How to hollow out an object for DLP printing

[WalterMo]

Bigger solid objects which should be printed need to be hollowed out to save resin. Of course the hollow part must not be enclosed all around. It must have a free connection to the outside so that liquid resin which wasn't completely cured by light can flow out. Also it could be possible to insert an UV LED to post-cure the resin.
Newly I asked Sven to program a software which hollows out objects to help me to print the DAVID-Angel:
viewtopic.php?f=9&t=5461

And here it is for a free download. Thanks to Sven!

Two parameters must be set in the Hollow Maker software, the wall thickness (in mm) and the level for smoothing of the inner surface. Of course the outer surface will be the same as before. Good smoothing values will be 100-1000. But test it, this value depends on the state of the outer surface. A strongly structured one, like my example here of the Morpheus sculpture needs a higher value. I had set '500'. And as you can see on the attached image of the three slices the wall thickness varies. So don't set the thickness parameter too small, otherwise the inner skin will come to the outside.

This Morpheus bust was scanned by Mattia. The first image is a screen shot of the scan and the letters A, B an C indicate the cross sections of the next shown 3 layers (of 824 layers) after slicing, which was made by the B9C software of Michael Joyce.

How to use the Hollow Maker:
Download the zip file, unzip it into one folder and don't remove the 3 *.dll files. The Hollow Maker can only import and export OBJ files, therefore if you e.g. have a STL file use the free MeshLab software to convert it. Load the OBJ file which should be hollowed into the folder mentioned above. Move this OBJ file by drag and drop onto the Hollow Maker exe.
Set the 2 parameters on demand. The output result will be two OBJ files: One with the addition 'hollow' and the other one with the addition 'inner'. Latter can be used for checking. Don't try to upload an OBJ file to the B9C software, for me it didn't work. Convert it to STL before.

Give it a try!

Walter

PS. The white dot in layer A on the left side of the head is the tip of the (free) down hanging hair. Here it is necessary to set a supporting rod before 3D printing!
If you like to know how the bust was scanned, look here:
http://www.david-laserscanner.com/wiki/ ... els_by_hal

Edit: If you want to use the software for a XP pc, please download Sven's "Make Hollow", version 0.4. His post of Jan 18, same thread.

[VDX]

Hi Walter,

thanks! - will test this later ...

I'm mostly using comercial programs that can create 'shells' from solid objects ... or the RepRap-slicers, that calculate the outline and an adjustable count of shells and adjustable infill for inner volumes, that can be set to zero - but the RepRap-slicers output path-curves, what's not direct usable for DLP-printing.

One more point remaining is automatic calculation of supporting structures ...

Viktor

[hunkatibor2]

Hi Walter
I do not work in the program. What is the Operating System requirements??
Tibor

[WalterMo]

Tibor,
I have tested the *.exe and it seems that it doesn't run on Windows XP with 32 Bit.

On my Win7 64 Bit it works fine.
I am sure Sven will solve the problem.

What experience have other users made?

Walter

Edit: In the meantime the versions 03 and 04 were downloaded altogether 73 x, and no feedback? Strange....I give up

[hunkatibor2]

Hi Walter
Operating System Windows 7 32-bit.
Tibor
Send me a picture of the operational program, which comes up.

[L.J.P.S]

there is a tric for this with Blender, that works well especialy when you have one side that is flat or of less importance ====>
open STL in Blender , go to => editmode and delete the vertices of the bottempart (be carfull : alone the inner vertices and leave those who are
visuable at the outside, so the outher ring , then in Object mode => duplicate the object , you can take it outside and then first smooth it as you wich
then you scale it down for some litelbit as much as you need for the wall ticknes
place it again in the center of the first one
join the two and fill the bottem row
some work: but once familiar with this you can handle it without other software
and the advantage is that you make your wall thikness like you want and smooth where you want or even make bridges
(note: it is always good to controle the mesh for "holes"...I do this with Meshlab)
regards
Luc

[hunkatibor2]

Hi Luc
Please put a picture on the steps of the Blender software.
I know the pictures or videos I can learn. The text description is not good for me. I asked the Hungarians used to help with this, but I'm told it can not be solved.
Tibor

[L.J.P.S]

ok Tibor but give me some time ,shall make a screenshot short storry
Luc

[L.J.P.S]

Solidify Modifier in Blender 2.65
hallo Tibor
the duplicate/scale tric dont work well for complicated models / to difficult (for simple and geometrical forms its good)
but see the Solidify Modifier
trying to make an exemple I used as model the "head" of a bone that I cut in the middle so you can see the inside
how it works: take an object (best OBJ)
then you go to => Modifiers => Solidify
in that panel ==> Thickness play with it and see wat it gives
"Fill Rim" has to be actif and I think in "Crease" all values are best 0 (zerro)
and you can activate "Even Thicness"
in my attempt to visualize I made duplicates and turned them in different angles of vieuw
note: the second image: there the model left is the original without a "thickness
regards
Luc

[hunkatibor2]

Hi 3DPrintDavidias
I managed to take at the end of a self portrait of the digitized 3D Printing Software.
I see that the inside triangles appear to be. If the blender and watch Meshlaban you can not see. What could be the source of errors.??

[hunkatibor2]

Hi Luc
Thank you very much for your help, I really appreciate you.
Tibor

[WalterMo]

Tibor,
Now and then I have the same problem after slicing. One of about 500 slices shows a white triangle or something with a similar shape like your example.
I don't know what the reason is, maybe the object wasn't completely watertight before slicing.

So we have three possibilities:
1. To paint over the imperfection black by hand via the pencil tool. (I see you are also using the B9C Layout).
2. To substitute this slice (BMP image after export) by a good neighbour slice. Then to do some little corrections by hand because of the difference between the original slice and the neighbour ones.
3. To delete it completely.

Walter

[hunkatibor2]

Hi Walter
I managed to solve the problem. The good old 10 Geomagic software handled. The eliminated unnecessary triangles.
I typed in 32-bit field. This means that 32-bit version works?.
Tibor

[Sven]

Hello all,
This version, makeHollow 0.4, should also work on XP.
Sven

[WalterMo]

Just tested, it's OK. Thanks!

Walter