I’m an industry service engineer for food packaging machines rather than an automation specialist, however i can present you with few hints.
For those automation systems to be effective, you must first have a very clear and detailed mechanical plan with all of details finalized. When you do this, you need to specify the type of motions involved, e.g.: linear or rotary. Each day understand the number and kinds of motors and actuators you may need(servo, ac single phase, ac 3 phase, pneumatic actuator).
Per 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 regulate 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 when needed. The main reason i’m stating out this routine would be to allow 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 a CPU which is master brain that is supplemented with I/O device that can be slotted in like cards. Additional complex systems which needs servo motor may 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 may want additional hardware necessary for for fancy touchscreen technology HMI, line automation and internet-based diagnostic and asset monitoring functions. That’s what sort of guy with mechanical background can approach complex automation problems.
The solutions may vary depending on different manufacturer offering particularly if you use beckhoff based systems. A sensible way to start will be to develop existing machines so that you educate yourself on the basics. Then go get a few catalogs from reputable manufacturers to understand what industry can give. It’s my job to suggest people to go through Omron catalogues. Next to your skin a no cost automation online course which will teach you the infant 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 all you need is extra training around the information every piece of kit, concerning how to program or properly connect them, however it is not rocket science, a great mechanical engineer should probably excel on this every other engineer. The main aspect of control system design would be to see the process you are likely to control along with the goals you would like to achieve.