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Dress-up: Drag Knife

In one sentence: Adapt a toolpath for a drag knife cutter by adding small swivel arcs at sharp corners so the blade can rotate to the new direction.

Overview

Workbench: CAM
Menu: CAM → Dress-up → Drag Knife
Command: CAM_DressupDragKnife
Shortcut: none

Modifies a toolpath to accommodate a drag knife — a blade that trails behind the motion direction rather than cutting from the front like a rotating mill. At each sharp corner, the path is extended with a small "swivel" arc that allows the blade to pivot to the new cutting direction before the corner is reached.

Intuition

A drag knife blade offset from its pivot point. As the machine changes direction, the blade needs to swing around before it can track the new direction correctly — if the machine simply turns the corner, the blade drags sideways and leaves a ragged cut. The swivel arc gives the blade room to pivot while keeping the cutting point stationary.

When to use it

  • Vinyl cutting, foam cutting, or paper cutting with a drag knife tool.
  • Any machine equipped with a trailing blade rather than a rotating spindle.

When NOT to use it

  • Rotating end mill or drill operations — swivel arcs make no sense with a spinning cutter.

Key parameters

Parameter Description
Angle Minimum corner angle (degrees) that triggers a swivel arc
Radius Radius of the swivel arc

See also