Count, park, repeat

Everything in this course lands in one machine: the auto-cycle print — a carriage that runs forward, counts its strokes, pauses, reverses, counts again, pauses again, and starts itself over. Seal-ins, interlocks, counters, timers, and the scan working together.

The cycle

forward ──(10 hits on the fwd limit)──▶ park 5 s
   ▲                                        │
   │                                        ▼
restart ◀──(5 s pause)──(10 hits home)── reverse

Four phases, and each handoff is a different mechanism:

1. Forward. The classic sealed start — plus /C1.DN in series. The forward counter's done bit is wired to end this phase: at the 10th hit on the forward limit, C1.DN goes true and breaks the seal. The phase carries its own exit.
2. Pause. C1.DN starts a 5-second TON. Nothing moves — the machine is parked on purpose, and the timer is the whole phase.
3. Reverse. T1.DN (with the carriage on the forward limit) starts the reverse motor, sealed the same way, with /C2.DN as its exit. Counter 2 counts hits on the home limit.
4. Restart. C2.DN starts timer 2; T2.DN does two jobs at once — it resets both counters (RES) and reappears in rung 0 as an alternative start contact: (PB1 OR T2.DN). The machine presses its own start button.

The two ideas worth keeping

A phase's exit condition rides inside its own rung. Forward doesn't run until something else stops it — it runs until its own counter says done. Every sealed rung in the print carries a /something.DN that defines when the phase is over. When you read an unfamiliar print, find those XIOs first: they're the map of the sequence.

The restart is just another start. T2.DN sitting in parallel with the start button is the entire "auto" in auto-cycle. One contact. If you ever need "run once vs run continuously," that's a selector switch in series with that one branch — try adding it.

Count, pause, repeat — everywhere

Swap the words and this is a pallet stretch-wrapper (wrap 10 turns, pause, reverse), a batching auger (10 pulses of product, settle, discharge), a test rig cycling a part 10 times per direction. The print is a machine shape, not one machine.

Run the full print

Load the auto-cycle in the builder: arm SS1, set the home limit IP1, pulse Start, then pulse IP3 ten times and watch the machine take over — pause, reverse, and restart itself via T2.DN. You built up every piece of this; now read the whole print and name what each contact is doing. That's the skill.