Keep in mind, I'm not trying to sway you or anyone else here, just explaining how it differs due to working with larger print volumes for so long.
What you have works great
at your scale, not everything works as well, or at all, as you scale up and that's a common misconception by people who think you can just make it bigger. Scaling a printer design is
relatively easy (to screw it up as well!), making it work well and understanding how printing changes as you do is where the learning curve comes in and what all of this discussion has been geared towards. While these techniques work on smaller scale, it's usually not necessary.
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- The red one, referring to lilly-pads... what do the flat hemispheres do? I Googled around they appear to be localised brims, but your example has a gap to the main object, so I don't see how they act as an adhesive brim. Is it because the gap is so small (0.1mm) that the object and pad are still attached?
Correct, it's a localized large brim, primarily aimed at corners (where lift happens most) the gap is supposed to be 0.01mm, not 0.1mm.
Never seen anyone else use the gap method on them but I prefer it.
The gap is small enough that it will still bond quite well but when broken off leaves a solid wall behind it. If there is zero gap the slicer will treat it as part of the object and not only will it not snap off clean but also leaves infill exposed. Horizontally the connection is strong, but vertically it is weak so it can snap off sort of easily when finished or worst case cleaved off with a razor leaving a smooth wall.
Basically it tricks the slicer into creating a solid wall behind it and also break away easier.
The Prusa relies on an inductive sensor, so glass is a bit of a no-go. I did have glass on the Ender, but getting prints off was occasionally a pain. The steel PEI sheets currently in use have been durable and convenient, and I have mistakenly stocked up on cheap third party replacements so now have far more plates than I need.
Inductive is not always as precise as people think.
The fake BL Touch probes (inductive but with a probe attached so it becomes mechanical) are not near as good as the real thing and even that varies. Most are unaware but the inductance probes are influenced by nearby voltage, I have a real BL Touch on my big printer and I have to disable the heater while it probes (firmware does this for me) or it will be off enough to notice. On a smaller printer it's not a big deal but small amounts grow big over long distances so every bit counts. Same applies to the surface itself, you can't have a 0.15mm dip in the bed when your layer height is 0.02mm and the larger your bed, the more it can vary, glass, steel, doesn't matter.
For getting prints off glass I use a bread peel/spatula and a razor blade (to get under initially) and if necessary, warm water.
On massive prints I sometimes need to deploy extras of everything and even throw in a few steak knives to act as wedges to get water underneath and loosen the glue. It's easy to think this is what breaks my beds but out of dozens of glass beds I've only broken one this way, a $2 home depot piece of glass and I pretty much knew it was doomed before I even hit "print" (I took a chance). The rest were thermal shock or accidents.
I'll try printing some materials without any heat at all, and see how that goes. What I'd really like to be able to do is print ABS and polycarbonate without going up to 100C, that's just hugely wasteful of heat.
Without heat from a heated bed it often leads to severe delamination on ABS and Nylon (and PC? been a while since I did it), they need a bit of extra warmth to create a stronger bond for each new layer (too little retained heat) or a lot of extra heat coming out of the nozzle to make up for it, this can cause more shrinkage, but also walks a fine line of bonding vs cooking. ABS has a rather small temp range, PET has modest one, PLA has a WIIIDE one, so long as you are printing, it's really hard to cook PLA. On smaller objects the nozzle comes back around fast enough that it never has a chance to fully cool so it can stick regardless but on big ones it needs that heat. This is why those plastics are so prone to air drafts destroying prints and you see people using cardboard walls to stop air flow through the machine and why the print can change as you get further off the bed and into cooler air, creating a hourglass effect on the shape of the object. This goes back to my claim of creating more problems than it can be worth, I had massive hourglassing. Even PET suffers from the layer adhesion problems to an extent but nowhere near what the others do. ABS can lose 80% of it's strength if done wrong.
When I do ABS, Nylon or PC it's always very small objects, anything larger I'd rather just re-engineer it to use some other plastic, like PET. As mentioned before, those plastics all have too much shrinkage to do large stuff anyhow, at least not without a complete temp controlled chamber and that brings all sorts of other issues.
Your bed may not sick well or at all without heat and if you do get it to stick, if it's a stick on coating (not baked on like Prusa) it can cause it to lift and stretch, wrecking the bed. Contrary to how it seems in the advertising, heat is the main component of these surfaces. Not saying the surface doesn't matter, just that it's a combination of the two and the sheet won't work well, if at all without any. This also is some of the reason the prints pop off so easy after. With a well tuned printer and heated bed you can actually print PLA directly onto clean bare glass, no glue stick or anything. It doesn't grip well enough for consistent printing and often comes loose later but it is very doable with the right printer.
Yeah, the new Prusa sounds very wizz bang, and there is a fair bit of excitement around it. But going to past history, I think that the people who signed up for pre-orders are highly optimistic. I wonder what sort of novel teething problems will arise when they start arriving.
Large single prints will have issues with bed uneven-ness and lines where joints are, you can probe all you want, it can only compensate so much for uneven surfaces. Remember you're crossing multiple beds, each with different tolerances. If you're doing a 0.2mm layer you can't have one at 0.05mm and other at 0.3mm. That sounds like a big gap, and it is, but not when you are screwing parts together and using multiple magnets covered in iron dust. That's not going to be easily solved.
The other thing is people and bad printing practices.
People will try to fill the bed with lots of small parts, this is effectively putting all your eggs in one basket. All it takes is for one object to come loose from the bed, crash into another and sends the nozzle on a wild goose chase and now instead of 2-4 hours of spaghetti on your print bed you're left with 8-12 hours of it. Make it a 0.8mm nozzle and you just ruined an entire spool of plastic and half a day of printing and electricity.
On the surface it sounds great, a large Prusa, excellent(!) but it compromises the very things it's supposed to deal with.
From experience, you're better off with multiple printers than trying to make one large printer do everything.
I do understand that going down the enthusiast CoreXY route isn't really compatible with the limited time statement though.
Printer reliability comes down to parts and how they're used, not so much the style of printer they're attached to, deltas actually rule in terms of duty cycle/reliability, mechanically they're super simple machines with little to wear out. Provided you use good parts, a well designed and assembled(!) enthusiast grade open source printer is going to be far less problematic so you actually spend less time messing with it. Enthusiasts mess with them to make them better/faster/reliable/capable, not because they have problems.
Corexy is popular because you get (most of) the speed of a delta with the accuracy of a cartesian for little to no cost (over a cartesian, deltas are cheaper).
