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Pre-Processing
Simcenter STAR-CCM+ solves physics problems on a computational mesh. To provide this mesh, you first define geometry using internal or external tools, and then create a mesh pipeline whose operations generate the mesh in repeatable steps.
3D-CAD
3D-CAD is a feature-based parametric modeler within Simcenter STAR-CCM+ that allows you to build geometries from scratch. The geometries that you create with 3D-CAD are stored as 3D-CAD models, which you can then convert to geometry parts for integration with the meshing and simulation process.
Sketches in 3D-CAD
3D-CAD supports two types of sketch—2D sketches that are created on a planar surface and 3D sketches that are built from points located anywhere in geometric space. You can use both types of sketch in 3D geometry operations such as extrude, revolve, or sweep.
Creating a Sketch
Sketch Entity Operations
Splitting and Trimming Sketch Entities

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Pre-Processing
Simcenter STAR-CCM+ solves physics problems on a computational mesh. To provide this mesh, you first define geometry using internal or external tools, and then create a mesh pipeline whose operations generate the mesh in repeatable steps.
- 3D-CAD
  3D-CAD is a feature-based parametric modeler within Simcenter STAR-CCM+ that allows you to build geometries from scratch. The geometries that you create with 3D-CAD are stored as 3D-CAD models, which you can then convert to geometry parts for integration with the meshing and simulation process.
  - 3D-CAD Environment
    The 3D-CAD environment provides you with a feature tree from which you can activate all steps for creating and modifying geometry, and a 3D-CAD View scene in which you interact with the geometry. Many of the same feature actions are available for selection in the 3D-CAD View scene.
  - Sketches in 3D-CAD
    3D-CAD supports two types of sketch—2D sketches that are created on a planar surface and 3D sketches that are built from points located anywhere in geometric space. You can use both types of sketch in 3D geometry operations such as extrude, revolve, or sweep.
    - Creating a Sketch
      - Creating a Sketch on a 3D-CAD Model
      - Sketch Planes
        A sketch plane is a flat surface on which you can draw a sketch.
      - Sketch Entity Operations
        Working with Construction Entities
        Construction entities are used within a sketch to aid the sketching process. 3D-CAD ignores construction entities unless the sketch is used to create a revolved feature.
        Splitting and Trimming Sketch Entities
        Creating An Arc
        Deleting and Duplicating Entities
        Moving Sketch Entities
      - Offsetting Sketch Entities
        The offset tool enables you to uniformly displace sketch entities within the sketch plane.
      - Pattern Offset Sketch
        In sketch mode, the pattern offset tool allows you to create a succession of displaced sketch entities based on a single set of source entities.
      - Trimming Sketches
        The trim tool enables you to quickly trim segments of overlapping sketch entities.
      - Sketch Display Options
      - Viewing the Status of Sketch Primitives
        The status of sketch primitives indicate the validity of the sketch. This feature is useful for finding issues with your sketch, such as small gaps in sketches or overlapping primitives, which otherwise can be hard to see and would return errors further down the pipeline.
      - 2D Sketch Entity Reference
    - Dimensioning Sketches
      Dimensions are used to control sizes, distances, and angles in a sketch.
    - Constraining a Sketch
      Constraints are used to impose geometric limitations on sketch entities as well as to control their position on the sketch plane.
    - Creating Sketch Fillets
      The Sketch Fillet option rounds off the corner that is formed between two lines on a sketch.
    - Creating Sketch Chamfers
      A sketch chamfer is a feature that makes a straight cut across the corner that is formed between two lines on a sketch.
    - Splines
      A spline is a smooth curve that is composed from a series of points (called spline points).
    - Projecting Entities to the Active Sketch
      You can project sketch entities from other sketches onto the active sketch.
    - Creating a Sketch in 3D
      Use 3D sketching to create sketches whose entities are constructed from points and lines located anywhere in 3D space. These 3D sketches can then be used to build or modify complex three-dimensional shapes.
  - 3D-CAD Geometry Modeling
    Bodies represent the individual objects that make up the 3D-CAD model. Imported CAD geometry appears as bodies in 3D-CAD, and you can also create your own bodies directly using 3D-CAD features.
  - Freeform Surface Modeling
    Freeform surface modeling is a modeling technique in 3D-CAD that allows you to deform existing surfaces for desired shapes.
  - Importing and Exporting Geometry
  - Working with 3D-CAD Models
  - Geometry Repair and Preparation
    Simcenter STAR-CCM+ provides a suite of tools in 3D-CAD that helps you to prepare your CAD geometry so that it is suitable for meshing. CAD that is designed for manufacture can have gaps or inaccuracies that cause problems when trying to generate a watertight mesh.
  - Design Parameters
    Design parameters allow Simcenter STAR-CCM+ to update geometry designs during design exploration studies. Although you define them within the 3D-CAD environment, they are exposed outside 3D-CAD for manual or automatic update.
- Modeling Geometry
  This part of the User Guide describes how to use 3D-CAD, the parametric solid modeler available within Simcenter STAR-CCM+. It also describes the features and tools available for further preparation of the geometry model and its surfaces.
- The Surface Repair Tool
  The Surface Repair tool diagnoses errors in, and provides repair tools for, tessellated surfaces and part curves. The same tool allows you to reorganize discretized geometry by searching for face-based features and attributes then assigning the results to new or existing part surfaces or curves.
- Defining the Regions Layout
  An essential part of the process in setting up your simulation is to define the relationship between geometry parts and regions, boundaries, and interfaces.
- Meshing
  A mesh is a discretized representation of a geometric domain. This domain can include real-world geometry, its content, and its surrounding environment.

Splitting and Trimming Sketch Entities

You can trim overlapping sketch entities by splitting them and deleting the unwanted segments. When using the Split for Trim operation, the entity that you select first is split where it intersects the sketch entities that you select next. The sketch entities that are used for splitting can either fully overlap the target, or have a point lying on the target.

Note	When a circle is split, the result is two circular arcs, therefore it must be intersected at a minimum of two points by the splitting entities. The same must be done when splitting an ellipse.

To split a sketch entity:

Select the target sketch entity in the 3D-CAD View scene (the circle that is highlighted in the screenshot below).
Hold down the <Ctrl> key and select the sketch entities that you want to use to split the target (the two perpendicular lines that are highlighted below).
Right-click on any of the selected entities and select Split For Trim.

The target sketch entity splits at the points of intersection. The entities that intersected the target sketch entity remain unchanged. You can use the delete operation to trim any unwanted entities, such as the arc highlighted below. To complete the sketch below, you could use Split for Trim to split each of the perpendicular lines, using the circular arc as the splitting entity in each operation.

It is good practice to check the connections between points after using the Split for Trim operation. To check whether the points are connected following a split operation:

Click the intersection point and drag it to one side.
If the two sketch entities come apart when the point is moved, apply a coincidence constraint between the two points to form a closed sketch. You can drag the point back onto the existing point on the sketch plane; a coincidence constraint is automatically applied.

Dimensions that are attached to a sketch entity are lost when the Split for Trim action is carried out.