Scientific Applications and Research Associates (SARA) Inc., has developed a proprietary and unique concept called - Dynamic Automated Visual Inspection System "DAVIS". This system is capable of capturing images of laser drilled holes and shapes in real time and analyzing the data on-the-fly for conformance to specification (such as hole size and projected coolant air flow). The "DAVIS" system can inspect holes at 5Hz and interacts with both the laser drilling workstation and its CNC controller to dynamically control and compensate for any deviations in real time.
SARA, Inc. has developed DAVIS in collaboration with the Connecticut Center for Advanced Technology (CCAT, Hartford CT), working under the auspices of the National Aerospace Leadership Initiative (NALI), and PRIMA North America, LASERDYNE SYSTEMS (Champlin, MN), as well as support from the Air Force and the Navy under the Small Business Innovative Research (SBIR) program.
Laser Drilling of Holes Photo © PRIMA N.A., Inc.
Test results conducted at CCAT on a CONVERGENT LASER P50L Nd:YAG Laser and an IPG fiber laser, and at LASERDYNE SYSTEMS on a LASERDYNE 795 workstation with CL50k YAG laser have demonstrated that our prototype system can:
- Interface with modern PC based as well as older CNC controlled laser workstation to dynamically control the size of laser drilled hole in real time
- Conduct Automated Visual Inspection of the drilling operations at 1000 times faster (msec) than present pin-gage inspection techniques (sec)
- Provide and maintain accuracies of 0.001” in determining hole size
- Measure the exit side of the holes (area of maximum restriction) in single walled combustors
Further Tests are planned to demonstrate that the system can:
- Eliminate or reduce labor intensive pin gage tests and flow bench tests
- Predict final coolant flow thru the component with an accuracy of +/- 2.5%
- Reduce overall cycle time (production + inspection) by a factor of two
- Measure hole sizes in double walled structures such a ducts, vanes and blades
DAVIS can precisely inspect laser drilled holes and control a variety of Laser Drilling Workstations. Photo © PRIMA N.A., Inc.
Automated inspection of laser drilled holes can be used in numerous industrial, medical and aerospace applications.
Its most immediate application is in the aerospace industry: The Joint Strike Fighter (JSF) gas turbine engines
(Pratt & Whitney F135 and GE F136) will require approximately 1.6 million holes to be drilled per engine for the
purpose of convective cooling of hot section parts. Using the DAVIS system could potentially increase production rates
and accuracy while reducing the overall cost of the JSF program.
The tighter tolerances achieved in production by using DAVIS will result in:
- Extended component lifetimes and improved maneuverability of the JSF
- Reduction in cooling air, resulting in better fuel economy
- Increased operating temperature of the turbine, resulting in higher thrust
DAVIS Software can achieve on the fly assessment and adjustment
- Prototype system design, software upgrades and design verification tests have been completed
- Integration with various industrial laser workstations have been achieved
- Custom made products, as well as one-of-a-kind applications tailored to specific platforms, are offered to OEMs
An example of the DAVIS software processing images of laser drilled holes
SARA's high speed Dynamic Visual Inspection System "DAVIS" uses a coaxial camera and proprietary illumination system to capture images of laser drilled holes in real time. The dedicated software processes the image to obtain area and calculate the expected coolant air flow through each hole. "DAVIS" controls the size of the next hole to be drilled using I/O functions by actively changing the diameter of the laser beam or pulse intensity/energy to maintain the average hole size and total flow in tolerance. When all the holes have been drilled, a detailed statistical reports on hole areas and cumulative air flow thru the component is generated for quality control purposes.