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You can create a swept surface
by sweeping out a profile in planes normal to a spine curve while taking
other user-defined parameters (such as guide curves and reference
elements) into account. You can sweep an
explicit profile:
- along one or two guide curves (in this case the first guide curve is
used as the spine by default)
- along one or two guide curves while respecting a specified spine.
The profile is swept out in planes normal to the spine.
In addition, you can control the positioning of the profile while it is
being swept by means of a reference surface.
The profile position may be fixed with respect to the guide curve
(positioned profile) or user-defined in the first sweep plane.
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You can sweep an
implicit linear profile along
a spine. This profile is defined by:
- two guide curves and two length values for extrapolating the profile
- a guide curve and a middle curve
- a guide curve, a reference curve, an angle and two length values for
extrapolating the profile
- a guide curve, a reference surface, an angle and two length values
for extrapolating the profile
- a guide curve, and a reference surface to which the sweep is to be
tangent
- a guide curve and a draft direction
- two tangency surfaces.
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You can sweep an
implicit circular profile
along a spine. This profile is defined by:
- three guide curves
- two guide curves and a radius value
- a center curve and two angle values defined from a reference curve
(that also defines the radius)
- a center curve and a radius
- two guides and tangency surface
- one guide and tangency surface
- a limit curve and a tangency surface
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You can sweep an
implicit conical profile
along a spine. This profile is defined by:
- two guide curves
- three guide curves
- four guide curves
- five guide curves
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- Generally speaking, the sweep operation has a derivative effect,
meaning that there may be a continuity loss when sweeping a profile
along a spine. If the spine presents a curvature continuity, the surface
presents at least a tangency continuity. If the spine presents a
tangency continuity, the surface presents at least a point continuity.
- Generally speaking, the spine must present a tangency continuity.
However, in a few cases, even though the spine is not tangent continuous,
the swept surface is computed:
- when the spine is by default the guide curve
and is planar, as the swept surface is extrapolated then trimmed to
connect each of its segments. Note that if a
spine is added by the user, the extrapolation and trim
operations are not performed.
- when consecutive segments of the resulting swept surface do not
present any gap.
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Tangency discontinuous spine
with connex swept segments
(the sweep is created) |
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Tangency discontinuous spine
with non connex swept segments
(the sweep is not created) |
- In case of multiple solutions, the solution number displayed in the
dialog box may not always be the same but the geometrical solution (that
is the result of the sweep) remains the same.
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Defining Laws
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Whatever the type of sweep, whenever a value is requested (angle or
length) you can click Law to display the Law Definition
dialog box. It allows you to define your own law to be applied rather
than the absolute value. |
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The Law
Viewer allows you to:
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visualize the law
evolution and the maximum and minimum values,
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navigate into the
viewer by panning and zooming (using to the mouse),
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trace the law
coordinates by using the manipulator,
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change the viewer
size by changing the dialog box size,
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fit all in by
using the viewer contextual menu,
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change the law
evaluation step by using the viewer contextual menu (from 0.1 (10
evaluations) to 0.001 (1000 evaluations)).
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Four types of laws are available:
- Constant: a regular law, only one value is needed.
- Linear: a linear progression law between the Start
and End indicated values
- S type: an S-shaped law between the two indicated values
- Advanced: allowing to select a Law element as defined in
Creating Laws.
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For Linear,
S type
and Advanced law
types, only one solution is proposed in opposition to
Constant
law type which gives four solutions (For further information,
refer to Preview the Angular Value in the
Creating Swept
Surfaces Using an Explicit Profile and
Creating Swept
Surfaces Using a Linear Profile).
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You can check the
Inverse law button to
reverse the law as defined using the above options.
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The law can be negative, providing the curves are curvature
continuous.
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You can also apply
laws created with the Knowledge
Advisor workbench to swept surfaces.
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This capability is available with all types of
swept surfaces, except for:
- explicit profile: With pulling direction subtype
- linear profile: Limit and middle, With
tangency surface and With two tangency surfaces
subtypes
- circular profile: Three guides and Two guides
and tangency surface subtypes
- conical profile: Five guide curves subtype.
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Defining Relimiters
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You can define relimiters (points or planes) in order to
longitudinally reduce the domain of the sweep, if the swept surface is
longer than necessary for instance.
Below is an example with a plane as Relimiter 1.
When there is only one relimiter, you are able to choose the direction of
the sweep by clicking the green arrow. |
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- 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 surface.
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Smoothing
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- In the Smooth sweeping section, you can check:
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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 the
input value, and therefore helps generating better quality for the
resulting swept surface.
Over 0.01 degree, the smoothing is cancelled.
By default, the angular correction is set to 0.5 degree.
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Deviation from guide(s) to smooth the sweeping
motion by deviating from the guide curve(s). A
smoothing is performed using correction
default parameters in tangency and curvature.
By default, the deviation is set to 0.001mm, as defined in Tools >
Options. Refer to
General
Settings for more information.
This option is not available with With tangency surface
subtype.
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If the Tolerant laydown option is activated in
Tools > Options, the guide curve is laid on the support in
order to create the swept surface. However, the resulting surface is
not based on the laid guide curve but on the initial guide curve. To
get a swept surface based on the laid guide curve, the initial guide
curve first needs to be projected. |
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Removing Twisted Areas
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During creation or edition, you can generate swept
surfaces that have a twisted area by delimiting the portions of the
swept surface to be kept. The generated surface is therefore composed of
several unconnected parts. |
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In the Twisted areas management section, the
Remove cutters on Preview option lets you remove the cutters each
time you click on Preview. |
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The Setback slider allows you
to define a distance to move all the cutters from the twisted areas. It
is defined as a percentage of the guide length from 0 to 20%. Its
default value is 2%. |
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The Fill twisted areas
check box allows you to fill the twisted zones. It is activated by
default.
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- When you select this
check box, the Setback slider affects only the
cutters that have not been previously moved.
- If you have not
manually moved any cutter, and if you replace the main guide of
the sweep, the twisted areas are filled with the defined
setback.
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The Compute C0 vertices as twisted areas check box allows
you to fill the C0 vertices areas taking into account the setback value.
C0 vertices are the vertices on the input curve where there are tangency
discontinuities.

