Definition: Reverse engineering is the reconstruction of 3D geometries and design data from physical objects through 3D scanning and CAD modeling. In mechanical engineering, companies use reverse engineering to create digital 3D models of existing components for which CAD data no longer exists.

In B2B mechanical engineering, companies use reverse engineering for: spare parts production for legacy machines (CAD data lost), documentation of existing plants for digital twins, quality control (target/actual comparison), competitive analysis (legal product analysis) and product improvement (optimization of an existing design).

Typical workflow: Physical part → 3D scan (LiDAR, photogrammetry) → point cloud → surface reconstruction (surfacing) → CAD model.

English: Reverse Engineering German: Rückwärtskonstruktion, Nachkonstruktion

Technologies

3D Scanning Methods

Laser scanning (LiDAR):

How it works: A laser measures distances and creates a point cloud.

Accuracy: 10-50 µm (0.01-0.05 mm) with industrial scanners.

Application: Precision parts, complex geometries, large components (housings, frames).

Advantages: High accuracy, fast, works on all surfaces.

Disadvantages: Expensive (€20,000-80,000 per scanner), reflection problems on mirror-like surfaces.

Example devices: Faro Freestyle, GOM ATOS, Artec Leo.

Structured light projection:

How it works: Projectors cast stripe patterns onto the object, and cameras capture the distortion.

Accuracy: 5-30 µm (highest precision).

Application: Small precision parts, quality control, tools.

Advantages: Very high accuracy, detailed capture.

Disadvantages: Slower than laser, sensitive to ambient light, only small objects.

Example devices: GOM ATOS, ZEISS COMET.

Photogrammetry:

How it works: Many photos from different angles → software reconstructs the 3D geometry.

Accuracy: 0.1-1 mm (depends on the camera and the object size).

Application: Large objects (complete machines, plants), cost-efficient scanning.

Advantages: Low cost (a normal camera is sufficient), large objects possible, no special hardware.

Disadvantages: Lower accuracy, labor-intensive (many photos necessary), needs good lighting.

Example software: Agisoft Metashape, RealityCapture.

Tactile coordinate measuring machines (CMM):

How it works: A mechanical probe moves along the object and records measurement points.

Accuracy: 1-5 µm (highest precision).

Application: Quality control, precision parts, reference measurements.

Advantages: Highest accuracy, certifiable measurements.

Disadvantages: Very slow (point by point), expensive, only small to medium-sized objects.

Scan-to-CAD Workflow

Step 1: Preparation

Clean the object: Remove dust and oil (they affect the scan quality).

Prepare the surface: Treat shiny or transparent parts with a matte spray (better laser reflection).

Reference markers: Adhesive markers on the object (for scan registration from several perspectives).

Step 2: 3D Scan

Procedure: - Scan the object from several angles (completeness) - Overlapping areas for registration - Capture critical details several times

Result: Raw point cloud (millions of 3D points).

Step 3: Point Cloud Processing

Registration: Merge several scans into one point cloud.

Cleaning: Remove noise, delete outliers, remove moving objects (people).

Decimation: Reduce the point density (for faster processing).

Software: CloudCompare (open source), Geomagic Wrap, Polyworks.

Step 4: Surface Reconstruction (Surfacing)

Mesh generation: Point cloud → polygon mesh (triangles).

NURBS surfacing: Polygon mesh → precise CAD surfaces (NURBS).

Methods: - Automatic: The software generates surfaces (fast, but imprecise) - Semi-automatic: The software makes suggestions, a person corrects them - Manual: A CAD designer creates surfaces over the point cloud (time-consuming, but precise)

Software: Geomagic Design X, Autodesk Fusion 360, SOLIDWORKS (with the ScanTo3D plugin).

Step 5: CAD Modeling

Create a parametric model: - Extract features (holes, threads, radii) - Parametric constraints (dimensions, relations) - Editable design (not only "frozen" geometry)

Result: Native CAD model (SLDPRT, IPT, PRT), fully editable.

Step 6: Validation

Target/actual comparison: Overlay the scan data and the CAD model, and measure the deviations.

Color-coded deviation analysis: Green = within tolerance, red = deviation.

Acceptance: Deviations <0.1 mm are usually acceptable (depends on the application).

