Stringing and missalignments in prints
Hi all,
I'm a palaeontologist and am trying to print some fossils for our research and teaching collections. I've recently come into an issue with my prints, where there are lots of stringing and shifting occurring (see included images). I've tried doing a factory settings reset on everything, changed spools, resliced my files, and am still getting the same print errors. To me, it looks like the filament is not flowing through the nozzle properly, but it seems to flow fine when I run it not during a print. Any advice would be valued.
After midpoint in print the printing started to fail, with progressively more strings and less material extruded and print shifting. 
This is the start of a reprint of the fossil skull with all settings reset after successful benchy. 
This is the start of a reprint of the fossil skull with only filament changed. 
This is the start of a skull print. 
This is directly after a successful benchy with nothing changed.
RE: Stringing and missalignments in prints
Update: I ran a temperature ramping tower and spatula print with no issues so set up a larger print and got the same failures as before. I'm completely stumped.
The light stringing is probably another case of damp filament, always a problem at this time of year. Museums usually have humidity controlled storage so you might beg a corner for your filament stock. Dry your working spool(s).
Your underlying problem is similar to those frequently encountered by medical 3D printing in that complex organic shapes with no simple flat surface to base the print on are inherently tricky on single material printers. The auto-generated supports approach closely to the surface of the model but do not quite touch (else they would fuse inseperably to the model) - so there is inherent 'though slight wobble. For most prints with a reasonable area actually contacting the base this doesn't cause issues as the stable part corrects the rest.
The best answer is to use a multi-toolhead machine and soluble support material which *can* be allowed to touch the surface.
But there are sometimes workarounds, if you would like one of us to take a closer look either post a link to the source file or save your project as a .3mf file
Files > Save Project as
Zip the .3mf and post it here. (Must be zipped, forum will silently drop unzipped 3mf)
- and may be able to derive a workable printing strategy.
And try contacting your local teaching hospital/university where the 3d printing techs face this sort of thing daily.
Cheerio,
RE:
Hi,
are you able to share an "interesting" skull e.g. on "Printables" that would somehow inspire the kids? I might give it a shot, let's see what I get. But I'd start with down-scaled versions.
(is the spatula broken or not? Some stringing wouldn't cause serious issues on that one, it's an extremely robust, popular design.
If problematic, stick to that one to sort out problems.)
RE: Stringing and missalignments in prints
Thanks for the suggestions. The problem is that it's also failing the same way for some of the calibration prints. I've been able to get a hold of PRUSA support, and it looks like one of the internal plastic parts was not formed properly, so the gearbox is overpushing the filament, which is causing sporadic jams. I'll be drilling out the piece, and we are hoping that will fix the issue.
RE: Stringing and missalignments in prints
If this solves the problem, it would be really nice if you could publish here a picture of the part and of the problem to help future members with the same issue
RE: Stringing and missalignments in prints
I had similar issues early on. The MK4S Bogie Idler & Main Plate mod fixed it for me.