FX Series Programmable Controllers STL Programming 3
3-18
3.11.2 A Selective Branch/ First State Merge Example Program
The followin
example depicts an automatic sortin
robot. The robot sorts two sizes of ball
bearin
s from a mixed ‘source pool’ into individual stora
e buckets containin
onl
one t
pe of
ball bearin
.
The sequence of ph
sical events (from initial power On) are:
1) The pickup arm is moved to its zero-point when the start button (X12) is pressed. When the
pickup arm reaches the zero-point the zero-point lamp (Y7) is lit.
2) The pickup arm is lowered (Y0) until a ball is collected (Y1). If the lower limit switch (X2) is
made a small ball bearin
has been collected; consequentl
no lower limit switch si
nal
means a lar
e ball bearin
has been collected. Note, a proximit
switch (X0) within the
‘source pool’ identifies the availabilit
of ball bearin
s.
3) Dependin
on the collected ball, the pickup arm retracts (output Y2 is operated until X3 is
received) and moves to the ri
ht (Y3) where it will stop at the limit switch (X4 or X5)
indicatin
the container required for stora
e.
4) The pro
ram continues b
lowerin
the pickup arm (Y0) until the lower limit switch (X2) is
reached.
5) The collected ball bein
is released (Y1 is reset).
6) The pickup arm is retracted (Y2) once more.
7) The pickup arm is traversed back (Y4) to the zero-point (X1).
Y3
Y4
X12 Y7
X1
X3
X4 X5
X2
X0
Y1
Y2
Y0
Points to note
• The Selective Branch is used to choose the deliver
pro
ram for either small ball
bearin
s or lar
e ball bearin
s. Once the destination has been reached (i.e. step S24
or S27 has been executed) the two independent pro
ram flows are re
oined at step
S30.
• The example pro
ram shown works on a sin
le c
cle, i.e. ever
time a ball is to be
retrieved the start button (X12) must be pressed to initiate the c
cle.
