PLC + LinuxCNC for industrial machine with simple HMI (non-G-code operators)

Thanks for sharing your experience — this is exactly the kind of real-world example we were hoping to hear about.
Your description matches very closely the architecture we are targeting: a PLC/HMI as the cell controller (sequencing, recipes, operator workflow, interlocks), and LinuxCNC used strictly as a motion controller. The Python “bridge” approach you described, using Modbus TCP on the PLC side and the LinuxCNC Python interface on the PC side, is a very pragmatic way to implement a clean command/status boundary between the two domains.
What I find especially valuable in your example is that the operator never interacts with LinuxCNC directly: the PLC/HMI owns the workflow, selects the product/recipe, and LinuxCNC is treated as a subordinate motion engine that executes the required paths and reports status back. That is exactly the separation of responsibilities we are aiming for.
It is also very useful to hear that this setup has been running in production for several years, daily, with good reliability. This addresses one of the main concerns in industrial environments: long-term robustness and maintainability, not just theoretical capability.
Your comment about Modbus TCP being “simple and universal” is also a good reminder that, in many industrial contexts, simplicity and familiarity often translate directly into better supportability and uptime.
Thanks again for sharing this — it’s a very strong reference point for PLC + LinuxCNC architectures in real machines.

There is also the option of equipping the LinuxCNC PC with an EtherCAT slave interface.
Data exchange can then take place via this interface.