1756-PM003H-EN-E, SFC and ST Programming Languages ...

4-12 Design a Sequential Function Chart
Here are some examples of SFC structures for different situations:
Example situation:
Station 45 and 46 of an assembly line work on parts
simultaneously. When both stations are done, the parts move
down 1 station.
Example solution:
Simultaneous Branch
45 46
Depending on the build code, a station either drills or polishes.
Selection Branch
Drill
Polish
To simplify my programming, I want to separate communications
and block transfers from other control logic. All occur at the same
time.
Simultaneous Branch
Control
Comms
BTs
In a heat treating area, the temperature ramps up at a specific
rate, maintains that temperature for a specific duration, and then
cools at a specific rate.
Sequence
Ramp
Maintain
Cool
At station 12, the machine drills, taps, and bolts a part. The steps
occur one after the other.
Sequence
Drill
Tap
Bolt
Step 12 inspects a process for the correct mix of chemicals.
• If OK, then continue with the remaining steps.
• If not OK, go to the top of the SFC and purge the system.
Wire
start of SFC
Step 12
Not OK
OK
Publication 1756-PM003H-EN-E (excerpt from 1756-PM001H-EN-P) - August 2005