Where Do Machine Builders Find Components and Devices They Can't Get Anywhere Else?

Mitsui Seiki Is the Answer. The Company's Pursuit of Ultimate Precision Enables Innovations in Aerospace, Power Generation and Machine Building

By Jim Montague

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When end users need machine parts, they go to their suppliers; when suppliers need parts and equipment, they ask their machine builders. So, where do builders find specialized components and devices they can't get anywhere else? They go to Mitsui Seiki USA in Franklin Lakes, New Jersey.

This is not an idle sales boast. The 33-year-old U.S. subsidiary and its 87-year-old parent company, Mitsui Seiki Kogyo in Kawajima, Japan, is one of just a few firms whose equipment enables users to do high-precision machining of the hardest types of titanium, tungsten and new intermetallic composites like titanium aluminide (TiAL). The parts that Mitsui Seiki's machines produce are used to build everything from other machine tools and critical power-generating components to next-generation aircraft engine turbines and landing gear.

"We aren't the biggest machine builder, but our core competency is precision in serving OEMs and the machine tool market," says Scott Walker, president of Mitsui Seiki USA. "As a result, we have to maintain one decimal place more accuracy than other builders because our machines are often used to manufacture many of the parts that go into their machines. Because we also lead in R&D and special applications, we can change designs for tapers, tools and controls and build whatever our customers want within any size range."

Also Read: Hand Scraping Sets the Foundation for CNC Machining Accuracy and Long-Term Stability

Mother Machines
Long based in Tokyo, Mitsui Seiki started making measurement instruments such as block gauges and micrometers in 1928, but it developed its first medium-sized, jig-boring machine in 1935, which meant Japan no longer had to rely on imports. It was called the nation's first "mother machine" because it was mostly used by other tool builders to make critical components for their machines, and it helped to establish Japan's machine tool industry. Presently, Mitsui Seiki offers jig borers, jig grinders, horizontal and vertical machining centers, five-axis machining centers and screw grinders, all of which support builders and other users worldwide.

To achieve and maintain the order-of-magnitude better precision that its mother machines require, Mitsui Seiki must reduce vibrations, temperature and humidity changes and other adverse ambient conditions in its manufacturing areas. As a result, it incorporated some unique environmental attributes when it built its main plant in Kawajima in 2001. The factory's 1,700 pilings go 120 ft deep into the remote site's bedrock, while its floors are 4 ft thick in critical areas and 3.28 ft thick elsewhere. A laminar-flow air-conditioning system exchanges air in the factory 24 times/hr but still ensures a uniform, floor-to-ceiling temperature of 68 °F with ±9 °F accuracy and humidity of 55% with ±5% accuracy.

"We even have our own foundry, make our own spindles and tools and build our machines in place," says Bob Anderson, Mitsui Seiki's senior applications engineer. "This gives us better control over the accuracy of our machines."

New Controls, Hand Scraping
To keep improving its precision while meeting end users' needs at the same time, Anderson reports that Mitsui Seiki recently updated the controls on its HU100-5X horizontal, five-axis machining center (Figure 1).

"We been building this machine for 20 years, but now its Fanuc 31iM controls and spindle interface are all new," adds Anderson. "This interface has to be extremely stiff and rigid because the geared spindle on the HU100-5X and our other machines run at low rpm and very high torque because they need to make deep cuts and get out fast."

Ideal for making larger aerospace and power-generation parts, HU100-5X has an XYZ workzone capacity of 1,500 by 1,200 by 1200 mm, and it accommodates material weights up to 4,400 lb. It also includes a maximum spindle torque of 2,000 ft-lb, an HSK 125A tool taper, dual-pallet changer, automatic workpiece/fixture measuring and compensation system, non-contact-laser tool setter, 3D tool compensation and dynamic feature offset.

Walker adds that HU100-5X is used to cut 553 and 1023 titanium for critical parts of the landing gear on Boeing's aircraft. It can typically cut about 100 units for landing gear per year over a projected 25-year lifecycle. However, the extreme weight of the machine and its workpieces require some special treatment to maintain precision. "The machine assembly and its parts can weigh about 75,000 lb, so it can flex downward as it moves along its x-axis," explains Walker. "We have to hand-scrape the machine's platform to compensate for this flexing, and hold it to its 25-micron true position in the work envelope."

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