Siemens Sinumerik 840D sl Programming Manual page 580

Motion synchronous actions
10.3 Main run variables for synchronized actions
Example: Circulating memory
During a production run, a conveyor belt is used to transport products of different lengths (a,
b, c, d). The conveyor belt of transport length therefore carries a varying number of products
depending on the lengths of individual products involved in the process. With a constant
speed of transport, the function for removing the products from the belt must be adapted to
the variable arrival times of the products.
Program code
DEF REAL INTV=2.5
DEF REAL TOTAL=270
EVERY $A_IN[1]==1 DO $AC_FIFO1[4]=0
EVERY $A_IN[2]==1 DO $AC_TIMER[0]=0
EVERY $A_IN[2]==0 DO $AC_FIFO1[0]=$AC_TIMER[0]*$AA_VACTM[B] ; If the product leaves the light
EVERY $AC_FIFO1[3]+$AC_FIFO1[4]*ZWI>=GESAMT DO POS[Y]=-30
$R1=$AC_FIFO1[0]
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Comments
; Constant distance between products that
are placed down.
; Distance between the length measurement
and removal position.
; At the start of the process,
reset FIFO
; If a product interrupts the light
barrier, start the time measurement.
barrier, calculate the
product length from the measured time
and transport speed and save in FIFO.
; As soon as the sum of all product
lengths and intermediate distances are
greater than/equal to
the length between the position where
the product is placed down and where it
is removed, remove the product from
the conveyor belt at the removal
position, read-out the associated
product length from FIFO.
Programming Manual, 02/2011, 6FC5398-2BP40-1BA0
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