Lesson 3: Surface Creation

attached to the front door, for design feasibility study. ✓ Create a cross-section surface for 'Key-pad'. (for Electronic control) at a measured distance from the Arm ...
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V5 Surface Design

Lesson 3: Surface Creation In this lesson, you will learn how to create surfaces from wireframes. Lesson Contents:

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Case Study: Surface Creation Design Intent Stages in the Process Choice of Surface Sweeping a Profile Create a Multi-Section Surface Create an Adaptive Sweep Surface

Duration: Approximately 3 Hours

Instructor Notes:

$Speech: Objectives of the lesson: - inform on the tools available in the GSD workbench to create surfaces geometry%

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V5 Surface Design

Case Study The case study for this lesson is to create surfaces for design feasibility study of the given components.

Design Intent The substrate profile needs to be adaptable for design modification and changes without replacing the original input. Create a broad cross-section surface for an ‘Arm rest’ attached to the front door, for design feasibility study. Create a cross-section surface for ‘Key-pad’ (for Electronic control) at a measured distance from the Arm rest ankle point. Attain a single merged part using Arm rest and the keypad component. Close the end of the Arm rest and Key-pad with Door Substrate rounded ends. Design the door latch. Design a Map-Pocket with the rounded edges.

Key Pad Area Latch

Armrest & Key Pad

Map-Pocket

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Rounded Ends Arm Rest area

Instructor Notes:

$Speech: Objectives of the lesson: Inform on the tools available in the GSD workbench to create surfaces geometry Discuss the Design Intent of the case study. Tell the students to perform the case study, you will learn some concepts and tools and use them to perform the case study and other exercises Discuss the Design Intent of the case study. Tell the students to perform the case study, you will learn some concepts and tools and use them to perform the case study and other exercises To be able to perform the case study successfully we will learn some tools of Generative shape design workbench %

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V5 Surface Design

Stages in the Process

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1. Create an Adaptive Swept surface. 2. Sweep a Profile. 3. Revolve a Surface. 4. Create a Multi-Sections Surface.

Instructor Notes:

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V5 Surface Design

Step 1: Choice of Surfaces In this section, you will be introduced to the different types of ‘Surface Creation’ tools available in Generative Shape Design.

Use the following steps: 1. Choice of Surfaces Extruding or Revolving a Profile Sweep a Profile Create Multi-Section Surface Create an Adaptive Sweep Surface

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2. 3. 4. 5.

Instructor Notes:

$Speech: Objectives of the step: create

- Explain the criteria that can be used to help choose the surface you will

%

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V5 Surface Design

Choice of Surface (1/2) Category

Name

Surfaces extruded in a direction

Extrude

Icon

Illustration

Cylinder Surfaces revolved around an axis

Revolve Sphere

Surfaces connecting existing sections

Multi-section surface

Surfaces sweeping a profile Sweep along a guide curve

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Adaptive sweep Surfaces filling a gap

Fill

Surfaces offset from an existing surface

Offset

Instructor Notes:

$Speech: First: the surfaces simply based on a profile and an revolution axis or a direction Second: you need a surface to pass by a few pre-existing sections

Multi-section

Third: you need to sweep a profile (predefined or not) along a guide curve Sweep or adaptive sweep (if you want to manage the shape of the profile along the guide) Fifth: you need to fill a gap

Fill

Sixth: you need to simulate a thickness on an existing surface

Offset

So depending on what you need, you will choose the surface that goes with it

Now we’ll see for each of these surfaces the inputs that are needed%

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V5 Surface Design

Choice of Surface (2/2) The following table shows the wireframe required for each type of surface:

Inputs

Tools

Profile

Direction/Axis

Guide Curve

Section

Spine

Extrude Sphere Cylinder Revolve Loft

Optional

Optional

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Sweep Mandatory

Loft => Multi-Section Surface

Not Applicable

Instructor Notes:

$Speech: Here we talk only about the wireframe input (that’s why offset is not seen here). With the previous slide, you could see which surface to create in regards to the characteristics you wanted to give to your surface Here you can see the wireframe input necessary to achieve the surfaces NOTE: as you can see, most of the surfaces are based on more than one input. So, the input you have cannot be a unique criteria to know which surface to create. For instance: you have a profile: should you create an extrusion or a sweep ? depends if you want the profile to follow a special path that is not linear...

