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Module 03: Repairing Geometry

Introduction to ANSYS SpaceClaim Direct Modeler

17.0 Release

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In this module we will learn about:

    • Importing Geometry in SpaceClaim Direct Modeler (SCDM)
    • Need for repair
    • Common issues found in geometry
    • Fix Issues One-by-One Vs All-at-Once
    • Specialized tools for repair
    • Handling STL Geometry

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Overview

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Core Skills

Creating

Geometry

Repairing Geometry

CFD Modeling

Overall Process

Module 2

Module 3

Module 1

Module 4

Module 5

Module 6

FEA Modeling

SCDM to Workbench

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Two Import Options

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Insert CAD file to existing session

Open CAD file in new session

Importing Geometry (1)

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Supported Files

    • Supports import from major CAD packages (CATIA, Pro/E, NX, Solid Works, etc.)
      • Separate license not required
    • Neutral file formats like STEP and Parasolid are also supported
    • Additional license are required for
      • Faceted Data Toolkit
      • JT Exchange
      • 3D PDF
    • Bi-directional Attach mode with other CAD software is not supported
      • Needs a manual export from Spaceclaim into a format readable in the desired CAD software

File Formats

Importing Geometry (2)

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Import Options

    • There are advanced options available under SpaceClaim Options tab in File Menu
      • Useful for optimizing the importing and exporting process for your needs
    • Several translation methods available to enable data exchange with CAD/CAE systems
      • Direct Integration/CAD Readers
      • Import of generic CAD formats (IGES, ACIS etc)
    • Parameters, Named Selections, and Attributes can not be passed from CAD to SpaceClaim as SpaceClaim uses reader mode for all CAD files.
    • Enclosure and Symmetry Processing is not available
    • Work points (construction points) are not transferred

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SpaceClaim Options

Importing Geometry (3)

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    • Translation can:
      • Return incomplete, corrupt, or disconnected geometry
        • Requires repair
      • Return geometry details unnecessary for CAE analysis
        • Requires defeaturing
    • These issues must be fixed to
      • Create watertight fluid bodies
      • Prevent meshing issues

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CAD Import & Clean-up

Why the Need for Repair?

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  • Many potential issues
        • Missing faces
        • Small faces
        • Free faces
        • Sharp angles
        • Overdetailed features
        • Hard edges
        • Small edges
        • Others …

These problems can be fixed using several tools available under "Repair" menu

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Missing Faces

Free Faces

Small Faces

Small Edges

Sharp Angles

Hard Edges

Common Issues Found in Geometry (1)

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  • Stitch
        • The Stitch tool combines surface part faces that are touching at their edges
  • Tool Guides Options

Selects the location to repair one-by-one

Select and add locations to auto selection

Removes the location from selection

Repair all locations at a time

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Common Issues Found in Geometry (2)

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  • Gaps
        • The Gaps tool removes gaps between faces
        • Use the controls in the Navigate ribbon group to view each problem one at a time before you fix it

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        • Click “Next” or “Previous” to step through and highlight each identified problem
        • Select “Zoom to Fit” if you want to automatically zoom in on the problem

Common Issues Found in Geometry (3)

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  • Missing Faces
      • This tool automatically detects and fills missing faces of an object
      • This can fill the missing faces all-by-one or one-by-one
      • Find Options
        • Set criteria for auto problem selections
      • Fix Options
        • Different approaches to fill the missing faces

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Common Issues Found in Geometry (4)

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  • Split Edges
        • The Split Edges tool detects and merges coincident edges that do not mark the boundaries of new faces

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  • Extra Edges
        • The Extra Edges tool works like Merge Faces but removes the edges between the faces
        • Merging faces simplifies the model by removing edges and makes the model more difficult to modify

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Common Issues Found in Geometry (5)

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  • Merge Faces
        • The Merge Faces tool replaces two or more neighboring faces with a single new face that closely fits the original faces

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  • Small Faces
        • The Small Faces tool detects and removes small and sliver faces

