Blisk inspection and 3D metrology
The challenge of measuring blisk blade surfaces
In aviation mechanics, a blisk (also known as an integrally bladed rotor, IBR) is an engine compressor component comprised of a rotor disc and blades. A blisk can be machined from a solid piece of material or made by welding individual blades to the rotor disk. The blades of some blisks are also pre-drilled with minute cooling holes. At inspection time, blisk blades are hard-to-reach surfaces that cannot be measured with microscope-like instruments. Additionally, the cooling holes on the blades present a sudden and sharp edge in the scanned surface and are problematic for many 3D measurement technologies.
Small-diameter probes to the rescue
Addressing this challenge, the non-contact small-diameter probes of Novacam’s 3D metrology systems easily reach between blisk blades to acquire high-precision topography measurements of hard-to-reach blisk surfaces.
How the measurement is done:
- The side-looking optical probes scan surfaces in a collinear fashion – the laser beam is emitted and received along an identical axis – and therefore sharp edges of cooling holes or other high-aspect ratio features do not present a problem. The size and incident angle of the minuscule cooling holes can be determined.
- The probes acquire surfaces at up to 100,000 3D point measurements per second, providing a dense point cloud for analysis.
- The acquired blade surface data may be imported into CAD software for defect detection (see images below).
Versatile blisk inspection solutions
Novacam’s 3D metrology systems can be adapted to all blisk inspection needs, providing capabilities from simple GD&T verification to 100% defect detection.
- To measure the hard-to-reach surfaces of blisks, solutions will typically involve a small-diameter rotational probe
- For edges and open surfaces on blisks, a galvo (raster) scanner (used by the EdgeInspect) acquires blade edges and open surfaces on the blades in the most efficient manner.
- To combine several types of measurement in one system, a custom system is configured with 2 or more probes (e.g. galvo scanner and a rotational probe) all connected to one interferometer, bringing additional return on investment (ROI) to our aerospace clients.
Advantage of scanning with fiber-based probes
Novacam systems are based on low-coherence interferometry (LCI) and are highly suitable for automated inspection applications.
Our probes and scanners come in a range of sizes and designs to suit each particular application. The probes and scanners are fiber-based and therefore they:
- Deploy at a distance from the detector, without signal degradation
- Are easily deployed either on robot end-effectors or as components in lab inspection stations with multi-axis displacement
- Can be made rugged to operate even in hostile environments (radioactive, very hot, or cryogenic)
- Allow for flexible in-process set-up.