Mori Seiki's NT Series mill/turn machines combine milling and turning within one platform without compromising either process.
Unlike other mill/turn machines based on either a lathe or machining center, Mori Seiki's NT Series mill/turn combines both within one platform and, most importantly, does so without compromising the milling or turning processes. The company, headquarted in Nagoya, Japan, achieves this "no-compromise" integration through box-in-box construction, its Driven at the Center of Gravity (DCG) technology, and special ram, lower turret, and Y-axis designs.
The machine's box-in-box construction incorporates an outside frame with an inside saddle, basically one machine built around another. This eliminates moving large machine structures, increases accuracy and rigidity, and reduces mass. This construction, in turn, also allows the NT to use DCG.
In DCG, two ballscrews drive a machine's moving structures at structure centers of gravity. The system enhances acceleration and suppresses vibration to shorten machining times, boost part roundness, improve surface finishes, and prolong tool life. For instance, maximum acceleration rates for one of the NT machine's X, Y, and Z axes run 0.8, 0.4, and 0.6 G, respectively. Typically, machine rams fall under the square or round categories, while the NT's is octagonal for strength and fewer interference zones. Also, guiding Vs, like on lathes, ensure accurate and stable ram movement.
The NT's lower turret comes from Mori Seiki's NL series of lathes and features integrated-motor/direct-drive technology. Such a design eliminates the need for gears or belts and provides backlash-free and high-speed rotation.
According to Mori Seiki, the Y-axis stroke on the NT is comparable to that of a machining center's. With the NT stroke, shops can machine holes in four locations over a distance of 250 mm with respect to chuck center and without using the machine's C axis. This stroke also provides room for running grinding wheels.
There are 9 machine models and 66 variations in the NT Series. Models include the NT3100DCG, NT3150DCG, NT3200DCG, NT4200DCG, NT4250DCG, NT4300DCG, NT5400DCG, NT5500DCG, and the NT5600DCG. Distances between centers measure 500 and 1,000 mm for the NT3000 machines; 700, 1,000, and 1,500 mm for the NT4000s; and 1,200 and 1,800 mm for the NT5000 machines.
All machines feature Mori Seiki's Mapps III high-performance operating system. Equipped with a collision function, it monitors machine movements in real time and frees operators from concerning themselves over typical machine interferences associated with the many functions and complex movements of mill/turn systems. In addition, Mapps III speeds programming through its conversational-input function and high-speed canned cycles.
Since a mill/turn system's numerous feed and rotating axes potentially generate heat, Mori Seiki equips NT machines with ballscrew and motorjacket cooling. Even from a cold start, when power has just been turned on, the system eliminates variations in precision.
For fast toolchanging, NT ATCs, with high-speed cams, deliver 1.0-sec tool-totool changes and 3.4-sec chip-to-chip times. Such short chip-to-chip times diminish noncutting intervals, and Mori Seiki reports that these times are half or less than those typical of conventional mill/turn models.