Nozzle hitting at the end of the print?  

Active Member


I've had some success in the last 3 weeks since I build my MK3S+ but recently running into an issue where it seems like the nozzle might be too close to the print on the last layers.  I've gotten a few where it looks like the nozzle swirled the plastic.  Here's a pic of two recent prints.  The whistle on the left actually got pulled off the bed with only 2 or 3 layers left to go.


I don't know if this is a bed or Z calibration issue - the first layer seems to be fine.  Here are the same prints from the 1st layer side.

Kind of has me scratching my head a bit.  This is a recent development.  I am using an MK3S+.  One of these was printed using 3.9.2 firmware and the other with 3.9.3.


This topic was modified 5 months ago by DadOf6
Posted : 28/01/2021 3:57 am
Dan Rogers
Prominent Member

In the spirit of ruling out causes - have you considered printing with a 3 or 4mm Brim to see if that eliminates your "head hits the print" problem?  Also, there is a new slicer feature that actually does mash the nozzle into previously laid down traces - the Ironing feature.  

Whenever I have had a "thunk" and the print gets ruined (layer shift or spaghetti monster both start with a sharp sound, it was because of warping.  Long parts tend to do this more often than tiny parts - a long thin rod, especially with PLA, starts to lift off the sheet as subsequent layers are added.  Causes all kinds of mischief where the nozzle at first only smashes the printed layers, but eventually as the warp progresses, you'll hear the thunk and it's all over.

I'd suggest trying again - making sure to turn off Ironing in the Infill settings tab, and then add a 3mm to 5mm brim in the skirt-and-brim tab and see if you have better luck.

Posted : 28/01/2021 10:19 pm
Estimable Member

I think your first layer looks a bit high and you could adjust live-z so its more squished.

Have a look at this thread, its much easier to make the adjustment than using the Prusa built in lines and very small square:


Posted : 29/01/2021 2:03 am
Active Member


Thanks Dan - I don't have Ironing enabled, and I will have to play with the Brim settings.  I have had some warping though not always on long pieces.  With these two, the whistle on the left warped, but the long beam did not.  I seem to have more issues with warping when I use PLA.  I did try the whistle again with PETG for fun, and it came out perfectly, though I did a couple things differently on the slicer - little thicker, wider, & slower on the 1st layer, changed top & bottom fill to monotonic, and slowed down the print to 75%.

I appreciate the advice!

Posted : 29/01/2021 7:21 am
Active Member


Thank you!  I've done some playing with that and actually I thought I had gotten pretty close the last time I ran it.  They seemed pretty tight.

Posted : 29/01/2021 7:34 am

This is one of My first layers in PLA

the second picture shows how relatively small changes in Live Z, can make large changes in first layer quality... 
Your strands are still showing completely separate lines, they should merge together into a single sheet. 

But that is for FIRST layer quality, your distortion on the last layer may be due to other reasons.   are you using Prusa Slicer? 
Is your extrusion Multiplier set to 1.0 0r lower? 
is your filament diameter set to match the actual diameter of your filament?  when printing does your flow rate (in the Tune Menu) show 95%?

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 29/01/2021 5:21 pm

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