Lenze PM94P01C - Manual (Page 61)

PM94P01C 59
Programming
2.15.3 Home Offset
The home offset is the difference between the zero position for the application and the machine home position (found
during homing). During homing the home position is found and once the homing is completed the zero position is offset
from the home position by adding the home offset to the home position. All subsequent absolute moves shall be taken
relative to this new zero position. This is illustrated in Figure 23. Offset can either be set in User Units (UU) by writing
to variable #240, or in encoder counts by writing to variable #241. Setting a value for either variable #240 or #241 will
result in the value being automatically calculated for the respective variable.
VAR_HOME_OFFSET (#240)
VAR_HOME_OFFSET_PULSES (#241) Home
Position
Zero
Position
home_offset
Figure 23: Home Offset
2.15.4 Homing Velocity
There are two homing velocities: fast and slow. These velocity variables are used to find the home switch and to find the
index pulse. Which velocity (fast or slow) is used to locate the home switch and the index pulse depends on the homing
routine selected.
VAR_HOME_FAST_VEL (#242)
VAR_HOME_SLOW_VEL (#243)
2.15.5 Homing Acceleration
Homing acceleration establishes the velocity ramp rate to be used for all accelerations and decelerations within the
standard homing modes. Note that in homing, it is not possible to program a separate deceleration rate.
VAR_HOME_ACCEL (#239)
2.15.6 Homing Switch
The homing switch variable enables the user to select the PositionServo input used for the Home Switch connection.
The Homing Switch Input Assignment range is 0 - 11. Inputs A1-A4 are assigned 0 to 3, respectively; inputs B1-B4 are
assigned 4 to 7, respectively; and inputs C1-C4 are assigned 8 to 11, respectively.
VAR_HOME_SWITCH_INPUT (#246)
WARNING!
• Setting inputs A1 and A2 as the home switch in methods that do NOT use limit switches can cause the drive to behave in an unexpected manner.
• Input A3 is a dedicated hardware enable input and should never be assigned as the homing switch input.
• Input C3 can be used as the homing switch input only in methods that do not home to an index pulse from an encoder. Methods that use an index
pulse automatically use Input C3 for capture of the index pulse, as described previously.
2.15.7 Homing Start
The homing operation is initiated using the home start variable. Start Homing range is: 0 or 1. When set to 0, no action
occurs. When set to 1, the homing operation is started. it is recommended to directly write to VAR_START_HOMING
solely via network communications.
VAR_START_HOMING (#245)
‘HOME’ is the logical command to set VAR_START_HOMING. Writing the word ‘HOME’ within the user program will
result in the homing operation commencing. After initiating the HOME command with firmware 3.60 (and later) the user
program will not execute subsequent lines of code until after homing is completed (similar to MOVE P). If either using
firmware prior to 3.60 or if user initiates homing in the indexer program via the statement VAR_START_HOMING=1,
then it is recommended to immediately follow that statement with the following code:
WAIT UNTIL VAR_EXSTATUS & 0x400000 == 0x400000.
Doing this ensures no further lines of code will be executed until homing is complete.