tutorial.pdf

CADfix 9.0

Introductory User Tutorial

Version 1.0 Date: 9 Nov 2012

©2012 TranscenData Europe Ltd CADfix 9.0 Introductory Tutorial Page 1 of 49

Contents 1 Introduction and Scope of Tutorial ....................................................................... 3 2 Different ways to use CADfix ............................................................................... 3 3 Mode 1: Fully Automatic Translation ................................................................... 4

3.1 CADfix Terminology: The CADfix Wizard Process ....................................... 4 3.1.1 Import .................................................................................................... 5 3.1.2 Repair ................................................................................................... 5 3.1.3 Transform .............................................................................................. 5 3.1.4 Prepare ................................................................................................. 5 3.1.5 Export .................................................................................................... 5

3.2 Performing a Fully Automatic Translation ..................................................... 6 3.2.1 File Import Options ................................................................................ 8 3.2.2 Select Target System for Export ........................................................... 8 3.2.3 Select Target Format for Export ............................................................ 8 3.2.4 Select Target Quality Standard ............................................................. 9 3.2.5 Changing Wizard Process Options ....................................................... 9

3.3 Just importing the model with no processing ................................................ 9 3.4 When the Automatic Translation process is not successful ........................ 10

4 Mode 2: Diagnostic Driven Interactive Processing ............................................ 11 4.1 CADfix Terminology: Topology and Geometry ........................................... 11 4.2 CADfix Basics: Viewing the Model ............................................................. 13

4.2.1 Connectivity display ............................................................................ 13 4.2.2 Picture controls ................................................................................... 14 4.2.3 View controls ....................................................................................... 15

4.3 Overview of Diagnostic Driven Interactive Processing ............................... 16 4.3.1 Scan Results/Problem Tree ................................................................ 16 4.3.2 Severity Indication ............................................................................... 16 4.3.3 Diagnostics Scan Target ..................................................................... 17 4.3.4 Diagnostic Summary ........................................................................... 17 4.3.5 Problem Description ............................................................................ 17 4.3.6 Possible Fix Methods .......................................................................... 18

4.4 Diagnostic Driven Manual Repair ............................................................... 19 4.4.1 Example 1 - Closing a Large Edge Gap .............................................. 19 4.4.2 Example 2 - Building Missing Faces and Solids .................................. 25

4.5 Diagnostic Driven Manual Prepare and Export Processing ........................ 29 4.5.1 Example 3 - Faces with Intersecting Loops (Partially Collapsed) ........ 30 4.5.2 Example 4 - Reducing High Degree Surfaces ..................................... 35 4.5.3 Example 5 - Fixing Self-intersecting Surfaces ..................................... 38

5 Mode 3: Manual Interactive Processing ............................................................. 42 5.1 CADfix Basics: Screen picks ...................................................................... 42

5.1.1 Dynamic Selection .............................................................................. 43 5.1.2 Basic Selection .................................................................................... 45 5.1.3 Smart Selection ................................................................................... 45

5.2 The Diagnostic Checks Tab ....................................................................... 47 5.2.1 Filtering the Criteria ............................................................................. 48

5.3 The Tools Tab ............................................................................................ 49


1 Introduction and Scope of Tutorial The aim of this tutorial is to give new CADfix users some basic guidance on getting started with CADfix. It will cover the various ways in which CADfix can be used to translate and process models. The tutorial is based on a hands-on approach that uses a set of example models that can be found with this tutorial. We recommend that you follow the steps of the tutorial whilst processing the various example models. Whilst this tutorial aims to give the user enough information to get started with CADfix and perform some of the more common operations, it does not aim to cover all aspects of CADfix. In particular the Manual Interactive Processing mode is only briefly touched upon. For more complete details on using CADfix please refer to the CADfix training material and/or the on-line HTML help manual.

2 Different ways to use CADfix CADfix has been designed around the principle of providing users with alternative levels of using the program, depending on their needs, experience and expertise. There are three main levels, or modes, of using CADfix. These three modes increase in the amount of knowledge and expertise that is required from the user. It is recommended that users start with the simplest level and progress through to the more complex levels as they require.

Mode 1. Fully Automatic Translation The simplest mode of using CADfix is the Automatic Model Translation mode, which attempts to process a model from input CAD system to the target CAD system with the minimum of user input. For the cases where an automatic translation is not possible, usually due to


problems with the CAD model, then the Automatic Model Translation mode will automatically put the user into the next level of CADfix use, the Diagnostic Driven Interactive Processing.

Mode 2. Diagnostic Driven Interactive Processing For models that do not process automatically, or if users want to have more control over the translation process, then the Diagnostic Driven Interactive Processing mode is the next level of using CADfix. In this interactive mode the user will see the model displayed and be able to query its structure. The user is guided through the problems in the model based on automatic diagnostic scanning. Once all problems have been resolved by the user, with help and advice from the CADfix Wizard, then the model can be exported. For more complex problems that are not easily resolved through the diagnostic driven process, the user may then use the lowest level of processing with CADfix.

