What Is 3D Scanning and How Does It Work?

You're producing great parts with 3D printing. But having to do CAD modeling from scratch every time is exhausting. What if you have a physical object in hand and want its digital copy? This is exactly where 3D scanning comes into play.

3D scanning is the art of transferring physical objects to the digital environment. In a sense, it's the reverse of 3D printing: printing goes from digital to physical, while scanning goes from physical to digital. This technology is used in a wide range from reverse engineering to preserving artworks, from prosthetic production to quality control.

In this article, we'll explore the basic principles of 3D scanning, different scanning methods, and practical applications.

What Is 3D Scanning?

3D scanning is a measurement technology that captures the three-dimensional geometry of an object. The scanner detects the position of thousands or millions of points on the object's surface. This point cloud is then converted into a digital 3D mesh.

Scanning Process: Step by Step

1. Data Capture The scanner reads the object from different angles. Each reading records the position of points on the surface.

2. Point Cloud Millions of 3D points are obtained. Each point has X, Y, Z coordinates. Some scanners also capture RGB color information.

3. Mesh Creation The point cloud is converted into a surface (mesh) made of triangles. This process is called "meshing."

4. Cleaning and Processing Errors in the mesh are corrected: holes are filled, noise is cleaned, smoothing is done.

5. Export The result is saved in standard 3D file formats like STL, OBJ, PLY.

Scanning Technologies and Methods

1. Structured Light Scanning

How It Works: A projector reflects a specific pattern (lines or grid) onto the object. The camera sees how this pattern deforms on the object's surface. Through mathematical calculations, surface geometry is determined.

Advantages:

• High precision (up to 0.05 mm)
• Fast scanning
• Medium range (10 cm - 2 meters)
• Texture/color capture available

Disadvantages:

• Difficulty with shiny or transparent surfaces
• Stable environment (sensitive to light changes)
• Suitable for medium-sized objects

Use:

• Reverse engineering
• Quality control
• Model extraction for 3D printing
• Human body scanning

Example: Creality CR-Scan Lizard, Revopoint POP 3

2. Laser Triangulation

How It Works: A laser beam projects a line onto the object. The camera sees this line. From the triangular angle between laser, camera, and object, distance is calculated.

Advantages:

• Very high precision (0.01 mm)
• Good on shiny surfaces
• Industrial quality

Disadvantages:

• Slow (scans line by line)
• Expensive
• Complex setup

Use:

• Precise industrial measurement
• CMM (Coordinate Measuring Machine) integration
• Quality control

3. Photogrammetry

How It Works: Dozens or hundreds of photos of the object are taken from different angles. Software finds common points in the photos and creates a 3D model.

Advantages:

• Zero equipment cost (phone camera sufficient)
• Very large objects (buildings, sculptures)
• Full-color texture automatic

Disadvantages:

• Time-consuming (photo taking + processing)
• Lower precision (1-5 mm)
• Good lighting required
• Fails on monotonous surfaces

Use:

• Architectural documentation
• Archaeological excavation
• Large sculptures
• Assets for film and games

Software: Meshroom (free), RealityCapture, Agisoft Metashape

4. LiDAR (Light Detection and Ranging)

How It Works: Sends laser pulses, measures return time. Distance is calculated. Millions of points collected per second.

Advantages:

• Very fast
• Very long range (100+ meters)
• Works in darkness

Disadvantages:

• Expensive equipment
• Low detail (for small objects)
• Limited color capture

Use:

• Mapping
• Autonomous vehicles
• Architectural measurement
• Forestry

Note: iPhone Pro models have LiDAR (can be used for small-scale scanning).

5. CT Scanning (Computed Tomography)

How It Works: Using X-ray or other radiation, images the internal structure of the object. Sections are taken, 3D model is created.