It

For instance: you have a 3D guide curve. Should you consider it as a guide for a sweep or as a guide for a multi-section surface ? it depends if you want the surface to have sections that are totally different along this guide. If so, then you’ll have to create the sections and use a multi-section surface. If the surface you want to create is monoprofile, then you will certainly choose a sweep and you will have to create the profile you need. After this global view of what the surfaces can do, let’s see in details the specificities of each type of surfaces%

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V5 Surface Design

Step 2: Extruding or Revolving A Profile In this section you will learn to create a basic surface. Use the following steps: Choice of Surfaces

2.

Extruding or Revolving a Profile

3. 4. 5.

Sweep a Profile Create Multi-Section Surface Create an Adaptive Sweep Surface

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1.

Instructor Notes:

$Speech: Objective of the step: show the extrusion and revolution%

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V5 Surface Design

Profiles That can be Used An Extrude or a Revolve tool uses a profile to create a surface. A Profile can be a Sketch, a 3D curve, an edge of an existing surface or a solid.

Inputs Surface

Sketch profile

3D profile

Surface edge profile

Solid edge profile

Extrude

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Revolve

Instructor Notes:

$Speech: The Extrude and Revolve are the basic surface creation tool of Generative Shape Design. Discuss the options in the table. Profiles that can be used. NOTE: self intersecting profile or profile intersecting the axe cannot be used % $Show: Explain and DEMONSTRATE that when you use a sketch to create these items, the normal plane is automatically detected (and the same, you can include an axis in the sketch) DEMONSTRATE that there’s a risk creating on solids edges (show what happens when an edge disappears or something like this)% $Speech: Extrude is very similar to creation of PAD in part design Explain that: The characteristics of a Extrude and the Cylinder command are similar when a profile is circular. The characteristic of a Revolve and Sphere command are similar when a profile is circular. %

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V5 Surface Design

Step 3: Sweeping a Profile In this section, you will learn about the different types of Sweep surface tools.

Use the following steps: Choice of Surfaces Extruding or Revolving a Profile

3.

Sweep a Profile

4. 5.

Create Multi-Section Surface Create an Adaptive Sweep Surface

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1. 2.

9

Instructor Notes:

$Speech: Objective of the step: show the sweep (not adaptive)%

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V5 Surface Design

Computation of Sweep Sweep is a surface generated by sweeping a profile along a guide curve with respect to a spine. The profile can be a user-defined or pre-defined profile. Sweeping a profile along a guide curve with respect to a spine means:

Spine Guide

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- Planes are calculated - The profile is repeated on these planes - A surface passing through these profiles is generated

Surface passing through the repeated sections

Profile

Profiles repeated in the planes Show the influence of spine on sweep shape (L3.CATPart/SPLIT_TRIM)

Instructor Notes:

$Speech: Explain the student the computation of the sweep internally. The 3 steps explains the internal computation of the surface. When a profile is swept along the guide curve to generate the surface, sweep internally computes planes normal the spine along the guide curve. The profile to sweep is repeated in all the planes along the guide curve. Thus a surface is generated passing through these profiles which is normal to the plane at any point. So: - The shape of the sweep depends on the planes in which the sections are calculated - The planes depends on the spine The shape of the sweep highly depends on the spine Not only of course: guide and profile also. But spine is really the key concept to understand when we talk about sweep in CATIA V5 because the spine has an impact on: - The sweep shape - The sweep quality (next slide)%

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V5 Surface Design

Why is the Choice of the Spine Important ? The quality of the spine defines the quality of the sweep: Tangency discontinuities on the spine impact the quality of the final sweep.

A

B

Defects

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The spine is not tangency continuous The sweep inherits the faults of the spine.

The same spine has been made continuous. The default is gone.

Show the influence of spine on sweep quality (L3.CATPart/SPINE/SPINE_QUALITY)

Instructor Notes:

$Speech: The spine plays an important role in deciding the quality of the swept surface. The spine has to be tangent continuous. % $Show: DEMONSTRATE using GS “SPINE “ - Create a sweep with the provided curves - Show the discontinuity by changing the tangency value from 0deg to 0.5 deg in the DISCONTINUOUS SPINE sketch and show the impact on the sweep with the connect checker tool - Show the impact of the spine on the shape of the sweep using the different shape spines provided% $Speech: The end and start planes are also deduced from the spine (remember that the planes are calculated in regards to the spine) By default the spine used is the guide curve of the sweep Explain that a sweep can be created using 2 guide curves (see this later) How to choose the good start and end planes ?% $Show: Demonstrate this last point% $Speech: A spine can be generated in the GSD workbench using the spine calculation tool. Let’s see how to calculate the spine.%

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V5 Surface Design

Spine Calculation Section

Spine can be calculated using the Spine tool available in the Generative Shape Design workbench.

