To me that's one of the hidden advantages of a "real" fuse. You don't get into the cycling process. You also get a much better ability to interrupt a dead short (high current fault).
The question still comes back to - how much current will you be handling? I'd take the easy way out (now that you have real fuse) - make it a 24 to 32V design. Forget about 12V high power loads. Except for fans, all the stuff on a printer is just as cheap at 24 as it is at 12. Current isn't just an issue with the traces, the connectors that get the wires in and out are at least as big a problem. They rate them correctly for a good solid single wire into the connector with plenty of torque on the screw. We don't always meet all of those constraints ....
For the fans, if you have:
1) Fan on each extruder hot end (2)
2) Fan on the print (1)
3) Fan on the electronics (1)
I'd say you have a lot of fans. If they each pull 0.1A at 12V that's pretty typical. A 7812 running at 1/2 A will try to dissipate 6W off of 24V. With a cheap 10W wire wound resistor in series with it you can get the max power down to a bit under 2 watts. There are some other tricks (like a 15 V regulator, a few diodes, a switcher, a cheap +12 supply) that you also could use.
I'd just go with a $10 +12V industrial supply and make the big supply something at 24V. The cost impact is pretty small and the system will be very rugged. Since you are laying out the board from scratch, a dual +12/+24 setup would be pretty easy to drop in.
The question still comes back to - how much current will you be handling? I'd take the easy way out (now that you have real fuse) - make it a 24 to 32V design. Forget about 12V high power loads. Except for fans, all the stuff on a printer is just as cheap at 24 as it is at 12. Current isn't just an issue with the traces, the connectors that get the wires in and out are at least as big a problem. They rate them correctly for a good solid single wire into the connector with plenty of torque on the screw. We don't always meet all of those constraints ....
For the fans, if you have:
1) Fan on each extruder hot end (2)
2) Fan on the print (1)
3) Fan on the electronics (1)
I'd say you have a lot of fans. If they each pull 0.1A at 12V that's pretty typical. A 7812 running at 1/2 A will try to dissipate 6W off of 24V. With a cheap 10W wire wound resistor in series with it you can get the max power down to a bit under 2 watts. There are some other tricks (like a 15 V regulator, a few diodes, a switcher, a cheap +12 supply) that you also could use.
I'd just go with a $10 +12V industrial supply and make the big supply something at 24V. The cost impact is pretty small and the system will be very rugged. Since you are laying out the board from scratch, a dual +12/+24 setup would be pretty easy to drop in.