Runnable simulator field guide
Weld-cell PLC cycle scenario: test checklist
Direct answer
The learner can require safe entry conditions, prove fixture and part state, exchange bounded ready and complete signals and recover without automatic hazardous motion.
Written for automation learners modeling a weld-cell handshake without exposure to real arc, motion or hazardous energy.

Scenario setup
Cell safe state, guard and safety status, part present, fixture clamp, robot ready, cycle request, weld complete, quality result, unload and reset policy.
I/O and state map
Operator load through part and clamp proof, controller handshake, robot cycle, weld result, release, unload and return-to-ready evidence.
Normal run
One correctly loaded part completes the declared handshake while entry demand or lost permissive prevents further hazardous sequence.
Boundary run
Part missing, double part, clamp not made, robot not ready, handshake stuck, cycle timeout, weld fault, quality fail, stop, restart and manual recovery.
Injected fault
A safety-status, part, fixture, handshake, robot, weld, quality, timeout or recovery mismatch.
Target check
The production cell validated by qualified robotics, welding, safety and process specialists under applicable standards.
What signals should a PLC exchange with a weld robot?
Use a documented handshake separating cell permission, robot ready, cycle request, in-cycle, complete, fault and reset, with independent safety functions outside standard control logic.
How should a weld cell recover after a stopped cycle?
First establish actual robot, fixture and part state, then follow an approved bounded recovery path that cannot silently resume hazardous motion.