Layer thickness x number of lays when sliced would not equal model height

[SeanAZ 0]

I'm completely new to 3D printing.  I'm slicing my first model and noticed something I am not sure I should be concerned about or not. I'm using a .06mm layer thickness, and my model is 5.40mm tall.  When Cura slices it, preview says it will be 86 layers.    5.4/.06 equals 90.      My concern is the model is made up a .06mm tall piece, stacked 90 times with a 2 degree rotation per stack. A screw of sorts.  IF the preview is supposed to accurately show the slices then its missing 4.

Is this a normal slicing thing that happens?

OR 

Is it an issue?

OR 

Is there possibly a setting I'm missing that it is not following scale exactly in some way?

Thanks for any education and/or help.

[gr5 2,192]

There is another parameter, "initial layer height".  This is the height of the first layer.  I'm not sure what the default is - it depends on nozzle diameter and material but 0.27mm is not uncommon.  .27 + .06*85 = 5.37mm

 

Or maybe your first layer is 0.3mm.

 

[gr5 2,192]

By the way, I don't recommend .06mm for beginners.  Better to get some good quality prints with 0.2 or 0.1 layer height first before moving to 0.06mm.

[SeanAZ 0]

Thanks you for responding gr5.   I know that printing at .06mm is going to be tricky.   It is just one piece of a multipiece project that I happened to design first, figured I start looking at Cura to start getting familier with it.  But adventually I need to go there.    I'll double check for first layer height..  I did find top and bottem height and tried adjusting them but he numbers of layers still remained 86.  But am I right in thinking that it should slice to 90 layers? 

 

[gr5 2,192]

It should slice to 86 layers if the first layer is 0.3mm thick.

 

The top/bottom thickness...

 

So cura has the word "wall "and "top/bottom skin".  When you think of a single slice, wall is the interface between air and part.  The wall separates air on one side and infill on the other side of the "wall".

 

Skin is in the Z direction.  If you print a cube, it's obvious what's top and bottom.  If you print a pyramid there will be some "skin" all the way up the side of the pyramid.  At least if the top/bottom thickness is say 2mm.  If top/bottom thickness is only 0.06mm then you will only get one layer of skin on "top" and "bottom" surfaces.  Again for something like a sphere there are lots of little tiny "top" and "bottom" surfaces/skin.

 

[SeanAZ 0]

Ah see "skin" is a new term for me,  but makes perfect since that "wall" would have a z axis equivalent.

So now my question is what am I doing wrong parameter wise that I am not getting a 0.06mm first(bottom) layer and/or 0.06mm last (Top) layer?

 

So currently under Shell

Extruder 1

Wall Thickness               to 0.80mm

WalLine Count               to 2  

Top/Bottom thickness   to 0.06mm

Top Thickness               to 0.06mm

Top Layers                     to 1   (I have tried 0 to 10 with no change in sliced layers)

Bottom Thickness          to 0.06 mm

Bottom Layers               to 1  (Also 0 to 10 with no change)

Extruder 2

Wall Thickness               to 0.80mm

WalLine Count               to 2  

Top/Bottom thickness   to 0.80mm (This default, it was letting me change it but now it does not)

Top Thickness               to 0.06mm

Top Layers                     to 0   (I have tried 0 to 10 with no change in sliced layers)

Bottom Thickness          to 0.06 mm

Bottom Layers               to 0  (Also 0 to 10 with no change)

 

Seems no mater what I do it results in 86 layers.

Not sure if I'm even in the right area.

 

I originally had extruder 1 and 2 both matching like Extruder 1 above. Since I have been playing around Extruder 2 wont let me change Top/Bottom Thickness from the default 0.80mm so not sure why that is.

 

[SeanAZ 0]

Sorry, I was on basic fuctions all this time, switched to Expert and the intial layer thickness you mentioned earlier popped up and upon changing that I got my 90 layers.    That you for the your time and help Gr5.  Gratelly appreciated.