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R1: Reference point approach

15.9 Referencing with absolute value encoders

Basic Functions

Function Manual, 09/2011, 6FC5397-0BP40-2BA0

1237

15.9.2 Calibration by entering a reference point offset

Function

During adjustment by entering the reference point offset, the difference between the position displayed on the

operator interface and the true actual position in the machine is determined and made known to the NC as

reference point offset.

Procedure

1. Determining the position of the machine axis with reference to the machine zero point via e.g.:

- position measurement (e.g. laser interferometer)

- Moving the machine axis to a known position (e.g., fixed stop)

2. Reading the displayed actual position of the machine axis on the operator interface.

3. Calculating the reference point offset (difference between the actual positions determined under point 1 and

2) and entering in machine data:

MD34090 $MA_REFP_MOVE_DIST_CORR (reference point offset)

4. Marking the absolute value encoder as adjusted:

MD34210 $MA_ENC_REFP_STATE = 2

5. Initiate POWER ON reset.

6. Controlling the position of the machine axis displayed on the operator interface.

Note

The encoder adjustment does not become active until the next time the encoder is

activated (e.g., when the controller is powered up).

Note

Backlash compensation

If backlash compensation is parameterized for a measuring system with absolute value

encoder, the following must be observed:

No backlash is permitted during machine axis travel to the adjusted machine position.

Activate reference point offset permanently

The entered reference point offset (MD34090) will be permanently active only after initial

POWERON-Reset. If the machine axis is moved after the absolute encoder adjustment

without an interim POWERON-Reset, the reference point offset entered in the machine

data can be overwritten, for example, as part of internal overrun offset.

Checking the actual position

Following adjustment of the absolute encoder, we recommend that you verify the actual

position of the machine axis the next time you power up the controller (POWER ON).

Siemens SINUMERIK 828D Function Manual

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