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TB026 Rev1 Position Error & Full Power Without Motion
Overview
This document describes the steps needed to efficiently resolve the following error message "410__ Axis
position error" and "411__ Axis Full power without motion"
Understanding the theory
Any time that the CPU10 expecting the motor to turn and not getting a correct encoder response for > 25" a "
Position error
" results
When 90% power is applied and no motion is detected for the time specified in parameter 61 usually 5 sec
a " Full power without motion
" error occurs
In the following diagram locate the CPU10 SERVO drive and the MOTOR ENCODERS
The CPU10 receives a command to move a motor either from a running program or the operator's
jog panel
This command is then forwarded to the Servo Drive through the data & sync fiber cables The servo
drive outputs approximately 110 Vdc to the proper motor
The motor encoder turns along with the motor and outputs digital pulses on A and B channels at an
equivalent rate of 8 000 counts per revolution
The pulses are counted by a Lattice IC on the CPU10 that is used by the CNC10 software to
determine the position of the motor relative to the machine home position The DRO Digital Read
Out is updated to display this correct value
Example
A user is getting "Y axis position error" By swapping both the X and Y wires at the drive and also at
the encoder DB9 cables it is possible to determine whether the problem is in the motor or motor cable or
whether the problem is with the drive or CPU10 After swapping the motor and encoder cables between the X
and Y axes the error is "X axis position error" Thus the X axis motor and/or cable is the problem which is
physically the Y motor since it was just swapped with X
What causes a position error?
Cause Possible Problem Troubleshoot / Cure
Bad encoder Coolant fluid or dirt
penetrating the seal and
giving bad pulses to the
CPU10 card Replace motor with a known good motor possibly
from a different axis or swap out the cables
between two axes The error will follow the motor
See diagram and example
Bad encoder cable Broken wire or connection
at the pins of the cable  Move the suspected bad motor power and encoder
cables to another axis's motor If the problem is in
the cable then you will still get an error on that
cable
Binding or mechanical
problems such as
excessive lash The CPU10 board has
detected > 25" error on an
axis Slow down the feedrate and watch for errors If
slower speeds or unbelting the motor eliminates the
errors have the machine mechanics checked out
Encoder connectors
are on the wrong axis One motor is turning but the
position displays on another
axis You can force position errors simply by wiring the
motor wrong Check and re check for proper
encoder wiring
Motor power wiring is
backwards  The CPU10 board is getting
backwards encoder counts Watch the DRO display If the DRO is always
increasing or decreasing regardless of the direction
jogged the motor wires at the drive are reversed
Max Rate in the
parameters are set too
high The motor may not be
capable of maintaining the
maximum rate Autotune F1 Setup F3 Config Password=137 F4
PID and the F5 Tune Try commanding slower
speeds to check for a rate related position error
Bad CPU10 board The CPU10 board is losing
encoder counts and giving
false DRO reading Very low probability as the cause for errors Note 8
missing counts on the Lattice IC or DSP time out
will produce an "Encoder connection" error
What causes a "Full Power Without Motion" Error?
Cause Possible Problem Troubleshoot / Cure
Axis is against a
physical stop Program exceeds the travel limit or
the part zero was set incorrect Use the slow jog button to move the axis away
from the end Reset your part zero to a point
which permits the CNC program move
Limit switch header
cables or noisy limit
switch The drive is seeing the limit switch
input as open but it is still closed at
the PLC Remove the limit switch header cable at the
Servo Drive and defeat the limit switches as
shown on the servo drive cover Test
Servo Drive failure See "Servo Drive Troubleshooting" Â Troubleshoot the servo drive for errors; call
Tech Support
Fiber Optics on DC
brush system Fiber optic cables to the drive are
plugged in backwards broken or not
plugged in Check the fibers labeled 4 and 5 data and
sync in the above picture
Encoder Loose Set screw loose or missing that
holds encoder onto motor shaft Tighten set screw
No power to the
moter The motor is not getting power from
the drive See "Servo Drive
Troubleshooting" Check motor cable and connectors
Troubleshoot the servo drive for errors; call
Tech Support
Bad Motor Coolant in motor or motor
overheated and burned up Replace motor and ensure motors are
protected from coolant TB009 and/or check
motor heating parameters
WARNING
Never remove the brushes from a DC motor They do not wear out and more costly damage my
result by removing them unnecessarily
Document History
Rev1 Created on 1998 02 13