Offset 2D¶

In one sentence: Offset a 2-D wire or face inward or outward within its plane — the 2-D equivalent of inflating or deflating a closed profile.

Overview¶

Workbench: Part · Menu: Part → Offset 2D
Toolbar: Part Modeling · Shortcut: none

Offset 2D offsets a 2-D closed wire or face in its own plane by a uniform distance. The result is a new wire or face at the specified offset. This is the planar equivalent of Offset 3D.

Intuition¶

Given a square profile, Offset 2D with a positive value produces a larger square with rounded or chamfered corners. With a negative value it produces a smaller square. This is the same operation performed by a router following an offset toolpath, or by the "expand/contract selection" operation in a vector graphics editor.

Common uses: - Generating a clearance profile around a 2-D outline. - Creating a slightly smaller inner profile for a snap-fit feature. - Offsetting a sketch profile before extruding (instead of changing the sketch dimensions one by one).

When to use it¶

You have a 2-D wire or face and need a uniformly grown or shrunk version of it.
Creating a wall-thickness offset of a 2-D profile before extruding.

When NOT to use it¶

3-D shape offset — use Offset 3D.
Non-uniform scaling — use Scale.

Parameters¶

Parameter	Type	Default	Description
Source	Wire or Face	—	The 2-D profile to offset
Value	Distance	1 mm	Offset distance (positive = outward, negative = inward)
Mode	Skin / Pipe	Skin	Outer face handling
Join	Arc / Tangent / Intersect	Arc	How convex corners are joined
Inner Mode	Ignore / Fill	Ignore	Handling of inner (concave) corners
Open Result	Bool	No	Allow open result wire (no closing caps)

Join modes¶

Mode	Description
Arc	Convex corners are rounded with an arc of the offset radius
Tangent	Convex corners are extended to tangent intersection (sharp miter)
Intersect	Convex corners are extended to their intersection (miter, may spike)

Step-by-step walkthrough¶

Select the 2-D wire or face in the viewport.
Part → Offset 2D.
Set the Value (positive to grow, negative to shrink).
Choose the Join mode for how convex corners are treated.
Click OK.

Python API¶

import FreeCAD as App
import Part

doc = App.newDocument()

# Square wire in XY plane
p1 = App.Vector(0, 0, 0); p2 = App.Vector(20, 0, 0)
p3 = App.Vector(20, 20, 0); p4 = App.Vector(0, 20, 0)
wire = Part.Wire([
    Part.makeLine(p1, p2), Part.makeLine(p2, p3),
    Part.makeLine(p3, p4), Part.makeLine(p4, p1)
])
face = Part.Face(wire)

# Offset outward by 3 mm with arc corners
offset_shape = face.makeOffset2D(3.0, join=0)  # join 0=Arc, 1=Tangent, 2=Intersect
feat = doc.addObject("Part::Feature", "OffsetFace")
feat.Shape = offset_shape
doc.recompute()

Common mistakes and pitfalls¶

Negative offset past the inscribed circle

If the inward offset is larger than the inscribed circle radius of the profile, the profile collapses. For a square of side 20 mm, the maximum inward offset is 10 mm.