Since 1988 after leaving the NSW State Rail Authourity I have constructed hundreds of control panels for clients & my own machinery. Control panels for everything from CNC machines to Municipal waste water treatment plants.
My preference has always been to use stainless steel cabinets. These are design in 3D & have laser cut & folded. They are then TIG welded together. They do not rust and do not attract magnetic particles. And labour saving buy not having to powder coat after fabrication. Drill extra holes & rust will not start on the cut edges with a stainless emclosure. Cutouts such as for touchscreen bezels, push buttons, toggle switch's cooling fans, vents & cable glnds etc are enacted doing the laser cutting. No extra work required.
Cabling....? As small as can get away with. Current draw is no longer what it was in the past for switching & sensors. Why use 1.5mm conductors for control wiring like inputs to a PLC. Or even for outputs tp coils & sensor field wiring. .5mm is more than enough & still gives a good mesure of mechanical strength.
Colour coding is probably the biggest bug bear. My own preference is orange for 24VDC. Purple for 0V and red for 240AC active and blue for Neutral. Field wirng is best done with numbered cores for ELV stuff. That way OEM boxes need not waste time with cable marking . Use colours, wire numbers & YOUR BRAIN.
PLCs . My favourite are the Jap ones. Most reliable by far & of these my own personal preference is for Panasonic . Omron comes a close second with Mitsubish not far behind. Allen Bradley is down the back end of the field. Why you ask? Because firstly they are the size of a London bus. More real estate needed in an enclosure/& frankly they are inferior in capability compared to the Jap ones. The software is a ripoff & they hook you onto proprietry products like DeviceNET. Speaking of DeviceNET. Of all the fieldbuses on the market. None comes close to stock standard MODBUS. Everyman & his dog offer MODBUS gear like sensor terminals, Variable Frequency Drives, Stepper & Servo Drives etc etc.
Coding is easy. If I build a custom instrument the programming is transportable between both TCP/IP and RTU. Just tweak the numbers a bit for addressing & the Cyclical Redundancy Check. 32bit for TCP & 16 for RTU.
