When good machines go bad

This is a story about how the Universe likes to remind us that we should not be without humor and humility.

I've been 3D printing now for about 3 years or so.  In that time I've had my rocky experiences - 3D printers are as much art as science and the whole enterprise takes a decent deal of finesse and just a pinch of luck, so sometimes you see your machine printing in midair with the filament having run out long ago, or you get spaghetti when things don't adhere to the print bed properly, that sort of thing.  It happens, and I have to account for what retailers might file under loss, shrink, or breakage, in case of that exact type of happening.  But I haven't had it happen much, and not at a catastrophic level.  Well, I hadn't had it happen at a catastrophic level...

My very first machine was an XYZPrinting Da Vinci Junior.  Sub-$300 and with a couple of restrictions - it only prints PLA plastic, it only takes proprietary spools from XYZ themselves (unless you hack it), it doesn't have a heated bed and its build volume is 150mm (just under 6") cubed, but hey it's got automatic leveling!  In the beginning, I had to actually get the company to replace it twice due to some crazy problems.  But since then, it became a decent workhorse and aided in the development of my current products.  
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In 2018 I tried a bigger Da Vinci 1.0A, but didn't get along with it, so I added a Da Vinci Junior Pro to the mix instead - this one can use any type of PLA (and more!) and has more robust print settings in the company's proprietary slicer.  That Jr. Pro became my main machine and opened up more possibilities.  A few months ago, though, I realized that for lots of my printing goals I'd need a bigger printer.  Looking around at various costume and prop pieces I'd made over the years using the "bash together parts from wherever you find them" method, I wanted to be able to model and print similar pieces at scale.  So, I preordered a new-to-market Creality CR-10S Pro, with a huge 300x300x400mm build volume and all the nifty features like quiet drivers, a touchscreen, and a bed leveling sensor to assist beyond hand leveling!   

Also in the meantime, a friend of mine just plain gave me a small machine, which he had tried and failed to be able to use, with an extruder that had jammed up and he just kind of gave up on it.  A cheap machine from Monoprice, I'm trying to find a new entire extruder assembly for it but MP were either being elusive or didn't understand my question.

SO!  That all means that as of last week I had, ostensibly, two cheap working printers, one mid-grade large format printer, and one cheap dead printer.  None of these are expensive machines, and that is because I've found in all my research that people have exactly the same issues with 99% of printers at all pricepoints.  Sounds nice, right?   Until it's not.

Out of the gate, several days on end with the CR10S Pro and I can't get it to print anything well.  The test print built into the machine came out okay once I got the Z-height settled during the first few layers.  But since then, I can't even get the same performance from two prints back to back.  It's like the Z is just guessing at its own offset no matter what I do to set it, and it never guesses the same number twice.  Not usable for production items!  One down.

Then yesterday I came home to all pieces of a large batch of Bullseye Buttons having fallen off the bed of the Jr. Pro - and molten plastic clogging not just the nozzle but the entirety of the hotend - pushing some of the extruder housing's panels into complete deformation.  Even when heated completely to melt the plastic against the nozzle itself, the rest is rock solid and isn't near enough to be impacted by heating the extruder.  What the hell?  I've never seen anything like this before.

You can see in this photo here that the candylike melted PLA is jammed up next to the nozzle - that clog goes about halfway up the interior of the whole black casing.

And the crumpled metal attached to the blob I managed to wrench off?  That was the flat aluminum plate surrounding the nozzle to shield the surrounding area from the direct heat of the 200+ degree (Celsius) hotend itself.

XYZ DaVinci Junior Pro extruder alllll full of plastic after a mishap.

​With the Jr. Pro suddenly out of commission I tried to make do - the Junior can't print my Gizmodorks PLA without a chip hack that I never bothered to do, but the two models are extremely similar, so I set about putting the Junior's extruder into the Junior Pro.  Nope, apparently it isn't exactly the same model hotend so the workings don't exactly work even though it fits the slot and has the same connections.

So then I put the Junior's extruder back into its home.  And....  Can't load the filament.  Somehow, in my haste to connect and disconnect everything when switching it, I screwed something up inside - the metal receiver tube that the Bowden tube fits into came off its nut and fell sideways across the circuit board inside the extruder assembly - which shorted out the machine into a flashing flickering mess (temporarily), but moreover I cannot get everything inside there to align properly now, so filament gets down in there and apparently hits a physical dead end.

Great.  I've got deadlines on some of these things, ya freakin' robots!   And look at you, all four of you are useless!

Creality have been on vacation but they'd better grant me an RMA when they open back up tomorrow; their newest machine is just not ready for primetime as far as I can tell.  I ordered a new extruder for the one XYZ machine, and am going to just get another Jr Pro to replace the older Junior I think.  They're super cheap now, and like I said - XYZ machines get a bad rap because of the proprietary elements, but mine have been mostly stellar until last night!  As for the Monoprice machine, I will have to see when I can find a new hotend for it.

Or - Anybody want to buy some dead 3D printers, cheap?