Hollow Prints For Casting(ish)

[maxtim 0]

Hey ya'll,

I had this idea a while back to fill a 3d print with concrete to give it some heft and then paint it. That worked great, but I had a few issues. Namely, the stl I had needed some support on the inside to print well. My initial print had a few small holes and when I poured the concrete mixture, it made a bit of a mess.

 

Mind you, this was maybe last year, several months ago at least. So the exact details are a bit fuzzy.

 

Well, I started printing some new models from Scan The World and it got me pretty fired up to try this method again. Figured I'd try the same model since I know where the trouble spots are and if I can find a fix for it, well I can find a fix for any future prints I imagine.

 

I vaguely remember that I had 0% infill, and if I remember correctly I had no supports. I bumped the wall thickness up to 4 and had 4 for top and bottom layers.

 

I think what I'm looking for is an easy way to add supports to the inside of the model where necessary that clings to wall as if it were infill. Does that make sense?

Maybe this quick little drawing will help illustrate what I'm trying to say. So here we have a wall that might droop and cause holes. Next to it I have the desired affect, where the infill is essentially a thicker wall that helps bridge the gap and eliminate the possibility of a hole developing.

 

I've also attached the stl that I originally printed as a hollow shell. Note* It's not my work, I got it from thingiverse but I don't remember who made it.

 

ElderRemix2.stl

[geert_2 558]

I do understand what you mean, but I don't know if there is a setting for that. What could also help is making the walls and top shell thicker.

 

But if you are going to cast concrete anyway, what about using the model as a base for making a mould, and cast the whole model in concrete? So you have a fully concrete model without plastic?

 

In a CAD-editor, subtract the model from a block, so you have the inverse hollow shape of the model. Cut that block into two parts (or more if required), so the cast can be released from it later on. Add alignment features so both halves snap in place. Then add clamping features, and add pouring and venting holes. Think these over carefully. Smooth the inside, spray mould-release spray, and you have a mould that you can use for multiple concrete casts. This combines the advantages of 3D-printing with casting, and you have the stone-like texture of cement in the casts. You could add marble or other powder to the cement mix for additional effects.

 

On the internet you can find a lot of good tutorial videos on mould making and casting.