Siemens SINUMERIK 840Di Function Manual page 1454

Detailed Description
2.4 Referencing with incremental measurement systems
Fig. 2-7
Reference cam adjustment
Encoder with equidistant zero marks
Always ensure that the reference cam of encoders that supply zero marks at equidistances
is accurately adjusted so that the correct zero mark is always detected during reference point
approach.
Dynamic response
The following factors will influence the dynamic response between arrival at the reference
cam on the machine and detection of the reference cam signal transmitted from the PLC
user program to the NC:
• Switching accuracy of the reference cam switch
• Delay of the reference cam switch (NC contact)
• Delay at the PLC input
• PLC cycle time
• Cycle time for updating the VDI interface
• Interpolation cycle
• Position control cycle
2-14
Electronic reference cam offset
Reference Point Approach (R1)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0