Support not showing in preview.

[wirlybird]

I have two parts, one is a mirror of the other. Both have a small overhang which is perpendicular to the wall it is on. When I add supports it only shows on one of the parts. I haven't tried to print yet since it is a 3 hour print!

Is it normal for supports to not show but still print?

[dkightley]

The answer to the question you've asked is: No.

But I don't think the answer really helps! I think I know what your real question is...and what the answer is. But I'm not prepared to guess what your real question is without seeing the factory file.

[wirlybird]

OK, so why one support and not the other? Both pieces are identical except are mirror images. I change support pillar resolution and I get two supports. I put it back where it was and now no supports.
If I put the support back to 3.5 I get no supports and if I put it to 4 I get one support, back to 3.5 still 1 support and back to 3 and now 2 supports.

I added the file.

Thanks.

P.S. I figured that if the support didn't show it wouldn't print just checking.

[wirlybird]

OK, this is BS. I had both supports showing. Went back to check on a setting - didn't change anything. Hit prepare to print and didn't notice that one of the supports was no longer there. Now into the print for a while I see the support not printing.
I didn't change anything but the software changed the supports.

[dkightley]

Okay.......my theory, which is partially proven now I can play with the factory file.....

My understanding is that the support generation is based on an algorith that works on a grid pattern that overlays the model being printed. Let's say the grid is x mm. The two parts are a mirror of each other....but the size of the components and the distance between the components mean that the lines of the grid do not fall exactly in the same relative place on each of the mirrored parts.

The result...one overhang presents sufficient area for support to be generated, and the same overhang on the mirrored part presents smaller areas say on two adjacent rows on the grid, neither being sufficiently large enough to cause support to be generated.

Shift one of the parts slightly....and support is generated on both parts. Alternatively, lower the resolution of the support columns, and the respective areas now generate support.

The only part ofthis theory I can't replicate is the necessary distance needed to move one part to guarantee similar support generation....

EDIT.......perhaps a slight mod to my theory. The support grid is separate for the two parts....but the theory re location of the lines in the grid remains the same. Result....the two sets of support are different.

[wirlybird]

Great explanation! So, in summary I can try moving one part a bit and see what happens or just keep lowering the "support resolution until I get the supports I need?

I didn't need anything fancy for supports just to have them!!

Thanks for taking the time!

[dkightley]

I'd lower the support resolution. The overhanging ledge is quite small.

I'd also add 0.4 mm of Extra Inflation Distance and one dense solid layer on top at 100% to crisp up the overhung edge.

[JohnOCFII]

Great explanation! So, in summary I can try moving one part a bit and see what happens or just keep lowering the "support resolution until I get the supports I need?

At times when I didn't get automatic supports generated, I usually drop from the default size a bit, and then I'll get supports wherever I need them.

[wirlybird]

Great explanation! So, in summary I can try moving one part a bit and see what happens or just keep lowering the "support resolution until I get the supports I need?

At times when I didn't get automatic supports generated, I usually drop from the default size a bit, and then I'll get supports wherever I need them.

Seems the thing to do. Maddening when you have supports then go to check a setting and don't realize it didn't re-generate them this time and blow a print!