Niigata N500

The Niigata N500 is the smallest of the N series: a horizontal machining center with a 500 mm × 500 mm pallet, a BBT40 spindle that runs to 15,000 min-1 and rapids of 60 m/min on all three linear axes. Travels are 730 mm (28.7 in) in X, 700 mm (27.6 in) in Y and 760 mm (29.9 in) in Z, and the largest workpiece is φ700 mm × 1,000 mm on a pallet rated for 500 kg (1,102 lb).

What sets the N series apart inside Niigata's range is the structure. Most of the maker's horizontals are column-traverse machines on box slideways. The N500 instead uses what Niigata calls BOX in BOX: a fixed column with a wide guide space, a light moving mass and roller guides on every axis. Niigata's argument is that less moving weight means less inertia, which is where the 60 m/min figure comes from, and that the fixed column keeps cutting stable even at the top of the Y stroke. The base is T-shaped and sits on 3-point leveling.

The spindle is the interesting part for a 40-taper machine. Niigata rates it at 303 N·m (223 lb-ft) and describes it as a #40 spindle with heavy cutting capability comparable to a #50. A BIG-PLUS spindle, oil-air bearing lubrication and a spindle cooling system synchronized to machine temperature are listed as standard equipment.

Tool changes are handled by a cam-driven, servo-motor ATC. Niigata gives 1.2 s for a 4 kg tool and 1.7 s for a 12 kg tool, and the chain magazine is listed as 60 / 126 tools. The pallet indexes in 0.001° steps, so the fourth axis can be positioned finely enough for contouring. Two side-discharge chip conveyors are offered: a hinge pan type, and a double decker type with drum filter, scraper and hinged pan.