Why does this Boolean Difference not create solids?

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 From:  chippwalters
7039.1 
Just bought MoI. Woo-Woo!

When I subtract this "parting line" solid from the larger widget solid, the resulting object is hollow. Why is this? How do I fix? (Newbie issue).

Here's a link to the file:
https://altuit.cloud/web/dbpub/3D/booleanProb.3dm

Thanks!

EDITED: 18 Nov 2014 by CHIPPWALTERS

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 From:  bemfarmer
7039.2 In reply to 7039.1 
.

EDITED: 18 Nov 2014 by BEMFARMER

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 From:  Michael Gibson
7039.3 In reply to 7039.1 
Hi chipp, thanks for your order, I hope that MoI will be useful for you!

> When I subtract this "parting line" solid from the larger widget solid, the resulting
> object is hollow. Why is this? How do I fix? (Newbie issue).

The problem is that your larger widget solid is not actually a closed solid, it has some open areas in it and does not make a watertight volume yet.

You can tell if an object is a solid or not by the "object type indicator" that is displayed in the upper-right corner of the propeties panel when you select it. When you select a solid it will show like this:



If your object is an open surface, the object type will read as either "surface" if it's just one surface, or "joined srf" if it's made up of multiple joined surfaces but not all closed up to be a solid. Yours reads as "joined srf":



This usually means that there are some "naked edges" in the model which means edges that only belong to one surface rather than joined between 2 surfaces like edges of a watertight solid need to be.

The best way to find these naked edges is to set up a script on a shortcut key as described here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3540.2

Once you set that up you can then push N and have the "naked edges" of your model get highlighted so you can see if there are any, and where they are. If you do that on your model you'll see these areas highlight:




These areas will need some repair work on them.

There seems to be 4 areas and 2 naked edges in each of them, it looks like the fillets here slightly overshoot each other rather than coming to a single common ending spot:






Hope this helps!

- Michael

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 From:  Michael Gibson
7039.4 In reply to 7039.3 
Actually it's only one fillet that overshoots, the one on the right (the selected one) in the above screenshot. Then there's an additional little slivery piece like this:



Possibly just deleting that little slivery piece which is overlapping the end of the adjacent fillet would be enough to get things all tuned up, I will see if that does the trick.

- Michael
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 From:  Michael Gibson
7039.5 In reply to 7039.4 
Or it's slightly more complicated than that - the little slivery piece is pretty small, only about 0.005 units across and little things around that size can tend to complicate good joins, it can be possible for opposite sides of the sliver to get glued to the surrounding pieces, something like that seems to have happened.

I'll see if I can repair it by some untrim and retrimming work.

- Michael
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 From:  Michael Gibson
7039.6 In reply to 7039.5 
Hi Chipp, yeah something at one point got confused by that little slivery surface there and things got joined together on opposite sides of it. Things shaped like small thin slivers like that can cause various problems.

I was able to repair the object by separating out the 3 faces in each of those places which was 2 fillets and then that little sliver between them and then doing an "untrim" operation on all of them to get rid of the current messed up trimming boundary and restore their full underlying surface. Then after the untrim the pieces joined together ok with the join command to make a proper solid, I've got that in the attached file which should now boolean properly for you.

Probably the actual problem is some kind of bug but it's a bug in handling some kind of thin slivery surface condition in filleting, but somewhere in your original curves there is probably a little tiny 0.005 length curve segment as part of the profiles used for construction and it would be better if something that tiny was not in there.

If you are curious about how to do the untrimming stuff, there is some more information on untrim here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=444.4

And there's more detailed information on this kind of low level surface repair process in the object repair tutorial here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=446.17

Hope this helps!

- Michael

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 From:  chippwalters
7039.7 In reply to 7039.6 
Thanks Michael for the *TREMENDOUS* customer support and clear explanation. This was my first model and there's a chance I did something wrong. I'm working on another model right now and am having some similar problems and I'll try your technique and see if I can't fix. THANKS AGAIN!

(BTW, I'm pretty familiar with a lot of different apps. I own Lightwave, FormZ, Modo, SketchUp Pro, and use a couple other freebies for various other things-- and I have to say YOURS is the easiest BY FAR to date, w/regard to get up and running. I think I have all of 4 hours in by now and feel very comfortable. Thanks for paying attention to the UX-- really helps.)
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