Help with first print?  

RE: Help with first print?

Also trying to unload the filament this morning to check the hot end and extruder, and to remove the out of filament sensor...  but the filament won't unload.  I've tried a few times and the extruder tries to unload it but fails.  The mystery deepens.  

RE: Help with first print?

Got the filament unloaded.  It had deformed at the hot end so it wouldn't fit through the tube.  I unscrewed the tube, snipped off the chunk, and it backed out ok.  Now trying removing the filament sensor.

RE: Help with first print?

Update: I removed the filament sensor which seems to have helped with the uneven extrusion.  I had an experienced friend help me really dial in the XYZ calibration.  The fast even layers are now printing pretty well, but we are definitely still stumped by problems with detail areas where it seems like not enough material is coming out of the printer?  These three shots in particular show the issue:

https://drive.google.com/open?id=1ZAXy1ROjhjzoH3kGarTRyYPVP5Oncjnj
https://drive.google.com/open?id=1un75sYuH5TGo9KL5ijAmA5ydpbJNT4nB

And here's a picture of the back of that same piece to show that the Z axis is calibrated pretty well:

https://drive.google.com/open?id=1XDl14dXiNlvccVGaCG0hPcBkjqvnn_c6

Thanks for any help!!

-Cw

RE: Help with first print?

Ok, still struggling with this.  I tried really cranking down the Z offset which gave me a better result on the first layer, but then the same failure mode on subsequent layers where it just feels like not enough material is coming out of the nozzle or it's not coming out at the right rate.

Here are two more photos... this is the first two layers of the Prusa logo sample... the first layer is the smooth side:

https://drive.google.com/open?id=1C4BrDzsBsKS48uIX5iNUVKEHkovtLZST

https://drive.google.com/open?id=1ZK1C-gFhL-rkck18uHtGPPhEsyIWwPeJ

I'm going to take a break from it now because it's making me a little crazy :).

-Cw

RE: Help with first print?

I would say first thing to check is your hotend assembly. The gap between heater block and heat sink needs to be as short as possible.

See https://forum.prusa3d.com/forum/general-discussion-announcements-and-releases/prusa-mini-filament-frequently-jams-after-about-2-hours-of-printing/

RE: Help with first print?

what is your Z calibrate value, mine is  - 0.87

RE: Help with first print?

Final update because I'm glad to say this is resolved!

The first impactful thing I did was to follow the procedure to replace the hot end PTFE tube, and in that process of doing that significantly reduced the gap between the heater block and the heatsync (thank you for the tip @bobcousins).  That made things better but I was STILL having under-extrusion problems.

I then fiddled with increasing the flow rate and getting really aggressive on the z-axis calibration setting which helped a little more and confirmed that there was some sort of under-extrusion problem.  And then I saw firmware 4.0.5 RC go out and it also mentioned a fix for under-extrusion: "Based on the internal testing it was discovered that there is a slight under-extrusion during the print. To compensate for this behavior, the e-steps value was adjusted by 2.5 %."  I grabbed this firmware update and confirmed that it does indeed fix exactly the problem I was having!  What a huge relief.

So far everything I've printed has been tight.  Now onto the fun part of playing with it. 🙂

RE: Help with first print?

glad hear your success,  due to covid19 i cannot use my mini T_T. good luck.

RE: Help with first print?

Posted by: @corywest

Also trying to unload the filament this morning to check the hot end and extruder, and to remove the out of filament sensor...  but the filament won't unload.  I've tried a few times and the extruder tries to unload it but fails.  The mystery deepens.  

Try pulling the filament out as soon as it backs out of the extruder if the thing starts cooling off the filament gets hard and won't come out of the extruder.

RE: Help with first print?

Posted by: @charles-k9

Try pulling the filament out as soon as it backs out of the extruder if the thing starts cooling off the filament gets hard and won't come out of the extruder.

An old trick on the Mk3 is to heat up and extrude a bit of filament, then unload. This reduces the odds of forming any blobs from preventing removal.