M O T I O N C O N T R O L P R O G R A M M I N G
112
Motion Control Programming
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Galil Motion Control, Inc.
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800-377-6329
Rotating knife. Example:
The electronic gearing mode is also useful for rotating
knife applications. Suppose a rotating knife must cut mov-
ing paper at variable lengths between 8" and 40", and that
the circumference of the knife equals 20". During the cut-
ting interval, the linear velocity of the paper and the knife
must be equal.
The design approach is to run the knife in the electronic
gearing mode to match the paper speed and to advance or
retard the knife during the non-contact interval in order to
cut the paper the correct length. The position of the mov-
ing paper can be sensed by an encoder with a resolution of
2000 counts per inch. The encoder is the master and is con-
nected to the X axis. Suppose that the resolution of the
knife encoder is 20,000 counts per revolution, which equals
20". This results in 1000 counts per inch. To synchronize
the two, the knife may be set as the slave with a gear ratio
of 0.5. This, however, cuts the paper at 20" sections. To cut
12" sections, the knife must advance 8 additional inches, or
8000 counts, during the non-contact interval.
The following program performs the required move. It is
assumed that a sensor connected to Input 1 indicates the end
of the cutting interval.
Instruction Interpretation
#KNIFE
Label
GAX
Set X encoder as master
GR,0.5
Set Y gear ratio
#LOOP
AI 1
Wait for signal to end cutting interval
PR,8000
Move additional distance
BG Y
Start move
AM Y
After correction is completed
JP #LOOP
Repeat the cycle
EN
End program
ELECTRONIC GEARING
Gearing Example
MASTER Y AXIS
10000
TIME
X
VELOCITY
TIME
Y
VELOCITY
TIME
Z
VELOCITY
25000
SLAVE X AXIS
SLAVE Z AXIS
50000
