floating, unsupported overhangs in Cura

[beezerdesign 0]

I'm having this problem fairly regularly with the latest Cura 15.04.2 where it will leave some overhanging geometry entirely unsupported. In the past, when I notice in time, I have been able to resolve the issue by orienting the model in a different way on the build bed, but sometimes that doesn't even work or it results in super long print time that shouldn't be necessary if Cura would just be smarter about the placement of the support material.

here is one example:

The geometry indicated with the green arrow should go up at an angle and eventually meet the main dome structure, but it will never make it that far because all of its initial layers are being printed in mid air... I already reoriented this model once to fix a much worse floating overhang, but still Cura insists that these hooks (which are an important mechanical attachment feature in this print) can be printed in mid air. Unfortunately I didn't see this one in time and now more than halfway through my 16 hour print, there is a wad of spaghetti hanging off of my model where attachment hooks should be.

I suppose changing the value for overhang angle for support could fix the issue, but this also would add a significant amount of support material to the domed inside of my model where it actually isn't necessary.

Very frustrated. Any ideas or suggestions are greatly appreciated.

Thanks.

-Blake

[cloakfiend 962]

If you know you will have them, just put in manual supports. they will most likely be better than curas anyway, and considering the rest of your model doesnt look like it needs them you'll save a hell of a lot of time and filament while your at it.

[beezerdesign 0]

That's not a bad idea! Don't know why I didn't think of that...

I've never done manual supports before though, do you have any suggestions or do you know of any online tutorials or whatever for that kind of thing?

Thanks for the reply.

[cloakfiend 962]

Experiment and then save the shapes you like so you can re-use them on other prints. You need to experiment to get your thicknesses right.

[gr5 1,451]

This is a good read:

http://support.3dverkstan.se/article/38-designing-for-3d-printing

[cloakfiend 962]

Its a good read, but again i dont agree with all of it. And having to change my designs for ones that will print better is not always an option, and the whole cant print sharp corners seem like total BS as i have been printing nothing but sharp cornered objects lately with zero issues, so i take all that with a grain of salt. The theory behind it is sound however.

I would just experiment for yourself to see what you particularly have trouble printing and go from there. Don't concern yourself too much over having to model everything printer friendly, its not always or very likely necessary. different resolutions and filament make things more possible than others as well as many other factors. I only really have issues with sharp inclines, gaps, large circular holes and auto support for small objects.

My 'sharp' corners.

[gr5 1,451]

I think that sharp corner issue may have had to do with parts that need to fit inside each other? In that special case you have to cut the corners a bit or spend much too much time with the file.