STOPPED — at rest
The machine is powered but standing still, like a car in neutral with the engine running. It is not producing and not moving: it waits for someone to prepare it with the RESET button.
PackML · ISA-TR88 · waiting state
RESETTING — preparing itself
The machine prepares itself: it creeps forward until it finds its zero again, the position every cycle has to start from (here: jaws open). Until it is in phase, START stays locked. Once zero is found it stops and moves to IDLE on its own.
PackML · ISA-TR88 · acting state
IDLE — ready to go
Everything is ready and in order: the machine is only waiting for the operator to press START. It is the green light before the off.
PackML · ISA-TR88 · waiting state
STARTING — ramping up
The machine is taking up speed toward the setpoint. It is already moving but not yet at rate: the ramp is a motor ramp, not a jump, exactly as on the real line.
PackML · ISA-TR88 · acting state
EXECUTE — producing
The machine is running at its setpoint and producing. Every jaw stroke that finds material seals one pack, and a pack is counted only when it has actually left the discharge: what has not left the machine is not produced.
PackML · ISA-TR88 · acting state
COMPLETING — finishing the batch
The batch quantity has been reached: no more product is let in and the machine empties what is still inside, then ramps down. Nothing is thrown away, the line simply finishes what it started.
PackML · ISA-TR88 · acting state
COMPLETE — batch finished
The batch is finished and the line is physically empty. The machine waits: RESET prepares it for the next batch.
PackML · ISA-TR88 · waiting state
HOLDING — going on hold
Something the machine needs has run out - here the film - so it is stopping in a controlled way WITHOUT losing the batch. It is not a fault and not an emergency: it is a pause with an internal cause.
PackML · ISA-TR88 · acting state
HELD — paused (internal cause)
The machine is stopped and waiting for the operator to resolve the cause: the reel is empty and calls for a change in blue, the colour a standard reserves for an action the operator MUST take. The batch stays open and the material stays where it is, so production resumes from exactly where it stopped. Guard 1 covers the reel zone, so opening it here does not trigger an emergency: it only inhibits restart. Guards 2 to 5 cover the hazardous zone and always abort.
PackML · ISA-TR88 · waiting state · IEC 60204-1 blue
UNHOLDING — coming back
The cause is resolved and the machine is returning to production on its own, taking speed back up to the setpoint with the batch untouched.
PackML · ISA-TR88 · acting state
SUSPENDING — going idle
The machine is pausing for a cause OUTSIDE itself: upstream or downstream is not ready. The difference from HELD is who owns the downtime, and a real line measures the two separately.
PackML · ISA-TR88 · acting state
SUSPENDED — waiting on the line
Stopped and waiting for the rest of the line, not for the operator. The batch is kept.
PackML · ISA-TR88 · waiting state
UNSUSPENDING — resuming
The line is ready again and the machine is going back to producing by itself.
PackML · ISA-TR88 · acting state
STOPPING — braking
A normal stop has been commanded: the machine brakes in a controlled way and will end up STOPPED. Not an emergency, an ordinary stop.
PackML · ISA-TR88 · acting state
ABORTING — emergency
Emergency: the mushroom has been pressed or a guard has been opened while moving. Power is cut and the machine brakes as hard as it can. Nothing is asked of the operator here except that the machine come to rest.
PackML · ISA-TR88 · EN ISO 13850
ABORTED — emergency active
The machine is stopped by the safety circuit. The mushroom latches: RESET stays inhibited until the device is released by hand, which is exactly what the standard requires - no automatic restart is possible.
PackML · ISA-TR88 · EN ISO 13850 latching
CLEARING — purging the line
After an emergency the machine has to be emptied before it can produce again: it runs at minimum speed with the infeed shut, and whatever was sealed during the purge leaves as scrap, red, uncounted. When the line is physically empty it falls into STOPPED by itself.
PackML · ISA-TR88 · acting state
UNWINDER — the film reserve
A reel as wide as the pack, which can weigh tens of kilos. The dancer arm keeps the film under light tension: without it, every change of speed would print creases. An analogue sensor reads the roll diameter and reports how many mm of film are left; when it runs out, the machine goes to HELD and asks for a change.
Station 1 · unwind group
INFEED — the rhythm starts here
The chain with its flights brings the products in at the right pitch, one per lug. If a product is missing or arrives crooked, every station downstream feels it: the chain pitch IS the rhythm of the machine.
Station 2 · infeed chain
FORMING — pure geometry
The forming shoulder folds the flat film around the product and turns it into a continuous tube. There is no motor here: it is a piece of shaped sheet metal doing half the work of the machine, by geometry alone.
Station 3 · forming shoulder
SEALING — the heart of the machine
The jaws close once per pack: they seal the film, separate the pack from the tube and open again. One stroke = one product, so the speed in PPM is literally the rhythm of this member.
