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

K3: Compensations

5.2 Temperature compensation

5.2 Temperature compensation
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
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).
The error curve for a given temperature T can generally be represented with sufficient accuracy
by a straight line with a temperature dependent gradient and reference position:
252
is selected, an offset in the reference point (corresponds
0
Function Manual, 10/2015, 6FC5397-1BP40-5BA3
Extended Functions