA comes from the aerospace industry. The exterior of aeroplanes (whose panels buckle between frames and expand with every land-takeoff cycle) has very little "need" for curvature continuity and has 100% engineering factors driving its design (aerodynamics and structures).
Tha! t is, th ere is zero styling in the design of an aircraft body. The fact that aeroplanes looks good and "smooth" is by virtue of its operation (streamlined as possible), their general cleanliness and most importantly the distance that one generally views them. If one was to look carefully down the fuselage of an aircraft on the ground, there is nothing smooth about it!
Having the capability to cater for these industries in an engineering and process capacity with existing function and not requiring the ability to create Class-A, has made CATIA the de-facto standard for the aerospace and automotive industries.
As for Class-A, automotive manufacturers have utilised either or combinations of Alias and/or ICEM Surf (or others) to achieve these goals in a productive manner (remember the word productive). Alias has! the ability cover the entire industrial design process from Sketches TO Surfaces on sketches TO Surface manipulation and build and further onto rendering and animation.
In retrospect, CATIA V4 can create Class-A surfaces with (1) compromise (eg. this deviation is OK, because it can be polished by the toolmaker) and (2) an idiosyncratic approach by the CATIA operator - ie, it can be done but not as easily as with Alias or ICEM Surf.
Historically, its been "difficult" of Dassault to create software in V4 to easily create Class-A surfaces due to the use of Bezier (polynomial) based mathematics. There is nothing against Bezier based surfaces though. They are excellent for creating the engineering surfaces we have all come to love (BIW etc) utilising intelligent use of multi-patch surface methodology. I! n fact, I doubt NURBS surfaces could do a better job.
And without a doubt, V5, with its new architecture and use of Bezier and NURBS surfaces will go along way in being able to confidently and more importantly competently producing these Class-A surfaces for an ever growing aesthetic minded world.
And what about V4 CATIA??
CATIA V4 currently has the ability to create curvature continuous surfaces in two categories.
Surfaces:
a. Using SURF2 and SKIN (GSM) functions to sweep and loft as "long" a surface as possible. This will generally produce a curvature continuous surface with minimum deviation.
b. Intelligent use of SPINES and LIMIT curves when using SURF2 and SKIN to closely match curvature across boundaries.
c. Utilising conic surfaces and conic curve approximations to mimic curvature conditions.
d. For parts with large variations within its shape cause techniques a and b to struggle. For this reason, we may take three approaches.
d1. Create "unstressed" surfaces to the point of struggle and fill in the blank with blend surfaces and curvature continuity. This is very much situation dependant.
d2. Use ARC's and PATCHES's - ARC's and! PATCHES have the peculiar yet great ability to
* not go through all their constraints (good for the styling end of the design process)
* the ability to deform a arc or patch to a point
* the ability to deform the boundary of a patch to an arc whilst maintaining the opposing continuity.
* most importantly - the ability to reduce or increase degrees of arcs and patches to maximise or localise deformations.
I have found these most useful.
e. Utilise NURBSCRV and NURBSSRF when and arc or patch refuses to go close enough to the constraints of interest.
Blends:
These are a curious family of sur! faces. One can utilise two functions within CATIA V4.
The first is the ubiquitous BLENSURF functions, which allows a point/tangent/curvature continuos blend between any two curves on any part of any plane, FSUR, RSUR, surface, face or skin. OR automatically creating bi-rail curves along two surfaces at particular "radii" and placing a point/tangent/curvature continuous blend between them. Tensions and connectivity locations are also adjustable.
Although it is a great tool, one issue with Blensurf is its inability to blend around a large angle. For instance, if one constructs two segment surfaces to each other at right angles with a gap between them and then placing a curvature continuos surface to connect them. The result is very suprising. The surface comes off one with curvature continuity, takes! the shortest route to the other and then blends with curvatur! e again. It is not the expected shape in the blend, when comparing it to the curves created using CURVE2+CONNECT with curvature from the isoparametric curves of each surface.
The reason for this is that Blensurf creates purely mathematical curvature. For the correct shape, mathematical and isoparametric curvature is required. Guess what my friends, Dassault are already on the ball, this is possible using GSM's SKIN function blend and V5 GSD blends.
