One layer is black in PrusaSlicer  

RE: One layer is black in PrusaSlicer

@neophyl

Hmm .... regarding making bridged extrusion widths the same as normal extrusions, doesn't setting bridge flow to 1.00 from 0.90 or 0.85 do that? Or is there something else deeper going on?

RE: One layer is black in PrusaSlicer

Not really Tim.  I'm talking about the logic that PS uses for overhangs where extrusion layer height is assumed to be the same as nozzle diameter for those layers as theres nothing to squish against below for them.  So all those dark blue areas are assumed to be 0.4 height.  While that logic may be true I've found that printing them with a normal extrusion actually leaves the part looking better in many cases so disabling overhang detection stops the perimeters printing like that.  Doesnt stop PS using the same assumption with the overhang infill though.

RE: One layer is black in PrusaSlicer

Thank you all! 

so in future I will examine my prints myself and will not trust PrusaSlicer here. Thanks for the Tipps on that, I really appreciate this <3

I would just go forward and try to see that weird things as a single problem, which hopefully will not appear again, if I set the supports myself. 

RE: One layer is black in PrusaSlicer

And - in looking into this I found a massive defect in the Detect Bridging Perimeters... lmao.

What bridge? And why then isn't the left not-a-bridge 'detected' ??  So really, two defects.

No wonder why the sense angle has never really made sense to me.

ps: I'll need to hop over to github and check this. I made this part way back when - and pretty sure I reported defects based on it... but not this pair.

RE: One layer is black in PrusaSlicer

@tim-2

Hey, than this discussion had another benefit 😀

i assumed leaving everything on default would produce a solid print. Meh, I didn’t want to go too deep into all those things directly at the beginning. Taking step by step would make the learning much easier (and remembering too). 

prusa needs to revise the program (at least the beginner settings), or set up a proper tutorial. 

RE: One layer is black in PrusaSlicer

Posted by: @neophyl

Not really Tim.  I'm talking about the logic that PS uses for overhangs where extrusion layer height is assumed to be the same as nozzle diameter for those layers as theres nothing to squish against below for them.  So all those dark blue areas are assumed to be 0.4 height.  While that logic may be true I've found that printing them with a normal extrusion actually leaves the part looking better in many cases so disabling overhang detection stops the perimeters printing like that.  Doesnt stop PS using the same assumption with the overhang infill though.

You can also use those settings to adjust the perfect contact between supports and bottom layers, I don't often use prusa supports, I tend to model my own and I will use a combination of the bridging controls and layer height adjustments to bring them in for a perfect landing.

For example:

This is an example of a Ras Pie print.

bottom layer is all bridging done in Prusa slicer accept where noted.

The knife chip was done to demonstrate the strength of the bridging layer adhesion to a colleague. 

Top Layer

Tim, I felt this might be worthy of note, and perhaps you could find a use for this information.

Enjoy

Swiss_Cheese

RE: One layer is black in PrusaSlicer

@swiss_cheese

I've had very little success with printing flat layers with built in supports as configured. Generally, the part layer is either welded to the support, or is stranding and easily carveable as you've demonstrate - even to the point of the bottom part layer comes off with the support interface layers.

I generally dispense with the interface layers and control the vertical contact with horizontal spacing and angle.

  versus

RE: One layer is black in PrusaSlicer

@swiss_cheese

You need to write a short paper on your technique. It looks as if you used soluble supports to build that model.

RE: One layer is black in PrusaSlicer

This was all done in Prusa slicer  no soluble supports, I used a single TPU layer prior to bridging to facilitate separation. I've been using this method for 4 yrs now.

RE: One layer is black in PrusaSlicer

@swiss_cheese

Nice trick... may as well make that same layer soluble for even easier removal. Though, honestly, I've never printed TPU onto other plastic to check adhesion. Can I assume TPU doesn't stick to PLA or PETG very well?

RE: One layer is black in PrusaSlicer

If you press the layers TPE/TPU will stick to PLA, PETG,ASA and ABS like nobodies business (those being the only materials I've tried it with to date). However this example was meant to demonstrate the ability to use the bridging settings and layer adjustments to control the distance & pressure by which you can press the bridged layer to form a nice cohesive surface and still have the ability to separate the support from the model with a very acceptable finish on the bottom. I discovered this while trying to develop a certain type of tile covering for a factory setting. I agree with you about the soluble result, however I stuck with this method because it offers no clean up after, and it takes seconds to remove the support and your done no water, no D-limonene.

This method is not suitable to all areas and is best used on large flat areas and works well on multi-tier models with lots of flat raised areas.

Material changes are easy to keep to a minimum.

RE: One layer is black in PrusaSlicer

So, We've tried to print some parts of the Prusa suggested inclosure: the PSU holder and the PSU replacement.

We encountered the same issues (double the layer amount and the black layers with travel path on). We tried first (just to see how it's look like) with the auto supports on (a lot of black layers in the first part of the print) and then we tried to paint them ourself, which unfortunately is resulting in indeed less, but still several black layers. 

The black layers occur, when we put more than one stl in one print job and had supports on both stl's. I think it's not occurring, if just one of the stl's has supports. But it's still weird. In the end we printed without any supports and it turned out okayish. 

But it should not be the target to get okayish prints, then we wouldn't pick a Prusa 😉

SO at some point, as this is occurring now frequently, we need to find a solution, as this is not the state we want to have our prints and do so much of comprises.

Here is the project file, if someone wants to have a look: Black layers 2

RE: One layer is black in PrusaSlicer

@neophyl

Ditto on supports - 2.3 is disappointing for them.  

RE: One layer is black in PrusaSlicer

@sgt-freshmeat

The black layers are not an issue.  Its just an indication that a layer consists of only support for that layer.  Its normal as the support layer heights are NOT tied the object print later height.  If you turn support off/on you will notice the number of layers on the slicer in the preview usually changes as at that point the preview is only showing the object layers and then the layers including support ones.  

What are potential issues is that PS puts support in weird places sometimes.  However those issues are well known and being looked at so its pointless reporting them (there are probably a hundred on github and many more on this forum already).  Until they are fixed we will just have to use the usual workarounds that we have used before.  At least 2.3 gave us paint on enforcers which is the single most useful thing when it comes to support imo.