Starting up
7-26
FM 353 Stepper Drive Positioning Module
6ES7 353-1AH01-8BG0
7.3.7 Activating the software limit switches and backlash compensa-
tion
Software limit switches
Move the axis carefully to the end positions defined for normal machining. Enter
these position actual values into the machine data MD21/MD22 as software limit
switches, and activate them.
Note
If you change the reference point coordinates, you must redefine the positioning
values of the software limit switches.
If you do not need the software limit switches, the input limits −10
9
and 10
9
[MSR]
must be entered in MD21/MD22 (for default values, see Table 5-4).
Backlash compensation
Due to play in the mechanical transmission elements, position deviation of the ma-
chine component to be positioned (e.g. lathe slide) may occur when a stepper mo-
tor is used for positioning. Normally, some travel distance “turns up missing” follow-
ing a direction reversal. This backlash can be ascertained as an average at
different axis positions. This can then be entered in the machine data set.
You can use the following flow chart to determine backlash and activate backlash
compensation.
Also please refer to the information on “backlash compensation” presented in Sec-
tion 9.7!
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