Lines in layer uneven

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Niho3D
Posts: 13
Joined: Tue Dec 16, 2014 3:20 pm

Lines in layer uneven

Post by Niho3D »

As i start print (thats where it gets obvious) the lines within the layer are uneven.(see pic.)
It is wrinkled because i ripped it from the bed. :twisted:
I tried sloving it down a bit and increasing flow to compensate but unsuccessuful.
Its PLA printed at 204C and 60 C bed temp.

I have yet to check if there is something at the top of the nozzle that might cause dragging.

Any ideas?
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20150123_165021.jpg

Dreide
Posts: 176
Joined: Sun Sep 29, 2013 12:32 am
Location: Lausanne, Switzerland

Post by Dreide »

I guess the lines are printed diagonally? It this case it is probably just backlash and you could try minimizing it by putting a bit more tension on the belts, but you cannot avoid backlash completely.
Felix 2.0->3.0dual * Repetier (host+firmware) * KISSlicer Pro, Simplify3D * Cubify Design

Dreide
Posts: 176
Joined: Sun Sep 29, 2013 12:32 am
Location: Lausanne, Switzerland

Post by Dreide »

To be more clear, if this pattern is caused by backlash, then it is the balance between the X and Y backlash. If the backlash is the same for both dimensions, you should not see such pattern.
But loose timing belts are not the only source of backlash. Any mechanical play will cause backlash and I guess that it is worse along Y because of the longer moment arms and the more indirect force coupling as compared to X. Since the effective moment arm lengths are slightly different for different printing positions, the observed effects might look different depending where on the bed the object is printed.
One source of backlash might also be the print bed screws. If they are too loose, the force needed for shifting the bed laterally (with respect to the mounting) might be weak enough to be overcome by the acceleration momentum when reversing printing directions or by the drag created by the extruder when pushing down filament (especially for the first layer). Obviously, the print bed mounting should allow to give in to the lateral forces that develop when the print bed temperature changes. Otherwise, if the screws are too tight, these forces will bend the print bed when it is heated up. So the screws should not be tightened too much.
Felix 2.0->3.0dual * Repetier (host+firmware) * KISSlicer Pro, Simplify3D * Cubify Design

Niho3D
Posts: 13
Joined: Tue Dec 16, 2014 3:20 pm

Post by Niho3D »

Thanx guys.It was diagonal printing at this place.
I thought it may be that and i have noticed belts are a bit saggy.
I am trying to tighten them bit by bit as i am not quite sure when tight becomes too tight.I know this for belts on machinery but machinery has much sturdier construction.Other elements dont show (as far as i can see) any play.bed bolts are tight enough on springs to keep the bed from playing.

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