Turbine/compressor blade measurement system

Citation

(2001), "Turbine/compressor blade measurement system", Aircraft Engineering and Aerospace Technology, Vol. 73 No. 3. https://doi.org/10.1108/aeat.2001.12773cad.001

Turbine/compressor blade measurement system

Turbine/compressor blade measurement system

Keywords: Spectrum Metrology, Blades, Measurement, Gauges

Electro optical metrology company Spectrum Metrology informs us that it has applied the non contact "Conoprobe" gauge technology to provide rapid non-contact assessment of turbine and compressor blades, overcoming the traditional problem of measuring the steep angles and slopes of these components. Measurements can reportedly be taken along root forms, blade edges and aerofoils.

The main advantage claimed of the Conoprobe is that it creates extremely precise digital images of virtually any surface – including the most difficult to measure components – at very high speeds, and at stand-off distances once considered unfeasible. With measurement speeds of up to 500 points per second, the entire measurement process takes just a few seconds (depending on the lens diameter and selected data point spacing).

The turbine system uses two probes operating in tandem so that profiles of both sides of a blade can be assessed simultaneously. Scanning is accomplished in both X and Y axes by linear precision slideways mounted orthogonally. The fixture platform is mounted directly above this, with location features for precise location of the blade fixturing. Manual adjustment of the Z (probe) axis allows a large range of blade sizes to be accommodated.

Multiple sections of aerofoil blade profiles can be measured simultaneously on both sides and data compared with input design data. According to Spectrum, the Conoprobe's ability to measure steep angles enables the system to address blade-edge profiles. Single edge profiles can be measured or, depending on blade twist, 3D profiles of the full blade length can be produced.

The 3D capability of the Conoprobe also enables a large variety of root forms to be measured. Analysis of profile geometry can be made or, with suitable fixturing, the root form can be related to previously measured aerofoil data.

The technology behind this system is "conoscopic holography", which is the optical interference effect produced by doubly refracting crystals illuminated with convergent polarised light rays. This technology, developed by Optical Metrology Ltd (Optimet) in Israel (a sister company of the Ophir Group) and protected by nine patents, is said to solve the problems traditionally caused by awkward shapes, angles, materials or sizes. Applications are wide ranging and include the thickness of high density PCBs, radius and steep angle measurements of moulded plastics products and dimensions and radii of any precision machined parts, including metallic surfaces, with very high repeatability.

Details available from: Spectrum Metrology. Tel: +44 (0) 116 235 8355; Fax: +44 (0) 116 235 8344; E-mail: SpectrumMetrology@compuserve.com; Web site: www.spectrum-metrology.co.uk