Regarding Layout and Wire Ducts...
My thoughts, which don't bring me much money by the way, go along these lines:
Locate power devices (drives & circuit protection) in the upper quadrants of the panel, since heat rises. Make sure there is a path (wire duct) for line voltage wiring that stays away from the logic wiring.
Locate the plc close to the terminal strip, and use BIG wire duct in between to handle the density and crossing over of wires in this area.
Since the advent of finger safe terminal blocks, visibility for the poor slob that has to do the field wiring (sometimes that's me) is an issue. We always use the angled DIN rail standoffs for terminal blocks (note, the higher profile DIN rail is sturdier). This makes the wiring on the field side easier to see.
I use ACAD (because that's what we have here) to do panel layouts, and I start with an electronic drawing of the enclosure (available at
www.hoffmanonline.com) and other downloaded drawings whenever possible.
No matter what brand of terminal block you use, the 3-level terminal blocks for use with sensors are worth the extra money. Wherever possible, the prox/photo sensors are grouped such that all the 3-level terminal blocks are in one stretch. If you have remote junction boxes or are using device net, it doesn't apply.
I frequently use an excel spreadsheet (homemade form) for a terminal block layout/wire list. The size of the terminals is in a field, which gets tallied. When the tallied number is bigger than the width of the panel, I know I'm in trouble! (I haven't figured out how to attach to the thread yet, but I will be happy to e-mail a sample of the form to anyone who wants it).
Be careful how you treat your co-workers today, for tomorrow they may be your boss.