Station 4 · sealing jaws
DISCHARGE — where a piece becomes produced
The discharge belt carries the finished packs out. A piece counts as produced only when it leaves this edge: the counter fires here, not before. While it is still on the belt it is still inside the machine.
Station 5 · discharge belt
CABINET — brain and muscles
PLC, drives, power supplies and the safety circuits. On the door a small HMI panel and the pocket with the manual: everything needed by whoever arrives in front of the machine at three in the morning.
Station 6 · electrical cabinet
STACK LIGHT
The traffic light of the machine, mounted high so it can be seen from anywhere in the shop: GREEN is producing, AMBER asks for attention (and blinks during state changes), RED is emergency. The colours are not an aesthetic choice: a standard fixes them, the same one for every machine in the world.
IEC 60204-1 · indicator colours
EMERGENCY STOP
Red mushroom on a yellow background: the yellow is part of the normative marking, it is there so the device is found at a glance. It is mechanically latching: pressed, it stays down, and releasing it takes a second deliberate act. Note the detail that matters: releasing it restarts nothing, it only re-enables RESET.
EN ISO 13850 · IEC 60417-5638
I AND O — REGISTERED SYMBOLS
Why is START an I and STOP an O on every machine in the world? Not fashion: they are symbols registered in an international catalogue and called up by the electrical standard for machinery. Anyone who has worked on one machine finds them identical on any other. The circular arrow on RESET, by contrast, is not mandated: that one is industry practice.
IEC 60417-5007/-5008 · EN 60204-1
PPM — HONEST SPEED
Packs per minute, for real: the line speed is computed as ppm x pitch / 60, so one jaw stroke = one pack = one increment. ACT shows the true instantaneous speed, not the setpoint: during ramps and braking the two numbers diverge, exactly as on a real machine.
Practice · v = ppm x pitch / 60
TOTALIZER — THE ONE THAT DOES NOT RESET
A real machine carries two different counters. The batch one returns to zero with every order and tells the operator how much is left. The totalizer does not: it only climbs, because it answers a different question, namely how much this machine has produced. Here it counts the exact same event as the batch counter, the pack leaving the discharge belt, so the two numbers cannot disagree, and scrap enters neither. It is the count of THIS visit: there is no server behind this page, and a number claiming to be the all-time total would be a number nobody could verify.
Practice · non-resettable production totalizer
COUNT — ONLY WHAT LEAVES
The counter fires when the pack leaves the discharge belt, not when it enters the machine: a piece is produced only once it is out. That is why the batch closes exactly when the machine is empty. And the red scrap from a purge does not count: it is not product.
Practice · end-of-line counting
SAFETY GUARDS
Interlocked plexiglass guards: the machine stays visible, but opening one while it is running is an emergency and the machine aborts. While any guard is open RESET is inhibited: no restart with hands inside. Closing it restarts nothing by itself, the operator command is always required.
EN ISO 14119/14120 · ISO 14118
Every member of this machine derives from the master axis. One does not, and that is a decision, not an oversight.
DECISIOND1
The unwind is not geared to the master with a fixed ratio.
Rejected: a constant ratio, as for the film drive and the chain.
The roll diameter falls as the reel is consumed. At a fixed ratio the surface speed would change with the diameter, so the film would be pulled harder and harder: a ratio that is right on a full reel is wrong on an empty one. The unwind follows tension, not angle.
DECISIOND2
On the cam diagram it is drawn as a dashed band, not as a curve.
Rejected: drawing it like the others, for graphical consistency.
Drawing a function of the angle for a member that is not a function of the angle is a drawing that lies. The band says exactly what it is: a working zone, not a position.
DECISIOND3
Film out puts the unit in HELD, not in STOPPED.
Rejected: a general stop with a reset.
HELD is the state of something waiting for an intervention and then resuming where it was. Stopping everything would force the whole start sequence to be repeated for a reel change, which is ordinary shop-floor maintenance and happens several times a shift.
SCOPE
These notes describe this machine, which is a demonstration simulation: what they state about it is checkable against the behaviour of the synoptic above. No reference to any real customer installation.
The chain brings the products in at pitch. The chain pitch is the machine rhythm, and everything else depends on it.
DECISIOND1
There is one virtual master axis, modulo 360, and every member derives from it.
Rejected: independent axes kept in phase by synchronisation signals.
A phase you never have to maintain is a phase you cannot lose. With a single reference, synchronisation is true by construction: there is no instant at which two members can hold two different ideas of where the machine is.
DECISIOND2
The master is virtual, not the encoder of a real motor.
Rejected: electing the jaw motor as the physical master.
A physical master carries its own errors into the reference: slip, backlash, its own acceleration ramp. And if that motor fails, the machine loses the reference as well as the member. A virtual master moves exactly as it should, and can be cranked by hand during commissioning with nothing powered.
DECISIOND3
Speed is set in PPM, not in revolutions or metres per minute.
Rejected: the unit of the fastest member.
