Siemens SINUMERIK 840D sl Function Manual

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5.2 Temperature compensation5.2.1 Description of functionsDeformation due to temperature effectsHeat 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 expansiondepends, among other things, on the temperature and on the thermal conductivity of themachine parts.EffectsDue to the thermal expansion of the machinery, the actual positions of the axes changedepending on temperature. This has a negative impact on the precision of the workpiecesbeing machined.Temperature compensationBy activating the "temperature compensation" function, actual value changes due totemperature effects can be compensated on an axis-by-axis basis.Sensor equipmentTo provide effective temperature compensation, a number of temperature sensors for acquiringa 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 andpreprocess the temperature profile in a minutes cycle, for example.Error curvesIn order to implement temperature compensation, the actual-value offsets over the positioningrange of the axis must be measured at a given temperature (T) and plotted. This produces anerror curve for this temperature value. Error curves must be produced for differenttemperatures.Error curve characteristicIf an axis position reference point P0 is selected, an offset in the reference point (correspondsto the "position-independent component" of the temperature compensation) can be observedas the temperature changes, and because of the change in length an additional offset in theother position points, which increases with the distance to the reference point (corresponds tothe "position-dependent component" of the temperature compensation).The error curve for a given temperature T can generally be represented with sufficient accuracyby a straight line with a temperature dependent gradient and reference position:K3: Compensations5.2 Temperature compensationExtended Functions252 Function Manual, 10/2015, 6FC5397-1BP40-5BA3