CAM DressupDragKnife

CAM DressupDragKnife CAM DressupDragKnife

Menu location

CAM  Path Dressup  Drag Knife

Toolbar

Path Modification → Dressup Operations dropdown

Workbenches

CAM

Default shortcut

None

Introduced in version

-

See also

CAM DressupTag, CAM DressupRampEntry, CAM DressupDogbone

Description

The CAM DressupDragKnife CAM DressupDragKnife command supports a drag knife: a cutting edge on a pivot used to cut sheet material like vinyl, cardboard, and leather. The cutting point is not aligned with the center of the spindle but rather follows it as the spindle moves. Because the cutting point is offset, the Toolpath must be extended past the endpoint of each segment. Also, the drag knife is incapable of making extremely tight turns. To compensate, a pivot corner action is inserted, which momentarily lifts the blade slightly and then pivots into the new position.

This command dresses up an existing Toolpath to add corner actions and segment extensions for drag knife cutting. Its tooltip reads: Modifies a toolpath to add dragknife corner actions.

At every corner whose included angle is at least Filter Angle the dressup extends the incoming segment by the offset, lifts the knife to Pivot height with a rapid move, swings the blade around the corner with an arc (G2 or G3, whichever is the shorter rotation) and plunges back to the cutting depth with a feed move. At the end of a cut (before a rapid retract above Pivot height) the last segment is extended by the offset. Straight and arc segments are supported.

Usage

  1. Select one Operation or Dressup.

  2. There are several ways to invoke the command:

    • Select the CAM  Path Dressup  Drag Knife option from the menu.

    • Select the Dressup Operations dropdown on the Path Modification toolbar.

    • Select the Path Dressup  Drag Knife option from the Tree view context menu.

  3. Set Filter Angle, Offset distance and Pivot height in the task panel and press OK (values are applied on OK, not live).

Options

The task panel is titled Dragknife Dressup:

  • Filter Angle: Angles less than the filter angle will not receive corner actions; default 20°.

  • Offset distance: Distance the blade point trails behind the spindle center; default 2 mm.

  • Pivot height: Height to raise during a corner action; default 4 mm. This is material dependent; ideally the point should remain slightly in the material.

Properties

Path

  • Base (Link): The base Toolpath to modify.

  • filterAngle (Angle): Angles less than filter angle will not receive corner actions.

  • offset (Float): Distance the point trails behind the spindle.

  • pivotheight (Float): Height to raise during corner action.

Note the lower-case property names.

Scripting

import FreeCAD
import Path.Dressup.Gui.Dragknife as Dragknife
import PathScripts.PathUtils

obj = FreeCAD.ActiveDocument.addObject("Path::FeaturePython", "DragknifeDressup")
Dragknife.ObjectDressup(obj)
obj.Base = op
job = PathScripts.PathUtils.findParentJob(op)
job.Proxy.addOperation(obj, op)
obj.ViewObject.Proxy = Dragknife.ViewProviderDressup(obj.ViewObject)

obj.filterAngle = 20
obj.offset = 2
obj.pivotheight = 4
FreeCAD.ActiveDocument.recompute()