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The motor is a Nidec RK2-0419, which appears to be appears to be a fairly powerful "outrunner" style brushless motor rated for 1.3A at 24V. The rotor (the round metal part) is about 3 inches in diameter and the entire motor weighs about 15 ounces.
This motor might be a special motor designed for use in this printer, as it and many other components have a number with the format RK2-0xxx on them.
The single chip on the motor is a BD6761FS Brushless Motor Driver.