Mode 3. Manual Interactive processing This mode allows the user full access to all the tools available in CADfix. It requires more knowledge and experience from the user, so is not recommended for the novice. This mode is primarily for cases where the diagnostic driven processing could not identify the problem or the problem requires an unusual fix that was not on the list of recommended solutions from the diagnostic scan. This mode also allows the user access to the interactive model simplification tools such as hole removal, face joining, splitting, and more (provided these are available in the CADfix license).

Each of these modes of working with CADfix will be explained in the following sections. Each section will make use of example models that are supplied with this tutorial.

3 Mode 1: Fully Automatic Translation The Fully Automatic Translation mode is the simplest mode of using CADfix and requires the bare minimum of inputs from the user. It uses the CADfix Wizard process to automatically control the translation process.

3.1 CADfix Terminology: The CADfix Wizard Process

The engineer’s requirement is to take a CAD model from one ‘upstream’ system and to be able to re-use it in another ‘downstream’ system, often for a different application. In CADfix this translation process has been broken down into five


distinct steps – Import, Repair, Transform, Prepare and Export.

This process is controlled and automated by the CADfix Wizard, which forms the heart of the Fully Automatic Translation mode.

3.1.1 Import

A model can be imported into CADfix from a number of native CAD system formats and also neutral formats such as STEP and IGES. By default, the import stage will also perform some rudimentary model fixing operations, such as merging duplicate points and edges at an appropriate tolerance.

3.1.2 Repair

The repair stage attempts to stitch the model into a valid solid, or shell of faces, by predominately fixing the model TOPOLOGY.

3.1.3 Transform

Once the model has been topologically repaired to a valid solid, or shell of faces, the optional transform stage can be used to defeature the model as required for the downstream application. For example, the model may need to be defeatured by removing all short edges and sliver faces to facilitate meshing in the downstream system.

3.1.4 Prepare

This is the process of preparing (or flavouring) the model GEOMETRY so that it can be successfully imported into the downstream system.

3.1.5 Export

Having prepared the model to suit the requirements of a particular downstream system the model is exported by writing a file in the appropriate format.


The five steps of the CADfix process can each be configured by the user through the Process options settings.

3.2 Performing a Fully Automatic Translation

After starting CADfix there are just four steps to performing a simple automatic translation:

1. Select the import file type (e.g. IGES) 2. Select the file to process (e.g. auto.igs from the tutorial examples) 3. Select the target system (e.g. IDEAS NX 12. Note, format will default to IGES) 4. Press “Go” to start the translation

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Once the translation has started a Progress Monitor dialog will appear that will show how the translation is going:


After the Import stage of the automatic processing has been completed the model will be displayed in the CADfix graphics window:


The Progress Monitor will show the model passing through the Repair and Prepare stages of the Wizard process and finally being exported by the Export stage. The end result will be a fully automatically processed model ready to take into the target system, in this example I-DEAS NX 12. The following sections explain some of the options that can be changed during the automatic translation process.

3.2.1 File Import Options

Each file format that can be imported has a set of options for configuring the import. The options can be found under the “Import” link in the Wizard Process options:

These options typically contain settings for importing unused/free lines and points, attributes such as colour and label. These options only need to be changed if the model did not import the expected parts. For example if a Pro/E model contains open shells as well as solids then the default setting is to only import the solids.

3.2.2 Select Target System for Export

The target system can be selected from the pull-down menu of available systems. When a system is selected the format will also be changed automatically to the recommended value. Some systems will appear greyed out if they are not available in your CADfix licence file.

3.2.3 Select Target Format for Export

The target format can be selected from the pull-down menu of available formats for the selected system. CADfix automatically selects the recommended option when you change the target system.


3.2.4 Select Target Quality Standard

If a target quality standard is selected then CADfix will automatically run a diagnostic scan against the quality standard AFTER the model processing has finished. This option does not change the way that the model is translated; it only controls what additional criteria should be scanned against. The quality standard can be one of the fixed systems (for example the Japanese automotive PDQ standards JAMA), or a user defined quality standard.

3.2.5 Changing Wizard Process Options

CADfix will automatically configure the CADfix Wizard process settings based on the selected import file and the target system. To see and/or modify the settings for the various stages of the Wizard Process use the Process options

Click in the checkbox to turn each step on off. Click on the blue link next to the checkbox to see the options for that stage of the process. For most cases you will not need to modify these process options.

3.3 Just importing the model with no processing

If you do not want to process a model using the Fully Automatic Translation mode then there is an option to just import the model only. When the Import only option is active then the Process options will be temporarily disabled.


3.4 When the Automatic Translation process is not successful

Most CAD translations will process fully automatically through CADfix without interruption, but if CADfix does detect a problem with the data during the automatic Wizard processing that requires user intervention then the process is halted and CADfix switches to the Diagnostic Driven Interactive mode.


