Weird solid infill for chamfer  

RE: Weird solid infill for chamfer

I think it has to do with bottom and top layers. The chamfer starts at a higher level than the bottom and needs more layers to keep the right number of bottom layer. In the picture it is also colored the same as bottom layers.

RE: Weird solid infill for chamfer

BTW, that isn't a chamfer. It is a fillet. As used by the few 3D packages that I've used chamfers are flat, and fillets are curved. I'm not trying to lambaste you, I'm just trying to normalize terminology.

RE: Weird solid infill for chamfer

That is solid infill applied to overhang layers where there would otherwise be insufficient material to support overlaying layers.

Here's my test part that is similar to yours but with actual chamfers top and bottom:

You can see the extra infill applied to the bottom sloping perimeters to give overlaying layers purchase. Without this supporting infill, perimeters on those overhangs are very prone to sagging.

If I print a cube with vertical walls composed of layers with good support beneath, this extra infill is not necessary, so is not generated.

The decision of when to apply such infill is programmed into the slicer. It's automated, so there is will be some cases where a bit of extra infill is generated, but generally it does a good idea. Any such infill will be inside the print, so not a real issue unless you want to get pedantic about what's going on inside sealed structures. If this is a real problem, the part needs to be designed to print properly with a modern consumer-grade FFF 3D printer. Fillets on bottom edges are a known problem. In this case, invert the part for printing and you'll get better results. Note that supporting infill will still be required for the top filleted edges, but you won't be fighting gravity in this orientation.

RE: Weird solid infill for chamfer

@area51

Ah, thanks for the suggestion. I set the bottom solid infill layer to 0 and 100 percent infill for those layers, then the wiggles are gone. Still i think it is somewhat a bug.

RE: Weird solid infill for chamfer

@sembazuru

Thanks for correcting me. TBH, i still don't quite know the functional difference between the two.

RE: Weird solid infill for chamfer

@bobstro

Thanks for the detailed reply. I understand why those wiggle supports are needed. But I have two questions:

1. Why can't those wiggle support be replaced by regular internal infill. As you can see in both mine and your screenshot, those overhang supports are in different color from regular internal fill.

2. At first I thought it is (maybe impossible) to slice it in a way such that the internal fill is used to support those overhang. But as I shown in the screenshot below, when I set the bottom layer number to 0 (a unreasonable number just for testing), the slicer had no problem fill the entire layer with regular infill at the fillet region.

But once I set the bottom layer number to 3, you start to see the wiggle.

The even more confusing part is, even if I set the bottom layer number to 50, you will still see the wiggle at layer 51, but that is out of the fillet region already... So we don't need the overhang support there, right?

RE: Weird solid infill for chamfer

Posted by: @gangyuan-j

[...] Ah, thanks for the suggestion. I set the bottom solid infill layer to 0 and 100 percent infill for those layers, then the wiggles are gone. Still i think it is somewhat a bug.

If the printed part is accurate and looks good, I wouldn't consider it a bug. The internal slicer functions are always being improved, but I'm sure they're not too worried about functions that are producing quality prints.

RE: Weird solid infill for chamfer

Posted by: @gangyuan-j

I am very frustrated with some weird solid infill issue, mostly due to sloped wall such as chamfer for fillet.

Here is an example. I have a 20-20-20 mm cube with 2mm rounded chamfer at the bottom shown in the figure

...

I am using the most recent prusaslicer 2.2.0

The reason I want to get rid of those wiggles is because they create crazy vibrations which then create layer shift for me...

Any help will be appricated!

So, I have had this issue on a few prints with an actual chamfer, and after reading through this post and then trying some different things in the slicer I have narrowed down to where this bug can show up.

It appears to be related to the following two items working together

1) Ensure Vertical Shell Thickness (Checkbox)

2) Variable Layer Height (Layer's in top Rectangle Menu at the top, third from the left)

If you have a chamfer slanting into the part, so that it is entirely sloping inward on the part with infil below, this also happens. If you disable either of the two items above it goes away.

I disagree with two points above that this is not a bug, or that who should care what the inside of the part looks like. Those points don't help anyone better understand the issue or why someone may want to understand why a slicer may choose to do something.

Hope this helps the OP or anyone else who comes by wondering why their machine is going through an unexpected test of their acceleration and jerk settings laying down a squiggly line on the inside of their part for no apparent reason.

RE: Weird solid infill for chamfer

I am on the newest PrusaSlicer 2.3.1 at the time of writing this.

I was having major issues with this, too, on one particular print that had a lot of steep slopes. The extra solid infill was causing 1) a really rough texture for sloped underside and 2) crashes due to too much plastic on the solid infill, not enough to actually cause it to be detected, but the nozzle was hitting the plastic and shaking the printer violently. There was an upper part of the print that was on supports, and the violent motion would make the nozzle literally rip that portion off the bed because the supports were never strong enough.

