Tweet Like Share · 2018-01-23 · Tweet Modelling methodology in C ATIA V5 - Part 5 Posted by Alex...

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Tweet Modelling methodology in CATIA V5 - Part 5 Posted by Alex Fernandes on 01-Dec-2017 12:48:41 Find me on: The modelling stage This is the ×fth article of a series concerning how to implement and use modelling methodology in CATIA V5. In this article, we will discuss the modelling stage in detail. This is the second stage of the creation process; we already have all the elements de×ned in the Skeleton group, so now is the time to start modelling the solid geometry. We discussed, in article 2, the Hierarchy rule that strati×es all elements in a part ×le into diÖerent levels. For the modelling stage, we will be creating elements presented in the last level of the Hierarchy rule; solid geometry features. The fact they all belong to the last level of the Hierarchy rule is does not mean that we can create features at random without having to worry about their order, far from it in fact. Figure 1 represents the model as it was at the end of the Design stage, discussed in articles 3 and article 4. Figure 1 - The Design stage of Angle Bracket part The PartBody The PartBody is a First Level container. In it, we will insert the solid modelling features that de×ne the modelled geometry of a part. Let us have a look at ×gure 2, where we have represented the modelling stage of the Angle Bracket part we have been using in this series. Subscribe to Email Updates EMAIL* [email protected] NOTIFICATION FREQUENCY* Instant Daily Weekly Monthly Subscribe to our Newsletter SUBSCRIBE Recent Posts Modelling methodology in CATIA V5 - Part 7 Modelling methodology in CATIA V5 - Part 6 Training Certi×cation - why do it? Modelling methodology in CATIA V5 - Part 5 CATIA 3DEXPERIENCE contributes to two Construction Awards Birdstrike Simulation The importance of composites in Aerospace and Automotive industries Understanding the risks in the aerospace supply chain Zoom Modelling with MSC Marc Modelling Methodology in CATIA V5 - Part 4 Posts by Topic Aerospace (19) MSC Software (18) Finite Element Analysis (FEA) (17) CATIA (14) Dassault Systemes (10) see all Desktop Engineering Blog Share Share 0 Like 5 Share +44 (0)1993 883555 RESOURCES CASE STUDIES PRODUCTS INDUSTRIES TRAINING NEWS COMPANY

Transcript of Tweet Like Share · 2018-01-23 · Tweet Modelling methodology in C ATIA V5 - Part 5 Posted by Alex...

Page 1: Tweet Like Share · 2018-01-23 · Tweet Modelling methodology in C ATIA V5 - Part 5 Posted by Alex Fernandes on 01-Dec-2017 12:48:41 Find me on: EMAIL The modelling stage This is

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Modelling methodology in CATIA V5- Part 5Posted by Alex Fernandes on 01-Dec-2017 12:48:41Find me on:

The modelling stage

This is the fth article of a series concerning how to implement and use modelling methodology inCATIA V5.

In this article, we will discuss the modelling stage in detail.

This is the second stage of the creation process; we already have all the elements de ned in the Skeletongroup, so now is the time to start modelling the solid geometry.

We discussed, in article 2, the Hierarchy rule that strati es all elements in a part le into di erent levels.For the modelling stage, we will be creating elements presented in the last level of the Hierarchy rule;solid geometry features.

The fact they all belong to the last level of the Hierarchy rule is does not mean that we can create featuresat random without having to worry about their order, far from it in fact. Figure 1 represents the model as itwas at the end of the Design stage, discussed in articles 3 and article 4.

Figure 1 - The Design stage of Angle Bracket part

The PartBody

The PartBody is a First Level container. In it, we will insert the solid modelling features that de ne themodelled geometry of a part. Let us have a look at gure 2, where we have represented the modellingstage of the Angle Bracket part we have been using in this series.

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Recent PostsModelling methodology in CATIA V5 - Part 7Modelling methodology in CATIA V5 - Part 6Training Certi cation - why do it?Modelling methodology in CATIA V5 - Part 5CATIA 3DEXPERIENCE contributes to two

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and Automotive industriesUnderstanding the risks in the aerospace

supply chainZoom Modelling with MSC MarcModelling Methodology in CATIA V5 - Part 4

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Page 2: Tweet Like Share · 2018-01-23 · Tweet Modelling methodology in C ATIA V5 - Part 5 Posted by Alex Fernandes on 01-Dec-2017 12:48:41 Find me on: EMAIL The modelling stage This is

Figure 2 - The Angle Bracket part’s modelling stage

The PartBody is inserted by default in every part le, so we do not have to create a solid body to store oursolid geometry. We will leave multi-body modelling for a later article, so for now all the solid geometry isstored inside the PartBody.

The methodology presented here serves the purpose of building robust models without making theirfeatures either too brittle or too independent. A brittle model has such an intricate balance of associativitybetween features that it becomes uneditable. A model with all features independent is built using amethodology called horizontal modelling and gives the user maximum robustness by sacri cing thebene ts we can get from having feature associativity and design intent is lost upon modi cation. The greatadvantage of CATIA is that it can automatically update all children elements of an existing feature when itis edited, maintaining design intent upon edition. We will use associativity to our bene t, withoutoverdoing it and creating a brittle model in the process.

We are going to create features organized by groups, according to their function in the model and useassociativity to our advantage inside those groups. This will help us maintain design intent upon editionbut in a controlled way, so we can edit the model without it collapsing in a domino e ect of unresolvedfeatures.

 

 The feature groupsFigure 3 represents the PartBody structure. It also summarises the renaming convention used for eachgroup as well as typical features and some rules applicable in each group. All groups are presented in theirlogical order of insertion in a model.