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Common Issues Found in Geometry (6)

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  • SCDM allows fixing issues found at all locations at the same time
  • This is useful when repairing large models
  • But while fixing it may create invalid patches (surfaces) in the geometry
  • It is advisable to double-check the locations fixed by automatic operations
  • Check Geometry tool can be effectively used to validate the fixes

Fix Issues One-by-One Vs All-at-Once

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  • Actual designs created have lot of features which are unnecessary for CAE analysis
  • These features can be simplified using several Remove tools available under Prepare tab
  • Specialized tools are used to remove features
      • Rounds
      • Interferences
      • Faces
      • Short Edges

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Rounds

Faces

Interference

Short Edges

Specialized Tools (1)

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  • Rounds
        • It is similar to the Fill tool, except it only selects rounded edges
        • You will have a greater chance of success if you remove only a few rounds at a time

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    • Faces
      • The Faces tool allows you to quickly remove faces from your design. Use it to simplify your design by removing holes, protrusions, etc.

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Specialized Tools (2)

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    • Split and partially remove a round:
      • When a chain of rounds cannot be filled in its entirety, the rounds will be partially removed
      • Click on the edge to split the rounded face
      • From the Fix Options panel, change the Cap width option to adjust the percentage of the round face that is removed

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Use “Faces” tool to remove remaining part of fillets

Specialized Tools (3)

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  • Interference
        • The tool searches all visible bodies for interference
        • The interference is removed from the body with the largest volume

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    • Short Edges
      • This removes the small edges coincident with boundary edges
      • It connects the two vertices of the short edge to eliminate it

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Specialized Tools (4)

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  • STL Import Options
        • Similar to other CAD formats, STL import can be optimized through SpaceClaim Options tab
  • Import as:
  • Connected mesh: Create a lightweight mesh with full connectivity information between facets
  • Simple mesh: Create a lightweight mesh with no connectivity information between facets
  • Solid/surface body: Convert STL triangles into full geometry
          • Check the Merge faces checkbox to seamlessly merge one or more faces

Convert STL Mesh to Geometry (1)

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  • Converting to CAD
        • You can convert mesh files into CAD
        • Options are available if you right click on object in Graphics or Structure Tree
        • Options are available to convert by merging the faces or without merging them

Merge Faces

Do Not Merge Faces

Convert STL Mesh to Geometry (2)

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  • Extract Curves
        • Creates curves at the intersection of object cross-sections and planes

Convert STL Mesh to Geometry (3)

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  • Skin Surfaces (new in R17.0)
        • Helps to reverse-engineer a surface model

From faceted data

        • Single-click on the mesh where you want to start the sketch
        • Single-click to create internal edge points
        • Double-click to end the edge and create a corner
        • Continue creating edges and corners and close the shape by single-clicking on the start point
        • Hit the escape key to remove the current sketch. Click Complete to create the surface

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Note: You can edit a sketch by dragging a corner or by adding or dragging a control point

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Convert STL Mesh to Geometry (4)

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  • Skin Surfaces Options

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Samples

The value entered determines the number of Control Points on the Control Curves for the surface. Check the Full Preview option to change the value

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Smooth

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The Smooth option uses an algorithm to smooth out the 'noise' in the surface. The noise comes from the underlying facets and leads to a 'bumpy' surface

Full Preview

Helps to control the number of sample points used in the surface

Convert STL Mesh to Geometry (5)

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  • Skin Surfaces Tool Guides

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  • Using box-select

We can simply box-select the area where we want the sketch

Control points are automatically added in areas with curvature

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The Select Boundary sketch surfaces patch boundaries on the facets

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The Select Geometry tool guide helps to choose planes or existing patch edges to create boundary loops for surface patches

Convert STL Mesh to Geometry (6)

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  • Periodic Surfaces

Use the Select Geometry tool guide to select planes and create sections

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The tool displays preview for the closest loop. If there are multiple loops created. You can explicitly select a different loop if the default that is chosen is not the one you want.

