Shapeways: Bring your creativity to life in 3D

Hollow object more expensive?

wjhulzebosch — 2009-06-30T07:30:18-00:00

Ok,

I created a structure that, if you look at it from a specific position, looks like an impossible triangle. I uploaded V1.1, and it would cost me around $45,-. Quite expensive for a first try, so i hollowed it out. Uploaded it again, and now it's over $70,-. What could cause this? Is it possible that in the hollowed out model, they automatically added supports or something, that make the volume grow?

See att. v1.1 is the normal one, v1.11 is hollowed out.

Re: Hollow object more expensive?

Ushanka — 2009-06-30T23:36:01-00:00

Can you show us some pictures that aren't in .dae format? Also, how big was your impossible triangle? I made one that is <$10 and maybe 1.5 inches tall.

Re: Hollow object more expensive?

wjhulzebosch — 2009-07-02T13:29:22-00:00

At your request: A screenshot of my model, one x-rayed, one "normal". Size of the model:
Height 6.7 cm
Width 9.2 cm
Depth 7.2 cm, but those sizes are the same for both models.

Re: Hollow object more expensive?

Youknowwho4eva — 2009-07-02T15:33:59-00:00

My guess would be that it is not possible to do an object hollow, that the printer will automatically fill it with build material. Which I believe is more expensive then the model material.

Re: Hollow object more expensive?

WiKKiDWidgets — 2009-07-02T20:41:21-00:00

It is very possible to print hollow objects, in fact that is one of the unique attributes of 3D printing. Not only can you print hollow objects, but can have a separate manifold meshes printed inside a larger mesh.

I'll venture a guess that your issue is with Normals. If the normals are not oriented correctly, it can confuse the printer software as to what is inside and what is outside and make part of your model solid where you intended it to be hollow.

If you have Blender at your disposal, it can help.

Load your model into Blender. (Export it to a different format if you need to.)

First thing you want to do is remove all the duplicate Vertices which is common for imported meshes.
Go into edit mode by hitting {TAB} and then select all the vertices with the {A} key. (Note: The {A} Key is a Toggle That both Selects all and Deselects.) Once you have all Vertices selected, hit {W} and then choose [Remove Doubles] from the pop-up list.

A nifty trick in Blender is being able to actually see the orientation of the normals by making them visible. Hit the {F9} key and then on the far right hand side, look for the [Draw Normals] Button. Click that and your normals will be visible as light blue lines. (They may be too short to see them well. If so, just increase their size with the [NSize] slider just above the [Draw Normals] Button.

Try that and export it to a .STL file and see how much it costs.

Re: Hollow object more expensive?

wjhulzebosch — 2009-07-03T14:31:59-00:00

Ok, i know what went wrong... I forgot to invert the inner body, so there where actualy 2 (nearly) the same objects that would be printed, instead of 1 hollow one I uploaded v2.0 and it will cost me $ 3.53 :

Anyway, thanks everybody for the help!

Re: Hollow object more expensive?

WiKKiDWidgets — 2009-07-03T15:59:39-00:00

LOL

Don't be embarrassed, I've done the exact same thing.