REVERSE ENGINEERING FROM CT 3D SCAN TO CAD
What is reverse engineering?
Reverse engineering enables the digital reconstruction of physical objects when no CAD data is available. Whether design drawings have been lost, products have been modified after the fact or design studies were made by hand: the reverse engineering process turns physical components into usable digital files. The aim is to understand the design and function and to recreate them digitally for production, optimisation or documentation.
Which 3D scanners are suitable for reverse engineering?
Various technologies are available for capturing objects. The right 3D scanner depends on component size, complexity and the accuracy required.
Optical 3D scanners work with structured light or lasers and capture the visible surface of the object. They are well suited to freeform surfaces and organic shapes. Accuracy is typically 0.02 to 0.1 mm. The drawback: internal structures, undercuts and concealed areas cannot be captured. Complex assemblies require multiple scans from different angles, which then have to be merged.
Industrial computed tomography (CT) penetrates the entire object with X-rays and produces a complete 3D volume model. Unlike optical scanners, it also captures internal structures, cavities and hidden geometries. Modern CT systems achieve a precision of less than 10 micrometres. For reverse engineering complex components with internal geometries, CT is often the only practical method.
Tactile coordinate measuring machines (CMM) probe individual points on the surface. They deliver the highest accuracy but are too slow for capturing complex freeform surfaces and do not record any volume data.
When is CT better suited than a surface scanner?
Industrial computed tomography offers decisive advantages over optical 3D scanners in reverse engineering when certain requirements apply. A CT scan is particularly worthwhile for complex components.
CT is the better choice for:
- Internal structures: Channels, cavities and wall thicknesses are captured completely
- Complex assemblies: Assembled components do not have to be taken apart
- Undercuts: Geometries that are not visible from the outside
- Hard-to-reach areas: Deep bores, narrow gaps
- Material analysis: CT also shows the internal condition of the material
A turbocharger, for example, contains complex flow channels that are not visible from the outside. An optical scanner would require disassembly, which could damage sealing surfaces and fits. The CT scan captures the entire component non-destructively in a single scan.
Modern CT systems can also capture large components with an enveloping circle of up to 798 mm or a length of up to 1802 mm, depending on the component, weight, material and cumulative wall thickness. Even materials that are difficult to penetrate, such as iron or steel, can be analysed with sufficient tube power. This is a decisive advantage for reverse engineering large components.
Mesh model of a turbocharger
The 3D data obtained by CT was processed here into a closed surface mesh that also shows internal structures.
How is a CAD model created from 3D scan data?
The scan-to-CAD process converts the raw scan data into a parametric CAD model that can be used for manufacturing, simulation or 3D printing. This requires specialised software and experience in surface reconstruction.
After scanning, the result is first a point cloud, a cloud of millions of individual 3D points. This point cloud is processed into an STL mesh model that represents the surface as a triangle mesh. The mesh model is already suitable for visualisation and 3D printing, but cannot be used directly for most CAD applications.
The real challenge lies in surface reconstruction. Parametric surfaces are extracted from the triangle mesh so that they can be edited in CAD software. Depending on the assembly, two approaches are used:
- Automatic surface reconstruction: The software recognises basic geometric shapes (planes, cylinders, cones) automatically. Suitable for prismatic components with clear geometries.
- Design-based reconstruction: An engineer remodels the component in CAD software, using the scan data as a reference. Required for complex freeform surfaces or when a "clean" parametric model is needed.
The result is a CAD model that can be imported into common CAD tools and contains all dimensions of the original object.
Which software is used for reverse engineering?
The scan-to-CAD workflow relies on specialised software that processes point clouds and converts them into CAD files. The choice of software depends on the application and the CAD tools already in use.
Software for point cloud processing:
- CloudCompare (Open Source)
- VXelements
- Artec Studio
- Geomagic Design X / Wrap
CAD software with reverse engineering functions:
- Autodesk Inventor
- SolidWorks
- Siemens NX
- CATIA
The typical workflow: The scan data is first cleaned, aligned and processed into a mesh model in specialised software. Surface reconstruction then follows, either in the same software or by exporting the data for further processing in CAD software. The final model is exported as STEP, IGES or a native CAD format.
With automatic modelling, the software recognises geometric features such as bores, chamfers and fillets and creates parametric elements. The speed of this process depends heavily on the complexity of the component: a simple prismatic part is reconstructed in minutes, while an organic freeform surface can take hours or days.
How accurate is reverse engineering?
