ModifyGlobal Shape ModelingSpined Twist

The GSM Spined Twist command enables you to provide compensation to those parts in which the spring-back effect generates a twist. Using this command you can provide twist to a part along a predefined spine. It is also possible to define the degree of twist at various sections defined over the part.

Spined Twist modifies globally a whole shape. The command can be applied over a set of surfaces, curves or meshes that are twisted about a selected spine. The twisting is as per an interpolation twist-angle-law. The twist-angle-law is defined by the interpolation of angle values specified at some user-selected sections called the drive sections and applied at all defined sections. The sections that are not "drive sections" are called driven sections. You have the full control over the number and location of the sections, and the possibility to specify the twist angle value at each section. You can also control the preview of the sections and define the stamping direction.

On starting the command, you need to make two primary selections for the following two selectors:

Once the spine curve has been selected, the location of the section planes is displayed over it as a red handle. The location of these section planes demarcates the intersection of two sections. The preview of the section plane, if turned on, is displayed as two concentric circles. The twisting action of the GSM Spined Twist command is applied in the zone lying in-between the section plane limits (i.e. the two concentric circles).

You can modify the position of each section plane by dragging its handle. Additionally, you can right-click to display the context menu at each section with the following options in it.

Option	Drive Section	Driven Section	Description
Show preview			Toggles the display of the section plane preview
Enable Drive Section			Converts a drive section to a driven section and vice-versa. A check mark is displayed in case the section is a drive section.
Invert Angle Direction			Inverts the direction of the Angle handle over the section plane preview
Show Section Options			Displays additional options (Max. radius, Min. radius, Limited to curvature) exclusive to that section plane. Values specified for these options will override the settings made in the Advanced Options dialog box.
Remove Section			Deletes the current section plane
Add Section	Right-click in empty area, close to the spine curve		A new section plane is added at the nearest curve point from the pick point.

Under the Entities to Be Modified node, use the Entities selector to select the surfaces, curves, and mesh over which the twist will be applied, by choosing Surfaces, Curves or Mesh, respectively from its drop-down list.

• When the Include surfaces to be sectioned check box is selected, the twisting modification will be applied also on all the surfaces selected for the Surfaces to Be Sectioned selector.
• When the Include surfaces to be sectioned check box is cleared, no twist will be applied to the surfaces selected for the Surfaces to Be Sectioned selector. In case, you want to apply twist to these surfaces, then select them exclusively for the Entities selector.

Under the Preserving node, you can use the Entities selector to select the curves that will be preserved during the twist modification. You can make selection for:

• Curves: The position of the selected curves are preserved (maintaining the Positional G0 continuity).
• Tangency Curves: The position of the selected curves and their tangency conditions are preserved (maintaining the Tangency G1 continuity).

Additionally, you can define the preserving condition for the curve selected as the Spine Curve.

• When the Include spine curve check box is selected, the G0 continuity preserving conditions are automatically applied to the curve selected for the Spine Curve selector.
• When the Include spine curve check box is cleared, by default the curve selected for the Spine Curve selector is NOT preserved.

The setting for the Molding Direction option impacts the orientation of the section planes generated over the spine curve, as it defines the X-direction of the section plane. You need to make a selection based on the option chosen in the Molding Direction drop-down list:

Click here for graphic illustration.

The setting for the Section Direction option also impacts the orientation of the section planes generated over the spine curve, as it defines the Z-direction (or the normal) of the section plane. You need to make a selection based on the option chosen in the Section Direction drop-down list:

Click here for graphic illustration.

The More Options provides you additional standard GSM functionalities of Shape Control, Precision, and Approximation. However, the Advanced Options is explicit for the GSM Spined Twist command, click here for details.

On selecting the Show section curves check box, the preview of the twist on the section curves will be visible on the model.

Try to ...

• Create a Spined Twist Surface
• Create a Spined Twist Surface (Advanced)

Related topics

• Advanced Options of the GSM Spined Twist Command
• Managing the Section Planes
• Orientating the Section Planes

Methodology articles related to this topic

• The benefits of GSM

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