Siemens SINUMERIK 840C Installation Instructions Manual page 692

10 Axis and Spindle Installation
10.1 Determining sampling interval and interpolation time
Setting
• Enter drive basic cycle time in MD 168 (in 62.5 µs).
• Enter position control basic clock frequency in MD 155 (multiplier MD 168).
• Enter ratio to interpolation time in MD 160.
• If MD is incorrect, alarm 1012* "Parameterization error" drive MD is output.
• Set increase of position control basic clock frequency for each axis in MD 1396*
Relationship between interpolation time and position control sampling time must be integral and
larger than 1
–––––––––––––––––––> 1
Position control time
Example for setting the sampling interval
Available:
Desired sampling interval for machining axis
Desired interpolation cycle time
Possible sampling intervals for auxiliary axis:
1 ms, 2 ms. The selected interval is 2 ms.
MD values:
MD 168
MD 155
MD 160
MD 1396*
Display of the NC CPU utilization (SW 5 and higher)
The SINUMERIK 840C control has a real-time operating system that ensures that the moving
axes and spindles are supplied with setpoints in a defined timebase (position control and
interpolation cycles). All other control activities (display, input etc.) are dealt with a lower
priority by the operating system.
The value displayed for the NC CPU utilization when the control is in the reset state and no
operator actions are being performed is the basic CPU utilization.
The user can influence this basic utilization of the NC CPU by setting the position control and
interpolation cycles. It also depends on the number of channels, axes and spindles.
The interpolation cycle is the basic cycle in the control. Within the IPO cycle, all control
activities (calculation of the next partial setpoint, processing of keystrokes, refreshing the
active display etc.) must be terminated. If time is left at the end of a cycle, the control is idle.
The shorter the position control or interpolation cycles, the shorter the control idling time will
be.
The NC CPU utilization is the ratio of the idling time to the set IPO cycle. The NC CPU
is considered fully utilized if there is no more idling time within a cycle.
The value of the CPU utilization indicates to what extent the interpolation and position control
cycles can be set for the NC CPU used for a certain control configuration.
10–2
More user manuals on
IPO time
2 machining axes (X, Z)
2 auxiliary axes (Q1, Q2)
= 8 (0.5 ms)
= 2 (1 ms)
= 4 (4 ms)
= 2 (4 ms)
ManualsBase.com
1 ms
4 ms
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SINUMERIK 840C (IA)