I’m an industry service engineer for food packaging machines and never an automation specialist, however can provide you with few hints.
For many automation systems to function, you have to first have a clear and detailed mechanical plan with all of details finalized. If you do this, you must specify the motions involved, e.g.: linear or rotary. This allows you to be aware of number and kinds of motors and actuators you may need(servo, ac single phase, ac 3 phase, pneumatic actuator).
For every motors you may 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(a lot more like conveyors, liquid tank level control pumps or rollers).Servo motors need Servo drivers to control their precise movement.
They are your output devices, then you need your input devices to be set out. This can be level sensors, flow sensors, proximity switches along with other devices when needed. The key reason why i’m stating out this routine is always to permit you to define the specifications necessary for your control system hardware requirements. All PLC manufacturers layout their product line-up according to system complexity.
Most PLC hardware comes as reconfigurable rack chassis. Basically there is an CPU which is master brain that is supplemented with I/O device that could be slotted in like cards. Additional complex systems which needs servo motor will have servo card in order 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 workout you IO devices list, then receive the necessary hardware and software needed. You may need additional hardware essential for for fancy touchscreen display HMI, line automation and internet-based diagnostic and asset monitoring functions. That’s how a guy with mechanical background can approach complex automation problems.
The solutions varies based on different manufacturer offering particularly if you use beckhoff based systems. The best way to start may be to develop existing machines so that you can learn the basics. Go have a few catalogs from reputable manufacturers to understand the marketplace can give. I always suggest people to go through Omron catalogues. They also have a free of charge automation web based course that will teach you the infant steps needed.
You have to be able to design complete PLC systems: architecture design, hardware specfications and selection, logic narratives, logic programming, connection drawings. Everything. Perhaps you just need to extra training around the details of every bit of it technology, on the way to program or properly connect them, yet it’s not too difficult, an excellent mechanical engineer should probably excel for this every other engineer. The main aspect of control system design would be to view the process you’re going to control and also the goals you wish to achieve.