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hollow object prints solid

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Posted · hollow object prints solid

I'm fairly new to 3d printing. I'll try to get to the problem quickly. I have tried every suggestion I can find, but I'm missing some knowledge. I made a HOLLOW threaded hole in Sketchup that keeps converting to SOLID in a few different slicer softwares I have tried. I have already successfully printed parts like this using the same tool (EP Fasteners & Holes), and they looked and printed hollow. I've tried solid inspector, Netfabb online, Cura, ideaMaker. I even tried to print it anyway and it was printing solid, not hollow. I'm pretty sure my model has a problem, but I just can't figure it out. I could go on, but you get the point. I'm uploading a file that has my part and the threaded hole separately AND a screenshot of the sliced preview. If someone could fix the part, that would be AWESOME! But, I really would like to know how to fix the problem because I'll be doing this type of thing in the future. Help and suggestions would be greatly appreciated.



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    Posted · hollow object prints solid

    There are many solutions.

    1) In sketchup it's important to make sure surfaces are white, not gray.  Right click on the inside of the cylinder (in sketchup) and select "reverse faces".  This should fix your problem.

    2) Sometimes you can just uncheck "union overlapping volumes" (that's if your model is really messed up and has extra walls)

    3) You can try these repair services:

    netfabb free repair service is here (you have to create a free account first):

    Here's another service - drag and drop mesh repair service:

    I recommend you read this so you don't have these problems in the future:


    from labern: When using sketchup always use these 2 plugins:
    cleanup3 (may be 4 now)
    Solid inspector.

    Both of these plugins remove any problems with the model unseen by the eye and turn it into a solid model.


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    Posted · hollow object prints solid

    you were right that the model has flaws: the cylinder had 2 vertices inside out and the thread is not a solid.

    Combining the solid thread and the cylinder will print fine in Cura


    Schermafbeelding 2020-05-02 om 18.01.13.png


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    Posted · hollow object prints solid

    The quick answer is probably to use those 2 repair tools I linked you to.


    I used sketchup for several years and was quite good at it but I never learned how to do threads.


    I stopped using sketchup years ago and haven't looked back.  Sketchup is fine for 3d walkthroughs and architecture visualizations but not so good at creating solids.   I use DSM (design spark mechanical) but it's a big learning curve.  Actually for threads I don't know how to do that in DSM either so I use openSCAD.  But that also has a big learning curve.  But your project is perfect for many "free" CAD packages like onshape.  onshape is professional level but there is a free version.  onshape has thread libraries.  openSCAD also has thread libraries - it has built in standard threads or you can create your own - I created a double helix thread (for a maglight flashlight) and it worked perfectly the first time.

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    Posted · hollow object prints solid

    One more thing about sketchup - see in sketchup you can create panels - walls - cylinders - that are infinitely thin and just leave them there and sketchup is fine with that.  You can color one side of an infinitely thin wall with house siding and photos of windows and paint the inside with your interior wall color.


    But that's not real - it isn't solid - the wall has no thickness.


    Most CAD packages - packages meant to actually create things in real life - won't let you do that.  It doesn't even have the capability - you don't have to worry and go back and check your model (like you do in sketchup).  It's just impossible (or nearly impossible) to create non solids in most CAD.


    That's why I reocmmend DSM or openSCAD or onshape or tinkercad or any of 500 other programs if you will be doing this a lot.

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    Posted (edited) · hollow object prints solid

    Hi @davidmillertime 

    I use Meshmixer a lot for checking and cleaning, but it also takes a while to learn the details.

    You could fix this also in Sketchup, but like @gr5 said, other programs are better for 3d printing.

    A good indication for reversed vertices is to look at the color, inside and outside have different colors, in Meshmixer they are pink.

    The thread needed some extra vertices to make it solid.


    Schermafbeelding 2020-05-02 om 19.15.19.png

    Edited by peggyb
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    Posted · hollow object prints solid

    Thank you both for all of the great information!


    I downloaded Meshmixer and have been trying to work on it for an hour or so. I just can't figure it out.


    Peggy, would you be able to tell me the steps you did to fix it? I would really like to be able to do it on my own. Please?

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    Posted · hollow object prints solid

    Like I said, it is easier to do this in Sketchup... but I will try...

    When you start, make sure you have the Object Browser visible (under View)

    Select your part7 and 'Edit' --> 'Separate Shells', this separates your thread from the cylinder.

    In the Object Browser you can show/hide elements now.

    Looking at cylinder it has 2 reversed faces.

    To reverse the faces: choose 'Select' , tick 'Allow Back Faces' and hit the 2 faces, in the popup screen. Edit - Flip Normals.


    Now hide the cylinder and the extra thread (shell2), and it is always good to make a duplicate (symbol next to the trashcan in the Object Browser) of a part if you are working on it, so you can always go back to the original. Hide the original (shell3).


    The next part involves a lot of steps because Meshmixer is not so much a building program and these steps are easier in Sketchup, like creating an outer cylinder without a top/bottom and connecting it horizontal to the faces of the thread. The same can be done in Meshmixer but with more steps. 

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