Creating Swept Volumes

This task shows how to create swept volumes that use an explicit or an implicit circular or linear profile.
  You can create a swept volume by sweeping out a closed profile in planes normal to a spine curve while taking other user-defined parameters (such as guide curves and reference elements) into account.
 

Three type of profiles are available:
 

Explicit Profile
  The following sub-types are available:
Open the VolumeSweep1.CATPart document.
 

With reference surface

 

  1. Click Volume Sweep .

    The Swept Volume Definition dialog box appears.

  1. Click the Explicit profile type icon.

  2. Select With reference surface from the Subtype drop-down list.

  3. Select the Profile to be swept out (DemoProfile1).

  4. Select a Guide curve (DemoGuide1).

  5. Select a surface (by default, the reference surface is the mean plane of the spine) in order to control the position of the profile during the sweep.
    Note that in this case, the guiding curve must lie completely on this reference surface, except if it is a plane. You can impose an Angle on this surface.

  6. Click OK to create the swept volume.
 

With two guide curves

  1. Click Volume Sweep .

    The Swept Volume Definition dialog box appears.

  2. Click the Explicit profile type icon.

  3. Select With reference surface from the Subtype drop-down list.

  4. Select the Profile to be swept out (DemoProfile1).

  5. Select a first Guide curve (DemoGuide1).

  6. Select a second Guide curve (DemoGuide2).

    You can also specify anchor points for each guide. These anchor points are intersection points between the guides and the profile's plane or the profile itself, through which the guiding curves will pass.
    There are two anchoring types:

    • Two points: select anchor points on the profile that will be matched respectively to Guide Curve 1 and Guide Curve 2. These points must belong to the sweeping plane of the profile.
      If the profile is open, these points are optional and the extremities of the profile are used.

    • Point and direction: select an anchor point on the profile which will be matched onto Guide Curve 1 and an anchor direction.
      In each sweeping plane, the profile is rotated around the anchor point so that the anchor direction (linked to this profile) is aligned with the two guide curves, from Guide Curve 1 to Guide Curve 2.
    Sweep without positioning
    Two points anchoring type    		 Sweep without positioning
    Point and direction anchoring type
     
    If you do not explicitly select anchor points or anchor direction, they are automatically computed if the profile is planar. Note that the selection is still available. The anchor points are computed as follows:
    • for Anchor point 1: intersection between the profile plane and Guide curve 1 (I1).
    • for Anchor point 2: intersection between the plane, passing through Anchor point 1 and normal to the spine, with Guide curve 2 (I2).
    • for Anchor direction: line between I1 and I2
    Automatic computation for Two points anchoring type Automatic computation for Point and direction anchoring type

  7. Click OK to create the swept volume.
 

With pulling direction
  The With pulling Direction subtype is equivalent to the With reference surface subtype with a reference plane normal to the pulling direction.

  1. Click Volume Sweep .

    The Swept Volume Definition dialog box appears.

  2. Click the Explicit Profile type icon.

  3. Select With pulling direction from the Subtype drop-down list.

  4. Select the Profile to be swept out (DemoProfile1).

  5. Select a first Guide curve (DemoGuide1).

  6. Select a Direction (xy plane)

  7. Click OK to create the swept volume.
 

Linear Profile
Open the VolumeSweep3.CATPart document.

  1. Click Volume Sweep .

    The Swept Volume Definition dialog box appears.

  2. Click the Linear profile type icon.

    The With draft direction sub-type is automatically selected and grayed out.

  3. Select a guide curve (closed planar curve or any surface (planar or non-planar)) and a draft direction (a line, a plane or components).

  4. Select the draft computation mode:

    • Square: a plane normal to the draft direction is used as the reference surface and the projection of the guide curve onto this plane is used as the spine.
    • Cone: envelop of cones defined along a given curve. In order to have swept start and end planes similar as the square mode, the guide curve needs to be extrapolated and the resulting volume split.

  5. Choose the angular definition:

    • Wholly defined: the angular value varies during the whole sweeping operation.
      In this tab, you can click the Law... button to display the Law Definition dialog box.
      For further information, refer to the Creating Swept Surfaces Using a Linear Profile chapter - With Draft Direction.
    • G1-Constant: a different draft value for every G1 section can be set; in this case, a relimiting plane is requested when defining lengths
    • Location values: on given points on the curve, angular values can be defined.
      This tab is only available for a square computation mode and will work only on G1 curves.

