1.How to Achieve Power-off Reference Point Preservation in NC Systems with Absolute Encoders?
In an absolute encoder system, let's say at
your proximity switch position, the encoder feedback is 1000. If subsequently,
you lose power and the motor moves positively by 200 units, upon power
restoration, the encoder feedback will be 1200. This exemplifies the advantage
of absolute encoders over incremental encoders: the encoder keeps count
regardless of power status, as long as the motor moves. Thus, there's no
concern about losing the reference point.
If you wish to set the position of the proximity switch as 0 for programming convenience, instead of the encoder's actual position of 1000, you need to set an offset of -1000 in the axis-axis enc-parameter-position bias. After the motor moves positively by 200 units and power is restored, the encoder feedback will then be 200. (As shown in the figure below)
2.How to Reverse the Rotation Direction
of an NC-Controlled Motor (Opposite Rotation)? If the displayed position
indicates clockwise as positive but shows negative, how can I change the
settings?
To reverse the motor's rotation direction,
you need to set the following parameters to True:
Navigate to Axes->Axis_Enc->Parameter
and set Invert Encoder Counting Direction to True.
Then, go to
AXES->AXIS_DRIVE->parameter and set Invert motor polarity to True as
well.
It is crucial that both of these settings are either True or False simultaneously.
3.Why is the homing mode option missing
from my encoder settings?
ProblemDescription:
4.How to set the multi-turn upper limit
value for a Beckhoff drive?
5.Does TwinCAT 2 NC axis have the functionality to adjust backlash compensation (backlash correction) for gears?
First Step: Configure within the axis
parameters (set "position correction" to true for the corresponding
settings to take effect)
Step Two: Use the Function Block (FB) for
modification (mc_BacklashCompensation)
6.Instructions
for Multi-turn Encoder Usage (Actual Position Calculation)
Multi-turn
absolute encoders only require a single zero return to establish their
position.
The actual position of the axis can be modified through the application of a bias. P = P + P_bias
1.4096 Revolutions
2.After power loss and re-application, the
encoder's actual position (converted to physical units using the scaling
factor) ranges from -2048 to +2048. If it stops at 2048, upon restart, it will
read -2048.
The NC's actual position accumulates over
time, while the Position feedback within the drive is the encoder's actual
incremental (INC) feedback, which wraps around to the negative limit after
reaching the positive limit (ranging from +- 2048 * 1048576). If the feedback
is X pulses, the actual position is calculated as (X / 1048576) * 360°. This data can be directly read via PLC tags.
2.Recommendations for Use:
1)If using multi-turn positioning, it's
best to return the mechanical equipment to its zero point, disconnect the
coupling, and manually rotate the motor to approach -2048 revolutions by
observing the feedback value (activating the configuration file can set the NC
position to the encoder position, then running the motor to an absolute
position of ((-2048 * 360) / 1048576) effectively returns the encoder to -2048
revolutions. If the travel does not require this full range, returning to 0 is
sufficient, effectively placing the encoder at its mid-point (0). This
maximizes the chances that the motor will not exceed the maximum number of
revolutions during operation.
2)Reconnect the coupling and execute the
homing function. After completion, two data points can be read: NC position X
and encoder position Y (both in physical units). Set the bias as X - Y and
re-activate the configuration file. The modification is now complete. As long
as the motor does not exceed 2048 revolutions, the zero position will always
correspond to the actual zero point.
3)For applications requiring travel beyond
4096 revolutions, follow the above steps to return the motor to -2048, then
record the number of times N that the encoder exceeds 2048. Save N upon power
loss. Whenever the controller or drive restarts (detected through monitoring
communication status with the drive) or is manually triggered, adjust the
position as
N*X=4096*N+Y+Z
Z=-Y1.Z bias
Y1 is the encoder position at the time of
homing.
7.Where is the direction for MC_Home
set?
Question: Which one is Negative and which
one is Positive?
Answer:
By default, it searches for the reference point to the right and then retreats
to the left to find the falling edge. If you need it to search for the
reference point to the left and then retreat to the right to find the falling
edge, then simply invert both the directions.
8. Where are the soft limits set for
TwinCAT 2 NC?
Setting Soft Limits in the ENC of NC Axes
in TwinCAT Software
9.Does setting the soft limits have any
impact on the homing process? Is it necessary to complete the homing process
before enabling the soft limits?
The limits have no relation to the homing
process. You can set the soft limits in the SystemManager and enable them
without needing to complete the homing process first.
10.How exactly should the
"Reference Velocity" and "Maximum Velocity" be set in NC
parameters?
Generally, the reference velocity is set to
be 1.1 times the maximum velocity.