Aircraft Skin: Stereo Plus Laser Measures Without Tooling
An aircraft skin is a large thin-walled curved part. Dimensional tolerance and form-position relationships directly affect aerodynamic shape, while surface defects affect structural safety, so inspection standards sit well above general industrial work. This case measures the skin where it sits on the shop floor: an industrial robot works with optical tracking, and stereo vision and a laser sensor switch automatically by curvature to capture the external point cloud, completing 3D measurement, dimensional tolerance and form-position evaluation plus surface defect detection. Capability figures are subject to site acceptance results.
Tooling covers sections, not a surface
Dedicated tooling covers only limited sections and points, and curved regions still rely on manual template comparison. Coverage is one limitation; consistency is another. The same skin in the same attitude can produce different conclusions from different people. With small batches and many models, retooling becomes both slow and expensive.
Fit the nominal surface before judging deviation
The skin surface is one continuous large curve and cannot be summarized by a few feature points. Evaluation works by fitting the measured point cloud to the theoretical surface first, then computing the deviation between actual and nominal. If the fit is poor, every later deviation, tolerance and form-position result loses meaning. That is the essential algorithmic difference from routine hole measurement.
In gently curved regions, laser scanning takes points quickly and covers wide areas. At edges, local features and abrupt curvature changes, stereo vision gives more reliable local accuracy. The system sets scan parameters by curvature zone so point density and accuracy stay even, instead of using one recipe everywhere.
A datum without fixtures
The skin is placed on the shop floor with no dedicated fixture. Optical tracking measures the robot end-effector pose in real time, establishes an on-site datum and unifies data from multiple stations into one coordinate system. Because the skin is flexible, clamping and placement introduce small shape disturbances; measurement must handle them robustly at datum establishment, separating manufacturing deviation from clamping deformation.
Flexibility comes from programs, not from tooling
Measurement programs are called by skin model, with paths, parameters and evaluation datums switched through software configuration. Changeover is far shorter than retooling, which matches the small-batch, many-model organisation of aerospace manufacturing: instead of building equipment for each model, one set of equipment learns every model.
Non-contact is a precondition, not a bonus
Vision measurement does not touch the skin surface, so inspection causes no secondary damage. For thin-walled parts this is not an extra advantage; it is the condition that allows the method to be used at all.
Where the method stops
The approach targets aerospace structures with large curved surfaces, high accuracy and many models. For large parts with regular surfaces and moderate accuracy, a simpler single-sensor configuration may control investment better. For regions with extreme curvature change or severe occlusion, point-cloud coverage must be assessed station by station.
What aerospace buyers ask
Why does skin suit a stereo and laser combination?
The skin is large and curved: laser takes points quickly over broad surfaces, while stereo measures edges and local features more accurately. Automatic switching lets one capture serve both dimensional evaluation and defect detection.
How is a curved point cloud evaluated dimensionally?
The nominal surface datum is fitted first, then deviation between actual and nominal is computed to evaluate dimensional tolerance and form-position relationships. Fit accuracy directly determines whether the result is credible.
Without fixtures, what guarantees accuracy?
Optical tracking establishes the on-site datum and unifies multi-station coordinates. Robust handling of the flexible part's small shape disturbance separates manufacturing deviation from clamping deformation.
Is changeover hard with many models and small batches?
Changeover is mainly software: paths, parameters and evaluation datums switch by model, with no tooling remake. Actual time depends on model differences and program readiness.