Sweep computed using explicit spine

Using the Spine tool, you can calculate: A.

The spine with regard to end or intermediate planes. Spine computed using intermediate planes.

Guide Curves Sweep computed using explicit spine

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B.

The spine with regard to two or more guide curves facilitating the creation of swept surface, which runs along the guide curve.

Spine Calculation Calculating a Spine Regards to Plane or Guide Curve

Show the spine computation using guides or planes (L3.CATPart/SPINE/SPINE_COMPUTATION)

Instructor Notes:

$Speech: To prevent the problem we’ve seen just before (in the DEMONSTARTION), you can use the spine tool to generate a spine that will be consistent with the 2 guides % $Show: DEMONSTRATE using the guides available and show that using this new spine, the Sweep respect the start and end planes of each guide curve. DEMONSTRATE also the calculation of spine with respect to the planes: useful when you want to make sure that profile shape is respected in these planes.%

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V5 Surface Design

Explicit Sweep Following is the list of user-defined sweep options available in a sweep tool:

Sweep Type

Sweep Sub Types

With Reference surface

Illustration Profile

45 Deg

Guide curve

Reference Surface

With Two Guide curves

Anchor Points

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With Pulling Direction

Profile

Guide Curve 1

Guide Curve

Guide Curve 2 20 Deg

Profile

Pulling Direction

Explicit Sweep Sweeping a Profile (2/2)

Show the explicit sweep (L3.CATPart/SWEEP/EXPLICIT_SWEEP)

Instructor Notes:

$Speech: In Generative Shape design using the sweep tool you can sweep a user designed profile in three ways, - Using Reference surface: The guide curve must rely on the surface. Then an axis system positioned on the guide is calculated using the surface section and the normal to surface. The axis system in which are calculated the sections of the sweep along the guide is rotated in regards to the angle you give (DEMONSTRATE: do a rotation of 50deg on the axis system, apply a transformation axis-to-axis to the profile and show that giving an angle of 50deg to the sweep, the sweep passes by the rotated profile) - With two Guide Curves : The profile sweeps along the two guide curves and a surface is generated. You can also specify anchor points for each guide. These anchor points are intersection points between the guides and the profile' s plane or the profile itself, through which the guiding curves will pass. NOTE: the anchor points do not need to be on the profile (DEMONSTRATE) Which can be a good solution to position the profile - With Pulling Direction : This is similar to the sweep using reference surfaces. Here the direction of pulling decides the direction in which the surface would be removed from the mold.%

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V5 Surface Design

Profile Positioning You can manipulate the orientation and position of the swept surface without actually moving the parent curves. This is done by selecting the positioned profile option in swept surface dialog box. A.

Using no positioning:

Before Positioning

Guide Profile After Positioning

B.

Using positioning:

C.

Rotate the positioning axis system

D.

Translate the position of the origin of the

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Rotating the surface

Modifying the Position axis system

positioning axis system

Instructor Notes:

$Speech: You can position the profile with the guide curve. Using the Position profile mode, the reference is no more the profile but the Guide Curve. Using no positioning : When the profile position is fixed with respect to the guide curve, the sweep lies on the profile and on the guide curve (if it intersects the profile) or on the parallel to the guide curve crossing the profile (minimum distance). Using positioning: The profile is oriented in the guide curve axis system. The origin of the profile is positioned on the guided curve. Beware: if the profile is a sketch: the origin of the sketch is taken in account % $Show: Go through the dialog box Explain the students that CATIA will position the profile with respect to the guide curve when you select the ‘position profile’ option. You can manipulate the position of the profile by different parameter options available in the panel. Explain each step on the slide by demonstrating to the students.%

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V5 Surface Design

Linear, Circle and Conical Sweep (1/2) Pre-defined profiles are the implicit profiles like Line, Circle and Conic which are used to compute the sweep.