Advantages:

• Internal structure visible
• No transparent/shiny surface problem
• Very high detail

Disadvantages:

• Very expensive (100,000+ EUR)
• Radiation (safety requirements)
• Slow
• Not suitable for large objects

Use:

• Medical (bone, organ)
• Industrial (quality control, internal defect detection)
• Fossil analysis

Reverse Engineering

Reverse engineering is the process of extracting technical information from an existing product. 3D scanning is the fundamental tool of reverse engineering.

Usage Scenarios

1. Spare Part Production An old machine's part broke, manufacturer no longer produces it. Scan the part, extract 3D model, produce with 3D printing or CNC.

2. Design Improvement Scan competitor's product, analyze, improve your own design.

3. Lost CAD Model Product exists but CAD files lost. Recreate CAD through scanning.

4. Quality Control Scan manufactured part, compare with original CAD. Detect deviations.

Reverse Engineering Workflow

Step 1: Scanning Scan the object from all angles. Leave no missing parts.

Step 2: Mesh Processing

• Hole filling
• Noise cleaning
• Smoothing
• Decimation (reduce if too many polygons)

Step 3: Mesh to CAD Mesh is typically in STL format (triangles). For CAD, it needs to be converted to parametric model.

Software:

• Geomagic Design X (professional, expensive)
• Fusion 360 Mesh to BRep (intermediate level)
• FreeCAD (free, manual)

Step 4: CAD Modeling Using the shape obtained from scanning as reference, create parametric CAD model. This provides full precision and editability.

Scan + Print Workflow

3D scanning and 3D printing create a perfect combination. Here are practical examples:

Example 1: Broken Plastic Part Repair

Problem: Plastic bracket of an old device broke. Spare part not available.

Solution:

1. 3D scan the intact bracket
2. Clean the mesh, export STL
3. Mirror in slicer - because you scanned right side, need left
4. Print with FDM or resin
5. Install, problem solved!

Time: 2-3 hours (scanning 15 min, processing 30 min, printing 1-2 hours)

Example 2: Custom Prosthetic

Problem: Patient's finger missing, personalized prosthetic needed.

Solution:

1. 3D scan patient's hand
2. Process mesh, measure parameters
3. Design prosthetic in CAD (scan as reference)
4. Print with resin or PEEK
5. Fit to patient

Advantage: Personalized, perfect fit

Example 3: Artwork Replication

Problem: Want to replicate museum sculpture.

Solution:

1. Scan sculpture with photogrammetry or structured light
2. Obtain mesh with full-color texture
3. Scale (original 2 meters → 20 cm desktop version)
4. Print with resin or FDM
5. Paint or use texture mapping

Example 4: Product Customization

Problem: Customer wants custom version of your standard product.

Solution:

1. Scan standard product
2. Make customization in CAD (logo, name, special feature)
3. Print and ship

Advantage: Mass production + personalization

Practical Scanning Tips

1. Surface Preparation

Shiny Surfaces: Apply matte spray or powder. Cleaned after scanning.

Transparent Objects: Almost impossibly difficult. Painting or powder application mandatory.

Black Objects: Can be problematic for laser scanners. Spray white powder.

2. Reference Points

For complex objects, place stickers or markers on surface. Software uses these points to align different scans.

3. Multiple Scans

A single scan may not be sufficient. Scan object from different angles, software merges them.

4. Stable Environment

Light changes disrupt structured light scanners. Work under stable lighting.

5. Precision vs Speed

High precision = slow scanning + large file. Choose as much precision as you need. 0.2 mm sufficient for visual models, 0.05 mm may be needed for precise measurement.

Conclusion: Bridge Between Physical and Digital

3D scanning transfers the physical world to digital. Reverse engineering, prosthetic production, preservation of artworks, quality control... Applications are limitless. The combination of 3D scanning + 3D printing is opening a new era in manufacturing and design.

For Beginners:

• Low budget: Photogrammetry (phone + free software)
• Medium budget: Structured light scanner (Creality, Revopoint)
• Professional: Laser or industrial scanners

In our next article, we'll look in more detail at what can be done with 3D scanning. We'll give examples with case studies from industrial applications to art projects.