4 Mode 2: Diagnostic Driven Interactive Processing When the Fully Automatic Translation mode finds a problem with the model that cannot be automatically fixed then CADfix will switch into Diagnostic Driven Interactive Processing mode. The first thing that CADfix will do when it switches from Automatic mode into this mode is run a diagnostic scan of the current model. These diagnostics will then be used to guide the user to interactively fix the problem

Results of Diagnostic Scan

4.1 CADfix Terminology: Topology and Geometry

Before progressing further with the Diagnostic Driven Interactive Processing it will be helpful to introduce and explain some more CADfix terminology. A CAD part is typically made up from two types of entity: topology or geometry. There are various naming conventions in use today for the topological and geometrical entities of a CAD part. The following diagram illustrates how CADfix refers to these entities.


• Body

A CADfix body is a collection of faces that (usually) form a closed shell. The faces may form more than one closed shell in which case one shell will be the outer shell and the other shell(s) would be internal voids. A body is a topological entity as it just represents a collection of other entities.

• Face A CADfix face contains both an embedding surface and a collection of edges that (usually) form a closed loop. The edges may form more than one closed loop in which case one loop will be the outer and the other loop(s) will be internal holes. A face is a topological entity as it just represents a collection of other entities.

• Surface A CADfix surface defines the 3D “shape” of the interior of a face. There are several types of surface in CADfix including: NURBS, analytic surfaces (plane, cylinder, cone, sphere, torus) and blends (Coons, Barnhill and Gregory). A NURBS surface is a self-contained entity that does not refer to any other entity. The analytic surfaces refer to point entities to define their axis and/or centres, and the blend surfaces refer to 3, 4 or 5 edges. A surface is a geometrical entity as it just represents the 3D position of an entity.

• Edge A CADfix edge defines the 3D “shape” of the boundary of a face or a wire frame edge. The 3D definition of an edge is contained within the edge itself,


unlike other systems that use a separate curve entity. The start and end positions of an edge are defined by referring to two points. An edge is both a geometrical entity (because it contains the 3D definition) and a topological entity (because it contains the points that connect it to other edges).

• Point A CADfix point is defined by 3D position (X, Y Z). A point is both a geometrical entity (because it contains the 3D position) and a topological entity (because it is used to connect edges together).

CADfix does not have explicit entities to represent shells, loops or curves although these terms will be used to describe some of the problems found in a CAD model.

4.2 CADfix Basics: Viewing the Model

Once a model has been imported into an interactive session of CADfix then the user is able to view and display the model in various ways. The common view and display controls are available from the icon bar.

View controls: dynamic control, spin centre, frame image, zoom

Basic Display

Expand Display options

Picture controls: wipe, wipe last, wipe menu, and repaint

Display types: points, edges, surfaces, faces and bodies

4.2.1 Connectivity display

CADfix will automatically display a model as a colour coded wire frame model. The colours of the edges tell you how many faces are connected to each edge, and are the most informative way of displaying a model. In the majority of cases a “healthy” model will have two faces connected to each edge and the edges will be drawn in green. Gaps or overlapping parts usually result in red edges (connectivity 1) or yellow or blue edges (connectivity 3 and 4). Note: the colours used for this connectivity display can be changed through the Display Settings dialog found under the View menu.



4.2.2 Picture controls

CADfix has a very flexible approach for displaying the model in various ways. The row of five icons and drop-down menus in the icon bar under the Advanced display

options ( ) allow the user to build up a “picture” of the model by “adding” new display types to the current “picture”.

The drop-down menus next to each display icon contain alternative ways of display the type of entity. For example, points can be displayed with their CADfix label, or surfaces can be displayed shaded, or faces and bodies can be displayed as wire frame or partially transparent. Take a look at the drop-down menus to see the full range of display type for each entity. Display types can be removed or “wiped” from the current picture using one of the 3 “wipe” icons in the icon bar.

Display points

Display edges

(connectivity)

Display surfaces (grids)

Display faces

(shaded)

Display bodies

(shaded)

4.2.3 View controls

CADfix allows the model view to be changed dynamically by using the mouse. Simply click a mouse button inside the graphics window and drag. The three mouse buttons have different actions. The default actions are:

• Left button: Rotate view • Middle button: Pan view • Right button: Zoom view (move left to right)

When the mouse button is released the dynamic viewing will stop. For better performance when viewing large models hold down the Control key or toggle the dynamic manipulation icon in the icon bar The view controls can be customised using the View Controls dialog found under the main View menu. If you prefer the view controls to be similar to another system, say your usual CAD system, then there is an Emulation mode that supports most of the common CAD system settings.

Note that the I-DEAS controls of holding down F1, F2 or F3 are always available.


4.3 Overview of Diagnostic Driven Interactive Processing

The Diagnostics mode menu is contained in the third tab of the CADfix tool set. When CADfix invokes the Diagnostic mode it automatically Scans the model and presents the user with all of the information required to complete the processing.

