6 – 44 HEIDENHAIN Technical Manual TNC 426, TNC 430
6.4.4 Compensation of Thermal Expansion
To compensate thermal expansion, exact measurements of machine thermal
behavior as a function of temperature (e.g., the center of axis expansion, the
amount of the expansion) are necessary.
The temperatures measured by the Pt100 thermistors are saved in the PLC
words W486 to W490. Since the thermal expansion of the axes is largely
proportional to the temperature, you can directly determine the amount of
expansion by multiplying the temperature value by a certain factor.
Compensation:
7
77
7 Transfer the distance to be compensated to module 9231. At the same
time, “lag tracking” becomes active. This means that the actual position is
offset by a certain value per PLC cycle until the complete value is
compensated.
7
77
7 In MP4070, enter the value for the offset per PLC cycle.
For gantry axes, the compensation value must be transferred separately for
each axis.
Heat compensation when using tilting axes is defined through machine
parameters or the kinematics table. ((See “Temperature compensation” on
page 6 – 75).
The actual value display does not change during the compensation. As an
alternative, for axes 1 to 5 you can enter the value to be corrected in W576 to
W584.
MP4070 Compensation amount per PLC cycle for lagged-tracking
axis error compensation
Input: 0.0001 to 0.005 [mm]
Set Reset
W486 - 490 Temperature input at X48 [0.5 °C]
Inputs 1 to 3
NC NC
W576 - 584 Lag-tracking axis error compensation
For axes 1 to 5
Input: –32 768 to +32 767 [1/10 µm]
PLC PLC
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