NX

Siemens NX integrates CAD, CAM and CAE in one environment. Learn synchronous modelling, WAVE linking, PMI and GD&T, tolerance stack-ups, integrated CAM, NX Open automation and the Teamcenter digital thread.

NX is used across automotive, aerospace, machinery and medical industries where design, simulation and manufacturing need one connected model. The same geometry drives FEA meshes, CNC toolpaths and inspection programmes.

Its synchronous technology blends history-based and direct modelling, making it strong at editing imported and legacy geometry.

An analogy

NX is a workshop where the designer, analyst and machinist all work on the same bench with the same part — changes flow to everyone instantly.

Modelling in NX

Sketch-based features plus freeform surfaces, sheet metal, routing and weldments. Synchronous modelling lets you move, offset or resize faces directly while respecting relationships (parallel, concentric) — no rebuild history required.

PMI and GD&T

Annotate the 3D model with dimensions, datums and geometric tolerances (flatness, position, profile). GD&T expresses functional requirements unambiguously and feeds CMM inspection programs directly.

Tolerance stack-ups

Parts in an assembly each carry tolerances; the resulting gap varies. Worst-case (arithmetic) stacking guarantees fit but is costly; RSS (statistical) assumes independent normal variations and gives a realistic spread. NX (and tools like VSA) run 3D statistical stack analyses.

Integrated CAM/CAE and digital thread

NX CAM generates multi-axis toolpaths with post-processors and machine simulation; NX CAE / Simcenter meshes and solves structural, thermal and flow problems on associative geometry. WAVE links geometry between parts for top-down design, and Teamcenter manages the digital thread from requirements to manufacturing.

Formulas

• Worst-case stack: T_wc = Σ |t_i|
• Statistical (RSS) stack: T_rss = √(Σ t_i²)
• Nominal gap: G = Σ (± nominal dimensions around the loop)

Worked example: Tolerance stack

Given: 4 stacked parts, each ±0.1 mm

Find: Worst-case and RSS variation.

• Worst case = 4 × 0.1 = ±0.4 mm
• RSS = √(4 × 0.01) = ±0.2 mm

Answer: ±0.4 (WC), ±0.2 (RSS)

Worked example: Gap check

Given: Housing 50.0 ± 0.1; Parts 20.0 ± 0.05, 15.0 ± 0.05, 14.5 ± 0.05

Find: Nominal gap and worst-case range.

• Gap = 50 − (20 + 15 + 14.5) = 0.5 mm
• WC tolerance = 0.1 + 0.15 = ±0.25
• Range 0.25 … 0.75 mm

Answer: Always positive — assembles every time

NX Open (Python) journal: create a block

import NXOpen
import NXOpen.Features

def main():
    session = NXOpen.Session.GetSession()
    part = session.Parts.Work
    builder = part.Features.CreateBlockFeatureBuilder(NXOpen.Features.Feature.Null)
    builder.SetOriginAndLengths(NXOpen.Point3d(0.0, 0.0, 0.0), "100", "50", "20")
    block = builder.Commit()
    builder.Destroy()
    session.ListingWindow.Open()
    session.ListingWindow.WriteLine(f"Created {block.JournalIdentifier}")

if __name__ == "__main__":
    main()

NX Open exposes the full modelling API to Python, C#, C++ and Java — used for design automation and custom tools.

Common mistakes

• Wrong: Applying worst-case stacking to long stacks without thought. — Right: Use RSS/Monte Carlo where processes are in statistical control — it's far cheaper.
• Wrong: Plus/minus tolerancing of hole positions. — Right: Use GD&T position tolerances with datums (bigger tolerance zone, clear function).

Applications

• Automotive & aerospace: Powertrain, interiors and airframe parts with integrated CAM and CAE.
• Tooling: Mould and die design with electrode and CAM modules.
• Medical devices: Freeform implant design and 5-axis machining.

Key takeaways

• One environment for CAD, CAM and CAE.
• Synchronous modelling edits any geometry.
• PMI/GD&T define function; stack-ups verify fit.
• WC = Σt, RSS = √Σt².

Going further

• Monte Carlo stack-ups: Simulating thousands of assemblies with real process distributions predicts reject rates.
• Simcenter 3D: Multiphysics CAE (Nastran-based) associative to NX geometry.
• Knowledge Fusion: NX's rule language for design automation, alongside NX Open.