FANUC Series 30i/300i/300is-MODEL A. Machining Center System. User's manual - page 93

21.AXIS CONTROL FUNCTIONS

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  - Synchronous establishment based on absolute position detection 

When an absolute-position detector is used as the position detector, 
the machine positions on the master axis and slave axis are found at 
power-up time for automatic establish synchronization. 
 

  - Synchronous establishment after emergency stop cancellation, etc. 

Synchronous establishment is also performed when servo position 
control is turned on, for example, at emergency stop cancellation, 
servo alarm cancellation, or servo-off cancellation time. 
However, synchronous establishment is not performed at the time of 
axis removal cancellation.    So, synchronous establishment based on 
manual reference position return operation is required as in the case of 
power-up time. 
 

  - One-direction synchronous establishment 

When synchronous error compensation is disabled, synchronous 
establishment can be performed by setting bit 0 (SSO) of parameter 
No. 8305 to 1 to move the machine in one direction along the master 
axis and slave axis.  The move direction depends on the reference 
position setting based on bit 0 (SSA) of parameter No. 8304.    When 
SSA = 0, for example, the machine coordinate on the master axis or 
slave axis, whichever larger, is used as the reference point.    So, the 
machine moves in the + direction along the axes. 
When bit 1 (SSE) of parameter No. 8305 is set to 1, normal 
synchronous establishment is performed instead of one-direction 
synchronous establishment after an emergency stop. 
 

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21.1.4 

Automatic Setting for Grid Position Matching 

 

Explanation 

Before axis synchronous control can be performed, the reference 
position on the master axis must be matched with the reference 
position on the slave axis.  With this function, the CNC 
automatically matches the reference positions (grid positions) on the 
master axis and slave axis under axis synchronous control. 
 

[Operation procedure] 

The procedure below is usable when bit 0 (ATE) of parameter No. 
8303 is set to 1. 
1.  Set bit 1 (ATS) of parameter No. 8303 to 1. 
2.  Turn off the power then turn on the power. 
3.  Set the REF mode (or JOG mode in the case of reference position 

setting without dogs) when synchronous operation is ready, and 
make movements in the reference position return direction along 
the master axis and slave axis. 

4.  The movements along the master axis and slave axis 

automatically stop, and a grid difference value is set in parameter 
No. 8326.    At this time, bit 1 (ATS) of parameter No. 8303 is 
set to 0, and the power-off request alarm PW0000 is issued. 

5.  Turn off the power then turn on the power again. 
6.  Perform normal reference position return operation. 
 

NOTE 

1 Parameter 

setting 

 

When bit 1 (ATS) of parameter No. 8303 is set, bit 
4 (APZ) of parameter No. 1815 and parameter No. 
8326 for the master axis and slave axis are set to 
0. 

 

When the operator sets parameter No. 8326 (MDI, 
G10L50), bit 0 (ATE) of parameter No. 8303 is set 
to 0. 

2  This function cannot be used together with the 

reference position shift function. 

 

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21.1.5 

Synchronous Error Check 

 

Explanation 

A synchronous error value is monitored at all times.  If an error 
exceeding a certain limit is detected, an alarm is issued and the 
movement along the axis is stopped. 
When synchronous error compensation is performed, a check 
considering a positional deviation as well is made. 
When synchronous error compensation is not performed, a 
synchronous error check based on machine coordinates is made. 
 

  - Check made when synchronous error compensation is performed 

When synchronous error compensation is performed, a check 
considering a positional deviation is made.  The actual machine 
position shift considering a servo positional deviation as well is 
checked.    Depending on the value of a synchronous error, one of two 
alarms is issued: an alarm (DS alarm) for deceleration stop, and an 
alarm (SV alarm) for turning off the servo system immediately.    This 
check is enabled when a value other than 0 is set in the parameters 
Nos. 8331 and 8332 for specifying a maximum allowable synchronous 
error.  When using this method of checking a synchronous error 
value, disable "synchronous error check based on machine 
coordinates" described later by setting parameter No. 8314 to 0. 
 

  - Synchronous error excessive alarm 1 (DS0002) 

When a synchronous error exceeding the value set in parameter No. 
8331 is detected, synchronous error excessive alarm 1 is issued.  
When synchronous error excessive alarm 1 is issued, the motor 
gradually stops.  At this time, synchronous error compensation 
remains enabled, so that the synchronous error is reduced by 
compensation.  Accordingly, as the synchronous error value becomes 
smaller than the maximum allowable value, the alarm can be reset.    If 
the alarm cannot be reset, the synchronous error needs to be manually 
corrected by selecting the correction mode described later. 
 

