Product Description:

Okuma manufactures the E4809-045-019-E within the E4809 CNC Boards series. This spindle-drive printed circuit board serves as the DC spindle drive element in Okuma lathes and machining centers, providing closed-loop control of spindle speed and direction for automated cutting operations. By interfacing with the machine’s numerical controller and the associated DC spindle motor, the board modulates armature power and executes dynamic braking so the spindle can accelerate, decelerate, or hold the commanded velocities required during tool changes and cutting cycles.

The board is energized from a three-phase supply of 200/220 VAC at 50/60 Hz. Power is processed through a three-phase full-wave back-to-back thyristor bridge that rectifies and inverts current for bidirectional torque generation. Excess kinetic energy is returned to the mains through a regenerative braking path, reducing thermal loading on external resistors. Armature current is measured with a current transformer; this sensor feeds one of two internal feedback loops so the controller can maintain commanded torque and protect the motor from overcurrent conditions. A second loop monitors speed, allowing the board to correct any deviation between the reference input and actual spindle velocity.

Rotational speed is sensed by a tachogenerator that outputs 20 V/1000 rpm, producing a proportional DC voltage used for fine speed regulation. Direction changes are triggered electrically through thyristor gate switching, eliminating mechanical contactors and enabling rapid reversal during threading or tapping cycles. For position reference at low speeds or during spindle orientation, an optical pulse generator supplies discrete pulses to the CNC, complementing the analog speed loop. The board also handles the DC speed signal from the feedback device, aligning it with programmed setpoints to achieve accurate spindle performance across the full operating range.