Why does my first layer isn't showing when I use support?

[devilflash 2]

Hi everyone

I haven't tried it in a print but when I add supports on a print, Cura (3.0, 2.3,...) only shows supports on layer 1 even if the model has a flat surface.

The model appears on the second layer

Layer 1:

Layer 2:

It's quite strange.

Thank you

[smartavionics 289]

Hi. My guess is that the bottom surfaces of the model are not absolutely flat or that the bottom surfaces are not completely aligned with the build plate. What happens if you lower the model very slightly into the build plate (i.e. set model position z slightly -ve)?

[devilflash 2]

Well, the problem is that the model is perfectly flat. It has been cut in netfabb. And if I don't put the support material, I don't have this problem. It only occurs when I use support

Pretty weird huh?