PPM is the unit the customer measures the machine in, and the unit it is written in on the contract. Whoever stands at the pulpit thinks in packs, not in degrees per second: 60 PPM = 360 deg/s is a conversion, not a reading.
SCOPE
These notes describe this machine, which is a demonstration simulation: what they state about it is checkable against the behaviour of the synoptic above. No reference to any real customer installation.
The forming shoulder folds flat film into a continuous tube around the product. No motors, no sensors, no software.
DECISIOND1
Half the work of the machine is done by a shaped piece of sheet metal.
Rejected: assisting the forming with a motorised member.
One more axis is one more drive, cable, parameter, calibration, spare part and way to fail at three in the morning. Where geometry is enough, geometry wins. The most reliable software I write is the software I manage not to write.
DECISIOND2
The forming shoulder does not appear on the cam diagram at all.
Rejected: adding it as a constant-value track.
A flat track tells the reader there is something to synchronise. There is not. The absence is the information.
SCOPE
These notes describe this machine, which is a demonstration simulation: what they state about it is checkable against the behaviour of the synoptic above. No reference to any real customer installation.
The jaws close once per pack. One stroke, one product: the speed in PPM is literally the rhythm of this member.
DECISIOND1
The jaws are expressed in millimetres of stroke, not in degrees.
Rejected: 0-360 degrees as for the rotating shafts.
It is a linear actuator: it goes out and comes back once per cycle, it does not turn. Giving it an angle would force the reader to mentally convert a stroke into a rotation that does not exist. The unit has to be the member’s, not the chart’s.
DECISIOND2
The seal window is an arc of the cycle, highlighted on the diagram.
Rejected: treating it as an instant at 180 degrees.
A seal has a duration: the film has to sit still and hot under the jaws for a time, not for a point. That arc is the constraint that decides how fast everything else can go. It is where you start when the customer asks for more PPM, and the first thing I look at when seals open.
DECISIOND3
Every seal emits an event, and the rest of the page listens for it.
Rejected: letting whoever needs it poll the jaw state.
Whoever produces the fact announces it once; whoever cares subscribes. The counter, the diagram and the sound all react to the same event, so they cannot tell three different stories. Polling state is how systems that later disagree are built.
SCOPE
These notes describe this machine, which is a demonstration simulation: what they state about it is checkable against the behaviour of the synoptic above. No reference to any real customer installation.
The discharge belt carries the finished packs out. This is where the counter fires, and choosing to count here is the most argued decision on the machine.
DECISIOND1
A piece counts as produced only when it crosses the discharge edge.
Rejected: counting at the seal, which is where the pack is born.
At the seal you count intentions. At the discharge you count what the customer can be invoiced for. In between there is scrap, rejection and everything the machine does but does not deliver. A counter that reads above reality is a counter nobody looks at after the first week.
DECISIOND2
Scrap leaves the machine but returns to the balance still to produce.
Rejected: deducting it from the batch like any other piece.
A batch is a request: one hundred good pieces. If scrap deducted from the batch, the machine would stop at ninety-eight while declaring one hundred. The piece goes back into the balance because it has to be made again.
DECISIOND3
The totaliser is separate from the batch counter and never resets.
Rejected: a single resettable counter.
They answer two different questions. The batch says how much is left to finish; the totaliser says how much this machine has made. They count the same event, so they cannot disagree, but resetting them together would erase the second answer at every changeover.
SCOPE
These notes describe this machine, which is a demonstration simulation: what they state about it is checkable against the behaviour of the synoptic above. No reference to any real customer installation.
PLC, drives, power supplies and the safety circuits. This is where the choices stop being matters of style and become normative.
DECISIOND1
The state machine is ISA-TR88 (PackML), not a state machine of mine.
Rejected: a bespoke sequence, shorter and better suited to this machine.
A bespoke state machine has to be taught to every maintenance technician, every integrator and every supervisory system that will connect over the next ten years. And it will be taught badly, at three in the morning, by someone in a hurry. PackML is already in the head of whoever arrives: STOPPED, IDLE, EXECUTE, HELD, ABORTED read without a manual. A shared convention is paid for once.
DECISIOND2
The emergency stop latches mechanically, with the yellow surround.
Rejected: any red button, graphically cleaner.
The yellow around the red mushroom is not decoration: it is the marking required by EN ISO 13850, and it is there so someone who does not know this machine can find it. It latches because an emergency stop must not be able to release itself when the hand leaves the button.
DECISIOND3
An open guard removes power but does not zero the master position.
Rejected: open guard equals general reset.
Whoever opens a guard almost always closes it again straight away: a crooked product, a check, a wipe. If opening cost the phase, every ordinary gesture would become a full restart and the shop floor would learn to work with the guards defeated. Safety that gets worked around is not safety.
SCOPE
These notes describe this machine, which is a demonstration simulation: what they state about it is checkable against the behaviour of the synoptic above. No reference to any real customer installation.