Initial layer thickness range?

I noticed that CURA does not say anything about the valid range of values for the initial layer… LulzBot CURA manual gives a warning

Your LulzBot Mini auto leveling system could be affected if you change this from the standard profiles. Adjust at your own risk.

but gives no further information.

For example the functional part I designed in SolidWorks has a consistent minimum height of 2.25mm, and sides are all vertical. 2.25mm doesn’t really sound realistic, but CURA accepts the value without any sort of warning, and the calculated print time becomes ludicrously low. So how thick can the initial layer be?

There is a practical max layer height. I’ve read that you shouldn’t go above 80% of the nozzle diameter. I generally aim for about 0.4mm for the first layer. It’s thick enough to absorb any slight level differences on the bed, and prints well. I use the stock 0.5mm nozzle.

Since nozzle diameter is one of the settings I think CURA should automatically give a warning based on the value of the nozzle diameter. Can the initial layer thickness really be more than 100% of the nozzle diameter?

Cura doesn’t really say much about it. It could be better at catching issues of that sort. I think Simplify3D does a better job there, if you give it height/width values that don’t make sense, it often has a warning. Not that S3D is perfect either.

You can tell it to make layers 2x nozzle diameter. I doubt it will print well though. I honestly expect total failure. What I think it would end up doing is commanding the printer to output so much filament that the heating system can’t keep up, stripping the filament as the pressure got too high. There are hotends that are designed for thick layers like the E3D Volcano. The Hexagon isn’t designed for that.

I’ve tried 0.1mm initial layer thickness, it works, mostly. It doesn’t take much of an imperfection in the bed to screw it up though. Not worth it. Just keep it at about 0.4mm. It works, is reliable even when the bed isn’t perfect, and makes a nice surface for the rest of the print. It might be nice if Cura warned you about it, but 3d printing is kind of an art, you need to learn the machine, the tools, and how to use them.