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Deve

Looseness around holes

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I have been having this problem forever and I wonder if there is anyone here who might have suggestions. There is a lot of looseness around screw holes and any hole in the top skin. Here is the picture so you can see right away. Is there a setting in Cura that would fix this? Thank you! Look especially around the square one. Its worse.

WhatAmIDoingWrong.jpg

Edited by Deve

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My first impression was not enough top layers to cover the parts when changing directions as such.....but I am not familiar with your printer and I am not sold on my first impression. Something nags at me that it may be something else.

 

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I have three of these printers and I realize they are not top end printers, but the odd thing is the filament on the top layer doesnt go to the edge of the hole, rather there are circular (or rectangular) passes around the holes. I can see those passes on the infill, but shouldn't the top layer always go right up to the edge? So, I am hoping I have a setting in Cura that I can make to give the top layer control over that.

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A few questions:

 

1 -  How many walls are you using?

 

2 - How many "extra skin walls" are you using?

 

3 - what speeds are you using for the walls and skin?

 

4 - what temperature are you using?

 

Perhaps you could attach the project file, that would answer those questions (and more!)

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I can't tell anything from layer view. I am sure its my inexperience. I can't see any borders in layer view. Here is the .STL file. To answer your questions:

1) 12  (I keep upping it in hopes of something changing, so I know that is probably crazy high)

2) 1 extra skin wall     

3) Speeds: Outer Walls: 27.5 and Inner Walls: 55   (not sure about skin speed)

4) Temp: 200 first layer, 190 after that.

 

The project file means .STL file right? If not, I will get you whatever you need. Thank You!

WhatAmIDoingWrong.stl

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1 hour ago, Deve said:

Outer Walls: 27.5 and Inner Walls: 55

 

One distinct possibility is that it is underextruding. So try slowing the inner walls down to the same speed as the outer walls and see what happens. You could also increase the temp a little.

 

As a general principle (of mine), printing the inner and outer walls at different speeds should be avoided as it introduces a step-change in extruder rate which often produce either bumps or hollows.

 

Hope this help

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I did as you suggested and it still does it. I am not understanding something. Why would the top layer have about 6 circles all the way around a hole? Same for rectangular holes. Shouldn't the top layer go right up to the holes edge? Its like the priority is on the wrong axis or infill and not the top layer, or some setting is just not tightening things up because I don't know where to look. Thanks to everyone trying! This has been a problem forever now and there is no better place to ask this.

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I think it has something to do with under-extrusion. A few small gaps are probably normal and related to the slicing process, I think. But what you show us is actually too much. If it is not under-extrusion, then the material may cool down too fast. I know this from some materials that do not tolerate excessive cooling. However, if you have not already done so, try printing the same settings slower and with very little cooling.

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have you set 'enable ironing' to true ?

 

this will smoothe the top surface, diminishing the difference between the walls (around the holes) and lines of the top/bottom pattern

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I did some screenshots of all of my Cura settings down the page a ways in a yellow box here: http://devestechnet.com/NewTech/HeatBed

 

These are my standard settings for almost everything. My prints come out really nice except for this. I tried ironing, but that doesn't fix the problem with the gcode. A top layer should go all the way to the edge. The layer needs to be structured so that happens during slicing. As it is now, all of the rounds around the holes (appears to be six of them) are uniform all the way through the piece. The bottom and top layers should be different, thus reinforcing the piece and eliminating this problem. No?

 

I have tried different speeds and different temperatures and all still have the 6 extruded lines around each hole. Also, if my suggestion of making the layers different from the infill doesn't fly, is it possible to extrude over 100%? Can I simply type in 102 or 110 to see if that fixes it? I have always been afraid to try.

Edited by Deve

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16 minutes ago, Deve said:

I did some screenshots of all of my Cura settings down the page a ways in a yellow box here: http://devestechnet.com/NewTech/HeatBed

This is not the same as a screenshot of the layer view. Even if I used your settings, it would be completely different since I am on a different machine. I would like to see what your layer view looks like as that would tell me what cura is doing with your settings on your printer with this object.

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35 minutes ago, Deve said:

 Here it is. Let me know if you need more. You have to hit slice first! LOL!

DevesCuraLayer.jpg

This was helpful as it shows that according to the slice, there should be no looseness around the holes at all. Even with the layer view being a bit of an approximation, it looks tight. So, I am thinking that there is an issue with the instructions being sent to the printer. I am not sure if the question has been asked, but is the gcode being sent the flavor of gcode for your machine?

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How do I find that out? I would love to get this resolved. I have three of these anet a8 printers and some are tighter than others, but do you have suggestions on maybe changing different settings that would tighten things up? The choices in Cura are tremendous and very very flexible. Maybe I have something set wrong. Thank you!

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Yepp, the GCode flavor should be selected to match your machine. But I think it's mainly about the correct number of E-Steps for the extruder, so that in fact enough material is extruded.

 

If your material feeder works well and there is no excessive filament abrasion around it ... then it makes sense to dynamically raise or lower the material flow directly on the machine. Ideally, you should approach the desired optimum of the material flow in 10 percent steps. And watch closely how the printed structures change.

 

This is necessary even if changing the extrusion temperature does not bring any significant improvement. Any printable material does not behave exactly the same, even PLA is not the same as PLA when shrinking during cooling down. For example, different colors are very different in behavior. So you always have to approach the properties of the currently used material.

 

The change in the amount of material flow always has a direct impact on the dimensional accuracy of the entire object, as can be seen very clearly in holes and joints such as dovetails ...

 

Maybe you should also do some additional information in your forum profile, because this eliminates, for example, "unimportant" questions such as: Which machine do you currently use?

Edited by mnis

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And to get comparable results, all three printers must work with the same slicer settings. If you have accidentally made wrong settings sometime, it is best to start from scratch again. So slice a small test object for all printers with Cura default settings, and look what happens ...

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Does this mean in Cura to change flow to 110% and try that? Its fresh a .4 nozzle. There are so many settings that I have tried different things but probably was too stupid about how things work to make an intelligent decision on what to try. Also, I realize you are trying to tighten up the printing, but does my suggestion of changing the top layer pattern to go to the edge of the hole make no sense? Thanks everyone. 

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Although the surface generally looks good, I think there is not much missing to fill these gaps. And if you increase the number of top layers, but each additional layer has these gaps, then it will bring nothing. That's what I think anyway.

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