I’m a field service engineer for food packaging machines rather than an automation specialist, however can give you few hints.
For all automation systems to work, you must first have a very clear and detailed mechanical plan wonderful details finalized. If you do so, you must specify the type of motions involved, e.g.: linear or rotary. This allows you to know the number and types of motors and actuators you’ll need(servo, ac single phase, ac 3 phase, pneumatic actuator).
For 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(similar to conveyors, liquid tank level control pumps or rollers).Servo motors need Servo drivers to control their precise movement.
These are generally your output devices, you will want your input devices to get lay out. This could be level sensors, flow sensors, proximity switches and other devices if required. The key reason why i’m stating out this routine is always to allow you to define the specifications necessary for your control system hardware requirements. All PLC manufacturers layout their product line-up based on system complexity.
Most PLC hardware comes as reconfigurable rack chassis. Basically there is a CPU which is master brain which is supplemented with I/O device that could be slotted in like cards. Additional complex systems which needs servo motor can have servo card to get in touch 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 exercise you IO devices list, then get the necessary software and hardware needed. You may need additional hardware needed for for fancy touchscreen HMI, line automation and online diagnostic and asset monitoring functions. That’s how a guy with mechanical background can approach complex automation problems.
The solutions may differ based on different manufacturer offering specifically if you use beckhoff based systems. A great way to start will be to work with existing machines so that you study the basics. Go get yourself a few catalogs from reputable manufacturers to understand the market industry is offering. I usually suggest website visitors to go through Omron catalogues. Next to your skin a free automation online course that may teach you the baby steps needed.
You need to be capable of design complete PLC systems: architecture design, hardware specfications and selection, logic narratives, logic programming, connection drawings. Everything. Perhaps you just need extra training for the more knowledge about every piece of it technology, concerning how to program or properly connect them, however it is not nuclear physics, a good mechanical engineer should probably excel on this every other engineer. The key part of control system design is to understand the process you are likely to control and the goals you would like to achieve.