MES downtime without the license

What you actually need

• A run-state tag per line or cell — running, stopped, faulted.
• A downtime_events table: line, start, end, duration, reason code, operator.
• A short, standardized set of reason codes everyone agrees on.

The pattern

A gateway tag-change script watches the run-state and writes event boundaries on transitions:

def valueChanged(tag, previousValue, currentValue, ...):
    if currentValue.value == previousValue.value:
        return
    system.db.runNamedQuery("oee/LogStateChange", {
        "line": tag.parent,
        "state": currentValue.value,
        "ts": system.date.now()
    })

OEE then falls out of named queries: availability from the downtime table, performance from count versus ideal rate, quality from scrap counts. A small Perspective screen lets operators attach reason codes to the stops the system already caught.

When to buy the module

Roll your own when you've got a line or two and want answers this month. Move to the MES modules when you need it standardized across many lines, with the scheduling, genealogy and support that come with them. Starting lightweight also teaches you exactly what you need before you spend.