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JohanOirschot

Need some advice and help with my quality problem

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Posted · Need some advice and help with my quality problem

I'm struggling for a while to make my ultimakers S5/3 print better with a consistent skin quality with cura. I found changing the jerk and accelerate settings helped me a lot here together with some other small tweaks like lower themps and 25mm/s print speed (i printed around +-50 xyz test cubes to see what is happening with cura settings). But for some reason i get artifacts in the skin on places that i cannot explain (On the picture i pointed out what i mean with these artifacts). Its not always on a position were are bottom or top layer would start for example. The thing i'm looking for is a really high skin quality that is consistent i don't care about print time, consistent good quality is everything to me.  

 

20200203_152556.jpg.thumb.png.e2dfa115068250aa9093d6483da70596.png

 

20200203_152641.thumb.jpg.6adc5a7f685eab1808efba48136a2f7f.jpg

 

I hope some one can advice me what to do to get a better consistent surface quality with cura.  

 

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Posted · Need some advice and help with my quality problem

I don't have these printers, but on my older UM2, changes in print-area per layer can result in horizontal lines. Especially on smaller models. I think this is due to differences in cooling time per layer, but I am not sure. In your models, are the lines where the solid top and bottom layers begin or end, or where there are big changes in surface area to print?

 

If so, printing with thicker walls, or 100% infill for small models, could help. Also: placing a dummy block next to the real model can help, especially if it is less or more in the inverse shape, or inverse print-area per layer. So that the total printing time per layer is constant.

 

Also, make sure all printing speeds are equal (infill, outer walls,...), so that the material flow is as constant as possible.

 

Another issue could be with the Z-axis (play, dirt,...), but I don't have much experience with that, so I will leave that to others.

 

Printing slow may help too. Layer thickness might or might not help: in some prints I found that very thin layers (0.06mm) gave excellent results, while intermediate layers 0.15mm gave worse results than thinner or thicker layers (e.g. than 0.3mm), on my UM2. Not sure what causes this.

 

See the pics below. The blue/purple model gets severe horizontal lines without the dummy cooling block, at the moment the model transits from big to the small top. The cyan/red model shows the concepts.

 

dummy_inverse_block6.thumb.jpg.2bdb2396588983363b48127ee12d8174.jpg

 

dummy_cutout2.thumb.jpg.750722bab5fa1c22a5e38d2a5717ab5b.jpg

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Posted · Need some advice and help with my quality problem

Thank you Geert for your reply, but i also have this on large models 20x20cm. Any idea's?

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Posted · Need some advice and help with my quality problem

If it is at *random* heights, or at a fixed height not related to model-features, I would think of a Z-axis issue, such as dirt (thoroughly clean the screw), or play in the nut or driver. But I am not familiar with diagnosing and solving that.

 

If it is always at the exact same height as big changes in print-area, or changes in infill, or changes in wall-thickness, then I would think that there is still something there to improve (thicker walls?), even on bigger models. I have seen models where the infill-pattern shined through the walls, causing indents. A bit similar to the structural ribs shining through the hull of big container ships.

 

Or, if random: maybe a non-constant filament diameter? Or the filament temporary getting stuck, resulting in a lesser flow? Or minor changes in filament color, which show up as darker or lighter lines? I do have a yellow filament that has this: first I thought this was a printer-issue, but upon closer inspection, it was the filament that had those color changes; probably the pigment not mixed well enough.

 

Long ago there also has been a discussion about the bed-heater drawing a lot of current, which could shift the ground-level (zero-voltage) of the electronics, which in turn could shift the perceived temperature from the nozzle temperature sensor, which then could cause the printer to "adjust" nozzle temperature, resulting in a different viscosity of the melt and different nozzle pressure, which might show up in the print. But I have no idea if this could be the case here or not; I don't know the electronics.

 

Could be lots of things, hard to diagnose...

 

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Posted · Need some advice and help with my quality problem

Dear Geert,

 

Thank you for the long detailed reply. Like i suspected it would be a hard thing to figure out. I'm not sure it can be a hardware thing because i own 4 Ultimakers and all have this issue. But i'm gonna clean all the z lead screws to make sure. 

 

For settings i always print with 3 outlines to make sure infill wont show trough and because the problem we see is not the the layers where the model is the same i don't think its model related. Do you think 4 or 5 outlines would improve compared to 3?

Its also why i started changing jerk and accel to make the 3D printers print layers more consisted the Ultimaker default settings has so many variation in it.

 

For material i only use Ultimaker or Colorfabb and so far i know these are really consisted materials. For testing i tried other spools as well to make sure. 

 

The only thing i might need to improve is maybe the way i use the spools. I mount them on the back or on an external spool holder maybe this can use an upgrade to improve. i will look into it.

 

 

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Posted · Need some advice and help with my quality problem

If you are courageous and have some electronics knowledge, and you want to rule-out the bed-heater influence, you could try to fix a LED-lamp onto the heating-connector. And then babysit the printer to see if the bed-heating LED and print-lines occur at the same moment? (Use a diode + LED + suitable current-limiting resistor, all insulated, not a bare LED alone). But here you risk making short circuits and burning out electronics, so you must know what you are doing.

 

While babysitting a print, also watch if there are any feeding issues: bends in the filament cause increased resistance in the bowden tube and nozzle, or the filament momentarily stuck under other windings, etc.

 

There could also be dirt in the Z-bearings, not only the Z-screw. These are a sort of chain-ball bearings (don't know the correct name), which can get stuck if dirty, or if they are lubricated and the oil gets sticky (some types should not be lubricated, but I am not sure which are used here).

 

Or maybe place a heavy weight on the bed, left and right of the Z-screw, to compress any Z-play, and minimise any irregular friction caused by dirt, compared to this heavy load? And see if it gets worse or better? Not sure if this is a good idea though... Risks overloading the Z-drivers.

 

These things are getting more and more risky, so use them with caution, and only if you have a technical/electronics background.

 

Obviously, I am running out of ideas here...  :-)

 

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Posted · Need some advice and help with my quality problem

I will not mess around with the electronics of the 3D printers or any weights i'm convinced that and brand new Ultimaker S5 or an older 3 should be able to do the job. I'm more worried about the firmware that's updated and the Cura slicer itself. Or find a way within these to make the quality more consisted. But you idea to check the feed of the material and maybe a better spool holder with less friction might help a bit. So i will try those out. For settings i just have those lines on different places when i change settings. That is why i still suspect the problem is in there somewhere. Maybe its the pressure in the bowden system or any of those. Ill try to keep experimenting and maybe other people will place their idea's here on this post.

 

Its just i see so many great prints from for example filamentfrezy where all lines are so consisted and he uses Chinese 3D printers or from prusa i3. Ultimakers are way more expensive and should be able to live up to this is some way....

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