Industrial Engineer · phase 3 of 16 · noun
Sequential Function Chart (SFC)
IEC 61131-3 elements that organize programs and function blocks as steps, actions, and transitions.
The Explain card
- Plain English
- SFC lays a program out as steps, the actions that run inside each step, and the transitions that move from one step to the next. Only the active step's actions run.
- Example
- A wash cycle is Fill, Agitate, Drain, Spin. Each is a step, each transition is a condition like level reached or timer done, and the chart shows exactly where the machine is.
- Why it matters
- A machine that goes through phases is a state machine whether you draw it or not. SFC makes the states visible and stops two phases from fighting over the same outputs, which is the bug that hides in ladder sequencers.
- Hook
- The flowchart is the program.
Word knowledge
How the word is built, where it came from, and what it sits beside in memory.
In a sentence
The engineer used a Sequential Function Chart to advance the conveyor from motor start through the photoelectric sensor input to the indexing step.
Why these words
- sequential Late Latin sequentia, a following, from Latin sequi, to follow marks an ordered progression
- function Latin functio, performance or execution, from fungi, to perform identifies the operational behavior being represented
- chart Latin charta, paper or document, from Greek khartes, papyrus sheet names the visual form
Where it came from
- Origin
- English technical compound influenced by French GRAFCET terminology and standardized through IEC work
- Entered the language
- 1980s
- What changed
- Words for ordered following, performance, and a drawn document were combined, then shortened to SFC in industrial automation usage.
How it is spelled
- Pattern
- Sequential keeps the -ential ending also found in consequential.
- Pattern
- Function keeps the -ction spelling common in nouns derived from Latin stems.
- Pattern
- Chart begins with ch pronounced /tʃ/.
Spelled like
- consequential
- instruction
- junction
- charm
- charge
Broken into chunks
-
sequ
- sequence
- sequel
- consequence
-
funct
- functional
- malfunction
- functionality
-
chart
- charter
- charting
What it sits beside
Same subject
- Ladder Diagram
- Function Block Diagram
- Structured Text
- transition condition
- action qualifier
Same shape
- Function Block Diagram
- State Transition Diagram
- Finite State Machine
IEC 61131-3 graphical languages
industrial-control abbreviations
Where it sits in the deck
Phase 3: PLC Program Organization and Execution
How the logic is arranged and how the scan actually runs it, which is the difference between code that works and code that works every time.
