I am looking into updating the control panels we use for our OEM Mixing systems.
We currently have panels made up of push buttons, relays several red-lion process controllers and VFD.
There seems to be a variety of HMI / PLC combo units capable of multiple I/O and analog inputs.

Does anyone have experience with any of these units. I would like to keep cost down but not sacrifice maintainability by plant maintenance resources.
Like to stay away from obscure and proprietary software etc.