Three Keys to Faster Aero Engine Blade Measurement

by Aziz Tahiri on February 25, 2019 From Ask The Experts, Industry Focus, Technology

Over the next twenty years, the current global fleet of in-service commercial aircraft is expected to double. Around
39 000 of these aircrafts will be new. Inevitably, we’re going to see a significant ramp-up in the aerospace industry, and one question has to be how will manufacturers keep pace with the demand?

The effects of this need for increased production will be felt in many areas of the manufacturing cycle across aerospace OEMs, Tier 1 and Tier 2 companies. But in this blog I want to focus on how aero engine blade manufacturers can optimise their inspection methods and technologies to meet this challenge and turn it into an opportunity for greater output.

Of course, compressor and turbine blades are essential aero engine components, playing a crucial role in aerodynamic efficiency and ultimately the safe operation of the aircraft. With very tight tolerances, blades clearly demand high-accuracy inspection, but, given the production demands on the industry, manufacturers need to consider ways they can achieve the required precision while increasing throughput. Here are three inspection strategies that can help reduce manufacturing cycle times while maintaining the same high level of quality.

1. Bring Measurement Inline

Bringing metrology closer to production is an increasingly prevalent strategy across manufacturing industries. Inspecting large volumes of blades can contribute to production bottlenecks, so one area of focus for making time-savings may well be the time spent transporting blades from the shop floor to the metrology lab. 

For some aero engine manufactures, automated inline measurement will need to be balanced with two other concerns: factory space and environmental suitability. As relatively small-to-medium-sized parts, blades enable manufacturers to take advantage of the compactness of shop floor coordinate measuring machines (CMMs) on the market. But if active forging or press operations will be conducted on the same floor as the CMM, then the ideal solution will offer thermal compensation and passive vibration isolation to reduce any potential influence of these factors on measurement results.

Smaller blade production in particular can benefit from automated part loading with a robot. In such a setup, a CMM with three-sided open access to the measuring volume, like a TIGO SF CMM, is ideal. If you’re looking to save space on the shop floor, then the TIGO SF is suitably compact, offering a small footprint. Three Keys to Faster Aero Engine Blade Measurement AICON-StereoScan-neo

However, if increased inspection speed and precision is the bigger priority, then the blade-specialised GLOBAL Advantage HTA offers greater throughput with its high accuracy non-contact laser, collecting data at a rate of 1000 points per second. As well as enabling greater measurement flexibility to quickly capture more difficult-to-access blade surfaces, the infrared point sensor is ideal for measuring the blade’s highly reflective surface. 

CMMs can also be fitted with environmental monitoring tools, such as PULSE, that instantly alert users if any predefined operating conditions in areas such as temperature or air pressure are breached. This can increase confidence in blade measurement results while enabling operators to optimise their time and work away from the CMM.

A CMM isn’t the only option here; 3D optical scanning solutions allows you to identify any potential errors even earlier in the process. The AICON StereoScan neo, for instance, can be used to check results after a first stage of forging, enabling you to more proactively correct or improve the produced blade. This is a fast process, with such fringe-projection scanning technology able to perform a high-resolution scan of even the smallest details in just minutes. There’s a trade-off in terms of accuracy when compared with using the CMMs discussed, but if production errors are a recurring or costly problem then this flavour of 3D scanning provides potential for time and cost savings by integrating inspection earlier in production and allowing defects to be identified much sooner.


2. Reduce Manual Interventions

Three Keys to Faster Aero Engine Blade Measurement Global Advantage HTAblade measure in SF environme
Of course, the repeated operator interventions involved in manual reclamping is a major hindrance to achieving the time-savings of single setup measurement.

One solution is to equip your CMM with a rotary table, as demonstrated earlier with the GLOBAL Advantage HTA, or a similarly automated part rotation device like Optiv Dual Rotary. This increases sensor access to the blade’s features, enabling the single-setup capture of complex geometries such as the aerofoil’s leading and trailing edge, the chord and camber line, and firtree blade roots.

If you’re inspecting the blade’s cooling holes then a rotary table will help quicken the measuring cycle by automatically aligning the axis of the hole to be tested parallel to the CMM’s vertical axis. 

As discussed earlier, blade inspection also lends itself to non-contact measurement, which is another way to reduce reclamping. Blade surfaces can range from rough forged to micro-finish, so optical measurement saves time by quickly capturing 3D scans with a high point density while removing the need for additional coating or preparation of the part.

Given that cooling holes made with laser methods can often be irregular in shape, optical measurement is also ideal for quickly inspecting their locations, orientations, and dimensions.

3. Use Specialised Blade Software

Blades often feature complex characteristics like contours and twist angles to maximise aerodynamic efficiency. Software with algorithms supporting the necessary evaluation techniques for blade inspection can make measurement of these difficult parts much simpler and quicker.

Software like PC-DMIS Blade and QUINDOS BladeSmart are designed with command libraries and graphical interfaces that make it much simpler to implement the right alignment procedures and to identify and select sections of the blade to measure, enabling faster scanning. When you need to set up a different blade type on the machine, the software removes the need for further CMM programming – all you need to do is enter the new set of parameters into the software.

In addition, specialised software offers highly configurable graphical reports that enable you to deliver concise information to operators about various blade characteristics from twist angle, through mean camber line, to leading edge thickness.
Over the coming years, combining high accuracy and speed is going to be a key competitive differentiator in aero engine blade inspection. For more information on our relevant solutions and case studies, visit the Aero Engine Compressor and Turbine Blade Inspection page.

Aziz Tahiri

Aziz Tahiri is the Aerospace Marketing Manager at Hexagon Manufacturing Intelligence. He is responsible for the strategic positioning and marketing of Hexagon solutions to deliver greater productivity to the aircraft manufacturing industry. With over a decade of experience in the aerospace industry, Aziz holds an aerospace and automation engineering degree from the Toulouse ICAM school.

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