Chopping Compensation - Mitsubishi Electric MELDAS 60 Series Programming Manual

9.6.3 Chopping compensation

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
end) is adopted, 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: Refer to Fig.1)
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.
(Compensation value fixed method: Refer to Fig.2)
Fig.1 Chopping operation in compensation value sequential update method
Upper dead center point
Bottom dead center point
Positioning command
Fig.2 Chopping operation in compensation value fixed method
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.
Motion of the motor end
Motion of the motor end
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9. Exclusive Commands
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.