  - Synchronous error excessive alarm 2 (SV0002) 

When a synchronous error exceeding the value set in parameter No. 
8332 is detected, synchronous error excessive alarm 2 is issued.  
Before synchronous establishment is performed at power-up time, a 
value obtained by multiplying the value set in parameter No. 8332 by 
the coefficient set in parameter No. 8330 is used for judgement.  
When synchronous error excessive alarm 2 is issued, the motor 
immediately stops as in the case of other servo alarms.    Accordingly, 
the positional difference between the master axis and slave axis 
remains uncorrected, so that the alarm cannot be reset usually.  In 
this case, the synchronous error needs to be manually corrected by 
selecting the correction mode described later. 
 

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  - Synchronous error check based on machine coordinates 

When synchronous error compensation is not performed, a 
synchronous error check based on machine coordinates is made. 
The machine coordinate on the master axis is compared with that on 
the slave axis.  When the error between the machine coordinates 
exceeds the value set in parameter No. 8314, the SV0005 alarm is 
issued, and the motor is stopped immediately. 
A check can be made even in the emergency stop, servo off, and servo 
alarm states. 
If a synchronous error check is made when the mode of operation is 
switched between synchronous operation and normal operation with 
an input signal, an error check is made even in normal operation.    So, 
even if the axis synchronous control selection signal (SYNCx) or the 
axis synchronous control manual feed selection signal (SYNCJx) is set 
to 0 by mistake during synchronous operation, damage to the machine 
can be prevented. 
The machine coordinates on the master axis and slave axis can be 
checked using the machine coordinate match state output signal 
SYNMT <F0210>. 
 

  - Synchronous error check based on a positional deviation value 

The servo positional deviation value of the master axis and slave axis 
is monitored during axis synchronous control.  When the positional 
deviation value exceeds the limit value set in parameter No. 8323, the 
DS0001 alarm is issued, and the axis synchronous control positional 
deviation error alarm signal <F403.0> is output. 
The DS0001 alarm is issued to the master axis and slave axis. 
When bit 4 (SYA) of parameter No. 8301 is set to 1, the positional 
deviation limit value of the master axis and slave axis is checked even 
if a servo-off occurs during axis synchronous control. 
 

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21.1.6 

Methods of Alarm Recovery by Synchronous Error Check 

 

Explanation 

To recover from an alarm issued as a result of synchronous error 
check, two methods are available.  One method uses the correction 
mode, and the other uses normal operation. 
If the mode of operation is switched between synchronous operation 
and normal operation by using an input signal, only the method using 
normal operation can be used. 
If synchronous operation is used at all times, only the method using 
the correction mode can be used. 
 

  - Procedure for correcting a synchronous error by using the correction mode 

Use this method if synchronous operation is used at all times without 
using an input signal (when bit 5 (SCA) of parameter No. 8304 is set 
to 1). 
When the correction mode is used, synchronous error check can be 
temporarily disabled, and a movement can be made along the master 
axis or slave axis to correct a synchronous error. 
In the correction mode, synchronous error compensation and error 
check are not performed, so that an alarm DS0003 is issued as a 
warning. 
 
1.  Select the correction mode, and select an axis along which a 

movement is to be made by manual master axis feed.    Set bit 2 
(ADJ) of parameter No. 8304 of the master axis or slave axis to 1 
to set the correction mode.    Thus, by manual master axis feed, a 
movement can be made along the axis with this parameter set to 
1. 

 

When this parameter is set to 1, the DS0003 (axis synchronous 
control correction mode) alarm is issued. 

 
2.  Reset the synchronous error excessive alarm. 
 

In this state, synchronous error compensation and error check are 
not performed.  Be careful. 

 
3.  Select the manual mode (jog, incremental feed, or handle). 
 
4.  While checking the synchronous error value, make a movement 

along the master axis or slave axis in the direction that reduces 
the error. 

 

If one master axis has multiple slave axes, an attempt to reduce 
the synchronous error of one slave axis by master axis movement 
may increase the synchronous error of another slave axis, thus 
disabling a movement in any direction.  In such a case, by 
setting bit 4 (MVB) of parameter No. 8304 to 1, a movement can 
be made in a direction that increases the synchronous error. 