By selecting this option, C0 vertices that prevent from
building the sweep correctly are computed, and the area around these
vertices can be filled as standard twisted areas. You can use the
Setback slider or the green manipulators to enlarge or reduce the area
around the vertices.
Below is an example with filled C0 vertices area.

By default, this option is selected.
Note: This option is unavailable with the With tangency surface
and With two tangency surfaces subtypes of the linear
profile, and One guide and tangency surface subtype of the
circular profile.
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When you select this check box and the Fill twisted areas
check box is not selected, the C0 vertices areas are removed taking
into account the setback value. |
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The Connection
strategy drop-down list enables you to choose the connection mode
for the filled areas. The 3 options are:
- Automatic:
this mode chooses the best connection strategy depending on the
geometry.
- Standard:
this mode maintains the sweep profile.
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Similar to guide: this mode maintains the point continuity.
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- These modes force
the chosen connection.
- If Similar
to guide fails then the
Standard
connection strategy is applied. If this mode also fails, no
connection strategy is applied.
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The Add cutter
button allows you to create cutters on the main guide of the sweep.
Note:
- If you add cutters,
some points are automatically created along the guide curve of the sweep.
Using these points, you can split the guide curve
into multiple pieces and work on each piece of the sweep
individually. |
- If you want to select
the whole sweep (all the pieces of surfaces), select it directly
in the specification tree.
- Add cutter works also
for filling or removing a twisted area.
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If Fill twisted
areas
is checked, while the
Add
cutter
button is clicked, the created cutters define a filled area.
Otherwise, the cutters define a cutting zone. |
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Clearing Fill twisted areas
disables the Connection strategy
mode. |
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Detecting Canonical Portions for
Surfaces
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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.
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This option is unavailable for the following profile types:
- Explicit
- Linear
for subtypes:
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With tangency surface
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With two tangency surface
- Circular
for subtype One guide and tangency surface.
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Open the Sweep-Twist.CATPart
document. |
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Let's take an example by creating a swept surface with an implicit
linear profile. |

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Click Sweep
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The Swept Surface Definition dialog box appears. |
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Click the
Line
profile icon and choose the With reference surface
subtype.
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Select
Curve.1 as the Guide Curve 1.
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Select the
xy plane as the reference surface.
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Define
Length 1
as 30 mm and a Length 2 as 10 mm.
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Deselect
Remove cutters on Preview.
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Deselect
Fill twisted areas.
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Click
Preview.
An error message is displayed advising you to use a guide with a
smaller curvature and two manipulators ("cutters") appear for each
untwisted zone. Their default positions are the maximal zone
delimiters out of which they cannot be dragged. This maximal zone
corresponds to the larger untwisted portion of the swept surface. |
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Use these
manipulators to delimit the portions of the swept surface you want to
keep. These cutters are stored in the model as points on curve with
ratio parameters when the guide curve is not closed.
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We advise you cut a bit less than the
maximal zone to delimit a safety area around the twisted portion. |
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When you move the manipulators, the
Remove cutters on Preview option is automatically unchecked to
prevent the loss of manual adjustments after clicking Preview. |
A contextual menu is available on the manipulators: |
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Reset
to initial position: sets the manipulators back to their
default positions, that is the position defined as the maximal
zone.
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Remove twisted
areas management: removes the manipulators and performs
the swept surface generation again.
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Click
Preview again in the Swept Surface Definition dialog
box.
The swept surface is generated. |
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If you modify the length value after clicking
Preview, and the swept surface to be generated has no twisted
area, the generated swept surface will still be cut. Use the
Remove twisted areas management option to start the operation
again. |
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Check Remove
cutters on Preview and click Preview.
The error message is displayed again. |
This option amounts to using the Remove twisted areas
management contextual command before clicking on Preview: the
swept surface is recomputed without the green relimiters each time
you click on Preview. |
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Enter 15mm for
Length 1 to reduce the swept surface width.
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Click
Preview again.
The surface has no twisted areas any more nor any hole introduced
by a previous cusp or twist detection. |
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Click OK
to create the swept surface.
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