4.3.1 Scan Results/Problem Tree

The top half of the Diagnostics Panel shows the results of the automatic scan and provides a list detailing the problems encountered including:

- a description of the problem - an indication of the severity of the problem - the number of entities exhibiting this problem

Items listed within the tree structure can be selected with a left hand mouse button click and this will highlight the problem visually on the model in the graphics window. The selection of an item in the top tree triggers the display of the different possible fix methods in the bottom half of the Diagnostics panel.

4.3.2 Severity Indication

The severity of the issues found is identified by a colour-coded circle that provides a guide as to the severity and order in which they should be resolved.

(red) Is a serious issue that must be resolved (yellow) A less serious problem to be considered (cyan) May not be an issue but the user is informed

The example shown indicates that the model has a serious ‘Connectivity’ problem with 6 poorly connected edges. There are also 12 unused faces (i.e. do not form part of any solid body) but this classed as less serious than the connectivity issue.


4.3.3 Diagnostics Scan Target

Immediately below the Diagnostics results window is an indication of criteria against

which the Diagnostic scan has been performed, e.g. If the model fails to repair to a valid stitched solid part then the scan is performed against the “Valid Model” criteria which looks for fundamental topological and model construction issues that could prevent the solid being built. If the model is successfully repaired but subsequent flavouring and export operations identify edge or surface geometry issues that could be an issue for the downstream target system, then the scan is undertaken against the “Target System” criteria. It is possible to re scan the model manually against the specified target at any point by selecting the button.

4.3.4 Diagnostic Summary

A Diagnostic Summary is presented to the user below the Diagnostics results window. This provides a summary of the overall scan results and gives advise to the user. You can minimize or reopen the text in the Diagnostic Summary at any time by selecting the Diagnostic Summary >> link.

4.3.5 Problem Description

When a specific problem is selected from the main Diagnostic Results tree the text shown in the Problem Description window provides specific information on the problem. Many problems have an accompanying image as shown opposite that can be accessed by clicking on the ‘book’ icon with the left hand mouse button. The individual problem descriptions can be minimised or opened by selecting the link for Problem Description >>


4.3.6 Possible Fix Methods

When a specific problem is selected for resolution from the main Diagnostic Results tree, the bottom of the Diagnostics panel presents the different fix methods available. The possible fix methods are ordered with the likely preferred or best options at the top of the list. However the user should be aware that problems are specific to individual models and some of the alternative resolutions might be more appropriate. After all, if the first suggested fix always worked

then it would have been automated in the Wizard! The example opposite shows ten different fix options for resolving model connectivity problems.

Once the user has decided which fix method to use it is selected with a left mouse button click.

The specific fix controls and parameters made available at the bottom of the Diagnostics panel and the fix can be made. The image opposite shows the display of the fix parameters when the user selects Stitch at coarser tolerance from the menu. If the chosen fix does not achieve the required resolution, then the user can go back to the list of alternative fixes by selecting the double arrow icon, or by selecting the problem description again in the top Diagnostics Results tree. Once a fix operation has been completed CADfix will automatically update the model scan and Diagnostic Problem tree to reflect the changes.


4.4 Diagnostic Driven Manual Repair

If a model fails to repair it is usually as a result of a serious issue such as completely missing entities, excessive edge gaps and badly distorted geometry. The following examples demonstrate how such issues can be resolved using the CADfix Diagnostic driven repair process.

4.4.1 Example 1 - Closing a Large Edge Gap

This example demonstrates the use of CADfix to complete the repair of a model where a large edge gap exists that exceeds the automatic stitching tolerance. Step 1. Set up and start the Automatic Translation

1. Start CADfix and select STEP as the file type for processing 2. Select the file edge-gap.stp 3. Select the target system as IDEAS NX 12 and format IGES 4. Press “Go” to initiate the translation

Numbers refer to screen image below. (also see section 3.2)

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Step 2. Switch to Diagnostic Mode and Review Status

5. Notice the “Display” and “Work set” are showing “ALL” The automatic process stops after the Repair stage because CADfix fails to build a solid body. CADfix launches into the Diagnostic mode with the screen as shown below. A view of the model is given in the main graphics window with the Diagnostics panel on the left hand side.

The progress monitor displays messages as the CADfix Wizard translates the part. You can scroll back to review these messages if required and will notice the message that CADfix “Failed to build any new solid bodies” and that the Prepare and Export processes were skipped. When you have finished reviewing the information close the Progress Monitor by selecting the ‘Close’ button. It can be reopened at any stage using the icon at the top of the CADfix screen.

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The Diagnostic Summary presents a summary of the status of the processing along with recommendations for the next steps including:

Resolve first model problem or Change repair options Continue with Wizard

The Diagnostic Summary information should be reviewed in conjunction with the graphical display of the model to determine the best possible course of action. Step 3. Isolate and Investigate the Problem It is obvious from the model display that the reason the model failed to build a solid body is the excessive edge gaps indicated by the red edges on the model display.

