Runnable simulator field guide
Case-packer PLC scenario: test checklist
Direct answer
The learner can build one state-owned pack cycle, maintain count-to-case association, block conflicting motion and recover from a known material state.
Written for packaging automation learners coordinating product infeed, carton presence, grouped transfer, flap or discharge actions and fault recovery.

Scenario setup
Product detection, count edge, target pack quantity, carton available and positioned, pusher home and extend proof, discharge clear, state owner, timeout and reject or recovery policy.
I/O and state map
Products through sensing and count state to full-group decision, carton permissive, transfer command, motion feedback, packed-case confirmation and discharge.
Normal run
One declared group enters one ready case, transfer proves both positions, count resets once and the packed case clears before the next cycle.
Boundary run
Missing carton, double product, sensor bounce, count mismatch, pusher timeout, carton shift, blocked discharge, stop, restart and partial group.
Injected fault
A product, sensor, count, carton, state, command, actuator, feedback, timing or recovery mismatch.
Target check
The sequence recreated with exact mechanics, guarding, motion, product and carton acceptance tests.
How should a PLC track products into a case packer?
Create one event per accepted product, associate the count with a declared group and reset only after transfer and packed-case confirmation, not merely after issuing a pusher command.
What should happen after a stop with a partial product group?
The recovery policy must use actual product, carton and mechanism state; either resume the identified group or clear it through a controlled manual procedure.