I’m a field service engineer for food packaging machines instead of an automation specialist, however i can provide few hints.
For those automation systems to operate, you should first possess a clear and detailed mechanical plan with all details finalized. Whenever you do this, you need to specify the kind of motions involved, e.g.: linear or rotary. This enables you to understand the number and types of motors and actuators you will need(servo, ac single phase, ac 3 phase, pneumatic actuator).
For each and every motors you will need relay contactors (for single speed discrete/on-off type motors like blower fans and liquid pumps), VFD for speed controllable ac 3-phase motors(more like conveyors, liquid tank level control pumps or rollers).Servo motors need Servo drivers to control their precise movement.
These are generally your output devices, then you need your input devices to become set out. This is level sensors, flow sensors, proximity switches as well as other devices if required. The main reason i’m stating out this routine is always to permit you to define the specifications needed for your control system hardware requirements. All PLC manufacturers layout their product line-up depending on system complexity.
Most PLC hardware comes as reconfigurable rack chassis. Basically you will find the CPU which is the master brain which can be supplemented with I/O device that may be slotted in like cards. Additional complex systems which needs servo motor can have servo card to connect with servo driver, communication bus cards like CAN-BUS, PROFIBUS and DEVICENET and sensor cards for special sensors like RTD temperature sensors and level sensors.
So work out you IO devices list, then get the necessary hardware and software needed. You will need additional hardware necessary for for fancy touchscreen display HMI, line automation an internet-based diagnostic and asset monitoring functions. That’s that the guy with mechanical background can approach complex automation problems.
The solutions may differ based on different manufacturer offering particularly if use beckhoff based systems. A good way to start is to focus on existing machines so that you can educate yourself on the basics. Go get yourself a few catalogs from reputable manufacturers to understand what the market has to offer. I usually suggest visitors to go through Omron catalogues. There is also a free of charge automation online course that may educate you on the child steps needed.
You should be capable of design complete PLC systems: architecture design, hardware specfications and selection, logic narratives, logic programming, connection drawings. Everything. Perhaps you just need to extra training about the details of every piece of equipment, concerning how to program or properly connect them, but it’s not too difficult, a great mechanical engineer should probably excel about this as any other engineer. The main facet of control system design would be to view the process you are likely to control as well as the goals you want to achieve.