Notice the model summary in the bottom right hand corner of the CADfix window shows a globe (for the whole model) and summary of total parts in the model i.e. 9 faces, 9 surfaces, 25 edges and 17 points:

Go to the Diagnostic Results Tree and select Poorly connected edges. This highlights the problem edges on screen and presents below the possible resolutions available. The “Work set” is now showing “SELE” and a bar above the Display window shows the Basic Selection icon depressed and the summary of parts selected i.e. 3 edges: The “Basic selection”

mode has been entered

The problem parts have been isolated for fixing.


Use the dynamic display tools to zoom in on the area of the gap and measure the distance with the measurement tool. The measurement tool shows a gap between the two vertex points of 0.17mm. This is outside of the range that CADfix considers to be suitable for automatic stitching of this part by the Wizard and hence requires manual interaction to resolve. One option might be to build a face to fill the gap. However the creation of such a small sliver face could introduce further problems downstream. The most suitable option in this case is to merge the points and edges in the local area at a coarser tolerance. Step 4. Repair the Problem Select Stitching at coarser tolerance from the possible fix list and CADfix automatically presents the controlling parameters and options as shown below.

The 3 poorly connected edges are already isolated for repair, as indicated by the ‘Edges found: 3’ message. Check the tolerance to be used and notice that it is too small to close the 0.17mm gap as measured previously. Enter a new tolerance value for the stitch operation of 0.18mm. Press “Fix” to stitch the gap at the new tolerance.


Step 5. Problem Resolved The manual stitching operation repairs the large edge gap. The updated model connectivity display shows the model as being well connected (all edges are now green).

CADfix re-scans the model against the “Valid Model” target and new results are displayed. There are still Unused Faces detected in the model because a solid body has not yet been built. However, CADfix detects the improved condition of the model and that it could continue and automatically build a solid from the closed shell.


Step 6. Continue with Automatic Processing Prior to using the Quick-fix tool CADfix asked if it should attempt to build a solid and continue with the automated Wizard processing. Now CADfix has detected that the model is repaired. Select “Yes” and CADfix will automatically continue with the automatic translation process. The model successfully flavoured and exported to an IGES file flavoured for IDEAS. End of example.


4.4.2 Example 2 - Building Missing Faces and Solids

This example demonstrates the use of the CADfix Diagnostics driven repair process to resolve a model repair failure where a face entity is completely missing from the CAD model and this prevents a valid solid being built. Step 1. Set up the Automatic translation task

1. Start CADfix and select STEP as the file type for processing. 2. Select the file face-build.stp 3. Select the target system as Pro/E CREO 1.0 native 4. Press “Go” to initiate the translation


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Step 2. Switch to Diagnostic Mode and Review Status The automatic process stops after the Repair stage because CADfix fails to build a solid body. CADfix launches into the Diagnostic mode with the screen as shown below. A view of the model is given in the main graphics window with the Diagnostics panel on the left hand side.

Review the CADfix progress monitor and you will see that CADfix fails to make a solid model. When you have finished reviewing the information close the Progress Monitor by selecting the ‘Close’ button. Step 3. Isolate and Investigate the Problem Review the Diagnostic Summary information in conjunction with the graphical display of the model to determine the best possible action. It is obvious from the model display that the reason the model failed to generate a solid body is the ‘hole’ in the model indicated by the red edges on the model display. In this case you should go to the Diagnostic Results Tree and select Poorly connected edges. This highlights the problem edges on screen and presents the possible resolutions available as shown below.


It is apparent that there is a missing face the first option of Stitching at coarser tolerance will not help. The best option is to attempt to build the missing face. Step 4. Repair the Problem The loop of 4 lines are in the “SELE” set and you can select the Build Faces option from the “Possible fix methods” list. When selecting Build Faces CADfix presents the controlling parameters and options as shown opposite. The 4 poorly connected edges are already isolated for repair. Press “Fix” to build the missing face. CADfix automatically finds a closed loop of edges and builds the missing face as required.


Step 5. Problem Resolved You will be presented with an Accept or reject parts window which in situations where more than one surface is being built gives you the opportunity to review the results before acceptance. Once the face has been built, the updated model connectivity display shows the model as being well connected (all edges in green).

CADfix re scans the model against the “Valid Model” target and new results are displayed. There are still Unused Faces detected in the model because a solid body has not yet been built. However, CADfix detects the improved condition of the model and that it could continue and automatically build a solid from the closed shell. Step 6. Continue with Automatic Processing CADfix asks if it should attempt to build a solid and continue with the automated Wizard processing. Select “Yes” and CADfix will automatically build a solid and continue with the automatic translation process. The solid is built and the model successfully flavoured and exported to native Pro/E. End of example.


4.5 Diagnostic Driven Manual Prepare and Export Processing

The CADfix automatic prepare for Export (or flavouring) process will attempt to automatically resolve geometry issues to make sure that the model meets the requirements of the downstream system. There will be occasions where the model problems are such the automatic approaches are insufficient and user intervention is required to resolve the issues. The following examples demonstrate the use of the Diagnostic driven prepare process to address typical geometry issues that could exist after a model has been run through the Wizard. In these examples the Wizard Prepare process would normally fix all of the problems, so for the purposes of the tutorial we will only Import and Repair the files before doing a manual Scan. We are assuming that the prepare process has already been run and problems have been found but not fixed.


