Siemens NX Composite Curve Python Automation tool

A Python-based engineering tool that automates the extraction of composite curves from Siemens NX CAD models, reducing manual pre-processing time by 90%

Demo

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Problem Statement

In Aerospace,Wind and automotive composite workflows, engineers must prepare CAD geometry for downstream manufacturing activities like (Layup planning, Material Cutting and Kitting, Laser projection, etc.).

The Manual Process

1. Engineers manually identify curve boundaries on complex surfaces in 3D Model.
2. They use point-and-click operations to extract curves one by one and save this individually.
3. Result: This takes 30-40 minutes per part and is prone to human selection errors.

The Solution

I developed a Python script utilizing the NXOpen API to programmatically export the geometry. By inputting a single Feature Group, the algorithm detects, filters, and extracts the necessary composite curves automatically from the selected group.

Key Benefits: Efficiency: Reduces extraction time from minutes to seconds. Repeatability: Removes human variability; the output is standard every time. Scalability: Capable of processing complex assemblies that would be tedious to handle manually.

Architecture & Logic

The script follows a modular extraction pipeline:

graph LR
    Start([User Starts Tool]) --> GUI[GUI Opens];
    
    subgraph User_Inputs [Configuration]
        direction TB
        GUI --> SelectModel[/Select Model/];
        SelectModel --> SelectFolder[/Select Output/];
        SelectFolder --> TypeName[/Enter Group Name/];
        TypeName --> Run[Click 'Export'];
    end
    
    Run --> Open[Open Model];
    Open --> Search{Group Found?};
    
    Search -- No --> Error[Log Error];
    Search -- Yes --> Iterate[Iterate Curves];
    
    Iterate --> Export[Export IGES];
    Export --> Finish([Done]);

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Technical Implementation Details

The application is built on a hybrid architecture combining a standard Python GUI (Tkinter) with the proprietary Siemens NXOpen API.

1. NX Environment Integration

• Custom Environment Configuration: The script dynamically re-maps TCL_LIBRARY and TK_LIBRARY paths at runtime. This resolves conflicts between the standard Python interpreter and Siemens NX's embedded Tcl/Tk environment, ensuring the GUI renders correctly.
• Session Management: Utilizes NXOpen.Session.GetSession() to hook into the active CAD instance, allowing real-time manipulation of loaded parts.

2. The Extraction Algorithm

The core logic (_nx_export_composite_curves) follows a robust selection pipeline:

• Part Traversal: Iterates through a user-defined list of .prt files, opening them via Parts.OpenActiveDisplay.
• Smart Filtering: * Traverses the Feature Tree (work_part.Features).
  • Identifies NXOpen.Features.FeatureGroup objects matching the user's input string.
  • Extracts specific CompositeCurve members using .GetMembers(), ignoring irrelevant geometry.
• IGES Export Automation:
  • Instantiates the DexManager (Data Exchange Manager).
  • Configures the IgesCreator class programmatically (setting BcurveTol, ObjectTypes.Curves, and ReferenceType).
  • Executes the export commit without triggering UI dialogs (Headless execution).

3. Memory & Resource Management

• Clean Garbage Collection: Implements a strict _nx_close_part routine using NewPartCloseResponses to force-close parts after processing. This prevents RAM bloating and "Part Modified" warnings during large batch jobs.
• Event Loop Management: uses manual self.update() calls within the processing loop to prevent the Tkinter GUI from freezing ("Not Responding") during synchronous NX operations.

Code Snippet

The core logic that filters Feature Groups and configures the IGES exporter:

def _nx_export_composite_curves(self, part_file_path, output_dir):
    # ... (Session setup omitted for brevity) ...

    # 1. Feature Group Filtering Logic
    if target_group_name:
        for feature in work_part.Features:
            # Check if feature matches name AND is a Feature Group
            if feature.Name.upper() == target_group_name.upper():
                if isinstance(feature, NXOpen.Features.FeatureGroup):
                    # Extract members specifically from this group
                    members = feature.GetMembers()
                    for member in members:
                        if isinstance(member, NXOpen.Features.CompositeCurve):
                            composite_curve_features.append(member)

    # 2. Programmatic IGES Configuration
    igesCreator = self.theSession.DexManager.CreateIgesCreator()
    igesCreator.ExportModelData = True
    igesCreator.ObjectTypes.Curves = True
    igesCreator.BcurveTol = 0.0508  # Set precise tolerance
    
    # 3. Export Execution
    igesCreator.OutputFile = output_path
    igesCreator.Commit()
    igesCreator.Destroy()

Source Code & Collaboration

This project is currently closed-source for portfolio demonstration.

The full source code (Python scripts, NXOpen implementation, and Tkinter GUI) is available for Code Review or Collaboration upon request.

How to Request Access I am actively looking for collaborators and feedback! If you are a hiring manager or developer interested in the technical details:

Email: [Aneesh.binage06@gmail.com]

LinkedIn: [https://www.linkedin.com/in/aneesh-shridhar-b-165468154/]

Upon request, I can add you as a Collaborator to the repository or provide a secure code walkthrough.

About the Author

Aneesh Shridhar B Masters Student in Intelligent Manufacturing @ TU Clausthal, Germany | Composite Design & Manufacturing Engineer

With over 6 years of industrial experience at global leaders like General Electric, Tata Advanced Systems, and Enercon GmbH, I specialize in bridging the gap between physical composite manufacturing and digital automation.

My expertise lies in optimizing aerospace and wind energy workflows, moving from traditional design to Industry 4.0 implementation.

• Core Domain: Manufacturing Engineering, Composite Design (CATIA/NX), and Digital Manufacturing.
• Specialized Tech: CATIA V5, Siemens NX, Laser Projection Systems, Process Vision (Ply placement verification & wrinkle detection).
• Automation: Python scripting for CAD/CAM (NXOpen, CATIA Automation).