Bottom Thickness Calculation

[Reywas 0]

In Cura 3.6.0, the "Bottom Thickness" help dialog states:  "The thickness of the bottom layers in the print.  This value divided by the layer height defines the number of bottom layers".  How does the "Initial layer height" setting, which is typically thicker than the Layer Height, figure into this.  Looking at the sliced model, it looks to me like the thicker initial layer is followed by the remaining bottom layers of "layer height" thickness.  Does this result in a "Bottom Thickness" that is actually thicker than what is defined in the setting or does Cura compensate for this by printing the subsequent bottom layers thinner than the "Layer Thickness" setting?  

[geert_2 379]

In my very old Cura, it goes like this:

 

Let's say these are the settings:

- first layer = 0.3mm

- layer height = 0.1mm

- bottom thickness = 1.0mm

 

Then it does: bottom = 1 x 0.3mm + 7 x 0.1mm = 1.0mm in total

 

I would guess it is the same in Cura 3.6? You should be able to see this in layer preview, if you make a small test object?

 

[yellowshark 149]

The same for me on 2.7. of course using 0.1 takes the problem away but I guess that if your layer height is 0.3 and you set this thickness variable to 1.1 the question is does is print 0.9, 1.2 or does it throw in a 0.2 to give you 1.2?. If it were me I would set the thickness to equal what my layer heights add up to, i.e. at 0.3 either 0.9 or 1.2. I doubt it makes any difference to the finished article and it stops me worrying about it 😀

[Reywas 0]

I do always (as in "since I got my first 3D printer two weeks ago") set my top/bottom layer thickness to some multiple of the layer height, which is always set to some multiple of my printers z-step "magic number".  

 

I have looked at the layer preview and can see the thicker first layer but it's hard to tell if any adjustments have been made to the remaining bottom layers.  It would be nice if Cure would show the Z height when stepping through the layers.  I will take geert_2 suggestion and print a test bottom.  Not that any of this really matters to the final print quality, I just like to know how things work.