Technology Update
Hartzell's blade manufacturing
 As shown in this image, the cutting head of Hartzell's seven-axis mill is about half-way along a propeller blade forging. The left side shows the as-cut airfoil, the right side the aluminum blade forging as received. The airfoil is cut in one pass. |
Hartzell Propeller, Inc. has invested $3 million in a new propeller blade manufacturing process that it claims reduces blade-to-blade weight and aerodynamic variability, allowing for smoother-running propellers. By improving manufacturing accuracy, the new process—which the company claims is the industry's "first major technology leap" since the early 1980s— also "dramatically" reduces set-up and changeover times.
During the machining of propeller blade shanks, the process establishes all the dimensions of the blade, and is now controlled to 0.0001 in. The airfoil is then produced from the computer-generated solid model and cut in a single pass on a seven-axis mill. To ensure accuracy while operating at feed rates up to 900 in/min, the process employs tool and part probing. The use of CAD 3-D solid models makes the manufacture of a variety of propeller designs more practical.
In addition to the machining equipment, the company employs a new nondestructive test cell for more reliable blade testing. The semi-automated "dynamic cloud" fluorescent penetrant inspection process eliminates procedure and operator variability to ensure the blades are free from miniscule surface flaws. Hartzell claims the process requires no special tooling.
- Jean L. Broge
MTU smoothes the flow
A new, in-line crack inspection facility designed to reduce cycle times and make better use of space is now on-stream at MTU Aero Engines' Munich plant. Both new and service-exposed components are inspected for surface defects. The facility also has additional features to protect the environment and facilitate system operation. However, the traditional fluorescent penetrant inspection (FPI) procedure remains because, overall, it is still regarded as being the most effective technique for crack detection.
Defects in engine parts may be caused by thermal and mechanical stresses in service. But MTU claims they may also be present in parts coming off the production line such as in the form of internal voids or surface discon-tinuities, like pores or shrinkages. To prevent such flawed new or used parts from finding their way into engines, they are subjected to various inspections. One of these is FPI, which detects even microscopic surface defects. A mandatory procedure for all parts, FPI uses a fluorescent substance that is applied to part surfaces to penetrate into flaws and render them visible under UV light.
The company says that while FPI may be a "simple technique," it requires complex equipment designed to customers' specific requirements. MTU inaugurated one such system earlier this year. It used spearhead technology to optimize a number of operations and designed operators' suggestions into it. Cycle time reduced "appreciably," in some ways due to the new system's location. The facility is part of a new etching-cleaning FPI-workshop line, adjacent to the parts-cleaning station.
A rail-based conveyor system also helps cut time. It transports over two floors from station to station with its 32 baskets, "much like cars traveling on a roller coaster." Instead of placing parts singly on conveyor rollers, the new system sends a conveyor every eight minutes for loading. Past this point, all operations along the 110-m rail route conform to this rhythm. Such a high-precision system demands strict compliance with time and temperature specifications, according to MTU, which is why it incorporates some 500 probes and actuators to sense over-maximum or under-minimum conditions and relay them to a central computer to take the necessary action and, if need be, shut the system down.
The system operators can track the current location and processing status of parts on computer screens at any time. For large parts or unusual shapes, specific fixture settings are available. The company claims that the rail system "greatly reduces" space requirements, with some fully automated operations using ceiling fixtures, including hoists.
The environment of the plant has also received attention. There is a special ventilation system to protect operators from inhaling the fine mist in the penetrant application booth. And an integrated ultrafiltration system has been installed. This system continuously separates the coumarin (the dye used in the penetrant) from the circulating water, replacing active charcoal filters. The environment in inspection booths has also been radically improved. Previously, the temperature in the booths could reach more than 35°C. Air conditioning now controls the temperature to between 20 and 30°C.
MTU states that the 80-min journey of the engine parts through the new system before they reach the reading station breaks down into clearly defined sections. First, an operator sprays parts with penetrant. From there, they go into a "quiet zone" to allow the penetrant to soak into any flaws by capillary infiltration. The parts then proceed to a pre-rinse booth, where the oil is washed off surfaces, taking care not to flush penetrant from flaws.
Next, after an emulsifier and post-emulsifier dip, comes a final wash, the last manual operation prior to inspection. A hoisting mechanism then lifts parts to the drying oven at roof level. They are dusted with powder developer, after which they descend to one of three inspection booths, the top of which closes automatically to facilitate UV inspection of components. This phase may take between a few minutes and two hours, depending on part size and geometry.
- Stuart Birch
Boeing researches in Europe
Just as automotive companies have opened design and technology facilities in countries away from their headquarters to better integrate products with markets, so Boeing has chosen Madrid for its first Center of Excellence outside the U.S., focusing on environmental, safety, reliability, and air-traffic-control technologies. The company plans to work closely with industry, academia, and other research centers in Spain and throughout Europe.
The new research and technology center is part of Boeing's Phantom Works responsible for advanced research and development. Initially, some 30 engineers and scientists will work at the Madrid center under the directorship of Miguel A. Hernan. Two of the initial projects being tackled by the center concern fuel cells and noise reduction. Boeing is researching the possibility of using fuel cells to replace aircraft gas turbine auxiliary power units. Fuel cells also have potential applications for use in small, unmanned air vehicles. Fuel-cell-technology development is part of the National Program of Aeronautics/Strategic Action Over Advanced Aeronautical Systems.
With regard to research into noise-alleviation technologies, Boeing's new Spanish center is already working in cooperation with the Dutch National Aerospace Laboratory and both the Madrid and Barcelona Polytechnic University. A phased array noise study is currently under way at Amsterdam's Schipol Airport to investigate potential for reducing noise close to major airports. Research into advanced air-traffic-management concepts is also a priority for the center.
- Stuart Birch