Type

Type

Illustration

With Reference Curve

G2

With Two Limits

G1

Illustration G1

A

G2

Line joining two guides G

With Tangency Surface

S

M

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Limits and Middle

With Reference Surface

With Two Tangency Surfaces

G1

S G1

With Draft Direction

T1

T2

C

D

G A

Instructor Notes:

$Speech: Explain that, The shape of the profile is implicitly defined. The user do not have control over the profile to be swept, instead the user has the freedom to manipulate the dimensions and positions of the pre-defined profile along the sweep. In other word the user has the flexibility of modifying the parameters of the profile through sweep panel. The Line sweep creates a linear surface using the specified guides and references. However the parameters of the sweep can be controlled through the sweep panel. Explain each sub-options specified in the table in detail without using CATIA interface. this will help in understanding concept behind the surface computation. Explain the line sweep using a piece of plane paper, if required. The surface demonstrates the linear surface between two curves.%

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V5 Surface Design

Linear, Circle and Conical Sweep (2/2)

Type

Illustration

With Three Guide Curves Two Guide Curves and a Radius Center and Two Angles

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Illustration

G1 G2

G1

Two Guide Curves

G3

T1

G2

T2

G1 G2

Three Guide Curves

R

GR A1 GC

Center and Radius One Guide and one Tangency Surface

Type

GC

S

G1

T1

A2

Four Guide Curves

R

Five Guide Curves

G1 G2

G1

G3

G2 G3 G4

G4

G5

G2

Instructor Notes:

$Speech: Explain each sub-options specified in the table in detail without using CATIA interface. This will help in understanding concept behind the surface computation.%

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V5 Surface Design

What are Laws B

A Use Laws to vary the input parameters of the surfaces

Three types of Laws : A.

Linear Law

B.

‘S’ type of Law

C.

Advanced Law

Linear Law

C Reference Curve

‘S’ type Law

Definition Curve

d

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Advance Law The Law define the variation of d along L What are laws Sweeping a Profile Using Law

Show the linear sweep using laws (L3.CATPart/SWEEP/LINEAR_SWEEP)

Instructor Notes:

$Speech: Laws are used to define precisely the evolution of a value. This value can be used afterward as a length, an angle, a radius ... Laws can be: Linear S type Or user defined: using a reference line and a curve, the distance between these 2 geometry will give the evolution of the law%

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V5 Surface Design

Errors You Can Find While Computing the Sweep Error/Warning The moving plane (perpendicular to the Spine) and the guides do not always intersect.

Description

Solution The problem may arise when the spine is shorter than the guide curves or when the spine curvature is large. This error may also occur if the guides are parallel to the moving Plane. Modify the spine (with less curvature variation) or expand the guide curves

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The Extrusion of the vertex of a profile leads to a cusp. Use a guide with smaller curvature.

Change the sweep parameters or reduce the guide or spine curvature variations.

Show a few errors (L3.CATPart/SWEEP/ERRORS)

Instructor Notes:

$Speech: 1st error: The plane on the spine that does not intersect the guide is shown to help you solve the problem. the spine must be long enough for the planes that are calculated on it to intersect the guide curve. Sometimes the spine seems long enough, but it has such curvature at one place that the normal planes at this place do not intersect the guide 2nd error: The surface is pre-computed to show the place where the curvature variation of the guide curve is too important to show you the cusp and help you to solve the problem% $Show: Ask the students what could be done to avoid these mistakes in these concrete cases Most of the problems are due to a too brutal variation in the input wireframe curvature or to a tangency discontinuity in the wire%

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V5 Surface Design

Exercises Overview 3A,3B and 3C You will practice what you have learnt by working through the exercises: Exercise 3A

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Exercise 3B

Exercise 3C

You can also practice on the demonstration data that are provided

Instructor Notes:

$Speech: Present the exercise Have the students begin the exercise and note the time Assist students as needed with the exercise 3A-3B: detailed 3C: poorly detailed 3A: make you manipulate explicit sweep creation and test the influence of the spine 3B: makes you manipulate circle and conical sweep. You will also have the opportunity to quickly manipulate the fill tool 3C: create a sweep using a law. You will also manipulate a rotation operation on the surface (to complete the turbine)%

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V5 Surface Design

Exercise 3A: Recap Sweep a profile along a guide curve.

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Understand that Spine controls the orientation and shape of the surface.

Instructor Notes:

$Speech: Review the Exercise Recap slides after the students have attempted the exercises. Try to encourage group discussion on the exercises they have just completed. Discuss the different tools used.% $Ask: Ask if there are any questions about this exercise, any difficulties?%

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V5 Surface Design

Exercise 3B: Recap Extrude a profile in a direction. Create a Fill surface. Create a swept surface using the Two Guides and Tangency surface sub-type available in the Circle option.

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Create a swept surface using Two Guides available in the Conic option.

Instructor Notes:

$Speech: Review the Exercise Recap slides after the students have attempted the exercises. Try to encourage group discussion on the exercises they have just completed. Discuss the different tools used.% $Ask: Ask if there are any questions about this exercise, any difficulties?%

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V5 Surface Design

Exercise 3C: Recap

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Create a sweep using a law.

