Rivet hole and rivet flushness inspection

Measuring System: Novacam RivetInspect
Keywords: aircraft assembly, aeronautics, aviation, rivets, bolts, fasteners, countersinks, 3D industrial inspection

Within aircraft assembly, riveting is a multi-step fastening process that requires tight adherence to design specifications and stringent QA/QC standards.  Riveting is also being increasingly automated. Robots with automatic tool changers switch between drilling, counter-sinking, sealing, fastening, and inspection end-effectors to carry out a process that has traditionally required significant human skill and experience.

The triple challenge of riveting-process inspection

Defects can and do periodically occur at every stage of the riveting process. Aircraft makers today therefore require sophisticated inspection instruments that must perform on three fronts.  They must

  1. Measure surfaces that are difficult to access, such as the inside of rivet holes
  2. Help automate defect detection. High-speed and high-precision 3D measurements on all aspects (pre- and post-riveting) of the riveting process are imperative
  3. Be flexible and rugged enough to be deployed in process, within automated or semi-automated systems right on the aircraft assembly plant floor

Can these challenges be met by one instrument?

Novacam’s RivetInspect system does deliver on all three fronts. It provides

  1. Dual scanning capabilities to ensure complete characterization of all relevant surfaces:
    • Inside rivet holes – A rotational scanner with a side-looking small-diameter probe easily reaches inside rivet holes (below left) to acquire not just their roughness but also their complete 3D geometry (below right).

      Rivet hole being acquired by a rotational scanner with a small-diameter probe

      Rotational scanner with a small-diameter probe reaches into rivet holes

      3D geometry of  a rivet hole reveals a tool-mark defect at the interface of composite and aluminum layers

      3D geometry of  a rivet hole reveals a tool-mark defect at the interface of composite and aluminum layers

    • Countersink surfaces and rivet-head flushness – A galvo (raster) scanner (below left), attached to the same profilometer, acquires the 3D countersink geometry (below center) and the geometry of the rivet-head area following the rivet installation (below right).

      Galvo scanner

      The galvo scanner measures countersinks and installed rivet heads

      A countersink exhibiting  a surface defect

      A countersink exhibiting  a surface defect

      Image of rivet head post-installation

      Image of rivet head post-installation

  1. Unprecedented support for automated defect detection. The system acquires micron-precision 3D geometric dimensioning data at up to 30,000 points/second. The acquired data may be imported into automated defect detection software.
  2. Complete versatility for in-process set-up. RivetInspect is based on low-coherence interferometry technology.  It it is  a fiber-based optical system, meaning that its dual scanners (rotational and galvo) are connected to a single signal-processing MicroCam-type profilometer with an optical fiber that can be hundreds of meters long. As such, the scanners are easily integrated as either robot end-effectors or as 3D vision components in automated or semi-automated systems – right on the plant floor. They are even rugged enough to withstand hostile environments.