Top Layer not smooth

[jds22222 0]

Hi, anyone have any idea why the top of the 3d mold leaves these gaps and is not smooth? Ironing does not help.  The gaps are large.

Thanks

[gr5 2,187]

Are you talking about the staircase steps nature of your curved top surface?

 

If so then you need to decrease your layer height.  I can't quite read your layer height but I think it says 0.4mm?  You can reduce that to 0.1 and still get good quality.  The limit (before you get diminishing returns) is around .06 or .08mm (less than 0.1mm - I clarify as people often accidentally add or remove a zero, including me).

 

But 0.1mm layer height will print 4X slower than .4mm layer height.  So there is another option - you can do thicker layers up until your first "top" layer at the bottom of that curve by using adaptive layers.  Check that box.  If you want layer heights to be .4mm in the bottom portion (to save hours of time) and the thinnest layers to be .1mm then you need to find the average and difference of those two values.  The difference is .3mm and the average is .25mm.  So in this example (.1 to .4) set the layer height to 0.25 and set the adaptive layers maximum variation to .15mm.

 

ironing will only smooth each of those flat "steps" in your image above.  And it will waste lots of time.  You have so many steps that I think ironing is probably not worth the extra print time.  You can experiment and decide.  Ironing is tricky and you may have to play with the parameters a lot to get best results so if you play with ironing you should do it on a small part first (say 2cm by 2cm by 5mm tall).

 

By the way, all the yellow shown in your picture are thought as "top skin" or "top layers" by cura.  Each and are thought of as separate surfaces - separate layers.  Cura tends to mostly think of one slice at a time.  So when it is doing that middle yellow strip that portion is a "top" (aka skin) layer and then there are other portions of that layer that are not skin which will be other colors (but hidden from this view by layers above).

 

 

 

[jds22222 0]

Makes sense. I am using a .8 nozzle.  I was trying to get a mold I could inlay some carbon fiber for a part. Thanks for the answer.  Will try again.

[gr5 2,187]

Oh gosh.  There is a different minimum layer height for bigger nozzles.  I'm not sure what it is for .8mm nozzle.  .15mm layer height should be fine.  I'm not sure if it can go down to 0.1mm layer height and still have as good quality.  I'd print a tiny test print - maybe a 2cm cube with a slightly tilted top.

 

I think it might be fine but I'd test it first.

[Dadkitess 19]

Did not get beneficial returns using 0.8mm nozzle, when going from 0.2mm layers to 0.15mm layers on a big and detailed print. It feels like it was a bit more rough and innacurate to me, but I don't have much experience with this nozzle size.

 

For this particular case though, with large plane surfaces, it might be okay as the flow has time to get constant and homogeneous, as opposed to small discrete details I had on my tests.

 

Adaptative Layer is indeed a must for such a geometry, but unfortunately there is not asymetric layer heigh distribution : if you want to go as low as 0.15mm, you'll have to set 0.30mm as the standard layer eight and set the adjustment allowance to 0.15 so that it will go as low as 0.15mm (0.30 minus 0.15) and as high as 0.45mm (0.30 plus 0.15). This is pretty okay here but i've found some case where I would have like to set the base layer height to 0.XXmm and allow for minus 0.1mm and plus 0.3mm 🙂

 

[GregValiant 1,283]

One thing I noticed about my nozzles is that they are all the same exterior shape.  Whether it's the .20 I.D. or the .80 I.D. the outside diameter of the tip is 1.0.  So the .20 nozzle has an "ironing surface" of .4mm all around the inside diameter but the .80 nozzle only has an "ironing surface" of .10mm around the ID.  Admittedly I didn't pay a lot for the nozzles and I suppose I shouldn't have expected anything different, but if the .80 nozzle had some more land around the ID I think I'd get a better finish.  As it is, even a little bit of over-extrusion wants to sneak past that small "ironing area" and make ridges on skins.

Edited January 17, 2023 by GregValiant