Typical accuracy by device or technology:
Technology
Accuracy
Suitable for
Optical 3D scanner
0.02 - 0.1 mm
Surfaces, freeform surfaces
Industrial CT
0.015 - 0.05 mm
Complete components incl. internal geometry
Coordinate measuring machine
0.001 - 0.01 mm
Individual dimensions, reference points
The accuracy achievable in reverse engineering depends on the scanning technology, the size of the component and post-processing. Tolerances in the hundredth-of-a-millimetre range can be achieved for most industrial applications.
The precision of the scan alone does not guarantee an accurate CAD model. Deviations arise during surface reconstruction when freeform surfaces are approximated by mathematical surfaces. An experienced engineer can minimise these deviations and optimise critical dimensions in a targeted manner.
For prototype production and spare part manufacture, an accuracy of 0.1 mm is usually sufficient. Fits, sealing surfaces or functionally critical dimensions require higher precision. In these cases, we recommend combining the scan with targeted re-measurement of critical dimensions.
What are the industrial applications of reverse engineering?
Reverse engineering is used in almost every industry. Digitally recreating existing products speeds up development and enables innovation based on existing designs. The demand for reverse engineering grows with increasing product complexity and longer life cycles of capital goods.
Typical industrial applications:
- Spare parts procurement: Reproducing components that are no longer available. Particularly relevant for long-life machinery where spare parts are needed after 20+ years.
- Product development: Analysing a product as the starting point for further development. Existing components are digitised and used as a basis for optimisation.
- Quality control: Nominal/actual comparison between CAD design and manufactured component. Deviations are colour-coded and quantified.
- Maintenance and repair: Documenting the current condition of equipment. In the event of wear or damage, the scan data serves as a reference for repair.
- Additive manufacturing: Preparing components for 3D printing. The scanned object is optimised for additive manufacturing and exported as STL.
- Prototype development: Rapid creation of prototypes from physical samples. Handmade design studies are digitised and prepared for series production.
Digitally capturing physical objects is also relevant for documenting cultural assets, analysing competitor products and creating training materials. The 3D scan provides precise spatial documentation that can be used for a wide range of purposes.
How does a reverse engineering project work at Microvista?
Microvista offers reverse engineering as a service for large and complex components. Industrial CT also captures internal structures that optical 3D scanners cannot reach. The process is optimised for efficiency and accuracy.
Project workflow:
- Clarifying the order: Defining the requirements (file formats, tolerances, scope of delivery)
- CT scan: Capturing the physical object with industrial computed tomography
- Generating a point cloud: A 3D point cloud is extracted from the CT data
- STL mesh model: The point cloud is processed into a closed surface mesh
- Surface reconstruction: Automatic or design-based, depending on requirements
- CAD delivery: Export in the desired format (STEP, IGES, native format)
Microvista’s CT systems capture components with an enveloping circle of up to 798 mm or a length of up to 1802 mm, depending on the component, weight, material and cumulative wall thickness. Materials that are difficult to penetrate, such as iron, steel or dense alloys, can also be processed. The latest software enables precise reconstruction even of demanding geometries.
For companies without their own CT capacity, this service provides access to high-resolution 3D digitisation without investing in their own equipment. The lead time for a typical project depends on its complexity.
Calculate reverse engineering costs
What does reverse engineering your assembly cost?
Answer three short questions on size, complexity and accuracy. We will email you a guide price for CT scanning and reverse engineering. It is a non-binding cost estimate, not an offer.
Reverse engineering calculator
How large is your assembly?
Rough outer dimensions are enough. Height is required, it determines the scanning effort.
How complex is the assembly?
Complexity is the main cost driver. Use the number of individual parts and the examples as a guide.
How accurate does the reconstruction need to be?
Functional analysis (G2) is sufficient for most applications.
Where should we send the guide price?
You will receive it by email straight away, split into reverse engineering and CT scan. Non-binding cost estimate, not an offer. For business customers only.
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What are the advantages of CT-based reverse engineering?
Industrial computed tomography offers specific advantages over optical scanning methods that are decisive for certain applications. The combination of complete capture and high accuracy makes CT the preferred technology for demanding reverse engineering projects.
Advantages of CT for reverse engineering:
- Complete capture: Internal and external geometry in one scan
- No disassembly: Assemblies are scanned in their assembled state
- Hidden structures: Undercuts, channels and cavities are captured
- Material information: Porosity, inclusions and wall thicknesses are visible
- Non-destructive: The object remains completely intact
- One data set: No need to merge multiple scans
Detailed capture enables precise reproduction of even complex mechanical parts. A gearbox housing with internal oil channels, a turbine blade with cooling holes or a plastic part with clips and snap-in lugs: all these geometries are captured digitally in full and can be reconstructed exactly.