  6. Choose the length types:

    • From curve: the swept volume starts from the curve
    • From/Up to: the length is computed by intersecting a plane or a surface; a point can be selected: a plane parallel to the draft plane would be computed
    • From extremum: the lengths are defined along the draft direction from an extremum plane; L1 corresponds to the maximum plane in the draft direction,  L2 corresponds to the minimum plane in the draft direction.
    In the above example, we selected the following values:

    Sketch.2 as guide curve
    Plane.1 as draft direction
    Square as computation mode
    G1-constant angles
    From Extremum Length types: 50mm as Length 1 and 20mm as Length 2
     

    In the above example, we selected the following values:

    Surface.1 as guide curve
    xy plane as draft direction
    Cone as computation mode
    0deg as Wholly constant angle
    From Extremum type

  7. Click OK to create the swept volume.
 

Previewing The Angular Value
 
This option is available with:
  • Explicit profile: With reference surface and With pulling direction sub-types.
  • Linear profile: With draft direction sub-type.
  When creating a swept volume, you are now able to preview the four solutions based on the values given for the Angle and Length. The first solution corresponds to Angle, Length1 and Length2 values, the second solution to -Angle, Length1 and Length2 values, the third solution to Angle, Length2 and Length1 values, and the fourth solution to -Angle, Length2 and Length1 values.
  Here is an example with the With draft direction sub-type, DemoGuide2 as the Guide curve 1, Plane.1 as the Draft direction, 20mm as  Length 1, 60mm as Length 2, and 45 deg as the Angle.
 

  The orange arrow corresponds to the current solution. You can click on any arrow then on Preview or OK to recompute the swept volume. You can also use the Previous or Next buttons or enter a solution number in the Angular sector field.
  Here is an example with Solution 4:
 

 

Defining Relimiters
  You can define relimiters (points or planes) in order to longitudinally reduce the domain of the sweep, if the swept volume is longer than necessary for example.
  Below is an example with a plane as Relimiter 1.
 

 
  • Relimiters can be selected on a closed curve (curve, spine, or default spine). In that case, you are advised to define points as relimiters, as plane selection may lead to unexpected results due to multi-intersection.
  • You can relimit the default spine, thus avoiding to split it to create the swept volume.
  • In the Smooth sweeping section, you can check:

    • Angular correction to smooth the sweeping motion along the reference surface.  This may be necessary when small discontinuities are detected with regards to the spine tangency or the reference surface's 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 swept surface.
      By default, the angular correction is set to 0.5 degree.

    • Deviation from guide(s) to smooth the sweeping motion by deviating from the guide curve(s).
      A curve smooth is performed using correction default parameters in tangency and curvature.
      This option is not available for with tangency surface subtype.
  • In the Twisted areas management section, Remove cutters on Preview lets you remove the twisted areas management each time you click on Preview.
    This option is selected by default.
    For further information, refer to Removing Twisted Areas.
   

 Detecting Canonical Portions for Volumes
 
  This check box allows you to compute automatically the regular shapes like cylinders, cones, and spheres. Moreover, it can automatically detect planer surfaces if they exist in the swept surface. These planer surfaces could be used as support for other features.
This option is unavailable for the Explicit profile type.
 

Circular Profile
  The following subtypes are available:
Open the VolumeSweep2.CATPart document.
 

Center and reference curve

 

  1. Click Volume Sweep .

    The Swept Volume Definition dialog box appears.

  2. Click the Circle profile icon.

  3. Select the Center and reference curve subtype from the drop-down list.

  4. Select a Center curve (Demo Curve1) and a Reference curve (DemoCurve2).

  5. Define a fixed radius if needed.

    No fixed radius defined Fixed radius = 40mm

  6. Click OK to create the swept volume.
 

Center and radius

  1. Click Volume Sweep .

    The Swept Volume Definition dialog box appears.

  2. Click the Circle profile icon.

  3. Select the Center and radius subtype from the drop-down list.

  4. Select a Center curve (DemoCurve2) and enter a Radius value (10mm).

  5. Click OK to create the swept volume.

 
For further information about the optional elements, please refer to the Creating Swept Surfaces Using an Explicit Profile and Creating Swept Surfaces Using a Circular Profile chapters.