why will some prints work perfectly and others not at all?  

RE: why will some prints work perfectly and others not at all?

I tried this print once more today.

1. cleaned the printbed with isopropyl alcohol
2. made sure to print from SD, not from octoprint
3. lowered "distance nozzle to printbed" so that the nozzle would not push the prints as much (hoping for better adhesion)

Result:

This time (as compared to the video I posted yesterday), at least the filament clips printed fine before things started going wrong; however, I don't understand why this is at all. The printbed was 100% clean. Nozzle had been further away (even though these steps are very small), extruder and bed had been preheated accordingly (PLA material).

I am kinda hesitant to keep trying this print, but I don't know what else to do. Those time I printed the prusa test prints, everything worked fine. So there is no point in keeping to print those tests.

One thing came to mind while typing this: I will try the failed print (from the image above) once more with different filament. If this changes things, what should I do when I want to print with this filament? The gray filament (first post, bottle opener and batman) worked fine and was delivered py prusa. This yellow stuff is no-name filament. Both were PLA.

How can I fix this? Thank you.

RE: why will some prints work perfectly and others not at all?

Just in case anybody else encounters a similar problem: I switched from PLA to PETG. This sticks fine now. I assume the filament itself was bad....

Either way, I'm still interested in a solution regarding the filament now. Should I change temperatures or what is the best way to experiment with this?

RE: why will some prints work perfectly and others not at all?

Posted by: @bnstr86

Hi everybody,

I have had my i3 mk2s for a couple of months, but due to problems have not been printing much. Last week, the spare parts I needed to fix it arrived, I finally fixed it, recalibrated it, etc., but printing still does not work as expected. Here is an image of two test prints I made.

They turned out pretty well. After a total of 4 test prints, I thought I'd print something other than these, but none of those prints worked.

https://forum.prusa3d.com/wp-content/uploads/2020/05/video_2020-05-14_09-42-16.mp4

EDIT: no matter what, the video doesn't seem to be embedded in the post. However, you can view it here https://forum.prusa3d.com/wp-content/uploads/2020/05/video_2020-05-14_09-42-16.mp4

(sorry, dumb instagram story video, the original file would not be accepted as upload media)

Printing starts out fine, but eventually parts will not stick to the bed any longer. I am using PLA; they gray PLA used for these test prints was by Prusa, the yellow was some generic brand. However, this happened with the prusa geometry dash PLA as well, when I tried to test print "Marvin" from the SD card that came with the printer.

It seems to me as if prints below a certain height will work, but once the height increases, something messes up. I calibrated X,Y,Z, Z on it's own, and the manual Z profile (sorry, English is not my native language; I mean the part where you manually adjust the Z axis in little steps to assure it is not too close or far away to/from the print bed). Self test was all positive as well.

I am running the latest official firmware. I have octoprint connected via USB. I don't know if it was coincidence, or if prints from the SD card worked fine and prints sent via octoprint won't; however, I don't exactly remember what I printed how (sd card / octoprint), so I cannot say for sure.

What can I do to fix this? Or to find the cause of the problem?

 

Thank you for your ideas 🙂

Try switching from PLA to PETG.

RE: why will some prints work perfectly and others not at all?

@bnstr86

Have a look there:
https://forum.prusa3d.com/forum/english-forum-general-discussion-announcements-and-releases/lets-talk-bed-adhesion/

I am sure that is the solution for you.

Best regards, Clemens

RE: why will some prints work perfectly and others not at all?

I think that the main reason that prints are sometimes inconsistent is that there are many, many variables, some of which are not obvious and that there are many unwritten details and techniques that are learned by trial and error while climbing the learning curve.

There also appear to be some 'magic bullets' which appear to work some times, but then fail at a later time.

I think that thread posted above about bed adhesion should be required reading, start to finish, for all new users.

There are some things that are agreed upon by the majority of the users, such as the printbed being Really Most Sincerely Clean.  We'll never agree on whether water-based solvents (dish detergent) or organic solvents (alcohol, acetone) are better, but we learn the hard way that a seemingly meaningless greasy fingerprint can and will totally ruin a print.

Another thing that's agreed upon by Prusa users is the importance of 'dialing in' that Z calibration.  Which method or which test print is used is subject to debate, but it's necessary to get a good handle on this with the I3.

Attention to detail during assembly.  Often overlooked.

I think that many of the reported failed and inconsistent prints have to do with the above three factors.  There are others, however.