Hello…newb here. I’m trying to cut a dinosaur model into multiple pieces because it won’t fit on a single build plate. I’m trying to cut it with a dovetail, but when I do, I notice that the 3d model is hollow. Can I still do this? Can I do a somewhat dense infill so that the dovetail will slide in place? Or is there a way to make the two faces solid? At first I assumed that when I cut it in half, it would make the faces solid, but no….you can just see on the inside, it’s hollow.
If you cut the model and let’s say it shows an inner cavity, then what you have is actually an interior mesh with an exterior shell. There is no easy one-click answer and the slicer can’t do this. However, if you cut it and it gives you an “open manifold” error, it should offer to fix it or you can right-click on the model and select “Fix model”
However, that method only works if it was a solid model to begin with which it sounds like it wasn’t. The best method is to go back into the application that created it and make it a solid.
There are free tools that come to mind that would convert a mesh into a solid. The first is Meshmixer, it’s older but still works and is free from Autodesk.
The second method is to bring it into CAD and then export as a STEP file. FreeCAD can do this but it requires a couple of steps. Just about any CAD that has the ability to export to a STEP file can do this but Meshmixer is easier.
Wow, thanks for the tips. Soon after I posted this, I did realize it asked me about the manifold edges, and I first clicked no, but then tried again and clicked yes, and it did fix the problem. But those other tools you mentioned are good to know for the future.
I do have a new problem though. Even though I now got the faces to be solid, I realized that I actually need the area with the eyes to be hollow. So here’s the thing. Imagine I’m viewing this dinosaur head from a side view. And I make a cut somewhere to the right of the eyes, and another cut over to the left of the eyes. I now have solid faces where I made those cuts. I actually need the area where the eyes are at to be at least somewhat hollow, because I plan to put some animatronics in there. But I also want the sides I cut to line up perfectly with the other parts, so I’m wanting to include some plugs or something, so that I can attach them together perfectly.
So I couldn’t sleep last night because I couldn’t stop thinking about how I’m going to do this, but I THINK I came up with a solution, but I haven’t tried it yet, and I haven’t had the time to try today, but I’d be curious to know your thoughts on it, hopefully assuming you understood what I was saying above. If not, lmk and I’ll try to clarify more. Thanks in advance for the help btw.
So now that I have faces to the parts, my first thought was to make the slices, adding some plugs around the perimeter and then hollow out the middle area using a negative part or two. But I realized the issue with that, is the eyeholes need to be exact, and I doubt I will be able to put a negative part through the eyes and match it perfectly with the shape of the eyes. Which leads me to my new idea.
I thought instead of fixing the manifold thing, I just leave that section hollow, and now forgive me if I’m completely wrong about this idea I’m about to say, because I’ve never used modifiers before, but I was thinking maybe I could make two flat square modifiers to close off both sides of this part, and give them a 100% infill. Would that work to create walls/sides? That way, the area inside remains completely hollow. I can then use a negative part to run through the middle of those walls I just made, so that I will be able to reach my hand inside to install the animatronics. Is this a good idea? Or is there a better way? Again, just to clarify….the reason I want the area around the eye holes hollow, is I don’t want to have to create artificial eyeholes. I’d prefer to keep the eyeholes exactly the shape and size they are now. But if there’s some way to create a negative part that could match the eyeholes perfectly, I’m all ears. Like, could I use the original eyes that used to go in those holes as negative parts? I’m assuming you would have to use a regular circle or sphere or whatever and attempt to shape it to the eyeholes if you were going to do it that way. I could be wrong, but I just started printing a few weeks ago.
Thanks in advance for any suggestions.
I think I understand what you are trying to do. It reminds me of the old saying:
“When the only tool you have is a hammer, everything looks like a nail.”
To answer your specific idea directly: I would not try to create those side walls with slicer modifiers. It might work in a narrow case, but it is the wrong level of tool for the job and will probably create more problems than it solves. The better approach is to keep the original eye geometry intact, hollow the mesh first, and then cut access openings using mesh/Boolean tools. If the original eye inserts match the eye holes, they may be useful as reference geometry or even as Boolean cutters, but that depends on whether they actually match the opening shape and intersect the mesh cleanly.
Don’t worry, you are not alone. What you are trying to do makes sense, but you are asking the slicer to do something far outside its intended design. We’ve all been there - trying to use the proverbial hammer to drive a screw when what we really need is a screwdriver.
If you’re asking my advice, the slicer is not the right tool for this. You may eventually force it to work, but you will likely waste hours trying to make it do something it was not designed to do.
In a nutshell, what you are attempting is the kind of problem Imagineers at Disney or model makers at Industrial Light & Magic would deal with when building robotic props. If you want some inspiration, I recommend Adam Savage’s YouTube channel. He has shown a lot of the tricks he used as a model maker at ILM during the George Lucas days.
The real challenge is that you are working with a mesh model, but you need to perform CAD-like operations on it. There are not many tools that handle that well. Blender is probably the best tool for this kind of work. It has a steep learning curve if you want to master the whole program, but doing a simple one-time modification may not be as bad as learning the entire suite.
