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Replace Object

In one sentence: Swap one object for another throughout the document dependency graph, rewiring all references in a single step.

Overview

Workbench: OpenSCAD
Menu: OpenSCAD → Replace Object
Shortcut: none

Substitutes one Part::Feature with another in the document's dependency graph. All objects that referenced the old object are updated to reference the new one. Used when a base shape is redesigned and must replace the old version throughout a tree of dependent features.

Intuition

Think of it like a global find-and-replace in a text document, but for 3-D objects. Every place the old object was used — as an input to a boolean, a reference in a feature, a shape source — gets updated to point to the new object instead. You don't have to hunt down and re-link each dependency manually.

When to use it

  • You redesigned a base part and want all assemblies and dependent features to use the new version.
  • You are swapping a placeholder shape for a final design.
  • You imported an updated version of a shape and need to splice it into the existing document tree.

When NOT to use it

  • When objects have incompatible topology — if the old and new shapes have different edge/face counts, dependent features that reference specific topology (e.g. a Pocket on Face6) may break after replacement.

Step-by-step

  1. Select 2 or 3 Part::Feature objects:
  2. 3 objects: select old, new, parent — replaces old with new inside parent.
  3. 2 objects: one with no parents (old), one with a parent (new) — the parentless one is replaced everywhere.
  4. Choose OpenSCAD → Replace Object.

Parameters

Input Description
Selection 2–3 Part::Feature objects (old, new, and optionally parent)

Common mistakes and pitfalls

Dependent features break after replacement

Cause: The new object has different face/edge indices than the old one. Features that reference specific topology by index lose their references.
Fix: Check all dependent features after replacement. Re-select the correct face or edge references where needed.

Python API

import FreeCADGui as Gui
# Trigger via GUI command after selecting the objects:
Gui.doCommand("Gui.runCommand('OpenSCAD_ReplaceObject', 0)")

See also