HEIDENHAIN PT 855 for Turning User Manual

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Fundamentals of Positioning

POSITIP 855

Operating Instructions

Position encoders

The position encoders convert the movements of the machine
axes into electrical signals. POSITIP then evaluates these signals,
determines the actual position of the machine axes, and displays
the position as a numerical value.

If power is interrupted, the relationship between the machine axis
positions and the calculated actual positions is lost. The reference
marks on the position encoders and the reference mark evaluation
feature (REF) enable POSITIP to re-establish this relationship again
when the power is restored.

Reference marks

The scales of the position encoders contain one or several refer-
ence marks. When a reference mark is crossed over, a signal is
generated identifying that position as a reference point
(scale datum = machine datum).

When this reference mark is crossed over, the POSITIP's refer-
ence mark evaluation feature restores the relationship between
axis slide positions and display values as you last defined it by set-
ting the datum. If the linear encoders have distance-coded refer-
ence marks, you only need to move the machine axes a maximum
of 20 mm to do this.

Fig. 10: Linear scales: with distance-coded

reference marks (upper illustration)
and one reference mark (lower
llustration)

Fig. 9:

Linear encoder, here for the Z axis