High-Speed, Five-Axis Machining--Japanese-Style

This Japanese five-axis aerospace shop believes that high speed machining is their future. Here's why, and some of what they've learned so far.

Article From: 3/15/1999 Modern Machine Shop, ,

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machines

AEC machines a range of structural aircraft parts.

accurately predicting

Understanding, and accurately predicting, tool performance is critical to AEC's overall process performance.

twin-pallet Toshiba

The twin-pallet Toshiba brought true high speed machining for large parts.

management team of AEC

The management team of AEC. Mr. Kanamaru is second from the left.

Aerospace shops tend to look fairly similar no matter where you find them. So we were not surprised to find five-axis machining centers inside the walls of Aikoku Alpha Engineering Corporation (AEC), an aerospace job shop near Nagoya, Japan. We were surprised, however, at how many. One of Japan's most experienced practitioners of five-axis machining, Aikoku Alpha first employed the technology 24 years ago, and currently operates some 17 five-axis machines in a wide variety of configurations. Along the way, many of the shop's people have become expert at both five-axis machining technique and NC programming. They've also acquired a blue-chip customer list, making structural and hydraulic parts for commercial and aircraft applications as well as turbine blades, impellers and other complicated parts for jet and rocket engines.

It also came as no surprise that Aikoku Alpha's business model is focused on delivering high value-added machining services to its customers. This shop does what few others in Japan can, and its margins are commensurate with that work. That does not mean, however, that this shop is immune to cost pressures. Like virtually everywhere else in Japan's production-driven metalworking community, aerospace suppliers are expected to continuously reduce cost, and Aikoku Alpha is no exception. According to Masaaki (Max) Kanamaru, AEC managing director, that was quickly bringing the company to a crossroads. Continually fine-tuning its five-axis expertise and acquiring more equipment had sustained Aikoku Alpha's progress toward higher efficiency for more than two decades. To reach the next level, however, the shop would have to execute a more dramatic shift in its machining processes.

Mr. Kanamaru believes that the key to achieving that level of improvement is high speed machining. So last year the company installed its first true high speed, five-axis machine, a Toshiba MPF-5A. Here's why they bought it, and what they've learned about the process so far.

A Bit Of History

Aikoku Alpha has an interesting history. Founded in 1943, the company began making metal parts for construction and agricultural machinery in 1946 and went on to manufacture a variety of components for other industries. In 1958, the company began a cold forming operation, which remains a substantial portion of the business today, mainly serving the auto industry. In 1969, the company acquired its first NC machine tools and began making aircraft parts. In 1975, Aikoku Alpha bought the first Japanese-made five-axis machining center—a Niigata OM3, manufactured under license from Sundstrand—and has been developing its five-axis process capabilities ever since.

The company expanded aggressively in the 1970s. It developed a manual workload manipulator, now marketed under the Raku-Raku Hand brand name. Aikoku Alpha also became more involved in exports. In the early '70s, the company began to sell cold formed parts in the United States and started supplying Boeing 747 parts to Mitsubishi Heavy Industries. By the end of the decade, the U.S. sales office of American Aikoku, Inc. was established in Deerfield, Illinois.

Today, Aikoku Alpha's "CF" division produces 2.5 million CV joint parts and one million precision-formed transmission spline shafts a month, as well as a range of cold-headed parts. AEC—which refers only to the aerospace division—manufactures a wide range of structural components, turbine blades, impellers, hydraulic parts and other components for many of the major aircraft and engine manufacturers as well as their subcontractors. As an offshoot of this business, AEC has a software division that develops and sells CAD/CAM applications and offers contract NC programming services. AEC sells and supports IBM's Catia system in Japan, and has developed applications of its own around Catia that simplify the interface for certain operations. AEC also has developed a special application in conjunction with Northern Research and Engineering Corp. (Woburn, Massachusetts) for programming impellers and A.S. Thomas (Westwood, Massachusetts) for programming turbine blades, and AEC markets its own five-axis postprocessor as well.

The Move To High Speed

While Aikoku Alpha today is a sizable auto and aerospace supplier, with more than 900 employees, the company was still quite small when it first made the strategic decision to develop five-axis machining capabilities. It had little choice but to internally build its own process knowledge, as it did not have the resources to acquire equipment on a large scale and there was no handbook to be found on five-axis machining. Aikoku Alpha even built some of its own equipment, and in a number of cases upgraded three- or four-axis machines to full five-axis capability with the addition of tables or heads, sometimes of their own design, and always with their own approach to integration. Along the way, the company's process engineers have done a great deal of work, figuring ways to increase cutting tool life and to dramatically reduce the need for special fixturing.

In short, the company's initial decision to move to five-axis machining was to secure high value-added, high-margin work, and the continual emphasis on process improvement was to keep the business competitive and profitable. Nowadays, that early decision seems prophetic, with simpler forms of contract machining increasingly leaving Japan for lower cost nations. AEC's management still believes complex part machining is going to be around for a long while, but also that it is subject to the unrelenting cost pressures as well. "Customers in Japan request cost reductions every year," says Mr. Kanamaru, and there's no reason to expect that pressure to subside anytime in the foreseeable future.

