Care is taken to assess uncertainties for all measured quantities during all steps, from errors in the conversion of digital geometry formats to delivered results. To avoid any format conversion errors, the geometries are provided to the manufacturers in agreed format or when the manufacturer is using own conversion, the converted geometry is verified by us. The manufacturing drawings and specifications are established in a dialogue with our clients before manufacturing. Controls on the manufacturing are done for crucial parts to ensure manufacturing will be performed satisfactorily. Our standard procedure for geometric conformance control for an OGV after delivery is described below:
1. The geometry is inspected and returned if any visible errors can be detected.
2. The geometry conformance is controlled, either by a coordinate measurement machine (CMM) or a ROMER measurement arm with external optical scanning head or a ruby ball. This is done in a tempered room and an example of a scan of an stereolithography (SLA) rapid prototyped vane for heat transfer measurement is shown in Fig. 1.13. The equipment can accommodate accuracy down to ±0.005 mm (CMM), ±0.025 (ROMER+Ruby) and ±0.05 mm (ROMER+Optical) in a volumetric accuracy.
Figure 1.13. Results from optical scanning of an OGV (left), measurement table, arm and CCM at CHALMERS Material Science Lab (mid) measurement of stator mounting ring on an assembly table (right).
3. Surface roughness of aero- surfaces is inspected and measured:
a. Either by a handheld roughness measurement device Surtronic 3+.
b. Or by stationary machines as a Wyko Optical Profile or a surfscan S3 that provide a 3D surface topology.
4. Defects and leakages of internal channels are inspected and evaluated by pressurizing each channel and controlling the response with a pressure transducer.
In addition, for the models instrumented for heat transfer measurements:
5. The wall thickness is measured with an ultra-sonic machine 38DL Plus down to ±0.005 mm accuracy.
6. Thermal conductivity of material samples is measured within ±1% or ±5% accuracy by HotDisk AB. The accuracy depends on sample dimensions.