Enter the trim line mode by clicking Trim Line on the Tools panel.

By values: Trim lines can be updated according to the parameters of offset and smoothness set in the settings or on the Trim Line panel. Steps:
Offset: The larger the value, the further the distance between trim line and gum line.
Smoothness: The larger the value, the smaller the curvature of the line.
Offset =0.50mm
Smoothness=1.0mm

Offset =1.10mm
Smoothness=3.0mm

By control points: Trim lines can be updated by applying the customized the positions of control points. Steps:

If you would like to customize trim line on different stages separately, you can enable Adjust Each Stage Separately. By doing so, trim line on different stages can be automatically updated at real time based on the customized position of control points.
View or generate trim line directions by clicking Trim Line (Direction) on the Tools panel in trim line mode. Trim line (direction) is currently only available for ArchMill users.
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View trim line directions
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Update trim line directions
Select the arch whose trim line directions need modifications at the top.
If needed, select a bit type and set its length.
Change parameters of trim line directions. If you would like to customize trim line directions on different stages separately, you can enable Adjust Each Stage Separately. By doing so, trim line on each stage can be automatically updated at real time based on the customized position of control points.
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Click Update Trim Lines to generation trim line directions based on the customized parameters.
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