I tried every single suggestion I could find online, including all of the above posts, and none of them worked. Finally, the only true workaround was adding modifier meshes where I could adjust the top and bottom layers to 0 (which completely gets rid of the solid infills), and some where I had to adjust it down to 1 or 2 (because some sloped surfaces ended up getting big gaps without the solid infills, so I had to add those back). There was a ton of trial and error, and my model has so many modifier meshes everywhere, but I finally have a file that prints well.

By description, unchecking "Ensure vertical shell thickness" should have solved the problem without this process of modifying top and bottom solid layers, but this was just not the case. I think there needs to be a fix on the software to make sure checking/unchecking "Ensure vertical shell thickness" is correct, or provide some other way of fixing this solid infill issue.

RE: Weird solid infill for chamfer

@nancy-s

Your problems might be caused by something else.  I think you have two issues:

The extra solid infill was causing 1) a really rough texture for sloped underside

If the slope was greater than about 45 degrees the layers would not support each other well and you might need to use supports.

crashes due to too much plastic on the solid infill, not enough to actually cause it to be detected, but the nozzle was hitting the plastic and shaking the printer violently. There was an upper part of the print that was on supports, and the violent motion would make the nozzle literally rip that portion off the bed

This sounds like poor adhesion.  Either due to a slightly miscalibrated first layer Z value or possibly to contamination on the print sheet.

There was a ton of trial and error, and my model has so many modifier meshes everywhere, but I finally have a file that prints well.

Please show us pictures of your failed prints and if you are still trying to print that part, save the project as a .3mf file, zip it and post it here for us to diagnose.

Cheerio,

RE: Weird solid infill for chamfer

@diem

Well, I already fixed the problem by modifying the file to get rid of/reducing the amount of solid infills so I'm not quite sure this is caused by anything else. Reasoning:

1) The slope is greater than 45 degrees, but I don't have any problems with those slopes on other files. The problem is not resolved by adding supports (when printing with supports, I remove the supports and there is still a rough underside). The rough texture also instantly goes away the second the print gets to a section with no solid infills. When examining what's going on during the print, the nozzle is basically pushing too much plastic downward and the melted plastic gets pushed down to create that bumpy texture. This is different from when you see the rough underside of a print that doesn't have proper supports. I'll show you an image below anyways...

2) I don't think this is a calibration issue. Reason being I have printed this with both my MINI and my MK3S+ and it's almost the exact same result (the MK3S+ had more bumpy texture than the MINI, but they still looked the same way), unless you're saying I have created the same improper calibration on both printers. Plus I have zero problems with adhesion on any other print.

3) As I said, the trial and error of adjusting the top layers has solved my problem, so I'm fairly certain the solid infill was the culprit. If I go into PrusaSlicer and look at the purple areas (solid infill), it does NOT go away when uncheck "ensure vertical shell thickness" but it DOES go away when I reduce the top and bottom layers to 0.

EDIT: Woops, just realized one is showing supports and one is not, but just so you know the purple solid infill doesn't change whether I add supports or not.

RE: Weird solid infill for chamfer

Actually, this is a better image. Here's my results of what happened when I had kept the solid infill vs. removing the solid infill. Again, you're seeing the underside of a print.

RE: Weird solid infill for chamfer

@nancy-s

Red is invisible to me, and trouble for 12% of men, even to a fraction of a percent of women. I can barely see the text in that image.

RE: Weird solid infill for chamfer

@tim-2

I have the same issue.  

I think this is wear it is nearing the need for supports.  

RE: Weird solid infill for chamfer

@tim-2

Sorry about that.  Red was default on my screenshot software. The top was without solid infill and bottom was with solid infill. Both in the photo were printed without supports, although I had also tested this with supports and there was no difference so I had ruled out supports initially.

RE: Weird solid infill for chamfer

@nancy-s

Hey - no problem at all - after 65 years of dealing with color normals it no longer surprises me. What does surprise me is that after thousands of years of men being color blind to reds greens and oranges red is still the international danger signal. Go figure: why use a color that so many can't distinguish for pointing out dangerous situations? My pet theory is culling of the herd -- color normals are trying to get rid of those color blind whackos once and for all!

I say that in jest - but every once in a while I have to stop and consider...

ps: we color blind are better at detecting camouflage .. so I guess it all evens out...

RE: Weird solid infill for chamfer

Cull the herd with colors?  I would be be wasted a long time ago.  

RE: Weird solid infill for chamfer

@nancy-s

No issues from me.  I hope we have helped and you find a solution.  If you need supports, try Cura or Simlify3D till the next version PrusaSlicer is released.