B2B Applications

Spare Parts Production for Legacy Machines

Problem: A machine from the 1990s has a defective part. The CAD data no longer exists, and the manufacturer is out of business.

Solution with reverse engineering: 1. 3D-scan the defective part 2. Reconstruct the CAD model 3. Manufacture the part (CNC, 3D printing, casting) 4. Install it in the machine

Benefit: The machine stays productive, and no expensive new purchase is necessary.

Example: Gear of a packaging machine (built in 1995) → scan → CAD → CNC milling → installed.

Creating a Digital Twin

Problem: You want to document an existing production plant as a digital twin, but the CAD data is out of date or not available.

Solution: 1. 3D-scan the complete plant (LiDAR) 2. Convert the point cloud into a 3D model 3. Add IoT sensor data 4. Use the digital twin for simulation and monitoring

Benefit: As-built documentation (the actual condition, not the planned condition).

Quality Control (Target/Actual Comparison)

Problem: Check produced parts for dimensional deviations.

Workflow: 1. CAD model as the target geometry 2. Scan the produced part (actual geometry) 3. Automatic comparison 4. Color-coded deviation analysis

Benefit: Faster than manual measurement, complete capture (not only random samples), visual display of problem zones.

Application: Cast parts, formed sheet metal parts, additively manufactured components.

Product Improvement

Scenario: You want to optimize an existing product (weight reduction, ergonomics).

Workflow: 1. Scan the current product (baseline) 2. Create the CAD model 3. Make optimizations (topology optimization, generative design) 4. Manufacture the new version 5. Scan and validate

Benefit: Iterative improvement based on real geometries.

Competitive Analysis (Legal)

Legal framework: You may analyze publicly available products (aspects that are not patented).

Workflow: 1. Scan the competitor's product 2. Understand the design principles 3. Develop your own solution (do not copy!)

Important: No 1:1 copy (respect patents and copyright). Use the analysis only for your own innovation.

Challenges

Accuracy vs. Cost-Efficiency

Dilemma: Higher accuracy = more expensive scanners + longer post-processing.

Decision criteria: - Precision parts (tolerances <0.1 mm): Structured light scanner, manual NURBS modeling (~20-40 h) - Standard components (tolerances 0.5-1 mm): Laser scanner, semi-automatic surfacing (~8-16 h) - Rough documentation (tolerances >1 mm): Photogrammetry, mesh model (~2-4 h)

Rule of thumb: Make the accuracy only as high as necessary (not as high as possible).

Complex Geometries

Problems: Undercuts, cavities, threads.

Solutions: - Several scan positions: Turn the object and scan it from all sides - Disassembly: Take the assembly apart and scan each part - CT scanning: Computed tomography for internal structures (expensive, only small parts) - Manual completion: Model the undercuts in CAD

Reflection Problems

Critical surfaces: Polished stainless steel, chrome, glass.

Solutions: - Matte spray: Temporary matte coating (soluble, removable) - Powder scanning: Apply a special powder - Photogrammetry: Less sensitive to reflections

Data Volume

Problem: Scans create very large files (point clouds of 10-100 GB).

Handling: - Powerful hardware: Workstations with 64+ GB RAM - Cloud processing: Server-based processing - Decimation: Reduce the point density (without loss of quality)

Patent Law

Rule: You must not reproduce patented inventions without a license.

Reverse engineering: Analysis is legal. Reproduction without a license is illegal.

Rule of thumb: Do a patent search before you reproduce a part (DPMA, EPO, USPTO).

Copyright

Design protection: Designs can be protected by copyright.

Reverse engineering: Analysis for compatibility is often permitted (Software Directive), but a 1:1 copy is prohibited.

Trade Secrets

Problem: Reverse engineering can reveal trade secrets.

Legal: Reverse engineering of legally acquired products is usually permitted.

Illegal: Theft of parts or confidential documents.

Contracts (NDA)

Important: Non-disclosure agreements can prohibit reverse engineering.

Example: A supplier receives components under an NDA → the supplier must not reverse-engineer them.

Recommendation: Get legal advice before you reverse-engineer third-party products.

Frequently Asked Questions (FAQ)

How accurate is reverse engineering?

