Computer Drive Installation Instructions

6 NC Machine Data (NC MD), NC Setting Data (NC SD) 09.95

6.5 Spindle-specific MD (spindle data)

Acceleration time constant

with position controller gears 1-8

478*-485*

Default value Lower input limit Upper input limit

2 000 0 50 000 1 ms

Active on

Power On

Assignments

Gear 1 2 3 4 5 6 7 8

NC MD 478* 479* 480* 481* 482* 483* 484* 485*

The control issues the ramp-form setpoints for acceleration and braking operations (ramp

function generator). The gradient of this ramp is determined by the acceleration time constant.

Notes

• Two acceleration time constants are provided for each gear ratio:

– Acceleration time constant without position controller (MD 419* to 426*)

– Acceleration time constant with position controller (MD 478* to 485*)

The time constants without position controller are used for the open-loop control mode, the

time constants with position controller for the position mode.

• MD 478* to 485* must be set such that the motor can follow the specified setpoints at any

one time without reaching the current limit. Particular care should be taken be taken that

this is also the case in the field weakening range.

• The data in 478* to 485* should always be greater than the data in 419* to 426*.

• You can set MD 419* to 426* so that the motor is accelerated to the current limit for a

certain time. If a ramp-up generator is built into the actuator, you can set MD 419* to 426*

to 0. In this case, the setpoint changes in steps on acceleration and deceleration.

Calculation of the permissible acceleration in position controlled spindle operation.

Development of spindle speed in controlled mode at the acceleration limit (M3/M4)

Speed

Maximum speed for position control mode

Time

SINUMERIK 840C (IA)