Layer misalignment

[Athul 0]

Hi,

I was getting reasonably good quality prints from my 3d printer. Yesterday I printed a pretty large model with lots of support(0.2 mm layer cura slicer also tried slic3r). It was a 25 hour print and at the middle of the print I noticed some layer misalignment or shifting(not sure which is). But I didn't tried to adjust anything since I didn't want to mess it up even more. But the finished print has lots of misalignment or shifting problems especially in area of solid layers. I printed another part which only has few supports(0.1 mm layer), it turned out good, no problems, then I tried a belt buckle with support which also has lots of layer misalignment or shifts. So i think this issue only happens when there's lots of supports. I re-tightened belts and slightly increased motor current for X and Y, after the first print.

While printing I noticed a lot of  nozlzle dragging with support and solid layers

I got lots of suggestion about over extrusion,

now I don't think it's due to over extrusion.

I marked 120mm in filament and tried to extrude 100mm, but I only got 93 mm, so I had to change my E_steps from 90.95 to 98.02 to get 100mm.

SO If 90.95 had dragging then 98.02 will have more dragging, So what could be the cause?

Any idea what causing it?

P.S :I don't own a ultimaker, it's prusa i3

Edited June 24, 2016 by Guest

[Nicolinux 288]

Hi,

it sure does look like a hardware issue. Maybe the way supports are printed triggers the hardware problem. My first idea would be the belts too, but you've checked that already.

How do you print? Via USB or local with an sd card? Maybe the .gcode is corrupted or the host produces errors during a print (bad RAM or something like that).

[Athul 0]

@Nicolinux

Tnx for the reply,

I use USB and Repetier host as the host . Computer wasn't busy at any time of the print, and I didn't do anything on it during the entire print time?

Can you tell me a better way to calibrate extruder

I use 0.4mm J head

my E_steps was 90.95 at the time of above print

I followed some videos

First measured 120 mm in filament extruded 100 mm

I didn't get 100mm only 95-96mm

recalculated Esteps to 98.02 to 100mm

Printed a single perimeter object

choose default extrusion width as 0.67

got 0.71 at the printed output

so extrusion multiplier (0.67*1)/0.71 =0.94

but with 98.0 E_steps and 0.94 extrusion multiplier my test print was clearly over extruding

[gr5 2,224]

I'm guessing backlash/play. I'd like to see an overhead view to be sure. On more photo zoomed in on part of your part please.

If it's play then it would shift on certain layers because it's going clockwise versus counter clockwise.

[Athul 0]

Hope these helps

What's a play???I'm heard of backlash

[gr5 2,224]

Play and backlash are the same thing. You can look the word backlash up on wikipedia.

From the top view I would say you have play. I'm not sure if it is serious enough to cause the problem the you show ("misalignment") but maybe. So fix the play first. Here is something that describes why you get the pattern you have on your top layer where you have 2 lines close together and then a gap:

https://ultimaker.com/en/community/2872-some-calibration-photographs#reply-16137

Play is usually caused by loose belts - usually the belt connected to the motor. It can also be caused by belts too tight (too much friction). What kind of printer is this? It can be caused by the head being a bit loose (see if you can push the nozzle around without the belts moving). Or the endcaps on a UMO can be too tight (try loosening 4 of the 8).

[Athul 0]

I'm using prusa i3 http://makemendel.com/3d-printer/prusa-i3-kit and I already have belt tighteners on both x and Y axis

Also during the print my nozzle was dragging on the solid layers and support structures

Could that be due to over extrusion

My nozzle size is 0.4 j head

layer height I used 0.2mm

jerk 10

acceleration 9000 for both x and y

Travel speed 130

bottom layer speed 0

infill speed 60 top/bottom speed 50

outer shell speed 5

inner shell speed 50

print speed 50

all in mm/s

materilal PLA temp 200

no bed temperature

Edited June 29, 2016 by Guest

[dobrikk 2]

Looks like Z wobble

Are you useing lead screws or threaded rods on the Z axis?

[Athul 0]

Looks like Z wobble

Are you using lead screws or threaded rods on the Z axis?

 

I'm using M8 threaded rod z axis. Like all prusa models I have two rods which are coupled to the motor using flexible couplers.

I replaced my two brass threaded rod nuts and bearings and done test cubes and they came out okay(there was banding issue but no layer misalignment)

but after that I print the same model that I posted above but scaled down to a small size, but they came out with the same defects

could this be a threaded rod problem, but how could a SS threaded rod become damaged??