Convert STL Mesh to Geometry (7)

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  • Periodic Surfaces

Periodic surfaces can also be conical

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Create a periodic edge on the section

Click on the apex of the cone to preview the surface

Convert STL Mesh to Geometry (8)

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If you have the Faceted Data Toolkit extra license, please consult the Appendix 4.1

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Convert STL Mesh to Geometry (9)

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What have we learnt in this session?

    • How can we import a geometry in SpaceClaim Direct Modeler?
    • Why do we need to repair the geometry?
    • What are the common issues found in geometry?
    • What are the tools to repair these issues in SCDM?
    • How can we handle STL geometry in SCDM?

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Summary

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Workshop 3.1 Repairing Geometry

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Demo of Import and Repair (09:13)

Module3_Basic_Import_Repair.mp4

Demo of Defeaturing (10:11)

Demo of STL Repair (16:24)

Module3_Defeaturing.mp4

Module3_STL_Repair.mp4

Videos available (look for separate directory)

Module3_Repair.mp4

Demo of Repair (08:50)

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Appendix: Handling STL Geometry

Introduction to ANSYS SpaceClaim Direct Modeler

17.0 Release

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If you have the Faceted Data Toolkit extra license, you should tick STL Prep option in File/SpaceClaim Options/License

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Handling STL Geometry (1)

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  • Issues with STL data
        • Intersections
        • Non-manifold/ Over connected
        • Holes/Gaps
        • Sharp Features
      • There are various tools available under Facets menu to fix the issues related to STL data

Intersection

Non-manifold

Holes

Sharps

Handling STL Geometry (2)

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  • Check Mesh
        • Use the Check Mesh tool to list problems with the Mesh such as
          • Intersection
          • Non-manifold connection
          • Multiple faces
          • Holes

Handling STL Geometry (3)

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  • Auto Fix
      • Use the Auto Fix tool to automatically search for, and fix, any mesh defects
      • The Auto Fix tool performs the following sequence:
      • Fix self-intersections
      • Close holes
      • Recheck for self-intersections
      • Fix self-intersections
      • Remove void shells
    • Auto Fix uses straight faces to fill the holes irrespective of the shape of the geometry

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    • It is advised to double-check the problems fixed by Auto Fix

Handling STL Geometry (4)

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  • Intersections
      • Use the Intersections tool to highlight & fix the areas of self-intersection
      • The model is also made transparent if any intersections are found

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Handling STL Geometry (5)

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  • Holes
      • You can find and fix holes using the Holes tool
      • It works like other Find-and-Fix tools in the Repair tab

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    • Options- Find/Fix

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Patch

Cap

Use “Faces” tool to remove remaining part of fillets

Handling STL Geometry (6)

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  • Fix Sharps
      • Meshes may contain sharp spikes that need to be flattened
  • Option- Find/Fix

This applies to the angle between normals of facets that share an edge

This applies to the angle between normals of any two facets that share a vertex

Convexity options specify which type of sharps to look for

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Handling STL Geometry (7)

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  • Over-connected/Non-manifold
      • The multiple connected faces are highlighted
      • If the problems are not fixed by the tools, then delete all the faces in local area and use fill holes option to recreate the patch

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Handling STL Geometry (8)

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  • Shrinkwrap (new in R17.0)
      • Some faceted models contain gaps that will cause problems for 3D Printing. For example, assemblies have multiple parts fastened together but there are small gaps between the component parts. The Shrinkwrap tool allows you to create a single, faceted model by closing gaps that can be sent to a 3D printer
  • Options Panel

Handling STL Geometry (9)

The foot model used in this example has small gaps between the bones of the foot

Gap size: Maximum distance between meshes that will be considered a gap

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Keep original bodies: When checked ON, the original faceted bodies will NOT be

removed after the Shrinkwrap is created

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Preserve features: When checked ON, you need to set an Angle threshold

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Angle Threshold: Angle, in degrees, that determines the smoothness of the shrinkwrap

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