Instructor Notes:

$Speech: Review the Exercise Recap slides after the students have attempted the exercises. Try to encourage group discussion on the exercises they have just completed. Discuss the different tools used.% $Ask: Ask if there are any questions about this exercise, any difficulties?%

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V5 Surface Design

Step 4: Create a Multi-Section Surface In this section you will learn to create Multi-Section Surface.

Use the following steps : 1. 2. 3.

Choice of Surfaces Extruding or Revolving a Profile Sweep a Profile

Create Multi-Section Surface

5.

Create an Adaptive Sweep Surface

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4.

Instructor Notes:

$Speech: Objective of the step: learn the multi-section surfaces Understand the importance of coupling and closing points on the quality of multi-section surfaces (previously called loft)%

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V5 Surface Design

What is a Multi-Section Surface A surface computed through two or more consecutive sections respecting guide curves. Multi-Section surface helps you to: - attain a smooth transition surface between sections - Maintain the G1 continuity with adjacent surfaces

Adjacent Surface Guide curves

Adjacent Surface

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Sections curves

Instructor Notes:

$Speech: A standard swept feature has a single trajectory and a constant [unchanging] cross section. The Multi section surface has an initial cross section which is referenced to multiple trajectories which influence the section as it travels along those trajectories. Here we cans see that: - A smooth surface has been created between the sections - The guide curves have been respected - The tangency with the 2 adjacent surfaces is also respected As you can observe, the number of vertices on the 3 sections is not the same: so CATIA needs to know how to join these sections, how to get from one section to the following if each vertex of the first section do not find a correspondent vertex on the following section ? This introduces the concept of coupling that is very important when we talk about multisection surfaces But first, let’s talk about the sections and the guide curves to know which requirements they need to meet%

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V5 Surface Design

What are Sections and Guide Curves

Section Curves

A section can be a planar or a non-planar curve. The Guide curve defines the path of the surface as it transits between two sections. The guide curve: - is point continuous curve - intersects with each consecutive section of a Multi-Section surface

Guide Curve

Guide Curve to give the correspondence between these 2 vertices

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Section Curves

Show the creation of a multi section surface (L3.CATPart/MULTI SECTION/GUIDE)

Instructor Notes:

$Speech: Sections can be 2D or 3D curves that are continuous (in point). You cannot use sections that are not connex curves The guide curves define how the multi-section must go from one section to the other. As you can see on the right, the shape of the guide curves are inducing a bump in the surface where the surface should have been linear The guides must also be continuous and they must intersect the sections (else the condition “passing by the section “and “respecting the guide curves” are getting contradictory. If you use adjacent tangent surfaces, the guides must also be tangent to the surface. The guide can be bound to the extremities of the sections and in this case, it becomes a boundary of the surfaces. The guide can also join vertices that are internal to the sections. In this case, the guide is not a boundary but defines an edge on the surface, this edge running through the vertex of each section that belongs to the guide: these vertices are what we call coupling points because they define a correspondence between the vertices of the sections ...% $Show: Demonstrate the creation of a multi section surface using the demonstration data%

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V5 Surface Design

What are Coupling Points Coupling Points are the connecting points used to compute the segmentation on the surface.

During the surface generation, the coupling points of one section are automatically connected to the corresponding coupling points of the consecutive section to attain a guided flow between two or more sections.

B

A C1

D1

B1 B1

C2 A1

E1

D2

B3

A2

E3

C2

B2 C3

E2

C1

B2

A1

B3

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A2 A3 A3 Show the use of coupling points (L3.CATPart/MULTI SECTION/COUPLING)

Instructor Notes:

$Speech: We have seen just before that concrete coupling curves could be used to define the shape of the surface between the sections, but could also define Coupling points on the sections (previous slide) But this correspondence between the sections vertices can also be specified without using guide curves, but simply specifying coupling points on the sections. Then : virtual guide curves joining these vertices will be computed and you will get the same result as if you created a spline passing through these vertices and used this spline as a guide curve. As on the illustration, specifying coupling points is merely useful when the sections do not have the same number of vertices. A- There are equal number of coupling points in all the three sections. The corresponding points of different sections couples with each other to form a segment. A1, A2 and A3 are the corresponding points of different sections coupled together. B- Each section has a different number of coupling points. You can couple the points manually according the required segmentation. Here C1 is coupled with the C2 and B3 points of second and third section respectively.% $Show: Show the importance of sections orientation: with automatic coupling modes, the vertices are taken from the origin of the sections that depend on their orientation (show a twist)%

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V5 Surface Design

What are Closing Points A closing point is the end point of the closed section. When a surface is generated, the closing point of one section is coupled with the closing point of the consecutive sections. You can change the closing point of one or more sections to modify the orientation of the surface.

