Temperature Compensation; Description Of Functions - Siemens SINUMERIK 840D sl Function Manual

5.2

Temperature compensation

5.2
5.2.1

Description of functions

Deformation due to temperature effects
Heat generated by the drive equipment or high ambient temperatures (e.g. caused by
sunlight, drafts) cause the machine base and parts of the machinery to expand. This
expansion depends, among other things, on the temperature and on the thermal conductivity
of the machine parts.
Effects
Due to the thermal expansion of the machinery, the actual positions of the axes change
depending on temperature. This has a negative impact on the precision of the workpieces
being machined.
Temperature compensation
By activating the "temperature compensation" function, actual value changes due to
temperature effects can be compensated on an axis-by-axis basis.
Sensor equipment
To provide effective temperature compensation, a number of temperature sensors for
acquiring a temperature profile are needed in addition to the actual position data from
existing encoders.
Since temperature-dependent changes occur relatively slowly, the PLC can acquire and
preprocess the temperature profile in a minutes cycle, for example.
Error curves
In order to implement temperature compensation, the actual-value offsets over the
positioning range of the axis must be measured at a given temperature (T) and plotted. This
produces an error curve for this temperature value. Error curves must be produced for
different temperatures.
Error curve characteristic
If an axis position reference point P
(corresponds to the "position-independent component" of the temperature compensation)
can be observed as the temperature changes, and because of the change in length an
additional offset in the other position points, which increases with the distance to the
reference point (corresponds to the "position-dependent component" of the temperature
compensation).
Extended Functions
Function Manual, 09/2009, 6FC5397-1BP20-0BA0
is selected, an offset in the reference point
0
K3: Compensation
5.2 Temperature compensation
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