Creating Multi-Sections Volumes

This task shows how to create a multi-sections volume by sweeping one or more closed section curves along an automatically computed or user-defined spine. The volume can be made to respect one or more guide curves.
Open the VolumeLoft1.CATPart document.

  1. Click Multi-sections Volume .

    The Multi-sections Volume Definition dialog box appears.

  2. Select one or more planar section curves.

    The curves must be continuous in point.
    A closing point can be selected for a closed section curves
    Example of a multi-sections volume defined by three planar sections:

  3. You can select a support surface for each of the extremity section curve.

  4. Select the Continuity type for each support surface.
    By default, the continuity is set to Tangent.

  5. If needed, select one or more guide curves.

    You can create a multi-sections volume by sweeping a section curve along two guide curves intersecting each other at one extremity.
    Guide curves must intersect each section curve and must be continuous in point.
    The first guide curve will be a boundary of the multi-sections volume if it intersects the first extremity of each sections curve.
    Similarly, the last guide curve will be a boundary of the multi-sections volume if it intersects the last extremity of each section curve.
    Example of a multi-sections volume defined by 2 planar sections and 2 guide curves:

    Imposing Tangency conditions
    • You can make a multi-sections volume tangent to an adjacent volume by selecting an end section that lies on the adjacent volume. In this case, the guides must also be tangent to the volume.
      In Figure 2 a multi-sections volume tangent to the existing volume has been created:
      Figure 1: Figure 2:
    • You can also impose tangency conditions by specifying a direction for the tangent vector (selecting a plane to take its normal, for example). This is useful for creating parts that are symmetrical with respect to a plane. Tangency conditions can be imposed on the two symmetrical halves.
    • Similarly, you can impose a tangency onto each guide, by selection of a surface or a  plane (the direction is tangent to the plane's normal). In this case, the sections must also be tangent to the volume.

  6. In the Spine tab page, select the Spine check box to use a spine that is automatically computed by the program or select a curve to impose that curve as the spine. 

    The spine curve must be normal to each section plane and must be continuous in tangency.

    Smoothing Parameters
    In the Smooth parameters section, you can check:
    • the Angular Correction option to smooth the lofting motion along the reference guide curves. This may be necessary when small discontinuities are detected with regards to the spine tangency or the reference guide curves' normal. The smoothing is done for any discontinuity which angular deviation is smaller than 0.5 degree, and therefore helps generating better quality for the resulting multi-sections volume.
    • the Deviation option to smooth the lofting motion by deviating from the guide curve(s).

  7. It is possible to edit the multi-sections volume reference elements by first selecting a curve in the dialog box list, or by selecting the text on the figure, then choosing a button to either:

    • remove the selected curve

    • replace the selected curve by another curve

    • add another curve
    More possibilities are available with the contextual menu and by right-clicking on the red text or on the object. For example, it is possible to remove and replace tangent volumes and closing points.

  8. Click OK to create the multi-sections volume.

    The volume (identified as Multi-sections Volume.xxx) is added to the specification tree.
    For further information about the other tabs, please refer to the Creating Multi-Sections Surfaces chapter.