SimTwin: An Open-Source Reproducible Simulator of Networked FDM/FFF Printer Fleets with Digital-Twin Synchronisation, Fault Injection and Communication Impairment

Digital-twin research on additive-manufacturing (AM) fleets needs experi-ments in which the physical process, the communication channel and thetwin’s synchronisation state can be manipulated and measured indepen-dently; existing tools cover only fragments. SimTwin is an open-sourcePython simulator that couples a lumped-parameter thermal plant withproportional–integral heater control, a per-device job and health state ma-chine, an explicit message-level transport with latency, jitter, loss, dupli-cation, outage and staleness-based discarding, and a twin registry writtenonly by delivered messages. Faults are injected as mechanisms acting onthe plant, not as scripted telemetry labels, so fault signatures emerge fromthe dynamics, and seeding gives byte-identical telemetry. Seven experimentsreport scalability to 1 000 printers, throughput to 70 363 msg s−1, twin stale-ness rising from 0.99 s to 6.99 s with loss, 10 of 11 fault families separable atCohen’s |d| ≥ 1.45, and QoS 1 holding 95th-percentile staleness at 1.2 s on areal broker where QoS 0 lets it grow 12.6-fold.