 

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5.  When the synchronous error is reduced to within the allowable 

value for suppressing the alarm, reset the value of bit 2 (ADJ) of 
parameter No. 8304 to the original value to switch from the 
correction mode to the normal synchronization mode. 

 

Synchronous error compensation and synchronous error check 
are restarted. 

 
6.  Reset the correction mode alarm.   
 

  - Method of recovery using normal operation 

Use this method when switching between synchronous operation and 
normal operation by using an input signal. 
Use the procedure below for recovery from alarm SV0005. 
 
1.  Set SYNCx/SYNCJx (with x representing a slave axis number) 

to 0 to select normal operation. 

 
2.  Set a value greater than the current value in the parameter No. 

8314 for specifying a maximum allowable synchronous error, 
then reset the alarm. 

 
3.  Make a movement along the master axis or slave axis by using 

the manual handle so that the machine coordinates of the master 
axis and slave axis match to a maximum possible extent. 

 
4.  Return the value of parameter No. 8314 for specifying a 

maximum allowable synchronous error to the original value. 

 

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21.1.7 

Axis Synchronous Control Torque Difference Alarm 

 

Explanation 

If a movement made along the master axis differs from a movement 
made along the slave axis during axis synchronous control, the 
machine can be damaged.  To prevent such damage, the torque 
command difference between the two axes is observed.  If the 
difference is abnormal, a servo alarm SV0420 can be issued. 
 

Kp

+

Slave axis
position

command

Alarm detection

Master axis
position

command

Position gain

Feedrate

control

Master axis

torque command

Master axis

position feedback

-

+

-

Torque command

difference

+

-

Kp

Compare absolute

value with threshold

Feedrate

control

Slave axis torque

command

Slave axis

position feedback

Position gain

 

Fig. 21.1.7 (a)    System configuration 

 

[Method of use] 

Specify the threshold parameter No. 2031 according to the procedure 
below. 
 
1.  Set 0 in parameter No. 2031, and disable the torque difference 

alarm detection function. 

2.  To check the absolute value of the torque difference between the 

synchronous axes, set the parameters below.    Set the same value 
for the two axes placed under axis synchronous control. 

Parameter No. 2115 = 0 
Parameter No. 2151 is as described below. 

•

 

For the servo software 90E0 series, set it to 434 if the 
setting of parameter No. 1023 is 1, 2, 5, 6, 9, 10… and 
to 6578 if it is 3, 4, 7, 8, 11, 12… 

•

 

For the servo software 90D0 series, set it to 434. 

3.  Display the diagnostic screen by pressing the function key 

 

then the [DGNOS] soft key. 

 

Diagnose No. 0353 indicates the absolute value of the torque 
difference between the two axes. 

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4.  Read the absolute torque difference value presented when normal 

operation is being performed.  In the threshold parameter No. 
2031, set a value obtained by adding some margin to the read 
absolute value. 

 

The absolute torque difference value can be observed with the 
Servo Guide Mate. 

 

  - Enabling/disabling of alarm detection 

Alarm detection is enabled when the time set in parameter No. 8327 
has elapsed after the servo ready signal SA <F000.6> is set to 1.  
When the input signal NSYNCA <G059.7> is set to 1, alarm detection 
is disabled. 
 

SA<F000#6>

1
0

Alarm detection function Enabled

Setting of parameter No. 8327

(512 msec when this parameter is not set)

Disabled

 

Fig. 21.1.7 (b)    Timing chart 

 
When the servo ready signal SA <F000.6> is set to 0, torque 
difference alarm detection is disabled. 
 

NOTE 

 

The servo axis number combination of the master 
axis and slave axis synchronized with each other 
must be such that an odd servo axis number is 
assigned to the master axis and the next servo axis 
number is assigned to the slave axis like (1,2) and 
(3,4). 

 

 CAUTION 

1  When making a synchronous error check, ensure 

that the reference position on the master axis and 
the reference position on the slave axis must be at 
the same position. 

2  In manual reference position return operation, the 

same operation is performed along the master axis 
and slave axis until a deceleration operation starts.   
After a deceleration operation starts, grid detection 
is performed for the master axis and slave axis 
independently of each other. 

3  Pitch error compensation and backlash 

compensation are performed for the master axis 
and slave axis independently of each other.