catia破面修复教程.ppt

Copyright DASSAULT SYSTEMES 2002,1,Healing Assistant,CATIA Training Foils,Version 5 Release 9 June 2002 EDU-CAT-E-HA1-FF-V5R9,Copyright DASSAULT SYSTEMES 2002,2,Course Presentation,Objectives of the course In this course you will learn why, when and how to use the application HA1 Healing Assistant Targeted audience All designers, especially tooling designers Prerequisites Wireframe & Surface Design,0.5 Day,Copyright DASSAULT SYSTEMES 2002,3,Table of Contents,Introduction to Healing Assistant p.4 Why do you need healing ? p.5 Some information on the Join operator p.6 How to choose a merging distance p.9 Workbench presentation p.11 Accessing the workbench p.12 The user interface p.13 Methodology for healing p.14 Model analysis with Healing Assistant p.15 Face Checker p.16 Surface Connection Checker p.17 Creating Topology p.20 Repairing invalid surfaces p.21 Face Smooth p.22 Repairing bad topology situations p.23 Checking for free sides p.24 Closing a topology p.27 Fixing free sides p.28 Local Join p.31 The healing operator p.32 Local Healing p.33,Copyright DASSAULT SYSTEMES 2002,4,Introduction to Healing Assistant,In this lesson, you will see some general information about : The Need for Healing The Join Operator The Merging Distance,Copyright DASSAULT SYSTEMES 2002,5,Healing = process of creating a valid V5 closed model out of any type of data, even not valid,Problems linked to imported data: accuracy uncontrolled validity criteria different from those of V5 data quality downgraded during transfer user mishandling (losses, duplications, …),Why Do You Need Healing ?,Foreign data: IGES, STEP, CATIA V4, other,,,,,,Closed model,Tooling Design,NC Manufacturing,Rapid Prototyping,Additional Design,Simulation,,,,,,Copyright DASSAULT SYSTEMES 2002,6,STEP 1 is done considering a tolerance parameter called merging distance. All surface boundaries are compared to find those which are close enough to become shared edges. PROBLEM: surface boundary curves are not always clean enough to sort out the shared edges,Some Information on the Join Operator (1/3),,JOIN is the main operator for the creation of topology Joining surfaces is done in 2 steps,d merging distance : edge is not shared, boundaries remain free sides,STEP 2 consists in giving consistent orientations to faces which have a shared edge. PROBLEM: it is not always possible to propagate a consistent orientation all over the Join.,Surface 2 is included to the Join with a flag specifying that the orientation of the face is opposed to the orientation of the original surface (the surface itself is not changed),,,Copyright DASSAULT SYSTEMES 2002,7,Problem 1: examples of surfaces with self-intersecting edges Most common case: surfaces with a thin area. Depending on the requested merging distance, edges in the thin area are considered as superimposed (impossible to find a single common vertex). This situation may disappear if the merging distance is decreased. Other situations which may exist in imported data :,Some Information on the Join Operator (2/3),,,,Incorrect boundary (the shaded display is also incorrect),Very small curves in the boundary (gives a multiple vertex),Not supported topology (example: surface lying on a closed surface),Copyright DASSAULT SYSTEMES 2002,8,Problem 2: examples of bad topology Most common case: small overlap Other case: no inside/outside definition possible (Moebius type situation),Some Information on the Join Operator (3/3),The edge is shared (d merging distance) The orientation of surface 2 is set according to the orientation of surface 1, but there is an ambiguity (cusp or no cusp?). If the wrong direction is chosen, an inconsistency may appear later. This situation may disappear if the Merging distance is increased.,,,,,,,,d,1,2,,,,,,?,?,It is not possible to define a consistent orientation all over the surface.,For example, the inconsistency may appear when adding surface 3 to the join.,Copyright DASSAULT SYSTEMES 2002,9,How to Choose a Merging Distance (1/2),you must take into account the accuracy of the data to Join: if you choose a strict tolerance, the Join has many free sides and it takes time to correct them also sometimes Join does not work with a strict tolerance (bad topology) On the other hand if you release the tolerance too much, some gaps are hidden but the geometry still has gaps and may be unusable for later processing For example gaps may cause visible marks on the manufactured part remember that a gap may be: or: finally Join removes all edges which are smaller than the merging distance, which can cause problems if the merging distance is too high The suppression of small curves may later produce invalid faces (with self-intersecting edges),Copyright DASSAULT SYSTEMES 2002,10,Practical tips: Start with a low value of the merging distance Increase the value only if needed to avoid bad topologies Once you have a Join you may still increase the value of the merging distance to hide gaps (。