Mitsui Seiki
Mitsui Seiki Pj303 X 800

5-Axis Machining for Smaller Workpieces

July 29, 2021
High precision and versatility for parts like lens molds, medical products, EDM electrodes and fuel cell components.

MITSUI SEIKI’s new PJ 303X five-axis machining center provides precision and versatility in processing of workpieces up to 230 mm tall and 280 mm in diameter (9x11" in.), and 20 kg (44 lbs.) in weight. Typical applications cover an extensive range of critical part,s such as lens molds, medical products, EDM electrodes and fuel cell components.

The machine’s X-, Y-, and Z-axis travels are 300, 325, and 200 mm (11.8, 12.8, 7.9 in.), respectively. A-axis rotation is +40˚ to -100˚, and the C-axis rotates a full 360˚. High-speed linear motors move the X-, Y- and Z-axes, while the rotary axes employ direct-drive motors. Rapid traverse speed for the X-, Y-, and Z-axes is 20 m/min (66 ft/min).

A 50,000-rpm, HSK-E25 taper spindle offers high-speed machining capability. An automatic tool changer engineered to store up to 24 tools as large as 40 mm (1.57 in.) in diameter and 120 mm (4.7 in.) in length provides tooling versatility.

To maximize precision, the sliding machine surfaces of the PJ 303X are hand-scraped.

Advanced spindle thermal displacement technology is standard, including a symmetrical gantry column structure that accommodates thermal deformation fluctuations and a thermal compensation mechanism for the machine spindle/head.

Operator-friendly features enhance precision further, including a 380-mm (15-in.) color display with touch panel capability that can be moved to the most convenient position relative to the work envelope. The machine’s double-stage rotary door offers wide access for visibility and set-up.

The compact PJ 303X occupies a 1,755x2,370x2,655 mm (5.75x7.77x8.7 ft. / LxWxH) of floor space, and weighs approximately 4,500 kg (9,900 lbs.)

“The compact PJ 303X machining center provides high precision, speed, and versatility for the processing of an important range of part sizes across a wide variety of applications,” according to Mitsui Seiki USA chief operating officer Bill Malanche. Learn more at

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