Reverse Engineering with Laser Arm Scanning: When You Have No Drawings
It happens more often than you would expect. A critical component needs replacing, a fixture needs modifying, or a legacy part needs to be put back into production, and there are no drawings. The original manufacturer closed down, the drawings were never digitised, or they simply got lost in a factory move twenty years ago.
This is where reverse engineering with laser arm scanning becomes a practical solution rather than an academic exercise.
The Equipment
We use articulated arm coordinate measuring machines (CMMs) fitted with laser line scanners for reverse engineering work. These are portable instruments with six or seven degrees of freedom and a laser scanner mounted on the end effector. The scanner projects a laser line onto the surface and captures the reflected profile at high speed, building a dense point cloud as the arm moves across the part.
Typical accuracy is in the range of 0.025mm to 0.050mm, depending on the arm model and scanning conditions. This is more than sufficient for most mechanical components and tooling applications. The advantage over a terrestrial LiDAR scanner is resolution at close range and the ability to capture internal features, undercuts, and tight radii.
The Scanning Process
The part is fixtured or placed on a stable surface. Reference points are identified. The operator then scans systematically, building coverage across all surfaces that need to be captured. For complex parts, multiple setups may be required, with alignment maintained through reference targets or geometric features.
The raw output is a point cloud containing millions of measurement points. This is processed to remove noise, fill minor gaps, and generate a triangulated mesh (STL). The mesh represents the scanned geometry as a surface, but it is not a parametric CAD model and cannot be directly used for manufacturing.
From Mesh to CAD
This is where the engineering happens. Converting a mesh into a usable CAD model requires decisions about design intent. A scanned surface is never perfectly flat, cylindrical, or concentric. The engineer must interpret the scan data and model the part as it was intended to be, not exactly as it was scanned.
We work in SolidWorks and Siemens NX for the CAD modelling stage. For prismatic parts (machined components, brackets, housings), we build parametric models from scratch using the mesh as a reference, extracting key dimensions and constraining the model to standard manufacturing tolerances.
For organic or complex freeform surfaces (body panels, moulded parts, aerodynamic components), the process involves fitting NURBS surfaces to the mesh data. This is more time-consuming and requires specialist surfacing skills, but the result is a smooth, manufacturable surface definition.
What You Get
The deliverable depends on what the client needs. For a replacement part, that is usually a fully dimensioned manufacturing drawing and a STEP or native CAD file. For a fixture modification, it might be the CAD model of the existing fixture integrated into an assembly with the proposed changes. For quality inspection, it could be a comparison report between the scanned part and a nominal CAD model.
We can also deliver the raw point cloud and mesh data if the client wants to work with it in their own CAD environment.
When It Makes Sense
Reverse engineering is not free. The scanning and modelling process takes time, and for a simple bracket, it might be faster and cheaper to measure it with a vernier and draw it from scratch. Where scanning proves its value is on complex parts with curved surfaces, castings with irregular geometry, or assemblies where the spatial relationships between components matter.
If you have a part with no drawings and need to get it back into production, laser arm scanning is the most reliable way to capture what is actually there and turn it into something manufacturable.