I’m an area service engineer for food packaging machines and not an automation specialist, on the other hand can present you with few hints.
For many automation systems to be effective, you must first possess a clear and detailed mechanical plan with all details finalized. When you do so, you should specify the motions involved, e.g.: linear or rotary. This allows you to understand the number and types of motors and actuators you’ll need(servo, ac single phase, ac 3 phase, pneumatic actuator).
For each motors you may want 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.
They are your output devices, then you need your input devices to become determined. This can be level sensors, flow sensors, proximity switches and other devices as required. The reason i’m stating out this routine would be to permit you to define the specifications needed for your control system hardware requirements. All PLC manufacturers layout their product line-up according to system complexity.
Most PLC hardware is sold as reconfigurable rack chassis. Basically you will find the 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 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 obtain the necessary software and hardware needed. You will need additional hardware essential for for fancy touchscreen display 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 could differ based on different manufacturer offering specifically if you use beckhoff based systems. The best way to start is to work with existing machines so you study the basics. Go get yourself a few catalogs from reputable manufacturers to understand industry is offering. I usually suggest people to go through Omron catalogues. Next to your skin a totally free automation web based course that will coach you on the baby steps needed.
You need to be in a position to design complete PLC systems: architecture design, hardware specfications and selection, logic narratives, logic programming, connection drawings. Everything. Perhaps you just need some additional training about the more knowledge about each piece of equipment, on how to program or properly connect them, but it’s not rocket science, a great mechanical engineer should probably excel with this because other engineer. The most important aspect of control system design is usually to view the process you are likely to control and also the goals you need to achieve.