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5 Spindle Adjustment
MITSUBISHI CNC
(2) Measuring the acceleration/deceleration waveforms
Outputs the motor rotation speed by using the spindle drive unit's D/A output function and check if
theoretical acceleration/deceleration time is within ±15%. Refer to "5-1 D/A output specifications for
spindle drive unit" for details on D/A output functions.
Phase current FB output can be measured by the waveform for either U or V phase FB.
The motor phase current cannot be measured on D/A output. Thus, measure the current in the motor
wire, using a measuring device, current clamp meter.
When acceleration/deceleration time does not match the theoretical value (an error rate 15% or more),
check the following items.
[1] There may be an error in calculating load inertia for the motor axis conversion used when
calculating the theoretical acceleration/deceleration time. Check the load inertia again.
[2] When acceleration time is long and deceleration time is short, friction torque is thought to be large.
Check load meter value at the maximum speed (spindle monitor screen). If the load is 10% or
more, friction torque is thought to be relatively large. Mechanical friction, such as bearing friction or
timing belt friction, is assumed to be large. Measure the acceleration/deceleration time again
following trial run.
[3] Even if the problems above are not found, when acceleration/deceleration time does not match,
there may be a possibility of using spindle motor and spindle drive unit that are not specified, or
using wrong parameters. Check the spindle motor type and spindle drive unit type again, as well as
the spindle parameter settings.
There are cases where acceleration/deceleration waveforms change depending on the spindle
temperature. Check the waveforms when the spindle temperature is high (after continuous operation)
and when it is low.
When performing measurement with a workpiece or tool installed, be careful during the operation at
the maximum rotation speed, which may be dangerous because of the increase of inertia.
Motor rotation speed
Acceleration/deceleration waveforms of spindle motor
0
0
U
(
V
)
p
hase current FB
Acceleration time: ta Deceleration time: td
POINT
CAUTION