Figure 3 - PartBody structure, with functional groups

Inserting features in a structured logical method will promote correct level of feature dependencies in amodel; these feature dependencies are called “parent-child relationships” and are created every time afeature uses inputs that are de ned by previously created features in the tree.

The usage of a correct methodology helps create these dependencies, only and wherever they clearlyde ne the design intent. It avoids creating unnecessary feature dependencies, making the model morerobust and the tree more exible for reordering if necessary.

Parent-child relationship is sensitive to feature sequence, thus using the correct one will minimize thenumber of features to edit in a part and minimize unresolved features failures.

The logic used for feature de nition is the same to be used for feature edition, starting from the beginningof the tree and going down. As we edit features in the model, their respective children features will beresolved with the new inputs de ned by their parent features.

A structured speci cation tree is easier to analyse and thus easier to edit as well.

The importance of organizing features by groups has to do with guaranteeing a structured modelling inputlogic. The groups, presented in gure 3, are to be interpreted as functional blocks; each one will ful l a roleaccording to the prede ned order presented above.

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Features are inserted in groups according to function inthe part’s modelling sequence. A speci c type of featuredoes not necessarily belong to a speci c group in everysingle model, their use can be typi ed inside speci cgroups but remember features are inserted in a groupaccording to their function in the model and not by type.

Figure 4 presents the PartBody structure for the Anglebracket part that exempli es this methodology in thisarticle.

All features are renamed, according to the group they tinto; considering their function in the part, and renamedaccording to the geometry they de ne and the locationwhere they are de ned. Additional information, such asdiameters and radii, is written in the feature to helpmodel interpretation.

This particular part, the angle bracket, does not requireall the groups presented in gure 3 to be correctlyde ned; for this reason, the Detail group and the Modifygroup are not in the speci cation tree presented in gure4.

 

Core Group

The Core group, black group in gure 3, is the rst set of solid modelling features in a part and de nes themodel’s main shape, its extents and orientation.

Figure 5 - Angle bracket Core group features

The rst features to be inserted should be the ones that use imported reference geometry as inputs, asthese elements drive the geometry of the part when it has to interact with other components at assemblylevel, so these features take precedence upon all others.

In the example, presented in gure 5, there are no imported elements, all core features were insertedusing sketched pro les de ned previously in the Skeleton.

Features in this group can be linked to other elements that were created before them. If you see solidgeometry in the background, then you can link your features to it because they will be other core groupfeatures or imported solid geometry.

De ne additive features rst and then the ones that remove material, subtractive features.

Edit the core features to make large changes to the model’s main shape.

Core group features are pre xed by letter Cxx-

 

Detail Group

The Detail group, presented in blue in gure 3, is the second set of modelling features in a part andde nes smaller geometrical entities that will help de ne the part without signi cantly altering its size andshape.

Features in this group are independent from each other, this way they can be edited, deactivated ordeleted without a ecting other features inside the detail group.

Features in the detail group can be linked to features created previously in the model. If you see solidgeometry in the background then you can link your features to it as long as they are either core groupfeatures or imported solid geometry

Just like in the core group, de ne features that add material rst and then the subtractive features.

Edit the detail features to make small changes to the model’s shape.

Detail group features are pre xed by letter Dxx-

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Hole Group

The Hole group is the third set of solid modelling features in a part’s speci cation tree, it is presented asthe green group in gure 3.

Figure 6 - The Hole group features inserted in the model

The Hole group is a speci cation of the Detail group which has hole features only. It is de ned as anindependent group only to emphasise the importance hole features have in a part.

Features in this group are independent from each other, this way they can be edited, deactivated ordeleted without a ecting other features inside the Hole group.

Features in the Hole group can be linked to features created in previous groups; if you see solid geometryin the background then you can link your features to it as long as they belong to either Core group, Detailgroup or imported solid geometry.

Holes should be renamed with descriptive information of hole type, location, size and threading.

Hole group features are pre xed by letter Hxx-

 

Modification Group

The Modi cation group, orange group presented in gure 3, is the fourth set of solid modelling features inthe tree.  This group de nes the nal features of the part.

Apply replication features are applied rst, usually patterns and mirror features when needed. Facere nement features are applied after replication; usually thickness, draft angle, thread.

Avoid replicating core features as these control the main dimensions of a model, apart for symmetricalparts.

Modi cation group features are pre xed by letter Mxx-

 

Quarantine Group

This group is the fth and nal group of features in a part. It is the grey group in gure 3. It has volatilefeatures that are failure-prone after model editing; for that reason, they are left for last.

Figure 7 - The Quarantine group features in the model

Quarantine features are the last features in a model and should not be linked between them althoughthey are always linked to previously created geometry.

Typical elements include all chamfers, rounds and llets. Start with the largest for each type and proceedto the smaller ones.

Page 5: Tweet Like Share · 2018-01-23 · Tweet Modelling methodology in C ATIA V5 - Part 5 Posted by Alex Fernandes on 01-Dec-2017 12:48:41 Find me on: EMAIL The modelling stage This is

Transformation features (that change the location of geometry or re-scale it) also belong to this group.

Quarantine features should be renamed with descriptive information of type, location and size.

Quarantine group features are pre xed by letter Qxx-

 

In this article, we discussed the PartBody’s structure, naming rules for features and feature sequencingand creation order.

In the next article, we are going to discuss some basic rules for feature de nition while we are in themodelling stage of a part.

Related articles:  

Modelling Methodology in CATIA V5 - Part 1 >>

Modelling Methodology in CATIA V5 - Part 2 >>

Modelling Methodology in CATIA V5 - Part 3 >>

Modelling Methodology in CATIA V5 - Part 4 >>

 

 Learn more about CATIA V5 >>

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