This depends on the scanner and the workflow. Laser scanning + manual NURBS modeling: 10-50 µm accuracy (0.01-0.05 mm), sufficient for precision parts. Photogrammetry + automatic surfacing: 0.1-1 mm accuracy, sufficient for rough documentation and spare parts. Structured light + CMM validation: 5-10 µm (highest precision), for quality control. Rule of thumb: Reverse engineering achieves 90-95% of the accuracy of the original CAD data (100% only under perfect conditions).

Can you reverse-engineer every part?

Most parts, yes, with limitations. Well suited: Housings, frames, gears, shafts, sheet metal parts, cast parts. Difficult: Very small parts (<5 mm), transparent parts (glass, acrylic), highly reflective parts (polished stainless steel), internal structures (cavities without access). Impossible: Completely hidden geometries (without disassembly or a CT scan), material composition (alloys, coatings). Solution: A combination of scanning, manual measurement and disassembly.

How long does reverse engineering take?

This depends on the complexity and the accuracy. Simple part (shaft, flange): 2-4 hours (scan + basic CAD). Medium part (housing, gear): 8-16 hours (scan + NURBS surfacing). Complex part (assembly, organic shape): 20-40 hours (multiple scans + manual modeling). Rule of thumb: Scan = 10% of the time, CAD modeling = 90% of the time. Automation: Software tools reduce the time, but manual work usually gives better quality.

Is reverse engineering legal?

In most cases, yes, with limitations. Legal: Reverse engineering of legally acquired products for analysis, compatibility (e.g. spare parts) and product improvement (your own innovation). Illegal: 1:1 copies of products that are protected by patents or copyright, violation of NDAs (non-disclosure agreements), theft of parts for reverse engineering. Recommendation: Get a legal review before commercial reverse engineering, do a patent search and respect NDA contracts.

Which software is used for reverse engineering?

Scan software: Manufacturer-specific (Faro Scene, GOM Inspect, Artec Studio). Point cloud processing: CloudCompare (open source), Geomagic Wrap, Polyworks. Surfacing/CAD: Geomagic Design X (market leader), Autodesk Fusion 360, SOLIDWORKS with ScanTo3D, Siemens NX, SpaceClaim. Quality control: GOM Inspect, Polyworks Inspector, Geomagic Control X. Workflow: Scan software → point cloud tool → CAD software → validation.

Industry Standards and Software

3D scanners: - Faro Technologies – Laser scanners, measuring arms - GOM (ZEISS) – Structured light scanners, metrology - Artec 3D – Handheld 3D scanners - Hexagon Metrology – CMM, laser trackers - Creaform (AMETEK) – Portable 3D scanners

Software: - Geomagic Design X – Scan-to-CAD (market leader) - Polyworks – Metrology, reverse engineering - Autodesk Fusion 360 – CAD with mesh-to-NURBS - SOLIDWORKS ScanTo3D – Reverse engineering plugin - CloudCompare – Open source point cloud tool

Standards: - VDI/VDE 2634 – Optical 3D measuring systems - ISO 10360 – Coordinate measuring machines - ASME B89 – Dimensional metrology (US)

3D scanning technologies: - LiDAR – Laser scanning - Photogrammetry – Image-based 3D capture - Structured light projection – Structured light scanning - CT scanning – Computed tomography for internal structures - Coordinate measuring machines – Tactile measurement

CAD and modeling: - 3D model – 3D geometry - NURBS surfacing – Surface reconstruction - Parametric modeling – CAD features - Mesh-to-CAD – From polygon mesh to CAD - CAD formats – STEP, IGES, Parasolid

Quality and metrology: - Target/actual comparison – Deviation analysis - Dimensional metrology – Measurement - First article inspection – Inspection of the first sample - GD&T – Geometric dimensioning and tolerancing - Metrology – Measurement standards

Applications: - Digital twin – Digital replicas - Spare parts production – Spare parts manufacturing - As-built documentation – Documentation of the existing condition - Quality control – Quality assurance - Product development – Development of new products

Data processing: - Point cloud processing – Processing of scan data - Mesh generation – Creation of polygon meshes - Registration – Scan alignment - Decimation – Data reduction - Surface reconstruction – Surfacing