38
Troubleshooting
Introduction
If you experience a problem with the
SMC20, it will normally be associated
with one of four conditions:
– Can’t test the initial set–up
– Can’t initiate motion
– Does not control motion well
– General failure
Through the use of the error bits
described in the General Faults section
(page ##) and helpful hints described in
the following sections, an operator, in
most instances, will be able to determine
a solution to a problem. If, after
following the troubleshooting procedure,
the unit is suspected of failure, call
Vickers and ask for a SMC20 service
representative to verify your diagnosis
and aid in resolution of the problem. Be
sure when you call, to have the model
number and serial number of the SMC20
in question.
Before performing troubleshooting
procedures, be sure you are intimately
familiar with the operation of the SMC20
and that a means to terminate
unintended motion and electrical power
to the unit exist and are easily
accessible.
Also, be sure to turn ‘Off’ all power
before attempting to remove the I/O
terminal strips, feedback devices or
communication devices (including the
Hand–Held Terminal) from the SMC20.
When starting up a system, it is best to
initialize the electronics first.
Can’t Test Initial Set–Up
InTesting Initial Set-Up section (page
##), the operator is instructed to jog the
SMC20 to initiate motion. If the axis
does not move, it is most likely because
the axis gains or axis parameters are
incorrect. Another possibility is the
actuator travels to an extreme limit in an
uncontrolled manner. Another type of
fault relates to the physical hardware.
Gains Not Set Properly
D
Make sure the Kp gain is set to at least
1000. Kp is one of the axis gain
parameters in the Configuration mode.
D
Try the default Jog Velocity first. If the
Jog Velocity is set too high and/or the
Maximum Position Error is set too low,
it is possible to trip the ‘Maximum
Position Error’ (Error bit I/O addresses
235 or 243 set ‘On’ – see General
Faults section, page ##).
D
Any time a position error bit (General
Faults section, page ##) is set ‘On’ by
a fault, as described in some of the
following descriptions, it is necessary
to first reset the error (see section)
using the Reset screen in the Run
mode before attempting a new
operation.
D
Verify that the run inputs are not
active.
D
Verify that the Maximum Position
Limits are not exceeded (Error bit I/O
addresses 232, 233, 240, and 241 set
‘On’ – see General Faults section,
page ##). It may be necessary to jog
in the opposite direction of the limit in
order to achieve motion.
D
Verify Enable (ENBL) input is active.
D
Verify the Enable Axis (EN*) input LED
is ‘On’. This input may be toggled
after occurrence of an error to reset.
Uncontrolled Motion
D
Loss of feedback while jogging will
cause the axis to move to either
extreme position out of control. Verify
the position feedback reading in the
Monitor mode. If there is no indication
of position and the Enable (ENBL) is
active, then the feedback device or the
related cabling is faulty or the
controller is set to open loop.
D
If the polarity of the feedback signal is
the same as the axis command signal,
a ‘run away’ condition will occur.
Power down and reverse the leads of
the feedback device or the axis
command signal, whichever is easiest.
Hardware Fault
D
Verify fuse is not blown or loose.
Replace with BUSS AGC 2 amp or
equivalent. See Table 2–1 for value.
D
If power supply LEDs are flashing,
check all power connections including
feedback device and communications
wiring for a short or improper
connection.
D
If the CPU fault LED is ‘On’, contact a
Vickers service representative.
D
Verify that the Hand-Held Terminal is
connected to the RS485
communication port.
Can’t Initiate Motion
In this section, it is assumed that the
SMC20 can be jogged, but motion
controlled by the execution of the
program cannot be initiated, or instantly
stops and sets an error when initiated. If
the unit cannot be jogged, refer to
Section 5.2 before attempting the
following procedure.
Whenever motion cannot be
commanded, it is most likely due to
conflicting operations that have been
invoked or the controlling program is not
selected correctly. The next likely
possibility is the existence of conflicting
axis parameters which allow the axis to
start, but then instantly stop.
Conflicting Operations or
Improper Program Selection
D
Verify that the Enable Axis (EN*) LED
is illuminated.
D
Verify that the Axis Run (*RUN) LED is
illuminated. It is possible to terminate
motion using the STOP function on the
Hand-Held Terminal and still have the
Axis Run LED illuminated. Toggle the
Axis Run input to ensure motion can
once again be initiated by the
program.
D
Verify that the open loop mode has not
been invoked in the Run mode.
D
If using the Home function, ensure the
Home Position has been established.
* = X or Y depending on which axis.
(Axis 1 = X, Axis 2 = Y)
D
If invoking the program through the
Program Select lines, be sure the right
combination of select lines are high to
select the intended program number.
(Remember each line represents a
weighted power of 2. For example, to
run program 10, select line 2 and
select line 8 must be high.)