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

I don't think many people use a PLC in conjunction with Linuxcnc. There is an Ethercat master we have a driver for so getting IO and the like is pretty easy. Stick to Beckhoff for best support but making a custom XML driver for other IO and drives is pretty simple. Whilst people have mentioned Ladder Logic which is available, the secret magic nobody seems to mention is you can write hal components which when built and installed with a 1 line command : sudo halcompile --install mycomp.comp. Once these are built, they are treated exactly as if they are part of the core program and run in real time.

I do know a guy who has retrofitted a lot of big machines and recently on one big 5 axis machine with 100 tools and multiple pallet changers, the ladder wasn't doing it for him so he learnt a smattering of C and knocked out his working high speed tool changer component over a weekend.