4.5.1 Example 3 - Faces with Intersecting Loops (Partially Collapsed)

This example demonstrates the use of the CADfix to resolve an issue with an apparently good model that effects a specific downstream application. When this model is processed fully automatically it successfully exports to the ACIS format, passing the ACIS Body Checker. However when it is used in a meshing application there is a meshing failure for a particular surface that contains touching or self intersecting loops. Step 1. Set up the Automatic translation task

1. Start CADfix and select STEP as the file type for processing. 2. Select the file partial-collapse.stp 3. Select the target system to be ACIS 22 4. Change the Process options >>, turning off Prepare and Export so that CADfix will only Import and Repair the model 5. Press “Go” to initiate the translation


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Step 2. Switch to Diagnostic Mode and Scan for Problem Face The model imports and repairs to a valid solid body as shown below.

You now need to perform a Diagnostic Scan to look for the problem face. Close the Wizard progress monitor and select the CADfix Diagnostic tab to go into Diagnostic mode.

CADfix is already set up to scan against the target system criteria Select the Scan button to run the scanning process. The results of the scan are presented in the Diagnostic results window with a single partially collapsed face identified as shown below. Notice that this is classed as a less serious model problem and highlighted with a yellow indicator. This is because the feature is not a critical error that prevents the


model from being exported, and so it is still a valid model. The problem is more of an application specific issue, in this case a meshing failure.

Select the Partially collapsed faces problem and the face is highlighted on the model. The face clearly consists of two loops of edges that intersect at a common vertex point. The face and vertex point are highlighted on the above image. Step 3. Repair the Problem Having selected the partially collapsed faces problem there are several possible resolution methods listed:

Fix partially collapsed faces Create/edit faces Split face by sketching Split faces with a plane Collapse points Fix T-junctions intersections Sharp corner angle

Selecting the first option Fix partially collapsed faces will be unsuccessful because this automatic solution is looking for virtually collapsed faces that have a definitive split boundary dividing them into more than one area. Upon inspection the solution required should split the face in some way or other. In this instance a satisfactory solution would be to split the face into two equal parts by a line running through the over-used vertex point.


Two split methods are available, either by sketching a line on the face or splitting with a planar surface, and both are applicable in this case. Select the option to Split faces with a plane as the fix method to access the repair dialogue.

The face is automatically selected and you now need to select or create a plane to split the face. In this case there is no existing plane to use to split the face so select the ‘New plane’ button. Now screen pick to select the three points to define the plane. Select the over-used vertex point that is already highlighted on screen and two other vertex points as shown on the image below to create a plane running through the face.


Select Apply and the face is split in two.

The partially collapse face issue has been resolved and the model could now be re-exported to ACIS for the downstream meshing system if required. End of example.


4.5.2 Example 4 - Reducing High Degree Surfaces

This example demonstrates the use of Diagnostic Driven processing to reduce the degree of some surfaces to suite the needs of a particular CAD system. This is not necessarily a serious problem in most CAD to CAD translations. Step 1. Set up the Automatic translation task

1. Start CADfix and select STEP as the file type for processing. 2. Select the file trim-surf.stp 3. Select the target system to be CADDS 5 4. Change the Process options >>, turning off Prepare and Export so that CADfix will only Import and Repair the model 5. Press “Go” to initiate the translation


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Step 2. Switch to Diagnostic Mode and Scan for Problem Face The model imports and repairs to a valid solid body as shown below.

You now need to perform a Diagnostic Scan against the CADDS export criteria. Close the Wizard progress monitor and select the CADfix Diagnostic tab to go into Diagnostic mode.

CADfix is already set up to scan against the target system criteria Select the Scan button to run the scanning process. The results of the scan are presented in the Diagnostic results window with 5 high degree surfaces identified as shown below. Notice that this is classed as a serious model problem and highlighted with a red indicator. This is because the feature is a critical error for CADDS 5.


Select the High-degree surfaces problem and the 5 faces along with their surfaces are highlighted on the model as shown above. Step 3. Repair the Problem Having selected the partially collapsed faces problem there are several possible resolution methods listed:

Reduce max. NURBS degree Simplify NURBS surfaces

The problem could be corrected by either of the fix methods, but for the purposes of this example we will assume that the system to which we are exporting only accepts NURBS geometry and we do not want to simplify to primitive forms. Select the first fix method to reduce the NURBS degree. The model can now be exported to CADDS for the downstream system as required. End of example.


