The SHX and SPX brushless servomotors for CNC machinery applications are available from NUM Corp. (Naperville, IL). They eliminate the need for a separate encoder cable; machine builders can use a single drive-to-motor cable for each motion axis. Available in 75-, 95-, 126-, and 155-mm frame sizes and three different lengths, the servomotors provide a choice of output power and speed ratings to match different machinery applications. Both motor ranges feature high mass moments of rotor inertia, optimized for machine tool feed axes. The SHX range includes models with continuous torque outputs from 1.2 to 20 Nm, and the SPX range offers units with continuous torque ratings from 1.4 to 23 Nm.
An embedded digital interface scheme allows the encoder power and position feedback data — together with diagnostic information and thermal data from the motor’s temperature sensor — to be carried on two shielded wires contained within the motor’s power cable. All servomotors offer a choice of single- or multi-turn digital encoders with medium, 20-bit resolution and ±60 arc seconds accuracy. The motors are available with plain or keyed shafts, an optional electrically actuated permanent magnet holding brake, and a choice of stator winding configurations.