Unattached Strings On Disk Above Supports  

RE: Unattached Strings On Disk Above Supports

Here's what it looks like from the bottom.

RE: Unattached Strings On Disk Above Supports

The forum doesnt allow many file types.  You need to zip them up into an archive.

However don't post the stl file.  It is much better to save your project with the part in slicer (File>Save as).  This will save a *.3mf file.  Zip that up and attach it to a post here.  The 3mf will contain your model and all of the settings you are using, print, filament and printer.  Its a MUCH better way to debug issues as you don't need to post any of the hundreds of settings that could be causing issues.  We can slice and look at he preview etc and try and spot potential issues.

Also a picture showing these loose strings would go a long way to actually understanding what your exact problem is.

RE: Unattached Strings On Disk Above Supports

I'm attaching the ZIP file here.Milk-6

I can't get a meaningful photo with white strands on a white background.

The problem is that the strands being laid down are not sticking to the strands next to them.

Thanks for the info about the ZIP file.

Ken

RE: Unattached Strings On Disk Above Supports

Ok, I have I think a pretty good guess as to your issue.  That area inside is basically all bridges, and while the mk3 is ok at bridges, it isnt the best.  With bridges that length I think it cant do them properly.  So they are sagging down.

The setting you have enabled (as its the default) is under Print Settings>Support Material>Dont Support Bridges.  Untick it and it will add support under them too as well as just the perimeter.  Also the default contact z distance of 0.1 is too close.  Its a crappy default and will make removing the supports much more difficult, especially with petg.  0.2 or even 0.25 is better. 

The underside still wont be pretty as Slicer (all the versions, PS, SuSie, Slic3r) don't do undersides of bridges well compared to some other slicers.  Its one area that could use a lot of improvement.  There's other threads about that already though so go do a bit of reading if you want to find out more.

I've attached a modified project with the changes I'd make (I also increased support x/y separation a bit, spaced them apart more and increased interface layers from 2 to 4) which are pretty much my normal support settings.  Give that a go.

RE: Unattached Strings On Disk Above Supports

Hi Neo,  I really appreciate your help.  The printer is running now, and I'll know in 8 hours if it worked.

Prior to Prusa Slicer, I used Cura which had a "Concentric" support pattern.  This seemed to work best with cylindrical projects.  I wish Slicer had this option.

Ken

RE: Unattached Strings On Disk Above Supports

Sorry missed your last reply.  The support itself doesn't have concentric but the support interface drop down contains many more options including concentric iirc.

RE: Unattached Strings On Disk Above Supports

Hi Neo,

I ran the print with your settings and it reduced the strings by about 75%, But they were still there.

I was thinking about maybe increasing the print head temperature just as it was getting to the transition point in an effort to get the filaments to stick together better.

Do you think that this might help?

Ken

RE: Unattached Strings On Disk Above Supports

When you say strings are they hanging down, like dangling or are they just not firmly fused together so the surface isn’t smooth ?  The first option would be some issue but the second option I’m afraid is pretty normal for slicer bridges. There’s a few threads around here about it and the general conclusion is a different slicer should be used if it’s vital.
There’s a few things you can try to help but without a zipped up 3mf project file to have a look at and experiment with a few settings it’s hard to say which of them will work. 

RE: Unattached Strings On Disk Above Supports

The strings don't sag, they are just not attached to the strings on either side or the ones above.  I'm going to make a smaller test with only a few mm of supports and experiment with different settings.

Ken

RE: Unattached Strings On Disk Above Supports

Posted by: @neophyl

The support itself doesn't have concentric but the support interface drop down contains many more options including concentric iirc.

Where do I find the "Support Interface Drop-down"?

RE: Unattached Strings On Disk Above Supports

Sorry Ken.  I use Super Slicer (SuSie) a lot.  Which is built on and takes a lot from Prusa Slicer.  Its just got way more settings and options, many of which have been requested for ages in PS but aren't there.  As such the drop down I mentioned is not in PS.  I'm just so used to having it and the programs are the same basically that I forget sometimes which ones are missing from PS (of which there are so so many).

At the moment you can even use the new monotonic or an ironed support interface.  

There's an earlier thread (one of several) https://forum.prusa3d.com/forum/prusaslicer/bridging-infill-settings/ where I posted some pictures of my experiments with bridges in SuSie.

RE: Unattached Strings On Disk Above Supports

Hi Neo, I have been experimenting for days and here is where I'm at (using the slicer with the Concentric option).

MAJOR PROBLEM

First layer on top of support does not properly adhere to the layer on top of it.

SECONDARY PROBLEM

Strands on first layer sometimes separate from adjacent strands.

OBSERVATION

The first layer prints at a much lower speed than subsequent layers.

THEORY

The first layer is not hot enough to stick properly because of cooler air rising up through the supports and the slow speed allowing the material to cool down too much between layers.

CONCLUSION

Other than manually altering things like temperature, speed, fan, and flow rate at the transition point, I can't think of what I can do to fix this.

Do you have any suggestions on things I can try?

Ken