4.5.3 Example 5 - Fixing Self-intersecting Surfaces

Models often contain surfaces that are distorted, sometimes folded or twisted or discontinuous but in this case self-intersecting. CADfix deals with many of these surface problems automatically in the flavouring process but this example demonstrates how they could be dealt manually if required. Step 1. Set up the Automatic translation task

1. Start CADfix and select STEP as the file type for processing. 2. Select the file folded.stp 3. Select the target system to be Neutral - Generic STEP 4. Change the Process options >>, turning off Prepare and Export so that CADfix will only Import and Repair the model 5. Press “Go” to initiate the translation


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Step 2. Switch to Diagnostic Mode and Scan for Problems The model imports and repairs to a valid solid body. You now need to perform a Diagnostic Scan to look for the problem face. Close the Wizard progress monitor and select the CADfix Diagnostic tab to go into Diagnostic mode.

CADfix is already set up to scan against the target system criteria for Generic STEP export. Select the Scan button to run the scanning process. The results of the scan are presented in the Diagnostic results window as shown CADfix has detected 4 Folded surfaces. Notice that the problem types are classed as a less serious model problem and highlighted with a blue indicator. This is because the feature is not a critical error that prevents the model from being exported, and so it is still a valid model. The problem is more of an application specific issue that may or may not need to be addressed.


Select Folded surfaces and you will see the problem surfaces displayed on screen as shown in the above image. Use the dynamic viewing capabilities to zoom into the corner of one of the surfaces and the problem will be apparent.

Step 3. Repair the Problem Surfaces Select the Self-intersecting problem from the Diagnostics results tree and the possible resolution methods listed:

Simplify NURBS surfaces Trim-back NURBS to face Reduce knot count Smooth surfaces Re-embed faces Split face along iso-line Split face by sketching Refit faces

In many cases it is often possible to convert the surface into another representation, such as a primitive plane, cylinder or sphere, and in doing so this will move the problem. Select Simplify NURBS surfaces to access the controlling parameters and options.


The four problem surfaces are already isolated. Press the Fix button and CADfix tests whether the problem surfaces can be represented by a primitive surface within the specified tolerance value, and if so converts them. Note that this conversion tolerance can be changed as required by the user. In this case all four surfaces can be converted to primitive spheres at the 0.01 tolerance.

The folded surface issues have been fixed. End of example.


5 Mode 3: Manual Interactive Processing The previous mode of operation, Diagnostic Driven Interactive Processing is designed to guide the user to the best way to interactively fix any problem in a model. However there will be cases where the problem requires an unusual fix that is not on the recommended list of fixes. Or as a more experienced user you may want to skip the use of the diagnostic driven process and manually Find and Fix the problems. The third mode of using CADfix, Manual Interactive Processing allows the user access all the tools available within CADfix. The following sections provide a brief overview of how to access the manual tools.

5.1 CADfix Basics: Screen picks

Many tools within CADfix require the user to identify entities by picking them from the screen. CADfix has a convention for letting the user know when a screen pick can be made. Nearly all tools that allow a screen pick will have an entry field that is coloured yellow when it is active.

Active screen pick

Disabled screen pick

When you see an entry field like this then you can move your mouse onto the graphics window and select an entity. If the screen pick does not appear to be responding then it may be that the pick entry is not active. When a pick entry is not active it only has a yellow border. To re-activate a pick entry simply click the left mouse button inside the entry once.


5.1.1 Dynamic Selection

When a screen pick is active you can move the mouse over entities in the graphics window and they will highlight as the mouse passes over them. When the display only consists of a wire frame display, like the default connectivity display, then it is possible to pick faces and bodies by selecting one of the edges from the desired face or body. In most cases there will be more than one face connected to each edge in the model (usually its two for a healthy solid model), so how do you select the one you want? CADfix uses the Tab key to allow you to cycle over the possible faces/bodies connected to the currently highlighted edge. When an edge is highlighted the list of possible faces connected to the edge is displayed in the status bar at the bottom of the graphics window.

Alternative face

Highlighted edge

Selected face

Use the Tab key to cycle through the list of alternative faces until the one you want is highlighted. Alternatively move the mouse away from the highlighted edge so that no faces are selected, then move it back to the same edge again. When the edge is highlighted this time it will automatically select the next face from the list of alternatives. The currently selected face/body will be drawn with thicker lines than the alternative faces and its CADfix label will also be displayed. Once you are happy that the correct entity is highlighted then select it by clicking the left mouse button.


When the cursor is within the graphics area a number of functions are controlled from under the right mouse click. Along with the display functions shown below in the basic menu are two methods of entity group selection:

Basic selection and Smart selection offer the user ways of collecting parts into a dynamic set called the SELE set upon which fixes can be applied from the various tools supplied, but mainly the from the Quick-fix tool bar down the right hand side of the screen. Entry into these selection methods can also be made from the top of the Quick-fix tool bar itself. As you will have already noticed from the exercises above selecting specific results from under Diagnostic tab also enters these problem parts into the SELE set for application of an appropriate fix. The user should always be aware of their current state during manual interactive processing regarding selection as this can be entered dynamically and then naturally switches from processing of the whole model. In particular this affects the display. A number of clues are available on the screen to re-enforce the users awareness:

1. Problem result highlighted 2. SELE as the working set

3. The depression icon indicates the Basic selection mode has been entered

4. Right click menu shows the Basic selection mode functions 5. Part summary relates to the contents of the SELE set

Numbers refer to screen image below.


