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Hollow Object [message #20260] Tue, 09 November 2010 03:25 UTC Go to next message
avatar amiller  is currently offline amiller
Messages: 2
Registered: October 2009
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Junior Member
I am trying to create a hollow object, so I have an outer shell and an inner shell, the inner faces have the normal facing inward, and the outer faces have the normals facing outward. also attached to the outer faces are several other solid shapes that intersect it.

For some reason, when I upload the model, it doesn't make it hollow, the volume i the same as if it were solid.

I have attached the .stl file, if someone could help me with this, it would be greatly appreciated. (it is a gift for one of my physics professors)

Thanks!

-Andrew

  • Attachment: alfred8.stl
    (Size: 5.61MB, Downloaded 68 time(s))

Re: Hollow Object [message #20265 is a reply to message #20260 ] Tue, 09 November 2010 04:49 UTC Go to previous messageGo to next message
avatar clsn  is currently offline clsn
Messages: 151
Registered: July 2010
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Senior Member
I just cleverly posted this in response to the wrong post. Woops. This is where I meant to say it.

I can't find the official FAQ/tutorial/post, but here's the situation:

Owing to the way Shapeways figures volume, things aren't considered hollow unless there's some hole joining the inside to the outside. That is, there has to be a way for the support material on the inside to get out. You can't just have a vacant space in the middle that isn't connected to the outside world.

That said, you *are* allowed to make that connecting hole really really small, such that the support material can't actually get out (and in that case you essentially get the support material for free. Don't abuse this.) But that looks like the problem you have here: you have an empty space in the middle, but it isn't connected to the outside, so it is still considered solid.

What's the link to the post or whatever that explains all this? Also, some of the tutorials are out-of-date: they talk about how overlapping solids are double-charged (they aren't anymore), etc.
Re: Hollow Object [message #20271 is a reply to message #20265 ] Tue, 09 November 2010 06:26 UTC Go to previous messageGo to next message
avatar amiller  is currently offline amiller
Messages: 2
Registered: October 2009
Go to all my models
Junior Member
I'm sure that I printed a model this way before, maybe it didn't print hollow, and I just didn't notice... (it was very small) I made a tunnel to the outside, and it recognized that it was hollow.

Looking back, I am sure that it worked that way before, because I uploaded this model a year ago, and you can see that it calculated it as being hollow. I noticed an announcement that they change the merging system recently, so maybe that had something to do with it...

Thanks!

-Andrew
Re: Hollow Object [message #20564 is a reply to message #20271 ] Tue, 16 November 2010 09:54 UTC Go to previous message
avatar bartv  is currently offline bartv
Messages: 1668
Registered: December 2007
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Shapie Expert
Hi Andrew,

you are correct - in the past you didn't need to create a hole. We changed our calculations in July to filter out overlapping parts. At that time we had to include the restriction of adding a hole. Here's more info:

http://www.shapeways.com/blog/archives/515-Website-Update-Ne w-Volume-Calculation.html

Cheers,

Bart


Community Manager Europe | Shapeways

 
   
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