Small skip on Y-axis when the movement changes from forward to backward.
 
Notifications
Clear all

Small skip on Y-axis when the movement changes from forward to backward.  

  RSS
lawhi
(@lawhi)
New Member
Small skip on Y-axis when the movement changes from forward to backward.

Hi, 
I have been struggling with ugly edges on the part of the print that faces toward the back of the printer. After a lot of tests both adjusting print settings and checking belt tension, re-tightening screws etc. I looked and felt on the bed while doing a print. Every time the bed has moved forward and changes direction to move backward I can feel a small skip in the movement. This is not present when going backwards and making a change in direction to go forward. 

Does anyone have a clue as to what can cause this?

Regards, 
Lars

Posted : 11/03/2021 12:57 pm
Clarmrrsn
(@clarmrrsn)
Honorable Member
RE: Small skip on Y-axis when the movement changes from forward to backward.

Have you checked the pulley on the motor is installed correctly onto the flat with the grub screws and tightened enough, check the idler pulley as well, make sure neither is wearing/running rough.

If belt tension is OK and pulleys are OK, and everything on the carriage and frame is tightened correctly also check the bearings and rods are lubricated correctly.

That's about all I can think of.

Tank you very much!...
Posted : 11/03/2021 1:08 pm
lawhi
(@lawhi)
New Member
Topic starter answered:
RE: Small skip on Y-axis when the movement changes from forward to backward.

Thanks for you suggestions, but I have already checked this.

What I think is strange, is that it happens at the exact same moment as the movement changes direction and only from forward to backward. Not the other way around.

Posted : 11/03/2021 2:09 pm
JoanTabb
(@joantabb)
Moderator
RE: Small skip on Y-axis when the movement changes from forward to backward.

are you saying that the print ends up sloping continually in one direction, 
most likely issue is Loose grub screws, but you have discounted that. 

another possibility is poorly functioning bearings and smooth rods. 

have you ever lubricated the smoothrods and linear bearings 
If the carriage doesn't move smoothly, this may be an issue, 

If you have a Mk3 or Mk3S the  Y axis Ubolts can cause distortion in the bearing cases. (the Mk3S+ doesn''t have this problem. )

could you give us a picture of a failed Print, and maybe we can make more intelligent guesses.

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 11/03/2021 4:03 pm
lawhi
(@lawhi)
New Member
Topic starter answered:
RE: Small skip on Y-axis when the movement changes from forward to backward.

Thanks Joan,

I think I found the reason to the small skipping, I had set the seam position to rear. I assume this will make a small 'jump' in the Y-direction for each perimeter round. 

I attached images of the problem, but it is a bit hard to see.

I have lubricated the rods/bearings at regular intervals and everything seems to run smoothly. I have the mk3s, and have tried to adjust the nuts of the Ubolts, according to the manual. However, I think it it hard to know when at the sweetspot between too tight and too loose. 😉

Thanks again for helping out! 

 

Regards,

Lars

Posted : 11/03/2021 8:38 pm
JoanTabb
(@joantabb)
Moderator
RE: Small skip on Y-axis when the movement changes from forward to backward.

Retractions do  affect your prints... sometimes causing a swirl after the retraction.

Is it possible to save a Project file for this model and zip compress the file, before attaching it to your next post, so that we can see what your settings are? 

is the filament PLA? have you tried another filament? 

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 11/03/2021 11:11 pm
lawhi
(@lawhi)
New Member
Topic starter answered:
RE: Small skip on Y-axis when the movement changes from forward to backward.

Thanks Joan, 
If it were retraction, wouldn't it be more random where these poor "corner resolutions" appear? It is always on the side of the print that is towards the back of the printer. 

The images are from a previous print, that I don't have the settings for anymore. I will see if I can create a profile to attach, the next time this appears.

I see it on several filaments, PLA, Impact PLA, PETG. I think the images are from the Impact PLA from Fiberlogy.

Regards, 
Lars

Posted : 12/03/2021 7:38 am
JoanTabb
(@joantabb)
Moderator
RE: Small skip on Y-axis when the movement changes from forward to backward.

@lawhi

the actions of your printer are controlled by the settings of your slicer, and the automatic algorythm's in the slicer. (which is why I asked to se them. )

generally a slicer will try and hide retractions in corners. however your model may not have suitable corners (Cylinders for example have no corners) 
then the seam position will be taken into account..   
Rear seams will put the seam towards the rear of the model. 
Aligned Seams will cause the retractions to be aligned (Often this also occurs towards the rear of the model)
Nearest seams, allows the slicer to manage seam placement to improve print time
Random seams causes the slicer to place the retractions randomly, which may benefit cylinders. 

in the case of this model, you appear to have a number of things going on. 

there appears to be some poor bed adhesion, allowing the corner of the model to lift you appear to have some retractions at the corners, 
Possibly the filament temperature is a little high, maybe a little over extrusion. (increased extrusion can be symptomatic of higher temperature, because the filament flows more readily. )

when the corner of a model lifts, the succeeding layers try and complete normally, but there is less space for the filament to be placed in an orderly manner, with the result that the print quality suffers, 
It looks as if the jagged edges are more untidy towards the bottom of the print, and begin to improve as the print progresses away from the warped corner, this tends to happen because at the lower layers, the model 'Springs away from the extruder' as the extruder tries to lay down new layers, and these movements cause unexpected distortion tot he new filament. then as the model gets taller, the flex reduces because the model becomes stiffer, but there is still excess filament in a reduced area of the print because of lower layers being warped and deflected. as the model height continues to grow, these effects tend to reduce and the print becomes more regular. 

3D printing is a balancing act of many factors to attain a satisfactory result,  often when there are issues, there is often No Single 'Fix' that resolves all of the issues

regards Joan

 

 

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 12/03/2021 11:45 am
Share: