Question Nozzle rubbing previous layers

[Charlie_Brown 0]

Hello everyone, I have an Anycubic Vyper, and I am using Cura to slice my files ... and on some prints, mostly taller thinner prints like say a helmet ... you can hear the nozzle rubbing on the previous layer making like a grinding noise as it rubs across the filament that it has already layed down. It doesn't seem to affect the quality of the print, but it some cases it can knock the print loose from the bed. So i am forced to use a large raft area on all prints to avoid this happening. Sometimes it will stop for a few layers, and then back to rubbing again. Although it seems fairly steady the taller the print gets.

 

I have only been 3d printing for a month or two, so I am totally new to the scene and have no idea where to start ... so does anyone have any suggestions as to what settings I should try and modify to stop this from happening? If i was to guess, I would say that maybe to much filament is being pushed out, and its taller then what the printer thinks it is, but is there a way to control the amount of filament that flows? 

 

Thanx in advance guys

 

 

[Big_Ron 1]

did you try changing you Z hop?

[GregValiant 1,330]

Enabling Z-Hops at .2 to .5 will fix it but the noise might be a symptom and not the real problem.

If you have calibrated your E-steps then I would leave the flow numbers alone.

 

 

If there is sloppiness in your Z system on the printer, then it won't increment upwards consistently.  That can cause the rubbing as well.  Make sure your Z couplers are tight and they don't rub on the Z motor housings.  Some dry lubricant on the threaded rods can help.  Make sure your Z trolley wheels are adjusted correctly.  You shouldn't be able to wiggle the ends of the X gantry up and down.  You want that gantry to be nice and rigid but it should move smoothly up and down.

If the print head has looseness in it's trolley wheels then it can wobble and cause the problem as well.  Since yours is doing it up higher then the Z system could likely use an inspection and maybe some attention.

[Big_Ron 1]

how do you calibrate the-steps?

[GregValiant 1,330]

A fella named CHEP has a YouTube series called Filament Friday.  I'm sure he has a video on calibrating the E-steps.  It isn't difficult.  It needs to be done because the Steps/mm of the E motor determines how much filament is actually pushed.  When Cura asks for 10mm of filament it should get exactly 10mm of filament.  If it 9 then there will be under-extrusion.  If it pushes 11 then there will be over-extrusion.  Over-extrusion could be a reason why your nozzle is dragging.  When the E-steps are calibrated the prints turn out better so it's worth doing even if it isn't the main cause of your problem.