Siemens 611-D, 840C 244*

6 NC Machine Data (NC MD), NC Setting Data (NC SD) 10.94

6.4 Axis-specific MD 1 (axial data 1)

Reference point shift

244*

Default value Lower input limit Upper input limit Units

0 - 99 999 999 99 999 999 units (MS)

Active on

NC Stop

Reference point shift is used to shift the reference points of the measuring system. Instead of

mechanical shifting or rotating of the measuring equipment (and thus of the "deceleration"

cam), the reference point can be shifted electrically by up to ±9 999 units.

The reference point shift path is traversed at the cutoff speed (NC MD 284*), which must

already have been reached at the operating cam (also see Section Axis (Analog) and Spindle

Installation for details on reference point approach).

The reference point shift is also effective in conjunction with automatic reference point

approach (NC MD 560*, bit 6).

Without reference point shift, the reference point is 2000 units behind the first zero mark after

the operating cam has become free again.

If the entry in NC MD 244* is positive, the axis travels the specified number of units beyond

the normal reference point (2000 units beyond the zero mark) in a positive direction.

If the entry in NC MD 244* is negative, the axis, after overrunning the zero mark, travels to

the value represented by the difference between 2000 units and the input value. In the event

of a reference point shift of more than approximately 2000 units, the axis reverses its direction

of travel (backlash on reversal).

Reference point pulse = zero marker from encoder

MD 244* = 0

MD 296*

Ref. point

Velocity

Ref. cam

Ref. point pulse

Path

2000 units

MD 284*

SINUMERIK 840C (IA)