While an incremental approach to continuous improvement had met customer demands in the past, company management recognized several years ago that they'd have to step up the pace of improvement in the future. Indeed, the company set objectives calling for cost reductions averaging one percent a month over a three-year period. As such, it became clear that the company needed technology capable of delivering more dramatic gains, and management decided that high speed machining would provide a big part of the answer. Or as Mr. Kanamaru succinctly puts it, "High speed machining was the only way we could survive."

Choosing Technology

Now the question was what equipment was best for AEC's business. A great deal of scrutiny went into that decision before they finally decided on the Toshiba. First of all, AEC's engineers took a hard look at the mix of parts they want to produce. That review obviously included workpiece size and material, but also took into account much finer distinctions. They looked at the machining processes, evaluating their needs for achievable rpm range and spindle power. They looked at required tool lengths to help determine taper size. They even looked at the required directional changes in cutter paths to help determine what the acceleration/deceleration performance of the machine should be.

As should be the case in high speed machining, those judgements focused, not on getting the highest specifications in all areas, but in achieving the proper balance of trade-offs for the kind of work a shop does. With AEC being a job shop, they had to plan both for current and future parts, and had to assume a large variety of materials and workpiece configurations in the mix. So, a big part of the balance for AEC was to achieve a high combination of speed, power and stiffness. They chose a 12,000-rpm, 50/60-hp spindle with a 50-taper bore. "We could get higher speed with a 40-taper spindle," says Mr. Kanamaru, "but the machine would only be good at cutting aluminum." That wasn't a luxury AEC could afford, as they'd have to also cut stainless steel, titanium and other tough alloys, and frequently would have to use long tools to do it. The requirement for stiffness is also why they chose a machine with a single-piece bridge-and-column construction. It's also why they wanted a ballscrew drive on the A-axis head tilt, which Mr. Kanamaru says is stiffer than a rack-and-pinion drive, faster and more resistant to wear.

For the size (177 × 83 × 24-inch X-Y-Z travel), the machine also offers very good dynamic performance with top linear feed rates of 400 ipm and head tilt feeds of 1,000 degrees per minute. For dynamic accuracy, the machine employs a "CNCSHAPE" control feature that uses a look-ahead function to automatically manage feed rates in order to stay within a prescribed tolerance of the programmed tool path at the fastest possible feed.

And for efficiency, the machine is equipped with a pallet changer so that one job can be set up while another workpiece is being machined.

Relearning Machining

Of course, having a good machining platform is one thing, applying it to the greatest effect is quite another. And AEC's engineers found that much of what they knew about the five-axis machining process didn't necessarily apply at very high speeds and feeds. It's been a learning process that they continue to fine tune over time.

Like many new users of high speed machining, AEC's first approach was to transfer existing processes to the new machine, and just run them faster. But they quickly found out that wasn't going to work at the higher speeds and feeds of which the machine was capable. For example, where they might have run 3,000 rpm and 20 ipm in the past, now they would be running at 10,000 rpm and over 150 ipm. So rather that trying to incrementally adjust existing part programs, they began to take test cuts to see what tools and cutting strategies worked best in different materials. That research, along with data they secured from other industry sources, has resulted in AEC writing their own manual on the best approaches to high speed machining.

While Mr. Kanamaru is understandably unwilling to share all of AEC's hard-earned knowledge, he does give some general clues about where they've focused their efforts. A big shift is making sure that cutter paths avoid any unnecessary changes in direction. So, for instance, zigzag cuts have given way to spiral pocketing routines. They developed a better method for thin wall machining that involved finding, not only the right feeds, speeds and cutter path, but the correct depth of cut as well. They also developed a special corner-cutting method that reduces vibration, which results in better surface finish and longer tool life. They generally are using smaller, shorter tools than before. And where they might have used four-flute cutters in the past, now they frequently use two because they now have the necessary spindle speed.

As they came to understand the process better, they also came to understand the machine better too. As a consequence, they realized that the machine's servo system could be better tuned for the type of cutting they were doing. With the help of Toshiba technicians, the acceleration/deceleration characteristics of the machine were re-tuned to deliver significantly faster performance overall.

Now with the basics down, AEC continues to fine-tune their high speed machining processes on real parts—an improvement process that will never end. Right now Mr. Kanamaru figures that, in comparison to their old processes, high speed machining has resulted in a 60-to 80-percent reduction in machining time, and a 40- to 60-percent reduction in cost.

As for the future, AEC intends to apply high speed machining techniques more broadly across the business. That will involve retrofitting some of the older equipment with higher speed capabilities, and surely will require new equipment purchases as well. And it will absolutely require the continuing process education they pursue on a daily basis. AEC's clearly stated goal for the business is to be Japan's leader in five-axis machining. In the past, five-axis machining expertise alone was enough to achieve that objective. But the future, they know, will require speed too.

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