Need direction / guidance on further troubleshooting. Mk3S acting erratically.
Hello,
I have been trying to get my Mk3S up and running for w hile now.. It was OK for a couple weeks, then everything just went sideways, and I can't seem to get it dialed in. Sometimes prints will adhere, then immediately after printing a small successful print, nothing will adhere, even after cleaning the bed. I print mostly in PLA, and have been witing to try PETG until I know things are more dialed in. I have the Textured sheet, have washed with soap and water, 91% IPA, and still nothing.
Last night, I was able to print a test square, and the adhesion was good, (Live Z was at -1.380) then I immediately tried to print it again, and the filament just became a big blob. My Mesh Bed Leveling in Prusa Connect shows that it's at .426mm.. Self-test says the machine is perpendicular.. I was able to print a PINDA probe tool last night and reset it to .8mm, and then calibrated Z axis, and then I got my good test square. I have tried to up my probe and bed temps because where I print currenlty sits at 14-15C and that still hasn't helped. I have gotten a filament dryer, and that seems to have evened out the filament when it exits the nozzle, but I have seen a severe contraction of filament when I load filament. It extrudes looking good, then when it stops extruding, the filament shrinks up really quick into a thick extrusion, not the normal thin one you would expect. I have done several cold pulls, and just put on a brand new nozzle last night as well.
The weird thing, is sometimes when the machine starts with the pressure line before printing the border, it will have little edges that stick up at the beginning or end of the line. Then the border might have the same thing and not adhere to the bed. I keep reading that ambient temperatures aren't supposed to affect PLA, and that moisture isn't supposed be be as big of an issue either, but at this point I'm not sure. Because of the cold, I am tempted to build a Lack or similar enclosure, but I can't get my printer to print reliably enough that I could print the brackets or hinges for the doors.
Then there is the random crashes.. Filament is not pulling hard on the extruder, but if the printer had a random Z crash, the print will for sure fail when it recovers. It will still try to print, but I am almost guaranteed that the layer will not adhere, or it will fail somewhere in the first layer or two. I recently added an RPI 4 and Prusa Connect, but I don't think this would have this kind of effect on the printer to have this kind of print failures. I know the Prusa is supposed to be awesome, and it is supposed to print reliably, but this kit has been a problem for my uncle in-law who built it before he passed, and now for me since I got it from his widow. I want it to be awesome, but I just don't know where to got without some kind of direction, or throwing parts at it that it may not need..
RE: Need direction / guidance on further troubleshooting. Mk3S acting erratically.
Hi SpinningHat, that's a lot of text and no pictures which makes it a bit hard to find a point to start. But let's try anyway.
You are right, the MK3 is a very reliabe printer and should be printing PLA repeatingly without issues.
Most of the things you describe, including the random crashes, can be explained by bad adhesion causing models to detache from the bed. The most commen reasons are: inadequate first layer calibration and greasy surface. To rule out the former you should run the first layer calibration (the build in one from the LCD menu) and take a picture of the resulting square still on the bed and post it here. Since you inherited the printer it might be a good idea to do a factory reset first to make sure there are no desturbing values stored for example in the bed level correction.
Cleaning the surface is the second most important thing. A lot of soap and hot water work very well, IPA does as well BUT you used 91% IPA, depending on the remaining 9% that might be a problem. If you got this from the drugstore there might be oil or other remoisturizing things in there to make it better for the skin which make it worse for bed cleaning. The textured PEI sheet is particularly difficult to get grease free once it is contaminated...
The described behaviour of the filament after extrusion sounds like normal behaviour for silk PLA, regular PLA should not behave like that. What kind do you use?
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RE: Need direction / guidance on further troubleshooting. Mk3S acting erratically.
Hi Robin,
Most of the time, there wasn't anything left to really take a photo of. The 91% IPA I use is a sterile antiseptic IPA. ( https://www.target.com/p/isopropyl-alcohol-91-32oz-up-38-up-8482/-/A-13970972) Per the info it is only IPA and sterile water. Once I use this up, I will look for a higher %, but this is ok for now. I think I may have solved the bed adhesion through a couple different things. I re-sliced some models that I know were good with higher overall 1st layer temp, and then higher print temps for the reamining layers, and a warmer print bed. Also, I washed the plate with hot water and dishsoap, then used 1200 grit paper to lightly rough up the surface. I had read here and other places that 6-800 grit paper was acceptable, or 0000 steel wool others had suggestted.
That has gotten me to be able to print successfully small items, as well as a larger terrain STL That I have been waiting to print for a while now. I was also able to print some of my own designs overnight in PETG that have turned out very nice.
My new question, is I had a print fail because the filament broke, but the filament sensor didn't trigger the printer to pause. I have never been able to get the autoload to work, so I have reverted to manual load of my filament. When I try to test the sensor, it keeps telling me to unload the filament and try again, even though there is no filament in the printer. I tried to unload and reload, I even found some spacers on printables that didn't seem to help, and I have the screw just barely tight on top.. Do I just have a bad filament sensor?