On an SPM, the cycle is set by the slowest station.
Machine-level timing says the machine got slower. Station-level timing says which station did — usually the difference between a week of investigation and an afternoon.
A special-purpose machine is, by definition, unlike any other machine on the floor, which makes generic monitoring assumptions unusually likely to be wrong. What an SPM does have is a PLC that already knows a great deal — cycle state, station status, counts, faults — because it had to in order to run the machine at all.
Monitoring an SPM is therefore rarely an acquisition problem. It is an agreement problem: deciding which of the PLC's existing signals represent the things you want to measure.
This is the single highest-value configuration decision on an SPM. Machine-level cycle timing tells you the machine got slower; station-level timing tells you which station did, which is usually the difference between a week of investigation and an afternoon.
What one cycle produces
Multi-station and multi-cavity SPMs frequently produce several components per cycle. Establish this before any count is reported.
Which faults stop production
An SPM annunciates many conditions. Only some stop output, and treating all of them equally makes the Pareto meaningless.
Station boundaries
Where one station's time ends and the next begins, as the PLC sees it — not as the mechanical layout suggests.
Idle versus starved
An SPM waiting for input material is a supply problem, not a machine problem. Distinguish them or the wrong team gets the action.
Almost everything you need, usually. Cycle running, station states, counters and fault bits are typically already in the program because the machine needs them. Acquisition is configured by the MachineWise engineering team, read-only, with nothing written to the PLC.
The work is mapping — deciding which tag means what, with its data type, scaling and edge behaviour recorded — and it is a conversation involving your maintenance team, your production team and ours. On a bespoke machine there is no shortcut and no library to look it up in, which is why the method matters. It is set out in PLC signal mapping for machine monitoring.
Two special-purpose machines on a live dashboard this week.
Bring the SPM whose cycle time everyone argues about. Station-level timing usually ends the argument within a fortnight.
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