Second Layer Center prints rough while corners always good
Having an odd issue with my MK3S. Recently took apart part of the extruder due to a clog and now I'm getting great first layers but my second layers always have the corners where the layer starts and ends printed good but the center is really messy like the z-height is too low. I've done some testing by moving the square I'm printing to different part of the build plates and the failures are always about the same size. If I enlarge the print the well printed corners about the same size but the messed up area enlarges significantly.
I really don't know what's causing this on the second layer as z-height shouldn't affect this at all, but I've tried changing it with no luck. But all my prints do it, old ones I've printed before, new ones. and I'm really not sure what I did.
Printed on PLA with the same brand/color that I had no problem printing with 2 days ago (clog was caused by a different PLA).
Best Answer by Neophyl:
Could be cooling related. As an experiment try the same square but with the filament settings set to have no fan for the first 2 layers instead on just for first layer. If the 2 layers at that point look ok then it would be an indication that its fan related.
RE: Second Layer Center prints rough while corners always good
Could be cooling related. As an experiment try the same square but with the filament settings set to have no fan for the first 2 layers instead on just for first layer. If the 2 layers at that point look ok then it would be an indication that its fan related.
RE: Second Layer Center prints rough while corners always good
@neophyl
Thanks, this it. I've printing at slower speeds (instead of fan off) for a few tries now and so far has shown the problem goes away just at a 10% decrease in speed. Now I guess I just need to figure out why my extruder fan/duct isn't working as well as it should. Looking at the assembly guide I see that the fanduct is supposed to be parallel with the build plate so that's correct. Maybe there's some dust that needs to be cleaned out.
But now that I know that the problem is cooling I can work to get it solved. Appreciate the help.
RE: Second Layer Center prints rough while corners always good
Actually I was thinking it may be working too well. The fan will spend longer over those middle areas as the lines are longer than in the corners, so that means there will be a lot more cooling in the middle, which may be causing the non adhesion of the print layer. That's why I suggested trying it without fan for both layers.
RE: Second Layer Center prints rough while corners always good
You might want to consider a cold pull to clean out any of that PLA that was clogging. A small chuck of it might still be in the nozzle and causing the reduced flow you are seeing.
RE: Second Layer Center prints rough while corners always good
Interesting. I'll play around with the fan speeds too. Never would have thought of that.
I did several cold pulls when I had the clog and one of them was the reason I had to take apart the extruder as the tube inside had moved with the pull so I had to push it back down.
RE: Second Layer Center prints rough while corners always good
One thing you may want to print out several of are the little bowden clips that e3d supply with their V6 hotends but that for some reason Prusa don't seem to fit. Basically they go in under the black plastic ptfe tube clip to keep it raised. That locks the tube in place. Then when you next have to go into the extruder you can fit one.
Something like https://www.thingiverse.com/thing:2478545
RE: Second Layer Center prints rough while corners always good
Ya, I've seen people with some of those. Thanks for the link.
RE: Second Layer Center prints rough while corners always good
Also - if you disassembled the hot end (removed nozzle/heat break from heater block) - did you follow the E3D V6 assembly guide when putting it back together? Minor but essential details in the process can cause what you are seeing, too.