Good to know. I see a lot of models with 1.75mm filament out there. I will look for 3mm models, but if I end up with 1.75mm how easy is it to upgrade to 3mm?
Not very easy. I guess it depends on the printer, but you may need another extruder (at least another hobbed bolt) and hotend, and you may need another stepper motor too.
How often do you have to level the bed and how long does it take? I would rather not have to spend a good deal of time before every print making adjustments to the printer.
Not that often, although once more, it will depend on the printer. For instance on my K8200 the thumb wheels that level the bed tend to shake lose with time. The hot bed may also warp a little with temperature, so you may want to check when switching between materials that require different bed temperatures. But other than that, it should only be when you do maintenance, like cleaning (and thus removing) the nozzle or something.
Its not much work you know, just slide a piece of paper underneath the nozzle and turn the adjustment wheel until its correct. Auto Z adjustment is mostly useful if you are printing remotely, its one less thing to worry about or walk to your printer for. The first weeks/months of your first printer, you're not likely to want to printer far away anyway, you'll likely be staring at it for hours while it prints
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I'll probably go with bowden so I don't have to worry about swinging the mass of a direct extruder around.
You'll have other things to worry about then, there is no free lunch. Also dont overstate the mass of the extruder, its not that heavy (depending of course on design), when compared to the moving bed. Especially a heated bed with mirror on it. Also consider that having one object move in 3 dimensions makes it more suspectable to errors accumulating. Its easier to build something sturdy and accurate if you only have to worry about 1 or 2 axis. I assume thats the main reason many high end machines have moving beds, despite the fact it reduces your print surface.
Dual extruders for dissolvable material sounds nice, I really don't care too much about printing in two colors though.
I dont care about colors either,but dissolvable support material has to be awesome. So many things Ive wanted to print, but then I looked at the amount of support material id have to dremel out (can be a real PITA) and decided not to print it.
With regards to sticking the print to the bed, I once used the printer at my school and it required painting the glass bed with a clear gel like glue. It basically glues the plastic to the glass and took half an hour of prying to get off. Maybe we used too much, but I hope the printer I get secures the print in a way that is much easier to remove.
Got one with a hot bed then. You make it stick and unstick just by regulating the temperature. On large prints, after it finished and the bed cools, it will literally make a crackling or popping sound, and I can just take it off. While hot, its like glued to it.