A

C

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B

What are Closing Points Creating the Multi-Section Surface

Show the use of closing points (L3.CATPart/MULTI SECTION/CLOSING)

Instructor Notes:

$Speech: We have seen that the coupling points were taken in account from the beginning of the sections. When the sections are closed curves, there is no start point on them: a closing point is defined to give the automatic coupling modes a point to start from. There always one closing point by default on the closed sections. This closing point is clearly identified on the sections (as on the illustration) The closing points of the sections are coupled together. If the closing points are not in front of one another, you get a twist (see picture) So you need to change the closing points of the closed sections to avoid this twist (see picture)% $Show: Demonstrate the importance of closing point and how to change it%

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V5 Surface Design

Exercises Overview 3D You will practice what you have learnt by working through the exercises: Exercise 3D

Coupling 4 Coupling 3

Coupling 2

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Coupling 1

You can also practice on the demonstration data that is provided.

Instructor Notes:

$Speech: Present the exercise Have the students begin the exercise and note the time Assist students as needed with the exercise Create the upper shape of a shoe using a multi-section surface Manipulate the different coupling options, replace closing points and create manual coupling%

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V5 Surface Design

Exercise 3D: Recap Create a Multi-Section surface.

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Use different coupling options.

Instructor Notes:

$Speech: Review the Exercise Recap slides after the students have attempted the exercises. Try to encourage group discussion on the exercises they have just completed. Discuss the different tools used.% $Ask: Ask if there are any questions about this exercise, any difficulties?%

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V5 Surface Design

Step 5: Create an Adaptive Sweep Surface In this section you will learn to create Adaptive Sweep Surface

Use the following steps to: Choice of Surfaces Extruding or Revolving a Profile Sweep a Profile Create Multi-Section Surface

5.

Create an Adaptive Sweep Surface

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1. 2. 3. 4.

Instructor Notes:

$Speech: Objectives of the step: show how to create an adaptive sweep, explain how it is different from a sweep, and tell the mistakes to avoid while creating the parameterized sketch%

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V5 Surface Design

How CATIA calculates an Adaptive Sweep? An Adaptive Sweep Surface is a surface which can adapt to changing dimensions of the parent profile along the defined path. Sketch

A

Guide Curves 5

D 15

100

B 10 15

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UserSection .1 UserSection .2

110

C

Show the creation of adaptive sweep with or without references (L3.CATPart/ADAPTIVE SWEEP)

Instructor Notes:

$Speech: A-A constrained sketch profile is swept along the guide curve. B-The surface is computed along the guide curve respecting the sketch constraints and dimensions. The sketch is constrained with respect to external reference in order to maintain the associativity with these external references along the guide curve. C-You can vary the cross-section of the sweep along the guide curve by defining the user-sections. The User-section inherits the constraints of the parent sketch and allows you to modify them independently. D-You can specify different dimensions for the sketch at every user section. The surface is computed, adapting to the changing dimensions at each consecutive user-section. Even if the parameters used in a section are changing, the constraint with the external reference element is respected There can not be contradiction between the parameters value and the constraints with external references. Why ? Because both dimensions constrained and constraints on external geometry are specified in the sketch. So if there was contradictions, the sketch would be over constrained and you cannot create an adaptive sweep with a sketch that is over constrained% $Show: Demonstrate the creation of an adaptive sweep using the parametric sketch already created%

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V5 Surface Design

How an Adaptive Sweep is Different from a Simple Sweep? Let us see some salient features of an Adaptive Sweep which makes it different from a Simple Sweep. A. Adaptive swept surface inherits the sketch constraints B. Adaptive Sweep allows you to create intermediate sections (UserSections) on the fly along the guide curve. C. Adaptive Sweep allows you to modify the intermediate sections independently.

C

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B

Instructor Notes:

$Speech: A- the constrained defined in the profile are also applied on the surface (tangency with adjacent surface for instance or verticality of one of the section of the beam) B- the sections defined can be very different depending on the parameters applied Greater control on the shape of the sweep C- when you create the sketch on the fly, we have seen that we are placed in the sketcher and that the sketch plane is automatically normal to the guide so the profile will be normal to the guide/spine%

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V5 Surface Design

Constrained Sketch While creating an Adaptive sweep remember the following key points:

A.