5 3

2

1

4

5.1.2 Basic Selection

As the mouse cursor is run over the image, the “hot” edges it crosses are dynamically completed to their parent faces, which are dynamically highlighted in the image. The information banner or summary at the bottom of the screen is also updated dynamically with information about the selected entity.

Items maybe picked into the selection set from the screen with the mouse or via the right click menus. As items are picked they are highlighted in white on the screen. If the user wishes to remove items from the selection set they may do so by holding down the CTRL key and picking again with the mouse.

5.1.3 Smart Selection

The pointer is used to select groups of faces for suppression or other processing. When used for selecting fillets, as in the image below, each edge crossed by the cursor is dynamically completed to its neighbouring faces and these in turn to their



neighbours. In the process of tracking from face to face, the exit edge for each 4-sided face is “opposite” to the entry edge, so that ribbons of connected faces are highlighted. When a 3-sided face is reached the ribbon of connected faces will branch. The ribbon of faces associated with each edge in this way is highlighted dynamically as the cursor runs over the edges in the model.

In the figure the cursor has touched edge U205, which has caused a ribbon of 8 associated faces to be highlighted in the image and information banner – see below. A click on this edge causes it to be marked as the “seed” edge.

owever it’s associated ribbon of 8 faces are not yet copied into the SELE selection

t r

nce the ribbon has been

set

ted.

he smart selection process can be configured to top when 3-sided faces are encountered. This

Hset as you can see from the selection set summary. Although processing can be carried out on the feature selected if you wish to add further features you must firsAccept the current ribbon into the selection set from a either a middle mouse click ouse of the OK button.

Oaccepted into the selection further features can be identified and also accepThe user may also swap to theBasic selection mode at this point to add entities into the SELE set.

Tsribbon can next be edited by clicking on an interior “block” edge to reduce the number of faces in theselected ribbon, or by clicking on exterior “gate” edge, to increase the number of faces selected. Using this tool, groups of faces can be rapidly collected into the selection set for further processing.


5.2 The Diagnostic Checks Tab

n be accessed through the Checks tab found within the

tab is raised then the manual ols are presented in the tree view above. They

onnectivity 2. Unused

is displayed as a collapsible ranch in the tree view. Under each class you will

ria use the ght mouse button to access the pop-up menu

Select the “Scan this criterion” to start the scan. You can also modify the scan parameters for the

n alternative way to Scan the selected criteria is to select the corresponding fix from e list of possible fixes and then hit the Find button. This method of scanning or

The majority of the manual fixing tools ca

Diagnostics tab. When the Checks toare grouped into seven classes of problem, or criteria:

1. C

3. Topology 4. Integrity 5. Complexity6. Continuity7. Sloppiness

Each class of problembfind the individual problems. Selecting a particular problem will display the recommended fix methodsin the lower half of the diagnostics tab. To perform a Scan on the selected criteri

selected criteria from this pop-up menu. Athfinding selected criteria is only possible for those criteria that have a corresponding fix. In the above example “Self-intersecting curves” has a corresponding fix but forthe criteria below this of “Folded curves” there is no corresponding fix so doing a scan from the pop-up menu is the only way.

5.2.1 Filtering the Criteria

The tools displayed in the tree view can be filtered in two ways. The first way is to use the row of entity type filters at the top of the tree view.

These filters will limit the criteria displayed to only those that are relevant to the selected entity types. So for example if you are looking for a criteria that only affects surfaces, say “Closed surfaces” then press the surface filter icon. To restore the full view click the “All” filter. The second way to filter the tree view is to use the criteria filter

This allows you to filter the criteria based on a predefined target, such as the selected target system, or a Quality standard such as the JAMA PDQ criteria. To see all the possible criteria select the “Show all tests” option. This option is also available for each class of criteria in the tree view. Simply right click on the class type and the pop-up menu contains a “Show all tests” entry.


5.3 The Tools Tab

The third tab contains a collection of commonly used tools, such as the Delete and Replace tools. It also contains the Transformation tools such as Join and Collapse. The Geometry builder tools are also in this tab. Note: some of the Transformation and Defeaturing tools such as Join, Collapse faces and edges, Holes/Protrusions and Split, may not be available if your CADfix license does not include them.

The tools are presented in a collapsible tree view similar to the diagnostics checks tab. To use a tool open the appropriate branch and select the tool. For example to find and delete unused edges open the Delete branch and select the “Delete edges” tools. The delete edges tool will be displayed in the lower half of the work area. Press the Find button to automatically select all unused edges. Alternatively any type of edge can be deleted by using the Basic selection to select the edges from the screen into the SELE set. The use of the Manual Repair tools and the Transformation tools requires more expertise at using CADfix, and goes beyond the scope of this introductory tutorial. Please refer to the comprehensive on-line HTML help pages, or the CADfix training course.


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