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BernieC
(@berniec)
Trusted Member
maximum unsupported span

I  knew this once but I've forgotten.  how wide can I "leap" an unsupported span without supports?  This with PLA on my Mk3?

Posted : 24/04/2021 7:58 pm
BernieC
(@berniec)
Trusted Member
Topic starter answered:
RE: maximum unsupported span

I remembered a related question I forgot to ask: what is the maximum fillet under a surface that will work without supports.   I was disappointed to see that when i told prusaslicer to put in "all supports" it complete covered the fillet... I'd have thought at least half of it would have for-sure not needed supports.

Posted : 24/04/2021 8:11 pm
Swiss_Cheese
(@swiss_cheese)
Noble Member
RE: maximum unsupported span

the answer to the first question is, it depends on the filament your using, and the answer to the second is, it depends on the filament ,layer height, angle of fillet, temp of the filament, layer width, ....etc,,,, I hope your getting the idea by now. run some tests with the filament you intend to use and see what the results are.

 

It is the way,

 

Swiss_Cheese

The Filament Whisperer

Posted : 25/04/2021 2:01 am
Diem
 Diem
(@diem)
Illustrious Member
RE: maximum unsupported span

how wide can I "leap" an unsupported span without supports?

you *can* bridge nearly the whole width of the plate but the longer the bridge the looser the layer and the more layers that are affected.  You probably wouldn't like the look of a 180mm bridge...

So make a set of small test bridges and decide for yourself how long a bridge you consider to be of acceptable quality.

what is the maximum fillet under a surface that will work without supports

But here it's the other way around.  It's the first, very shallow part of the curve that cannot be supported and prints loosely.

To avoid this start the fillet at about 40 degrees and than curve the rest of the corner - or replace it with a chamfer.

Cheerio,

Posted : 25/04/2021 3:00 am
jsw
 jsw
(@jsw)
Famed Member
RE: maximum unsupported span

There are some bridging test prints available at the 'usual suspect' 3d print sites, including this one.  Often they are combined with the temperature test towers, so you can get an idea of what temperatures best work with bridging on your particular machine and filament.

Personally, I've done 'acceptable' (translated: only moderate droop) bridging in the 25-30mm range fairly consistently on the I3.

Posted : 25/04/2021 9:09 am
BernieC
(@berniec)
Trusted Member
Topic starter answered:
RE: maximum unsupported span

All correct -- I did a test and the span that it could manage was about .5 mm.  So I re-sliced it with enforcers and suppressors so it only supported the outermost part and that should be OK.

Posted : 25/04/2021 9:47 pm
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