Default constraints: sketch origin

B.

Variations in the Dimensions = dimensions in the sketch

C.

Respect to reference elements = constraints in the sketch

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No coincidence constraint, but a geometric superimposition

Surface is not computed along the guide curve. There is no associativity with the guide curve. Constrained Sketch Creating an Adaptive Sweep (3/3)

Sketch based on the point of intersection of the sketch and the guiding curve.

Surface is computed along the guide curve. Associativity with the guide curve is maintained. Show the creation of adaptive sweep with or without references (L3.CATPart/ADAPTIVE SWEEP)

Instructor Notes:

$Speech: B.C. you can use a sketch with no constraints to create an adaptive sweep. But it is useless. The interest is to be able to vary parameters all the sweep long so parameters have to be defined in the sketch (the same for constraints) C. always beware to constraint the sketch with intersections of sketch plane and ref elements (if necessary: hide the standard sketch elements such as axis, origin ...)% $Show: Demonstrate this last point% $Speech: You can define any number of user section along the guide curve to precise the flow of surface between varying dimensions. In case, you would want to exit the Adaptive sweep command, yet retain the sketch, you can press on To keep the command but keep the sketch button. This is because the constraints of the parent sketch are propagated to all the intermediate sections which can be modified independently.% $Show: DEMONSTRATE some mistakes while computing the adaptive sweep and ask the students what is the cause ? - Inconsistency between spine and guide - last point too fare compared to spine%

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V5 Surface Design

Errors that can be Found While Computing the Sweep

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Error/Warning

Description

Solution

The projection of 3D reference elements may become meaningless along the guide curve and produce unexpected result or sketch inconsistency.

When the sketch has used the projections/intersections from the 3D geometry, which cannot be referred through out the surface flow along the guide curve, CATIA gives this warning on exiting the sketch.

Try to avoid using 3D projections or intersections other than the reference element.

The Moving Plane (perpendicular to the spine )and guide do not always intersect.

When the Point specified in the sketch creation dialog box do not intersect with the guide curve, CATIA gives this error.

Whenever you select the point as an input for sketch center in 3D space, ensure that the plane, normal to the guide at that point, intersects the guide.

Section creation failed or sketch not normal to the spine

A plane normal to the spine and passing by a chosen point cannot be computed

Choose passing points carefully or use the “create section here” tool.

Error occurred during section computation. Please check if the reference elements or constraint of the sections are usable at the current place.

When the sketch has used the projections/intersections from the 3D geometry which cannot be referred through out the surface flow along the guide curve, CATIA gives this error on preview.

Try to avoid using 3D projections or intersections other than the reference element. Ensure that the references are intersected throughout the length of the sweep.

Instructor Notes:

$Speech: First error: use of bad constraint in the sketch Second error: bad point chosen

plane normal to the spine does not intersect the guide

Third error: extend the spine or use “create section here” tool Forth error: reference element is inconsistent during the sweep%

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V5 Surface Design

To Sum Up

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In the following slides you will find a summary of the topics covered in this lesson.

Instructor Notes:

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V5 Surface Design

Choice of Surface You can choose a surface depending upon their characteristics and function: The surfaces are based on a profile and a direction or revolution axis: Extrude, Cylinder, Revolve and Sphere The surface is defined by a few pre-existing sections: Multi-Sections Surface A profile (predefined or not) is swept along a guide curve: Sweep or Adaptive Sweep (in order to manage the shape of the profile along the guide curve) To fill a gap: Fill To simulate a thickness on an existing surface: Offset

Tools

Inputs

Profile

Direction/Axis

Guide Curve

Section

Spine

Extrude

Sphere

Cylinder

Revolve

Optional

Loft

Optional

Sweep

Mandatory

Not Applicable

Loft = Multi-Sections Surface

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You can also choose surface with regards to the wireframe features available. The table shows wireframe required for each type of surface.

Instructor Notes:

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V5 Surface Design

Sweeping a Profile Sweep is a surface generated by sweeping a profile along a guide curve with respect to a spine. The profile can be user-defined or pre-defined. The shape and quality of the sweep depends upon the spine. In GSD the Sweep tool can be used to sweep following profile types:

Spine Guide Profile

Explicit Line Circle Conic

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Sweeping a Profile along a Guide Curve with respect to a Spine

Instructor Notes:

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V5 Surface Design

Extruding or Revolving a Profile An Extrude or a Revolve tool uses a Sketch, a 3D curve, an edge of an existing surface or a solid. However self intersecting profiles or profile which intersect with the axis cannot be used. When a sketch is used to create these features, the normal plane is automatically detected (as with an axis, if included in the sketch). The characteristics of an Extrude and the Cylinder command are similar when a profile is circular. The characteristic of a Revolve and Sphere command are similar when a profile is circular.

