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Tyler Shuman
(@tyler-shuman)
Eminent Member
Nozzle dragging on top of prints

It seems that any time I print without zhop/zlift, the nozzle will audibly drag/catch on the top of the print, particularly during travel movements.

Is this just normal behavior? Do I pretty much need to always have zhop/zlift?

Posted : 20/03/2018 1:05 pm
RH_Dreambox
(@rh_dreambox)
Prominent Member
Re: Nozzle dragging on top of prints

I ask of pure curiosity. Why do you want to turn off Z-lift?
Is not that a good feature if it prevents the nozzle from scratching the surface?

Bear MK3 with Bondtech extruder

Posted : 20/03/2018 2:01 pm
Tyler Shuman
(@tyler-shuman)
Eminent Member
Topic starter answered:
Re: Nozzle dragging on top of prints


I ask of pure curiosity. Why do you want to turn off Z-lift?
Is not that a good feature if it prevents the nozzle from scratching the surface?

I don't necessarily want to turn it off. It does have a slight negative impact on the surface quality of some prints (for example, leaving little spots on the top of raised lettering), but that's all pretty negligible.

However, on my other printer (monoprice maker select), I haven't needed to use zhop.

So I guess I'm mostly just curious if it's normal to have to use this on the prusa. I don't mind using it, but I'm wondering if the fact that I need to use it is an indication of something being wrong with my printer. Like perhaps it's a sign that I'm overextruding.

Posted : 20/03/2018 2:54 pm
RH_Dreambox
(@rh_dreambox)
Prominent Member
Re: Nozzle dragging on top of prints

I have not yet written something with rasied letters yet, but it's like you say that small spots may sometimes occur on some top surfaces, but not always.

Bear MK3 with Bondtech extruder

Posted : 20/03/2018 4:57 pm
Kwaad2
(@kwaad2)
Honorable Member
Re: Nozzle dragging on top of prints

Once linear advance comes out those over-extrusion blobs will go away.

Hi, I'm Sean. I used to work on CNC machines.
I try to not make mistakes, but the decision is YOURS.
Please feel free to donate to my filament/maintance fund.

Posted : 20/03/2018 5:41 pm
freaky-m0
(@freaky-m0)
Active Member
Re: Nozzle dragging on top of prints


Once linear advance comes out those over-extrusion blobs will go away.

Do you mean the "blobs" and marks that we can see like mentioned in this thread? >> https://shop.prusa3d.com/forum/original-prusa-i3-mk3-f30/first-print-artifact-t14898.html#p72404

Posted : 21/03/2018 1:01 pm
Kwaad2
(@kwaad2)
Honorable Member
Re: Nozzle dragging on top of prints



Do you mean the "blobs" and marks that we can see like mentioned in this thread? >> https://shop.prusa3d.com/forum/original-prusa-i3-mk3-f30/first-print-artifact-t14898.html#p72404

Exactly what I mean. 😎

Hi, I'm Sean. I used to work on CNC machines.
I try to not make mistakes, but the decision is YOURS.
Please feel free to donate to my filament/maintance fund.

Posted : 21/03/2018 1:35 pm
freaky-m0
(@freaky-m0)
Active Member
Re: Nozzle dragging on top of prints




Do you mean the "blobs" and marks that we can see like mentioned in this thread? >> https://shop.prusa3d.com/forum/original-prusa-i3-mk3-f30/first-print-artifact-t14898.html#p72404

Exactly what I mean. 😎

I thought i read something that it shouldnt affect the print quality (disabled LA) 😕

But if that's correct, anyone should get those artifacts on their print? It's with every top layer for me.

Posted : 21/03/2018 2:42 pm
Kwaad2
(@kwaad2)
Honorable Member
Re: Nozzle dragging on top of prints





Do you mean the "blobs" and marks that we can see like mentioned in this thread? >> https://shop.prusa3d.com/forum/original-prusa-i3-mk3-f30/first-print-artifact-t14898.html#p72404

Exactly what I mean. 😎

I thought i read something that it shouldnt affect the print quality (disabled LA) 😕

But if that's correct, anyone should get those artifacts on their print? It's with every top layer for me.

Linear Advance is a "smart filament pressure management system".

EG: If you feed 1mm of filament, in 1 second, it will continue to ooze for 3 or 4 seconds.
LA somehow with voodoo magic... rather than "feeding the filament" it "applies the proper pressure to extrude at a certain speed."

Before I started butching/modifying the default Prusa profiles I was plauged with the same issues. I however made them much... smaller.
Simply updateing the firmware and turning on LA, has virtually removed all trace... I do have a new issue though, and it will require re-calibration.

Before I did the firmware update I could print support on/in/around/through/over/under anything, and just pop it off with my fingers with ease, leaving virtually no marks on the part. I tried to print something and it was a TOTAL FAILURE. Becuase the support struture was bonded in so main places. (I haven't done any tuning yet, as I expect things to change quite a bit when the offical 3.2 alpha is released, hopefully, this week.

Hi, I'm Sean. I used to work on CNC machines.
I try to not make mistakes, but the decision is YOURS.
Please feel free to donate to my filament/maintance fund.

Posted : 21/03/2018 4:04 pm
Chris
(@chris-16)
Reputable Member
Re: Nozzle dragging on top of prints


However, on my other printer (monoprice maker select), I haven't needed to use zhop.

it would work in the mp MS as well and keep it from dragging BUT the MS is so slow on zhop that you would double the print time. This is coming from a former wanhao duplicator i3 owner.

as far as why use z hop, There were many many times on my duplicator z hop would have been much better than dragging the nozzle across, it was just that printer was so slow that dragging usually was not that loud or particularly damaging, although on a couple of abs prints the layers shifted.

one thing to check, if you print high temp materials, is if the shroud is doing the dragging: https://shop.prusa3d.com/forum/original-prusa-i3-mk3-f30/drooping-fan-shield-t13911.html#p63266

Posted : 22/03/2018 5:51 am
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