Like you said I also noticed bandings

From my research through forums I found these causes for banding

1. Temperature variation

                    no matter what my print temperature it does not change even change 1 degree in both direction.

    eg:  print temp 190 degree the variation will be limiter to 180.90 - 190.30

so I think this is not the reason

2. Variation in filament diameter

 the filament I use do not have more than 0.02 mm variation

3. Bearing problem

                  I checked my bearings it moves smoothly over smooth rods. Even though I changed it , the new one also moves smoothly

4.  Threaded nut

   I replace those too. My printer is working for past 1 year and I work it every day. But I haven't greased it yet. I will do that

Is there any other causes for that?

Edited July 1, 2016 by Guest

[dobrikk 2]

Try to make a test cube that is abit higher than where your problem begins on your print.

I also had perfect test cubes 20x20mm and 40x40, but when I printed something higher I got problems on my Prusa I3 with lead screws.

I changed out the motor, cupling and rod with a fully integrated motor, and then may prints became much better.

All in all I got tired of fidling with the Prusa i3 and bought an Ultimaker 2. More prints and less adjusting and tweeking.

http://www.ebay.com/itm/NEMA-17-Stepper-Motor-Integrated-8mm-L100-600mm-Leadscrew-Nut-for-3D-Printer-/141947097310?var=&hash=item210cb4d0de:m:mVzGRJWpZfCgAf2PmD6LgCA

Edited July 4, 2016 by Guest

[Athul 0]

Try to make a test cube that is abit higher than where your problem begins on your print.

I also had perfect test cubes 20x20mm and 40x40, but when I printed something higher I got problems on my Prusa I3 with lead screws.

I changed out the motor, cupling and rod with a fully integrated motor, and then may prints became much better.

All in all I got tired of fidling with the Prusa i3 and bought an Ultimaker 2. More prints and adjusting and tweeking.

http://www.ebay.com/itm/NEMA-17-Stepper-Motor-Integrated-8mm-L100-600mm-Leadscrew-Nut-for-3D-Printer-/141947097310?var=&hash=item210cb4d0de:m:mVzGRJWpZfCgAf2PmD6LgCA

 

I think I found the problem.

Unlike other prusa models my X and Y axes are in linear guide way instead of smooth rods, and yesterday I noticed both my nozzle mount and bed moves when I shake them. Found out screws which attach bed and extruder assembly to the linear guide way were loose.

Now need to test.

I also changed flexible coupler and brass nut ,but I didn't have a spare threaded rod.After the change banding seems less

Edited July 4, 2016 by Guest

[Athul 0]

Unfortunately it didn't solve much

there's a reduction in banding

I printed 3d benchy

I'll upload some photos, can you guys show me what are the problems I have

[gr5 2,224]

lol. Play mostly affects the top and bottom layers but you didn't show that in any of your many pictures. horizontal banding as you have is usually caused by the Z axis moving inconsistent amounts.

[Athul 0]

lol.  Play mostly affects the top and bottom layers but you didn't show that in any of your many pictures.  horizontal banding as you have is usually caused by the Z axis moving inconsistent amounts.

 

I think you misunderstood all the phots I've uploaded, moste of them are side walls not the top layer. I'll post them once again. these are the photos of vertical perimeter

This is the top layer

Edited July 12, 2016 by Guest

[gr5 2,224]

I can tell side from top.  You don't seem to have much play. But you have some serious horizontal banding.  

Well in one of the photos from july 27 it looks like you have some layer shifting - a loose pulley maybe - or possibly play but it seems much more likely a stepper missed a step (due to friction?) or a pulley was a bit loose.

But for the rest of the issues - 90% of the problem looks like horizontal bands caused by the platform not moving up and down consistent amounts such that if the platform doesn't move far enough you get overextrusion and the layer sticks out.  And if the bed moves too far you get an underextruded layer.

Turn off power and move the bed up and down many times trying to feel for bad spots.  Try to fix the bad spots.  It can be caused by the 2 vertical rods not parallel.  Bad rods.  Bad screw.  Other obstructions e.g. bed hitting the spool holder in that gap where it's hard to see what's going on.  Bad Z nut.  And so on.

Here is a case recently where I simply spent a few minutes cleaning the gunk out of a Z screw and it improved the layering quite a bit (this was at the birthplace of UM in protospace Utrecht 9 days ago).  Not as serious banding as you have but you get the idea.  A "z movement problem".  Before and after cleaning:

Edited July 12, 2016 by Guest