Mitsubishi Electric M800VW Series Programming Manual page 652

M800V/M80V Series PLC Programming Manual (2/2)
14 PLC Help Function
14.12 Chopping
Chopping compensation method
Because this function involves high-speed repetitive motions, the positioning method allowing compensation based on the
calculation from the machinery operation (feedback position of the motor side) is adapted, rather than the method using in-
position check. Compensation amount used for positioning is calculated every 4 cycles from the start of chopping operation,
based on the difference between the commanded position and feedback position. Then the compensation amount is added to
the positioning command for the next cycle so that the difference between the commanded position and feedback position will
disappear (Compensation value sequential update method)
Upper dead center point
Bottom dead center point
Positioning command
However, with this method, if the grindstone contacts with the workpiece, the chopping width before and after compensation
may be differed, and which may affect the machining surface. In this case, the compensation value fixed method is
appropriate.
With the compensation amount fixed method, compensation amount based on a dry run operation is recorded in advance so
that, in the real operation, compensation is carried out from the first positioning to the bottom dead center point using the
compensation amount recorded earlier.
Upper dead centerpoint
Bottom dead center point
Positioning command:
Select the compensation value fixed method and set the compensation
amount so that compensation is carried out from the first bottom dead
center point position since the operation has started.
The stroke compensation completion signal is output when the difference between the commanded stroke and the actual
stroke has reached the tolerance specified with the parameter (#2080 chwid).
Motion of the motor side
Motion of the motor side
Compensation starts from
the 5th cycle.
Compensation in the 5th cycle or
later is carried out with the same
compensation amount as as in the
1st cycle.
631 IB-1501668-B