[PROBLEM] Bridge infill in mid-air when increasing number of perimeters.
 
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[PROBLEM] Bridge infill in mid-air when increasing number of perimeters.  

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zalexzperez
(@zalexzperez)
New Member
[PROBLEM] Bridge infill in mid-air when increasing number of perimeters.

Hello all,

I've been having a hard time getting the bridges to print properly for a while on my modded Ender-3. They're getting printed in mid-air.

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SITUATION: I performed a clean install of PS 2.2.0 rc4 and used the pre-configured profiles that come for my printer.

The only settings I changed on the printing profile are:

Detect thin walls (enabled)

Detect bridging perimeters (enabled)

Perimeters: 4 (changed from the default 2)

 

The part has 1.6mm thick walls 

Here's the STL file of my test part: https://drive.google.com/file/d/1ZwnU2j9Q8ikSUSBB6sowNaQKdII9CRX_/view

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SCREENSHOTS OF THE PROBLEM:

First image shows the slicing result when trying to print with 4 perimeters instead of 2 (second image).

Bridge infill printed mid-air Proper bridge infill

 

 

Experimenting a little bit, I see that the larger the set perimeter value, the least perimeters that the bridging will rest on. (E.g. if 2 perimeters: the bridging strands rest on 2 perimeters, if  3 perimeters: it rests on only 1. In case 4 perimeters: the bridging strands don't have any perimeters left so it gets printed mid-air)

Is this normal? 

You may say..."Okay, just set it to 2 perimeters" but what if I have another part that required thicker walls (E.g. 8 perimeters)  and there happened to be a bridging somewhere else between walls that are as thick as only 4 perimeters ?

 

Thanks

 

 

 

 

 

 

Posted : 16/03/2020 1:13 pm
bobstro
(@bobstro)
Illustrious Member
RE: [PROBLEM] Bridge infill in mid-air when increasing number of perimeters.

I wasn't clear on first reading your post what the issue was, but if you view the model from underneath in preview mode it's clear. Sliced with 2 perimeters, bridging strands start and stop atop the perimeter walls:

If sliced with 4 perimeters, they start and stop with a suspended layer which itself shows as a bridge:

I don't have a good answer for your on this, but it is probably worth opening an issue on the PrusaSlicer github page to ask the question.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 16/03/2020 4:00 pm
Chocki
(@chocki)
Prominent Member
RE: [PROBLEM] Bridge infill in mid-air when increasing number of perimeters.

Set your infill to 5% concentric, slice and see that the bridge is now fully supported.

Even works for 1 perimeter, but of course you have more walls due to the concentric infill.

I also use this trick to support bridges with modifiers.

This post was modified 2 years ago by Chocki
Normal people believe that if it ain’t broke, don’t fix it. Engineers believe that if it ain’t broke, it doesn’t have enough features yet....
Posted : 16/03/2020 4:31 pm
bobstro
(@bobstro)
Illustrious Member
RE: [PROBLEM] Bridge infill in mid-air when increasing number of perimeters.

FWIW: The bridges do work with 4 perimeters. Not sure why they print differently though.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 16/03/2020 6:02 pm
Chocki
(@chocki)
Prominent Member
RE: [PROBLEM] Bridge infill in mid-air when increasing number of perimeters.

Didn't read the OP post too clearly and now understand, he is trying to print with 4 perimeters and this is when the bridging prints in mid air, which I can confirm when viewing the slicer preview. Still, using concentric infill with 3 perimeters, actually results in 4 perimeters and a fully supported bridged layer.

Very strange behaviour from slicer, but this would result in a solution that works for the OP.

Normal people believe that if it ain’t broke, don’t fix it. Engineers believe that if it ain’t broke, it doesn’t have enough features yet....
Posted : 16/03/2020 7:09 pm
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