Fixes air prints because if the encoder is not seeing movement. No movement means not filament being pass thru and active gantry means airprint. The PEI has completely solves the part coming off the bed issue. With that combo no airprints.
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Your encoder rides behind the nozzle? I am not sure what you mean. The extruder is happily pushing filament along (movement) and the nozzle is happily melting it and laying it down. Just laying it down in the air, or beside the part, etc. The other day I had a belt decide to slip (no idea why, never before/since but whatever) on the Y-axis, and so my part had a 1cm shift to the side. A whole lot of air printing happened. But there is no way, short of a machine vision camera looking at the part being printed, that anything could detect the failure. filament was certainly moving, just not where I want. Itâs like having your dog knock your sprinkler, the sprinkler is still watering as far as it knows, itâs just now pointed at your open convertible instead of the lawnâŚ
Iâve had prints quite happily come off the PEI bed, just depends on what materials you print in. Nylon is meh on PEI, PETG is OK, nGen can be âtoo goodâ and PLA and PLA/PHA are perfect.
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Two classes of airprints.
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Part comes of the bed and you extrude a picasso. < PEI
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Filament stops extruding and you print nothing. The machine runs for hours laying no filament down. < Encoder.
As for miss steps. Closed-looped FTW. But the gantry I designed and the speeds Iâve been printing at Iâve yet to see issues.
Anyway- The point is I got sick of the issues and engineered a solution that works for me. Had no issues since.
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Went for the scorched earth approach (again) â clean install of S3D and ran the config helper. For the first time ever, itâs working a smooth as silk. Mechanical hypochondria â acts up until I talk to a doctor! 
Thanks for the consult!
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A full plate enable hand can take 24 hours to print. Iâll stay up watching a pork shoulder or brisket smoke but I wonât stay up all night watching a 3D printer 
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I think itâs unfair that 3D printers donât need babysitting.
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Yup â Raptor Reloaded @ 140% with a 0.4mm nozzle is a 30 hour job (which is why I now print with a 0.6mm nozzle).
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My Roboxs have most of this built in. 9 point bed mapping. AC powered PEI bed sheet. Filament detection - realtime. If the filament stops moving, the printer attempts to fix it. If it canât fix it, it pauses the print and cools off the head. The only thing it doesnât do is monitor for airprints where the part gets knocked over. I havenât had a print fail due to bed adhesion in a very long time. Lightly sanded PEI is wonderful. No coatings, no mess, just wait for it to cool and the print pops off.
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Sure you werenât trying to 3d print a tribble? 
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I am guess you more often print in PLA? Iâve certainly found lots of materials I print in that donât stick awesomely to PEI (like nylon 910 or Bluprint really doesnât stick), so then you end up coating on top of PEI, which always affects later prints as itâs hard to get it totally off. Iâve taken to printing more exotic stuff on my glass bed (borosilicate) on my E3D BigBox since I have more control over the coatings (mostly use the Wolfbite coatings for each material). But even so you will have adhesion issues (heck Thomas Sanderlader and Angus have adhesion failures too, so itâs really just part of the game). I also have 9 point leveling on the BigBox and 4 point on my Taz6 in the lab, but stillâŚ
You really canât with the length of jobs; a long laser job is still < 1 hour. Not saying they shouldnât be monitored, just not practical for those of us who do really long prototyping jobs. The longest print Iâve done in the last 2 weeks was 59 hours, maybe the shortest was 2.5. Pretty hard to monitor anything for that long (plus donât really want to stay in the printer room for that many hours and breath amphora fumes).
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I use mostly PET, though I use PLA, ABS, nylon, PMMA, and several other exotics. PEI works like a dream for most prints, though on occasion I have to switch to a special high-adhesion build plate, a GeckoTek, for long prints with certain high-warp materials.
Sand your PEI with 320-400 grit sandpaper. Alloy 910 will pull the binder out of the PEI if you arenât careful. I prefer GeckoTek NY plate for nylon though. The HT plate works well for HT and XT.
I havenât opened my BluPrint reel yet.
Adhesion issues are really not something I think about unless I am working with ABS or parts with really small contact areas. 99% of the parts I print I just lay them out and hit print. I check the first layer to make sure it looks good and then I stop worrying about it.
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Yikes that bone must have got in the way ?..lol
That is the rack (as in rack and pinion) of a sternal retractor (the thing we use to open your chest for surgery) that warped during print (no idea why, subsequent prints worked fine, well obviously after reconstruction of my printer) and actually had high enough adhesion over the rest of the part to split the carriage in 2 and tear the bed off the heater, but after that popped off⌠Never had a nylon part do this before or since, but man, nylon always winsâŚ
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wow the nylon will withstand the retraction part of the retractor ?..I thought they were all made in stainlessâŚIma dummyâŚbut I learnin.
The are generally (and have been since Dr. Finocchieto patented it in the early part of the 20th century. We were experimenting, since we had some really novel ideas on reducing rib fractures and some other complications, but first needed an experimental platform (and 3D printing nylon is way easier than steel). If I had a dollar for every colleague who scoffed as âit will just fall apart if made of plasticâŚâ Iâd be rich. Ugh. I first pointed out that nylon is stronger than the patient. They didnât believe me, so I took one of the blades (3D printed on my BigBox) off the retractor and did this:
Then we autoclaved it and repeated, to show that even that didnât degrade the part.
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Hahaha suhweetâŚI knew nylon was toughâŚused it all the time at workâŚbut was just curious about the shear effects in the retractors. Thanks for the vid. 
That is âcoffee black as midnight on a moonless nightâWell, sort of â but the nice thing is that one of mine, my Z18, can be watched over via my phone and the built in camera â can even pause or stop it if need be. I like that.
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I had a run of sponge prints recently. Thatâs when the filament sorta-kinda jams but not completely, so you get a 3D shape very like what you intended, but with only about half or a third of the plastic and very little of it solidly stuck together. You can watch the whole thing on webcam and think itâs fine, but it isnât.
Replacing the fan on the hotend seems to have fixed it (I think I should really lay in a supply).
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I have octoprint on all of my printers, so they all have HD cameras (both for monitoring, and to record time lapses) as well as full remote control. Although I have to say, I disabled the mobile version since it is a terrible UI, and just use the regular web interface on my phone (works fine and is ironically more readable than the mobile version). However, despite all that, and the rumors by my colleagues to the contrary, I do actually sleepâŚ
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