Issues with 0.1 mm printing and Infill

I had the top layer setting at 6, and it shows on the area that I've boxed in red below.  The problem is that the other areas (in blue) are slightly sloped (as seen below) resulting in them getting only perimeters which are over the sparse 30% infill, causing the perimeter layer to collapse in certain areas.  You can see that the 6 green layers are fine and solid, so I guess I'm wondering if there is a way to set a threshold much like overhang is to support so that things that are sloped a certain way can have either 1) denser infill or 2) multiple solid layers below.

Another example of this is my octopus that I printed at 0.1 mm and around 30% infill.  His head caved in at the end of the print and caused what remained of his head to be spaghettied on top of him, leaving the top open.  I cleaned the mess off and left his open head, but it's clear to me that the infill caused this.  You can see that at the top of his head, it becomes less sloped (or has a smaller slope angle) and that seems to be the setting in which this issue occurs.

I suppose that for prints like this I will need to do at least around 80% infill to prevent this from happening.

Boz, in your slicing profile, do you have it set to infill every 3 layers?  This is default in the Solidoodle 0.1mm profile.  If it is set this way, try changing it to infill on every layer.  This might give better support to the top-most layers.  Try the Trek insignia out again if this change is made.

I had the same issue that the OP had, and noticed that when doing the top layers Slic3r doesn't consider it a bridge and uses the perimeter speed settings. I'm not sure if it was just the specific model I was using, but it didn't change speed at all, so I lowered the perimeter speed and it helped bridge a lot of those gaps (granted they drooped, but it's getting covered up anyway), but it took longer for the prints obviously. I haven't experimented with different infill types so I can't help you there.

you know that the 0.9.9 final is already out ?

I actually had it set to every 3 layers, which I've now gone back and changed to your recommendation.  I appreciate it!  I will have to try the model again after I'm done printing some birthday presents for my brother.

I think that this as well as op7ical's suggestion might have been what did the octopus in (he was my first 0.1 mm print as well).  Since then I've used around 50% infill and infill every 1 layer and have gotten fantastic results.

Thank you all for your very helpful suggestions.  I'm hoping to learn what I can and help anyone else who may need it in the future.

Here's the present I mentioned for my brother (don't tell him!) printed at 0.1 mm with 50% infill every 1 layer:

I might need to look at some calibration on flow rate.  I noticed that on the outside edges the extrusion lanes aren't quite touching enough to make a solid surface.

He just got into it, but he's been playing quite a bit over the last few weeks (he's in college so he plays with his friends in their free time).  He showed me how to play a few days ago, and I really liked it.  I'm going to have to make myself a set sometime soon.  I'm starting now on the brick pieces and hoping to do 3 of them in one shot on my SD3.

I've been debating on whether or not to smooth them (I have a presto cooker and whatnot) or to use a different solvent that I used to use on 3D parts called Plastruct Bondene.

I've already used it on one of the "ore" pieces and it actually works much like acetone by softening the part enough to smooth it out while also making it glossy.  It's main use is to bond ABS parts much like superglue, but it has the consistency of acetone (it's really a great product for this use because it bonds similar to how wood glue does) I'm tempted to just do this for all of the parts because it allows for a more controlled application.  (Note: This chemical is still just as harmful as acetone and should be treated in much of the same manner regarding safety precautions)

I can try to take a picture comparing the untreated vs. treated tomorrow in the sunlight to show you what I mean.  I'm just afraid of nuking these 0.1 mm prints with acetone if I'm not careful!

A comparison:

No finishing done:

Plastruct Bondene: (Light Coat)

Presto Finished:

All parts: (Left to Right: Plastruct, Presto, Unfinished)

The Plastruct seems like a happy medium between unfinished and presto finished.  It keeps details while still "melting" some features that might be undesirable (on this model that would be the flat parts that show lines more obviously)