An OEM's unusual approach to defining next-generation CNC lathes.
The concept, design, and development effort behind Mori Seiki's new NL Series CNC lathes — a family of 30 machines in four series ranging in chuck sizes from 6 to 12 in. — is typical of the company's out-ofthebox approach to the machine tool business. Using a retrospective return to the basics of the cutting process, Mori Seiki built machines that are extremely accurate, rigid, and precise and that incorporate innovative technologies to promote productivity. For instance, in comparison tests with a 2000-vintage Mori Seiki SL-25MC, a new NL2500MC/700 lathe showed a 47% improvement in cycle time and a productivity increase of 100% (from 6 test pieces/8-hr shift to 12 pieces/shift).
The need for a totally new concept in small machining centers became evident during a series of shop surveys conducted by Mori Seiki involving mass producers and small, multiproduct shops in the U.S., Europe, and elsewhere. In July 2003, Dr. Masahiko Mori, Mori Seiki president and representative director, assigned the task of developing an advanced machine to Dr. Kazuyuki Hiramoto, managing director, development and manufacturing HQ executive officer and Nara Campus chief.
To stress the importance of the project, Hiramoto was directed to sequester his engineering staff in a remote retreat where they could develop a concept and hammer out the details. “We call this exercise ‘gasyuka,' which means to stay together,” says Hiramoto. “And stay together and think together we did, for five days and nights. Thus, the new NL Series was born.” Gasyuka is not a new concept at Mori Seiki and has been used successfully on previous projects.
“We approached the NL Series from the standpoint of workpieces and tools — the basis of the cutting process — rather than from the aspect of space and appearance,” explains Hiramoto. “We arrived at a balance between heat and force to produce lathes with extreme accuracy, rigidity, and high chip-removal rates.” Mori Seiki engineers refer to the developmental concept as an appropriate balance between rigidity and precision ( R& P technology).
The high spindle speeds and precision obtainable with NL lathes results from the attention designers paid to overall system and component rigidity and to the isolation and removal of heat to eliminate the accuracy-robbing effects of thermal displacement in critical components. For example, the spindle drive motor is integral with the spindle, eliminating the vibration and heatgenerating effects of drivetrain components between the motor and spindle of conventional systems. Designers also incorporated heat shields and structures to displace heat radiating from the oil controller, hydraulic unit, headstock, and servomotors.
Perhaps the most distinctive physical characteristic of the NL Series lathes is its built-in turret, which also serves as toolholder. The turret is ultrarigid and contains motors for rotary tools. It offers high transmission efficiency and low vibration — contributing to high precision, speed, and surface quality. The company claims these machining qualities are superior to those obtainable by a machining center.
The new MAPPS II operating system controls the NL Series machines. This system has Windows XP embedded, a 700-MHz-Pentium III CPU, and 256 MB of memory. It also sports an easy-to-read 15-in. TFT color LCD display. MAPPS II includes a scheduled-maintenance function, major-component-longevity tracking, and 3D-cutting simulations with the ability to zoom and rotate during simulation. Another feature is a toolpath display that highlights with each line of the program.
In addition to its new NL Series CNC lathes, Mori Seiki will exhibit several other systems at the upcoming IMTS in Chicago, including the NV4000 DCG and NH4000 DCG machining centers, several multitasking machines, and the MAPPS II operating system.