Pg 3.10 H22
PLC 100 TROUBLESHOOTING
PROBLEM #1, for automatic models with a shuttle.
PLC is not measuring lengths.
POSSIBLE CAUSES;
i) Encoder - pinion gear loose on encoder shaft
- bad encoder
ii) Encoder Cable - bad connection at encoder or PLC
- open or shorted wire
ii) PLC unit - damaged hardware
iii) Display unit - no power from PLC unit
- damaged hardware
iv) Actual Length (ACT LTH) - preform self calibration procedure and enter value.
Parameter value is set to 00.000
DIAGNOSIS;
I) With the machine in MANUAL mode; bring the shuttle forward to the home position and clear the
length display to read '0.000'. Run the shuttle, in slow speed, to the rear then back to home, moving full shuttle
strokes.
- length should accumulate on the display as a positive number when the shuttle moves away from
the blade and should count is negative going back and goes in a positive direction coming toward home,
then the green channel wire and the white channel wire should be reversed.
- if the display alters between 0.000 and 0.001 or 0.000 and -0.001, then one of the encoder
channels is not being recorded correctly.
ii) To determine the cause, first, check the encoder cable connections at both ends to be sure all four
wires are connected properly. (See page 3.18 for connection / wiring information).
Measure the voltage:
a) At encoder connector;
- between 0 V pin and 24 V pin. This voltage should be a minimum of 22 to 26 VDC.
If the voltage is incorrect; check encoder cable continuity - if OK, possible PLC problem.
If the voltage is correct, go to step b)
b) At encoder connector;
- between 0 V and channel A and 0V and channel B. This should be slightly less than supply
voltage at each channel.
If voltage is incorrect at this point, check for proper continuity of these wires and repair as
necessary.
NOTE: When checking the encoder cable for continuity, each wire should also be checked for
shorting to ground and shorting to each other.
If voltage to the encoder is correct; go to Step C).
c) At the encoder connection of the PLC; - between 0 V and A&B channels. With the shuttle moving
slow, voltage should be approximately 10 -13 VDC. Input LED's X0 and X1 should flicker or go dim
with the shuttle moving. If these LED's show no change with the shuttle moving, the encoder is
likely at fault. Check that the pinion gear is securely fastened to the encoder shaft and that it can
rotate along the rack as the shuttle moves.
If all mechanical components are functioning correctly then the encoder is defective.
If all tests check positive, the problem is in the PLC unit.
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