Reverse Engineering to Solid Model

The reverse engineering to solid model has the goal of converting a 3D scan as accurately as possible into a CAD solid model. If the 3D scan of a part contains both organically shaped surfaces and simple geometries (angular shapes, holes, threads), then this reverse engineering method is required.
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How We Do It?

Because NURBS surfaces and simple geometries can be combined in one model, this resulting model is also sometimes referred to as a “Hybrid” model.

We provide the CAD model in the neutral exchange formats STEP, IGES or X_T. During the reverse engineering to solid model, we do not optimize the 3D scanned part, which means that manufacturing defects are not corrected. We do this because correcting manufacturing defects could only be done at the expense of the reverse engineering accuracy. If an optimization is needed, we use a different reverse engineering technique called: “Reverse Engineering to parametric model with a history tree.”
Original 3D scan (left) vs CAD solid model (right)

How Does the Reverse Engineering
to Solid Model Work?

The reverse engineering process is the approximation of measured data (3D scan) by a CAD model. This means that we approach the 3D scan as close as possible by solid modeling. We use all CAD modeling techniques at our disposal to create a closed-and thus watertight-solid model.

Examples of techniques we use include:
  • Creation of solids by extrusion or rotation from 2D drawings.
  • Boolean operations to create solids from geometric primitives by unification and subtraction (CSG – Constructive Solid Geometry).
  • Surface modelling and closing to a solid model

Angular shapes are reconstructed with simple geometry while organically shaped surfaces are molded with NURBS Surfaces from the 3D scan. The NURBS curves must be generated manually in such a way that they can be optimally combined with the simple geometry. The goal is a solid model that is closed and waterproof.
If we combine NURBS surfaces and simple geometry inside one solid model, we sometimes call it a hybrid.
3D Scan of the part with the structured light 3D Scanner: “GOM Core”

The goal

CAD solid model generated by reverse engineering with NURBS surfaces and simple geometry
For us, accuracy is the decisive factor when we use the reverse engineering to solid model. This means that the reverse engineering and 3D scan should only differ minimally. This is the reason why we do not optimize the parts geometry, because that optimization would come at the expense of accuracy.

Real world example

Real objects, such as plastic parts, are often slightly deformed. When reverse engineering with solid modeling, we carry over these inaccuracies from the 3D Scan to the solid model. For example, a 3D scanned angle of 89° is not corrected to an angle of 90° because that would reduce the reverse engineering accuracy.

If a client prefers optimized scans, we can provide that using a separate reverse engineering technique called: “Reverse engineering to parametric model with a history tree.”

To document the unavoidable deviations between the original 3D scan and the solid model, we always provide a deviation analysis to our clients.
The deviation report shows the minimal difference between the 3D Scan and the CAD solid model created by reverse engineering

Advantages and Disadvantages of
the Reverse Engineering to Solid Model

Download the sample data

3D scanning of the part with simultaneous display on the computer monitor
We prepared all the data of our sample reverse engineering to solid model project for you to download: The original 3D scan, the solid model, and the deviation analysis. You can view the data in your CAD software and decide whether the solid model is well suited for your application:

Get to know more

For most applications, the reverse engineering to solid model is the best technique. Only when a history tree or a technical drawing is desired will we select another reverse engineering technique. We always provide a color-coded deviation analysis with every project we deliver so that the customer can compare the original 3D scan and the CAD solid model.
Overlay of the 3D Scan and the CAD solid model

Frequently Asked Questions

Reverse engineering to solid model allows the conversion of a 3D scan (STL) into a CAD solid model (STEP). The goal is to keep the deviations between the 3D scan and solid model as small as possible. There is no correction of manufacturing defects of the 3d scanned part so that accuracy can be maintained. The resulting solid model can consist of simple geometries or complex NURBs surfaces. When simple geometry and NURBS are combined in one model, it’s sometimes called a “hybrid”.
The basis for reverse engineering to solid model is a 3D scan which is provided as a polygon mesh (STL format) or as a point cloud. If a 3D scan is not available, Holocreators will be happy to 3D scan your part for you.

In reverse engineering to solid modelling, simply geometries are reconstructed manually and NURBs surfaces are molded from the 3D Scan. A Hybrid model combining both geometry variants is also possible. The resulting solid model can be edited only to a very limited extent. Simple geometries like holes and threads can be modified, but the NURBs surfaces cannot be edited.

Reverse engineering with solid modeling generates a solid model. This can be exported in the neutral CAD exchange formats STEP, IGES, or X_T.
Reverse engineering to solid model is accurate. On average there are deviations of 0.05mm to 0.1mm between the original 3D scan and the generated solid model.

Where NURB’s surfaces are molded automatically from the underlying 3D scan, the accuracy is higher than in areas where simple geometries are manually reconstructed.

May we help you with your reverse engineering project?

Holocreators offers professional 3D-scanning and reverse engineering services. We would love to help you with your project and advise you on how to create a CAD solid model from a 3D Scan.
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