Laser sensor vision system improves surface quality inspection

Jet engines typically contain hundreds of small stainless steel and Inconel fan blades to generate thrust. These blades usually wear and bend due to erosion and foreign object damage during normal flight operations. Overhaul facilities regrind or replace these blades after manual inspection. This slow, labor-intensive process checks the precise length and position of each blade in the engine's ...

11/01/2003


Jet engines typically contain hundreds of small stainless steel and Inconel fan blades to generate thrust. These blades usually wear and bend due to erosion and foreign object damage during normal flight operations. Overhaul facilities regrind or replace these blades after manual inspection. This slow, labor-intensive process checks the precise length and position of each blade in the engine's rotary intake.

To help replace manual inspection and measurement, LMI Technologies and system integrator Oryx Systems have jointly developed a vision system that can accurately inspect the blades on the fly at high speeds. LMI provided its Laser Twin Sensor (LTS) non-contact laser sensor, while Oryx contributed software, signal processing hardware, off-the-shelf designs, fixturing and a sensor software package. LMI reports that its LTS has twin-viewing axes and projects a small laser spot, about 30 micrometers in diameter, which allows it to meet extreme accuracy requirements.

LMI and Oryx recently implemented their first blade inspection system at an aircraft overhaul facility in the Southeastern U.S. Their second system will be installed soon at a Canadian aircraft facility that overhauls CF34 jet engines.

David Lacey, Oryx's president, reports that because the two firms' blade inspection system can measure very small items moving at high speeds, it can also be used in similar applications. These include commutator segments in electric motors and grinding calendared rolls.

Automating measurement

To automate the formerly manual blade inspection process, Oryx positioned the LTS sensor at a diagonal position below the rotor. As this rotor spins, the sensor measures the length of each blade tip from the center line of each wheel. These measurements are made within 200 milliseconds with a tolerance of 60.005 in. and at a resolution of 60.0001 in. LMI and Oryx's system likewise monitors the position of each blade in the intake to assure a precise fit.

LTS' measurement process begins when its sensor emits a single laser beam that strikes the blade's surface, and then reflects a spot through twin imaging optics onto two position-sensitive detectors (PSDs). If the reflected spot on one PSD is obscured by a change in the blade's surface, the other PSD will see it. Using the two PSDs compensates for intensity variations in the laser spot, which improves lateral sensitivity of the sensor.

Analog signal processing electronics then translate the PSD output current into a distance. Because differences in the blade or other object's color and surface can affect measurement data, LTS' software automatically compensates by varying power to the laser's diode.

Consequently, LTS can resolve thickness variations as fine as 0.007 mm when averaged at 100 Hz. It also has a 43-degree observation angle at stand off; ability to optimize contour tracking with sharp increases in object height; and can measure on frosted and refurbished surfaces.

Signals from the sensor are sent to Oryx's PC-based controller, and its software generates a report of the average readings for all the blades in each rotary intake, along with high and low readings. LMI and Oryx's system also reports the average measurement for each stage, which allows selection of blades that need to be replaced or repositioned. Following replacement, the system also makes sure that new blades are positioned properly in the intake, and that they're properly ground down to meet specifications.

"This system eliminates the need for by-hand measurements, which drastically reduces set-up time," says David Lacey, Oryx's president. "Repeatability is also much more consistent with our LMI/Oryx system because blades can be loaded uniformly outward. Manual measurement makes it difficult to load each blade in exactly the same manner."

For more information, visit LMI Technologies at www.lmint.com or Oryx at www.oryxsystems.com .

jmontague@reedbusiness.com





No comments
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Intelligent, efficient PLC programming: Cost-saving programming languages are available now; Automation system upgrades; Help from the cloud; Improving flow control; System integration tips
Smarter machines require smarter systems; Fixing PID, part 3; Process safety; Hardware and software integration; Legalities: Integrated lean project delivery
Choosing controllers: PLCs, PACs, IPCs, DCS? What's best for your application?; Wireless trends; Design, integration; Manufacturing Day; Product Exclusive
PLCs, robots, and the quest for a single controller; how OEE is key to automation solutions.
This article collection contains several articles on improving the use of PID.
Learn how Industry 4.0 adds supply chain efficiency, optimizes pricing, improves quality, and more.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Special report: U.S. natural gas; LNG transport technologies evolve to meet market demand; Understanding new methane regulations; Predictive maintenance for gas pipeline compressors
Cyber security cost-efficient for industrial control systems; Extracting full value from operational data; Managing cyber security risks
Drilling for Big Data: Managing the flow of information; Big data drilldown series: Challenge and opportunity; OT to IT: Creating a circle of improvement; Industry loses best workers, again