Molded Part Validation (DFM)

Analysis › Molded Part Validation on the Modeling ribbon checks a part against the rules of a manufacturing process before it goes to the toolmaker. The checks come from the DFM Workbench (Ryan Kembrey, LGPL-2.1-or-later), which NX-Style bundles unmodified in vendor/FreeCAD-DFM-Workbench and the launcher loads. Its commands exist from start-up, so they sit on the Modeling ribbon; there is no separate application to switch to. The add-on’s own command name is shown in each button’s tooltip (FreeCAD: DFM Analysis under Moldability Validation).

Before the first use

The add-on needs OCP (cadquery-ocp), which FreeCAD does not ship, and gmsh for its colour maps. Until they are installed the launcher prints DFM: off: it needs OCP and the group is not on the ribbon. Install them once:

python launch_nx.py --install-dfm-deps

This runs FreeCAD’s own Python (pip install --no-deps) and puts cadquery-ocp 7.8.1.1.post1, VTK 9.3.1 and gmsh 4.15.2 in FreeCAD-NXStyle/pydeps/py311, beside the NX profiles and outside the FreeCAD installation. cadquery-ocp 7.8.1 matches the OpenCASCADE 7.8.1 that FreeCAD 1.1 is built on. --no-deps keeps VTK from bringing in numpy 2 and matplotlib, which would shadow FreeCAD’s own copies. Of VTK only its DLLs are kept, which OCP links to: FreeCAD ships VTK 9.3.1’s Python package itself for Pre/Post (FEM), and a second copy on the path made switching to Pre/Post hang. The launcher then adds that folder to FreeCAD’s module path (-M) ahead of the add-on, and never downloads anything by itself.

The buttons

Button	Add-on command	Does
Moldability Validation	DFM Analysis	Checks the selected part (or the only body in the part) against every rule of a process and material, and lists the findings.
Check Wall Thickness	Thickness Analysis	Colours the part by wall thickness on a uniform mesh, with a legend.
Draft Analysis	Draft Analysis	Colours the part by draft angle to a pull direction on a uniform mesh.
Process Library	Process Library	Creates and edits processes, their rules and their materials' limits.

Button

Add-on command

Does

Moldability Validation

DFM Analysis

Checks the selected part (or the only body in the part) against every rule of a process and material, and lists the findings.

Check Wall Thickness

Thickness Analysis

Colours the part by wall thickness on a uniform mesh, with a legend.

Draft Analysis

Draft Analysis

Colours the part by draft angle to a pull direction on a uniform mesh.

Process Library

Process Library

Creates and edits processes, their rules and their materials' limits.

NX has the first three under the same names: Moldability Validation on the Molded Part Design tab, Check Wall Thickness under Molded Part Validation, and Draft Analysis in the Face Shape group of the Analysis tab. Process Library has no NX counterpart and keeps the add-on’s name. NX’s Check-Mate checkers are not mapped: the add-on has no checker framework of that kind.

What Moldability Validation checks

The add-on ships one process, Plastic Injection Molding, with these rules. The limits shown are its Default material’s; each other material (ABS, PC, PP, …) overrides some of them.

Rule	Severity	Finding
Minimum Draft Angle	error below 0.5°, warning below 1°	A face too close to parallel with the pull direction (default +Z), so it drags on ejection.
Minimum Wall Thickness	error below 0.5 mm, warning below 1 mm	A section too thin to fill.
Maximum Wall Thickness	error above 5 mm, warning above 4 mm	A section that cools slowly: sink marks and voids.
Undercut	error	A face trapped behind other geometry along the pull direction (needs a slider or lifter).
Sharp Internal Corners	error	A concave edge with no radius: a stress raiser that disturbs the flow.
Sharp External Corners	warning	A convex edge with no radius: a sharp inside corner in the mold, which needs EDM.

Rule

Severity

Finding

Minimum Draft Angle

error below 0.5°, warning below 1°

A face too close to parallel with the pull direction (default +Z), so it drags on ejection.

Minimum Wall Thickness

error below 0.5 mm, warning below 1 mm

A section too thin to fill.

Maximum Wall Thickness

error above 5 mm, warning above 4 mm

A section that cools slowly: sink marks and voids.

Undercut

error

A face trapped behind other geometry along the pull direction (needs a slider or lifter).

Sharp Internal Corners

error

A concave edge with no radius: a stress raiser that disturbs the flow.

Sharp External Corners

warning

A convex edge with no radius: a sharp inside corner in the mold, which needs EDM.

The add-on’s rulebook also has a maximum overhang angle and a maximum bridge span, for processes such as 3D printing that you define in the Process Library.

How to run it

Select the part (a Body, or a Part solid), then Analysis › Molded Part Validation › Moldability Validation.
In the task panel, choose the material. The category and the process fill themselves while the add-on has only one of each. The pull direction is +Z unless you click a face or an edge for it.
Run Analysis. The results panel lists the findings by criticality and rule; click one to highlight its face or edge, and double-click to zoom to it. Rules with no finding are listed under Passed.
Save keeps the results in the document; Close restores the part’s colours. The panel also exports CSV and compares runs (its History tab).

Switching it off

python launch_nx.py --no-dfm, or "dfm": "none" in nxstyle.json, starts without the add-on, and the Molded Part Validation group is not on the ribbon. A DFM Workbench already installed in the NX profile’s Mod folder (by the Addon Manager) is used instead of the bundled one, never both.

Limits

The checks are rule-of-thumb checks for a designer, not a mold-flow simulation.
Findings name faces and edges by number (Edge7). If the part changes after a saved analysis, the add-on warns when the document is opened again that those numbers may have moved.
Check Wall Thickness and Draft Analysis mesh the part with gmsh; a very fine mesh on a large part takes a while.