Support Horizontal Expansion in 5.4 doesn't seem to work correctly when set to 0.0

[DickQuaif 0]

When I set horizontal expansion to 0.0 it still expands some supports and leaves print in mid air.  Some support structures are actually missing.  See attached project.  This worked fine in 5.2.2.  With 5.4 I have to expand the support to 2.0 to get an acceptable print file with no mid air printing.  No expansion is actually needed for this print.

LuxSensorCase_V2C-Body.3mf

[GregValiant 1,409]

You might have run into the "Brim Bug".

If you have "Support Brim" enabled and you have "Build Plate Adhesion" set to "None" then the Support Brim isn't printed (Prime Tower brim isn't printed either).

There have been a couple of reports of that behavior on Github.

A fix is to enable the Skirt with a line count of 0.

You will get this

 

Instead of this

 

Without the Support Brim to rest on the support structure that is printed on Layer:2 is hanging in the breeze.

[LePaul 354]

I'm seeing this too.

If you use a prime tower, no real brim is there.  I've had 2 prints fail since the prime tower got knocked over.  Using Ultimaker default profiles for UM Tough PLA and PVA support.  

[DickQuaif 0]

My problem is actually higher up. There is a shallow slot on the inside of the right wall that should have a support structure in it.  In 5.3 and 5.4 it’s missing and replaced with a small loop that is in mid air.  I expected that if the expansion was set to 0 it would be the same as 5.2 but it’s not. If I increase the expansions to 2mm I get printable supports for the loop and the nearby hole but anything less is unprintable. Even with a support , the loop is not actually doing anything. Rev 5.2 works well and I have gone back to it for day to day work. 

[GregValiant 1,409]

This is in 5.4.0 with no Horizontal Expansion and the "Support XY Distance" at 0.20mm.

That feature looks to be about 1mm deep so it isn't easy to build support on such a small shelf.

Your Minimum Support Interface area is 10mm and you might want to lower that.

[GregValiant 1,409]

Since it was still loaded...

This is with "Interface Density" at 70% (gives it more of a zig-zag even though it's a grid), overhang angle 60° (to get away from the chamfer in the big part of the hole), Bottom Distance = 0.4mm (2 layers so it will break free easier).