CST2013: Curve Creation

The curve creation is strongly related to the shape generation. A curve is a line element in the three-dimensional space that does not influence the simulation by itself.

The main purpose of the curve generation is to provide flexible tools for the creation of more complex three-dimensional solid shapes. The following page will give you a basic overview of the available tools. Please refer to the specific manual pages for details.

Curves

Each curve item is assigned to a curve that is shown in the Curves folder in the navigation tree. The purpose of curves is to group together a collection of curve items such that these items can be used together in subsequent operations. A curve is considered closed if its items form a closed loop.

Basic curve creation

The easiest way to create a curve item is to define a curve item "primitive." The following table shows the toolbar items and the menu commands.

To generate such a primitive you will first need to select the appropriate menu or toolbar item. This will lead you to an interactive curve item generation mode where you can define the curve items’ parameters by using the mouse (while in this mode, press F1 for more information).

After you have finished all necessary steps (or pressed the ESC key) a curve item parameter dialog box will open showing a summary of all parameters for this curve item.

Within this dialog box, you can change the parameters and finally create the curve item.

After the curve item has been created it will appear in the navigation tree under it’s curve folder.

Blend and chamfer curve items

Common modifications of curve items are given by the application of chamfers or blends at its vertices. The corresponding tools can be activated by choosing Modeling: CurvesCurve ToolsChamfer () or Modeling: CurvesCurve ToolsBlend (). Then, an interactive mode will be entered to select the point at which the chamfer or blend will be applied afterwards.

Delete curve segments

Each curve item may consist of several curve item segments (e.g., a rectangle consists of four line segments, a simple circle consists of one segment only). The operation delete curve segments allows you to delete each of these segments individually without affecting the others. After invoking this command by choosing Modeling: CurvesCurve ToolsDelete Segments (), an interactive mode will be entered in which curve segments can be selected for deletion.

Trim curves

A trim curve operation works similar to the boolean operations on solids. The purpose of this operation is to trim one curve item with another one, e.g., to produce arc segments by trimming a full circle with a line. The trim curve operation is a very important tool for creating more complex curves. As soon as the operation is invoked by selecting Modeling: CurvesCurve ToolsTrim Curves (), an interactive mode is entered in which the two curve items for the trim operation have to first be selected. Afterwards, segments of the intersected curves can be chosen that will then be deleted from the resulting curve items.

Cover planar curve

A closed planar curve (all curve items are located in the same plane) can be covered with a planar surface. This operation generates a face from a closed chain of curve items and is invoked by selecting Modeling: CurvesCurve ToolsCover Curve (). The resulting face is an infinitely thin sheet and does not influence the simulation.

Extrude planar curve

This operation works similar to the cover operation and is invoked by choosing Modeling: CurvesCurve ToolsExtrude Curve (). The difference is that the extrusion will also extrude the infinitely thin sheet into a solid shape. The thickness of the extrusion can be specified in a dialog box.

Sweep curve along path

For the generation of more complex shapes, it is often useful to sweep a cross section profile along a path. The profile and the path need to be specified as two separate curves where each of these curves may either be open or closed. If the profile is a closed curve, the resulting shape will be a valid solid shape. Otherwise, the resulting shape will be an infinitely thin sheet body. This operation is invoked by choosing Modeling: CurvesCurve ToolsSweep Curve ().

Loft between curves

The loft curves operation (invoked by selecting Modeling: CurvesCurve ToolsLoft Curves ()) is the most powerful method for creating a solid shape from a set of curves. The loft operation will generate a free-form surface from the cross sections that must be given as a set of separate curves. If all profiles are closed, the top and bottom loops of the free-form surface can be covered, which will result in a valid solid shape. If the profiles are not closed or if the ”solid” switch is not checked, the result will be an infinitely thin sheet body that will not be considered for the simulation. In addition to the cross-section profiles, a path curve can optionally be specified that controls the tangency of the generated free-form surface at the location of the profiles.

Trace from curve

Closed and open planar curves can be traced. The width and thickness of the new shape can be specified in a dialog box. Optionally, on open curves, the end caps can be modelled as round. This operation is invoked by choosing Modeling: CurvesCurve ToolsTrace From Curve ().

Local coordinate systems

Besides the ability to create the curve items along the axes of the global x/y/z coordinate system, it is also possible to define local coordinate systems or working coordinate systems (WCS).

The usage of these coordinate systems allows the generation of curve elements with an arbitrary orientation in space. Furthermore, the local coordinates allow the construction of new model elements based on the picked locations (e.g. faces and points) of already existing ones.

See also

Modeler View