Travel always ends at the same place, causes bad layers

[charentejohn 0]

Had this before and thought it had gone, may have cured it but still printing.  Basically a model (usually the same type long thin bar shape) has bad layers at one corner, when I look at the travels in Cura they always end up there on every layer.

This and retraction are the cause I think.   I can attach a photo but really it is just every other layer is missing in one corner, once the nozzle has gone a cm or so all is well.

So - is there a way to randomise where the travels end up.  A bit like Z seam to say travel path = random.

This sometimes goes away if I don't use retraction (not a problem in this case) as I think what happens is the filament does not extrude fast enough.  I can see a long corner to corner travel then should extrude and continue.   Shorter travels seem ok.

 

What settings should I use to fix this, perhaps priming but then it doesen't need to prime for shorter runs ?  

I am always confused by minimum retraction distance, my part is 160mm long and 16mm wide and travel is corner to corner so if I say minimum 50mm would that help, if I say minimum 120mm a bit like no retraction at all in this case.

 

I had this doing 3dlab thin wall wing sections ages ago and never really resolved it.

Any help appreciated. 

[Shadowman 53]

I read your post and wish I had the steps for you nonetheless, if I understood correctly, then as I understand it; yes you can alter/stagger the starting point of the layers so as an example; on a wall you won’t see effectively a vertical line.

 

There was a thread I read that spoke of;

 

”It is a setting within the Shell settings group, called Z Seam alignment”

 

Here is a link to Ultimaker Cura’s information.

 

https://ultimaker.com/en/resources/52343-shell

 

Hopefully some one better suited will engage in your thread.

Edited October 24, 2018 by Shadowman
Additional

[charentejohn 0]

Thanks for the idea, I tried it but still the same.  Thought Z seam would start at different points and so also randomise travel points. Seems it does not .

I tried moving the part on the print bed, instead of left to right I put it at 30 deg and seems better.  Problem then is the grid infill is not lined up right.

Seems each layer does the following, put down an outer layer ending top right corner.  Then travel to the bottom left corner (quite a distance) and then start again.  It is this travel that is the problem as in lower layers especially it misses bits of the layer and is weak, rest is fine.

This happened randomly on 3dlab, and other, wing prints and could always be traced to a point in the print where the travel ended up in the same place travelling a distance to do so.  I believe this is the problem but can't think how to make it stop this.

 

I think if it did a layer and started again at the same point that would be ok, just that sometimes it travels from far away to start a layer causing loss of filament at the nozzle.

Probably prime speed and amounts, currently 40mm/s and 0.6mm2.  The wonders of 3d printing is that problems are a moving target, change one thing and two others change as well ?   For example, if I set the prime amount to 3mm2 (to be silly) it may fix this but I guess I would get blobbing all over at points that were ok before.  All just getting a balance. 

[Shadowman 53]

5 hours ago, charentejohn said:

Thanks for the idea, I tried it but still the same.  Thought Z seam would start at different points and so also randomise travel points. Seems it does not .

I tried moving the part on the print bed, instead of left to right I put it at 30 deg and seems better.  Problem then is the grid infill is not lined up right.

Seems each layer does the following, put down an outer layer ending top right corner.  Then travel to the bottom left corner (quite a distance) and then start again.  It is this travel that is the problem as in lower layers especially it misses bits of the layer and is weak, rest is fine.

This happened randomly on 3dlab, and other, wing prints and could always be traced to a point in the print where the travel ended up in the same place travelling a distance to do so.  I believe this is the problem but can't think how to make it stop this.

 

I think if it did a layer and started again at the same point that would be ok, just that sometimes it travels from far away to start a layer causing loss of filament at the nozzle.

Probably prime speed and amounts, currently 40mm/s and 0.6mm2.  The wonders of 3d printing is that problems are a moving target, change one thing and two others change as well ?   For example, if I set the prime amount to 3mm2 (to be silly) it may fix this but I guess I would get blobbing all over at points that were ok before.  All just getting a balance. 

Bummer.....

 

It is obvious that you are giving it best efforts as such again I say; hopefully someone with greater knowledge with engage this thread as I understand it is frustrating.

 

I wish that I could assist with additional ideas.

[charentejohn 0]

No problem.  I think it is just a case of trying different stuff.  Just to add to the confusion I think filament make / age is also a factor.

A lis of things to play around with would be nice, in the meantime I will play with retraction settings, my best bet I think.

[Shadowman 53]

32 minutes ago, charentejohn said:

No problem.  I think it is just a case of trying different stuff.  Just to add to the confusion I think filament make / age is also a factor.

A lis of things to play around with would be nice, in the meantime I will play with retraction settings, my best bet I think.

Your attitude is awesome.

 

Let me/us know how you do.