ABS Bridging again

I've attached the model I'm using to test bridging with ABS. I can't make it work. I can get close, but the underside always looks, at best, a little bit like the various strands melted and sagged a little.

I've used two ABS's so far. I have one more to try, but I've no reason to think it's much better. The other two are absolutely fine for all models, just not this bridging.

The lowest temperature they print at is (let's say) 230. Any lower and it won't come out the extruder.

I've tried:

Temperature, from 230 - 280. At higher temperatures I hoped it would contract as it cooled pulling it into place. But no.
Print speed from 5mm/s (reallllly slow) up to the fastest the printer will go (not sure in reality, let's say 60 for argument's sake).
Bridging extruder multiplier from -70pc (i.e. only 30pc the width) up to 180pc (i.e. fat fat fat).
Heated bed 100-120.

And I've tried these all in various combinations.

The only things I can think of now are dropping the temperature of the heated bed further, risking it not sticking, and using a fan (My ABS print head mount is different to my PLA one and doesn't have a fan).
The fan idea I know is stupid (probably).

I'm honestly at my wits end with it. I've printed probably 50 of the little things and none of them look great on the underside. I've got to a point where it is useable, just ugly.

If you're wondering why I don't just enable support. It's simply because I want to tune it to bridge well, if that's even possible.

Help!

What slicer are you using? I've noticed cura does a better job in some cases than slic3r. Also check if theres a newer version of the slicer software, improvements are made every so often. Also play with the feed rate in slic3r for bridges under advanced tab. I use a cooling fan with abs, especially for bridging and layers under 10 seconds at 270 deg. C. Little to no warping, good layer adhesion, delamination is rare, even with higher builds.

Bridging is never going to be perfect, normally the very first bridge layer is loose and possibly a little sagging, just cut it and remove and the rest should be fine. Bridging is a method to get the printer to do what it really should not be able to do (print in air).

Quote
tmorris9
Bridging is never going to be perfect, normally the very first bridge layer is loose and possibly a little sagging, just cut it and remove and the rest should be fine. Bridging is a method to get the printer to do what it really should not be able to do (print in air).

hah, I want it perfect, but I get what you mean. I can bridge well as part of a model, short distances, or doing cut outs, it's only really these fake tests that it fails at. Even then, it's not failing per se, it's just not as neat as I want.

Immqmi, I'm using Simplify3D. It's good, seriously good actually, but as Cura just updated itself I might give it a go just to prove it isn't the actual software

The purpose of the tests is to test and adjust the machine and software so you get a descent print (like you already have). Many people end up with just drooped strings on the build plate. When you dial in bridging with these tests it means that shorter bridges in actual objects should be perfect. Many times bridges in objects will only be like 1/4 the length of the test so they print much easier.

I have Simplify3D as well and I keep going back and forth between it and slic3r. I have tried Cura but never had a lot of luck with it though I know it's been improved since I last tried it.

Haha, no the purpose of the tests is to drive myself mental trying to go after perfection

I do produce really nice prints. I had to print out some Mendel 90 parts, and I've got a set of Nophead printed parts which I consider to be the gold standard. Mine are pretty good in comparison. Not perfect, but pretty damn good.

Cura never worked for me so I never persisted with it much. I did get a few nice prints out of it. I think it defaulted to some weird settings when I first tried it and that put me off as I didn't really know what I was doing. Slic3r frustrates me. It seems we're trapped in some really old version while the newer versions get worse and more buggy :/

Simplify is fantastic though. Not perfect. The UI has some odd design ideas and bits of it are a little rough, but I've been delighted with it so far.