1. Background of Reverse Modeling

When original drawings are unavailable and weld seams are rough or worn, using 3D scanning to capture the workpiece’s geometry and performing reverse engineering is the best solution for restoring the original design intent. This process provides accurate, reliable digital data that can be used directly in subsequent manufacturing processes such as CNC machining, casting, and 3D printing.

2. Reverse Engineering Workflow

Step 1: Scan the workpiece to acquire data

1.1 Scan 3D data

First, use a 3D scanning device (3DeVOK scanner) to accurately scan the workpiece and obtain high-precision 3D data. During scanning, ensure that all key features of the workpiece are captured, especially details such as weld seams and wear. After the scan data is obtained, it can be imported into DefinSight Model for subsequent modeling work.

1.2 Import 3D data

Import 3d data from 3DeVOK Studio into DefinSight Model.

Step 2: Reverse Engineering

Extract geometric features to establish planes

Using DefinSight Model, extract the geometric features of the workpiece based on the scan data. First, we need to fit the bottom surface as a datum to define the Z-axis direction and height of the workpiece. By fitting the geometric features of the bottom surface, we can ensure that the coordinate system aligns with the actual features of the workpiece. Then, create additional reference planes by fitting other surfaces (e.g., side surfaces), laying a solid foundation for the entire model

Click the bottom surface, slide to adjust the selection sensitivity; ensure the blue area does not exceed the plane. Click the bottom surface to maintain the accuracy of the fitted plane.

Align the coordinate system

Ensuring that the workpiece's coordinate system aligns with its main features is a key step in the entire reverse engineering process. By setting up the coordinate system in DefinSight Model, you can easily align the geometric features of the workpiece. By selecting the bottom surface and the Middle Plane, define the orientation of the coordinate axes and the origin, ensuring that all subsequent sketch creation and feature generation are based on an accurate coordinate system.

Next, use the two side faces to create a Middle Plane. The intersection of the Middle Plane and the Bottom Plane will establish the coordinate system origin.

Using the same method, select the two side faces separately to create a "Left Plane" and a "Right Plane".

Click the "Create" button and select the "Middle Plane" function.

Click on the two side faces separately to create the Middle Plane.

Click "Align" -> "Align by Coordinate System". The first feature should be the fitted Bottom Plane, used to establish the Z-axis. If the Z-axis is found pointing downwards, click the "Reverse" function to adjust its orientation upwards.

Select the "Middle Plane" as the element for the second feature. After selecting the features, click the "Apply" function to perform the alignment. If adjustment of the XY-axis orientation is needed, click "Flip" to correctly align the coordinates.

Move the mouse to the view options in the top-right corner to check and confirm that the new coordinate system is aligned with the part's main features, ensuring the model is properly oriented (level and straight).

2.3 Create 2D Sketches Based on Planes

After establishing the coordinate system, we can start creating 2D sketches. By selecting a projection direction aligned with the main features of the workpiece, the contour of the workpiece can be automatically generated. DefinSight Model provides convenient sketch creation tools, such as holding the Shift key and selecting reference points with the mouse to quickly create lines and arcs. Use constraints such as parallelism and tangency to ensure sketch accuracy. When sketching, pay special attention to whether the endpoints of line segments are coincident, ensuring the sketch is closed so that it can be subsequently extruded into a solid.

2D Sketch Shortcut Keys and Operation Tips

• Hold the Shift key and drag the mouse to select reference points to quickly create lines/arcs.
• Hold the Ctrl key and drag the mouse to select the endpoints of two lines to quickly join them. Pressing Ctrl again while dragging will create a tangent arc.
• Set the radius (R) value based on the fitted radius data, preferably to a whole number.
• Add constraints to the lines: Parallel, Tangent.
• Ensure the endpoints of line segments coincide, guaranteeing the sketch is closed.
• Draw arcs and adjust line segments.
• Fast-forward...
• To ensure the upper and lower parts merge, when extending the sketch for the upper part, make it intersect with the lower part. This allows the two solid bodies to be merged later.

2.4 Extruding Sketch and Generating Solid

Once the 2D sketch is finished, extrude it to create a solid. First, click the yellow arrow on the top or bottom face, hold the Ctrl key, and move the pointer to the plane that needs alignment for snapping. The process is similar for the top and bottom faces. Click to confirm and finish, generating the solid body.

Once the sketch is extruded, the obtained solid represents the preliminary shape of the workpiece. After that, proceed to sketch the lower portion.

2.5 Merging and Subtracting Solid Bodies.

Since the upper and lower parts of the workpiece have different dimensions, you first need to draw 2D sketches for the upper and lower parts separately and extrude them to create two solids. After completing the solid extrusions, use the "Combine" tool in DefinSight Model to merge the upper and lower parts into one complete solid.

If there are holes or other complex shapes in the workpiece, you can perform cutting operations using tools such as fitting a cylinder. Through Boolean operations, remove unnecessary portions to finally obtain the precise geometric shape of the workpiece.

Operation Steps:

• Open the mesh from the left side bar, hide the solid, extract geometric features of the holes, and fit a cylinder.
• Fit the four cylinders individually; double-click each cylinder and extrude its top face and bottom face. (Note: The top and bottom faces of the cylinder must extend beyond the object for proper cutting.)
• Modify the diameter parameters, click Apply, and adjust the remaining cylinders to make their diameters consistent.
• Hide the mesh and show the solid.
• Perform Boolean operations: Use "Tool B" (the fitted cylinders) to precisely remove the space occupied by Tool B from "Target A" (the solid).
• Click the solid, select the "Cut Selected Solid" tool, click on the four cylinders to perform the cut, and click OK to complete the cutting.

2.6 Export STP Data

After completing reverse engineering, export the STEP file (STP format). This file can be used for CNC machining or other manufacturing processes.

3. Summary

This tutorial demonstrates step by step how to perform reverse engineering of a welded part using DefinSight Model. By combining high-precision data acquired from 3D scanning with the powerful modeling capabilities of DefinSight Model, damaged or undocumented workpieces can be effectively reconstructed. This provides accurate data for subsequent manufacturing processes, improving production quality and efficiency.