Create a Multi-Section Surface

Input

Sketch Profile

3D Profile

Surface Edge Solid Edge Profile Profile

Profiles That can be Used Section Curves

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A surface computed using two or more consecutive sections along a guide curve is called Multi-Section Surface. The guide curve defines the shape of the surface between two sections. This correspondence between the sections (vertices) can also be specified using coupling points on the sections. During the surface generation, the coupling points of one section are automatically connected to the corresponding coupling points of the consecutive section to attain a guided flow between two or more sections.

Guide Curves Sections and Guide Curves

Instructor Notes:

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V5 Surface Design

Create an Adaptive Sweep Surface An Adaptive Sweep Surface is a surface which can adapt to changing dimensions of the parent profile along the defined path.

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While creating an Adaptive Sweep remember the following key points: The sketch of an Adaptive surface has to be a constrained sketch. A constraint is created between the guide curve and the sketch origin so that the sketch origin is always placed on the guide curve throughout the length of the sweep. To make the dimensions of the sketch vary dimension the sketch during its creation. To ensure relative positioning of the sections with reference elements (parallelism, angle, offset) constrain the sketch on the intersections of the sketch plane and the reference elements. To use angle constraints, rather than tangency or perpendicularity constraints.

Sketch keeps its Coincidence with the Surfaces

Instructor Notes:

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V5 Surface Design

Main Tools

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Surface Toolbar 1

Extrude: Extrudes a user-defined profile in a specified direction.

2

Revolve: Revolve a user-defined profile around an axis.

3

Sphere: Creates full or partial spherical surface.

4

Cylinder: Extrudes an implicitly circular profile in a specified direction.

5

Sweep: Sweeps a profile along a path.

6

Adaptive Sweep: Sweeps a parametric profile along a path, allowing the parameters to evolve along the path.

7

Multi-Section Surface: Surface passing through multiple sections.

1

2

3

4

7

5

6

Instructor Notes:

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V5 Surface Design

Exercises Overview 3E You will practice what you have learned by working through exercises Exercise 3E

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You can also practice on the demonstration data that are provided

Instructor Notes:

$Speech: Present the exercise Have the students begin the exercise and note the time Assist students as needed with the exercise 3E: create a sweep adaptive using the sketch specifications given in the student book%

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V5 Surface Design

Case Study: Surface Creation You will practice what you learned, by completing the case study model . In this exercise, you will create the Door inner components. Recall the design intent of this model:

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Create a Door Substrate. The substrate profile needs to be adaptable for design modifications and changes without replacing the original input. Create a broad cross-section surface for an ‘Arm rest’ attached to the front door for design feasibility study. Create a cross-section surface for ‘Key-pad’ (for Electronic control ) at a measured distance from the Arm rest ankle point. Create a single merged part by using Arm rest and the key pad components. Close the ends of the Arm rest & Key-pad with rounded ends.

Instructor Notes:

$Speech: Present the recap exercise. The same manipulations as before are done except that now, you have less instructions and the organization that you give to the part will depend on your study of the data. They have 30 minutes to do this.%

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V5 Surface Design

Exercise 3E: Recap

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Create an Adaptive Swept surface.

Instructor Notes:

$Speech: Review the Exercise Recap slides after the students have attempted the exercises. Try to encourage group discussion on the exercises they have just completed. Discuss the different tools used.% $Ask: Ask if there are any questions about this exercise, any difficulties?%

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V5 Surface Design

Case Study: Surface Creation Recap

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Create a Door Substrate. The substrate profile needs to be adaptable for design modification and changes without replacing the original input. Create a broad cross-section surface for an ‘Arm rest’ attached to the front door for design feasibility study. Create a cross-section surface for ‘Key-pad’ (for Electronic control ) at a measured distance from the Arm rest ankle point. Create a single merged part by using Arm rest and the key pad component. Close the end of the Arm rest and Key-pad with rounded end. Design the door latch. Design a Map-Pocket with the rounded edges.

Instructor Notes:

$Speech: Recap what has been seen in the lesson: Next lesson: now we can go on and begin to learn how to create topologies%

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