hollow designs print our solid??

ok so any project i down load and print comes out fine, but my own prints using designspark to draw and then sli3er to slice come out pretty much as a solid,
in other words im trying to print a 20mm tube inside a 90mm tube joined together at the base with a 1mm deep plate but instead im getting the a 20mm hole inside a 90mm cylinder?

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razzadazzas
ok so any project i down load and print comes out fine, but my own prints using designspark to draw and then sli3er to slice come out pretty much as a solid,
in other words im trying to print a 20mm tube inside a 90mm tube joined together at the base with a 1mm deep plate but instead im getting the a 20mm hole inside a 90mm cylinder?

I have only used Designspark for a short period, but if I recall correctly, then as with most CAD tools to make a tube you need to extrude (draw) two cylinders for each tube. First you extrude a solid cylinder the size of the outside diameter (90mm), and then you extrude another tube the size of the inside diameter (maybe 88mm diameter if the tube has a 1mm thick wall). I think Designspark automatically switches to the "cut" function so it subtracts material instead of adding it to make the outer tube, but if not it can be selected. Then for your design you will make a third cylinder of 20mm inside that tube, and finally extrude a fourth cylinder of 18mm diameter to turn the cylinder into a tube.

Dave

What he said. . I've only used blender and have to do a Boolean (difference) operation to remove the smaller cylinder from the larger. Then another Boolean (union) operation to join the bits together (adding in the smaller cylinder in the middle). I've found that usually a repair is necessary (I use the auto repair in NetFab basic) to make it manifold after exporting the stl from Blender so that it can be sliced. Hope that makes sense. I made some nice beer can holders using this method [www.thingiverse.com]

Andrew

Edited 1 time(s). Last edit at 12/01/2014 05:03AM by Magoo.

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Magoo
I made some nice beer can holders using this method [www.thingiverse.com]
Andrew

Now that's a very useful design that I'll be printing soon. I might print a handle to glue onto it as well.

Dave