There's No Second Place in Aerospace

Manufacturing Engineering, Mar 2007 by Segal, Robert

Success requires matching equipment capabilities to the demands of the job

Driven by consumers to keep airfares and shipping rates low, aerospace OEMs need to reduce costs from 5 to 10% each year. That directive is passed down through the supply chain. Further, the greatest challenge facing our North American companies is global competition. The largest aircraft customers over the next decade will be China and India, and as a result, many aircraft components that traditionally would be made in Europe, the US, and Canada, are instead being made in these emerging markets. There is also an unusually high demand for titanium, which is impacting us greatly. The material for one of the titanium split-fan cases we produce costs $30,000 per part, compared to $5000 three years ago.

Remaining competitive in aerospace manufacturing, and likely most industries, is a challenge today. One never really wins once and for all time, but skills and results do improve as the bar is raised. That is what continuous improvement in manufacturing is all about-we keep progressing to the next level in process improvement and operational excellence with specific goals as signposts along the way, whether it is a reduction in cycle time, process run time, or manufacturing losses. Fortunately, the technology and lean initiatives we are establishing at Magellan seem to be working. We are still here.

At our Haverhill, MA facility we manufacture and assemble turbine engine support structures, and shafts for commercial and military aircraft. Our 85,000 ft^sup 2^ (7897 m^sup 2^) factory can turn, mill, and grind parts as large as 65'' (1650-mm) cube with a wide range of machine tools-a mix of about 60% turning and 40% milling.

Structural components support the rotating turbines of the aircraft engine while allowing air to pass through from front to rear. They are generally round, with several struts joining the inner and outer rings to a central bearing housing. Outside support structures may have mounting lugs as attachment points for external engine components, or for mounting the engine to the aircraft.

As in any assembly, each part impacts another. In the event of a turbine component failure, these structures are designed to isolate the problem so that the engine will not affect the body of the aircraft. The structures, like all aircraft components, must withstand a wide range of thermal and g-force conditions. To provide parts that can deal with these conditions, we machine a substantial amount of Inconel 718 and 907 and other nickel alloys for the parts closest to the engine, titanium 6-4 and 6-2-4-2 for its light weight, high strength, and heat-resistant characteristics, and aluminum or magnesium castings for the outer, cooler sections. From a machining viewpoint, one of the challenges we face is achieving high material removal rates while maintaining the form and function of the part.

The bottom line to remaining competitive is the ability to make parts quickly, and that is more than just the speed of the machine tool spindles-it's all of the aspects that need to be in place to bring a product to our customers as quickly as possible, from design through shipping. It's about taking advantage of current technology and applying it correctly.

One of our jobs at this facility is to help our customers design for manufacturability. We don't portray ourselves as designers, but we take advantage of NX (Unigraphics) design tools and automation within software to share our knowledge of fixture design, part families, or part-process families, so that we can plan our operations and setups faster. We also use machine tools that can accommodate the range of materials we use, and the complex part geometries we machine. We have developed the ability to select machine tools in a more standard way, and embark on a comprehensive process when we specify new machinery. We've created a matrix in which we identify our needs and compare those against the relevant machine tool features.

For example, a few years ago we needed to update our machining centers to accommodate larger structural parts that require five-axis machining. We went through an exhaustive survey of every CNC milling machine manufactured. Through our matrix of pluses and minuses, we narrowed the field to three and ultimately selected technology from Mitsui Seiki USA (Franklin Lakes, NJ). Currently we have two of their horizontal five-axis machines with another on order.

These models met all of our criteria, particularly for high-speed contouring with rapid traverse rates of 945 ipm (24 m/min), cutting feeds of 16 m/min, and positioning accuracies of 0.00006'' (0.0015 mm) on the larger HU80A-5X model's X, Y, Z envelope and ±2 arcsec on the tilting/rotating A-B-axis trunnion. Of course rigidity and ease of changeover came into play as well, so we can run Inconel, titanium, and magnesium parts on one machine. To be flexible, we need versatile machines.

A key aspect of the machine tool justification process is of course analyzing the cost. One of the great myths in machine tool purchasing is that the price of a piece of equipment is the cost of the equipment, and that is not so. Typically, the price of a machine tool may be as little as 8% of the total life-cycle cost of the machine. Rework, downtime, and maintenance costs increase over time with less-expensive machine tools. Purchasing machines with an effective life cycle of 30,000 operating hours versus machine tools providing 80,000 hours impacts the capital expenditure return significantly.