Here is what I would do.
Disclaimer:
This is a quick five-minute demonstration, and I am definitely not a Meshmixer expert. Someone else may have an easier method.
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Take the original model and use Meshmixer to create a hollow body with a thick shell. In this example, I am using our favorite STL, the Stanford Bunny, found in the Orca Slicer models.
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Use the Cut tool in Meshmixer to cut off the section where you want to insert the animatronics hardware. Do not use the slicer’s cut tool for this, because the slicer will simply close the mesh and create solid faces where you cut it.
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Import the part into the slicer and add any tabs, plugs, or locating features there.
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For the eyes, Blender is the better tool. However, to show the basic idea, here is what it looks like using negative Boolean shapes in Meshmixer.
If you are really a glutton for punishment, you can try doing this with the slicer’s Boolean tool. But if you are not in the madhouse by the end of that process, you soon will be. 
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Hey man, I’m sorry I haven’t even had time to read your reply yet. I’ve been exhausted all week and been going to bed as soon as I get home from work each day. I’ll review your suggestions this weekend and get back. Sorry for the late reply, and thanks for your input. I really appreciate it 
Once you get to this stage, it’s when you load up a full mesh modelling program like Blender (Meshmixer is a very lightweight version of such a tool, but you might be able to do it in Meshmixer with a lot of effort). Making orbs in the slicer and shoving them in there is not a particularly pleasant experience.
edit from the hole in the bottom it looks like this model was designed for resin printing, that looks like a drain hole for the liquid resin. Although it’s not where i would have put it. The general lack of fur texture on the model leads me to believe it’s a scan or AI image-to-mesh.
Okay, I finally was able to catch up on your post, thanks. I didn’t know Adam Savage had a YT channel. I’ll definitely need to check that out. I’ve tried Blender in the past, and it’s just not intuitive enough for me. It would take me a long time to learn just how to move around in there lol. I’ll check out Meshmixer, but although your solution sounds good….I still see a problem. Making sure the plugs that I add line up precisely on the other side. Is that easy to do in Meshmixer? It works fine in Bambu Studio just as long as you make a slice first, but if I’m doing it the way you’re saying, then I won’t be able to make those slices and have those plugs automatically match up. If I do it in Meshmixer, will I have to put the plugs and the holes for the plugs in by eyeballing it, or measuring? Or is there an automatic alignment thing so that I can do it quickly?
He was just showing that bunny as an example. I’m trying to put animatronics inside the eye area of a dinosaur head model.
Thanks so much for introducing me to this MeshMixer tool. I’ve been needing something like this since Blender is way over my head. Been watching some tutorials on Meshmixer, and this seems to be a very great tool to fix problems with meshes. This is what I’ve been needing. I was about to resort to paying someone on Fiverr or something to fix some of the problems with some of my models, but now I don’t need to. This is exactly the tool I need, so thanks for that. I’m going to see what I can do with this dinosaur now.
Update: I think I found the solution. I think I need to first make the slices in Bambu Studio, along with the plugs I need. Then load it into MeshMixer and hollow out each part individually. This way, they will be hollow, but still have the solid faces with the plugs. And I’m still not sure about the eyes, but I think you said it might be possible to use the original eyes in Bambu Studio, place them back into the eyeholes and change them to “negative parts”? Can I do that? If I can do that, then I think all of this will work now. I will update again once I have done all of this to confirm this works or not.
Nope. In theory it should have worked, but when I imported the model into MeshMixer, my plug holes were missing 
I tried some other things in Bambu Studio, but I’m about to pull my hair out trying to solve this. I may just have to forget the plugs and do my best, matching up the dinosaur’s skin. That’s kind of hard with super glue when you only have a few seconds to get it lined up right, and this is a huge print, so I can’t mess up. I wish there was a way to get it both hollow AND have the plugs lined up perfectly. I’m sure I’ll figure something out eventually, but this is a headache lol
There are probably a dozen or more ways to create cutouts for the eyeballs. You could create a cutout in mesh mixer but if you want a perfect fit:
- Import an STL or STEP file of the mode of the eyeball into the slicer.
- Clone it and add it to the object as part of an assembly. This will allow you to move the eyeballs around and rotate them into place.
- Then using Boolean subtraction, use the eyeball as a negative tool. It will create a cavity that is the exact shape and size of your eyeball. Before you do the Boolean operation, I would scale the eyeball by 1-2% simply to give you some gap.
Thanks. The eyeball cutouts aren’t my biggest issue though. I figured out a way with Bambu slicer to do it, although I may try the meshmixer because I can probably do it better there. My main thing is trying to both have the plugs present and also hollow the head out. Making the plugs inside Bambu slicer and then importing into meshmixer didn’t work, but I have a couple of ideas I’m going to try. But I haven’t had time today to try anything with it. But thanks for all your help and introducing me to Meshmixer. There’s a little bit of a learning curve, but it’s not too bad, and it has a lot of very useful tools that I will for sure be using from now on.