Hollow part printing issues

Bug reports
I could use some help. Basically what I have created is a hollow half sphere and exported it as an stl file. It prints solid. I thought it was an issue with the slicer, but I’ve talked with their support and they’ve looked at the file. Basically my shape is one dimensional so it doesn’t recognize that it’s hollow. How can I fix this?

So … if I got you right you created a sphere, cut it half and exported it? Then it should be a a half sphere. Does Nomad present it to you as a half, hollow empty sphere?

Just try to understand your problem…
Is the problem, you actually did not make it hollow, but on screen it is?

A screenshot would help, not sure what “hollow” means in your context.

Two photos of my part and one of the model kit I’m loosely basing it on. So, to answer the question, yes, I want it hollow, because I need room for the engine bells and fuel tanks to fit inside it. So when I made the part I started with a sphere and cut it in half and chose no fill so it would be hollow. Then I added a torus for the rim and proceeded to mangle it into the shape you see here. But because the shell is one dimensional, it doesn’t read as hollow for the slicer. It sees the outside and just fills it solid when it prints even though the slicer software shows it as hollow. I’m trying to figure out how to fix it so it will print. I am a complete n00b with this software. This is something I would sculpt with epoxy putty or make on my milling machine normally, but I’m trying to learn Nomad so I can sculpt digital and print copies rather than make everything by hand. Any help would be appreciated. :slight_smile:

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Apparently I’m not allowed to post more than one pic at a time yet.

I don’t know if this would work, but try starting back from the beginning.
Create the initial egg like shape.
Use a box to cut it in half with the voxel merge.
Copy the new shape and bring it straight down just a small bit with the gizmo.
Voxel merge that part out again.
Create a new box and voxel merge out the hole.
Now it should be a 3D part, instead of a 2d surface with no thickness, and ready for that torus rim.

I did a quick example to show what I mean. You can see the thickness to the part now.

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Yep, basically your mesh should be watertight, if you see “yellow” faces in Nomad then it’s no good.
Everything should have thickness, and depending on the printer there is a minimum value that needs to be respected.

Nomad main focus is not 3d printing but you can create shell from open surface with the mask and extract tool.

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Awesome! thank you, guys. I’m going to see if I can use the mask/extract option first. If not I’ll just start over. I appreciate the help. I’m not used to doing this with a program yet. I’m used to working with a pile or pare parts, epoxy clay, and milling shapes by hand out of Renshape. Thank you all so much. Happy Thanksgiving :slight_smile:

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Dumb question about this method. I see where you’re going, but once I do the voxel merge, does it treat it as a single layer of thickness or as a hollow core wall? Like…if I use Move to distort the surface is it only moving the outer “skin” later or does it now treat it as solid thin wall and by pulling the surface out, I should see that bump as an inverted dent on the inside? I’m assuming the latter, but assumptions about how this works have got me nowhere. :stuck_out_tongue:

It depends.

At the bottom of the stroke menu you will see an option « connected topology ».
If it’s enabled il will only move the external parts (unless your tool radius is big enough so that the internal part is connected,

There’s also the option « Front-facing vertex only » that could change the behavior.

Hi guys :slight_smile: So, I ended up using the mask and extract method mentioned in here and it works great. The scab on my forehead fro beating it against the wall has healed and I’ve even managed to print the part I needed. I also went back through everything I had that was hollow and fixed it before I forgot and ended up printing more garbage. Thank you all for the help :slight_smile:

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I did end up starting over since it wasn’t quite where I wanted it to be. I also did not delete the inner walls of the primitives because I wanted some internal structure for attaching the rest of the parts to later. What I DIDN’T expect was the weird double wall effect. It doesn’t matter for this since none of that will be visible in the finished model, but it’s good to find out now before it becomes a problem later. If you’re trying to figure it out, the basic shape was a sphere and a cone merged and then sliced off about 1/3rd of it (horizontally) and then stretched and bowed and moved it around. I think next time I try something with merged primitives I’ll merge them as solids and try shaping what I can prior to cutting them up with the fill turned off and see if they still leave a framework inside. I cut it in half with fill off before I merged because I was still moving them around. Thanks to you guys I have a slightly better understanding of what I’m doing with Nomad. I’ve still got a long way to go, but it’s an awesome program and every new thing I learn leads to a dozen new ideas for how to apply it. Thank you again for the help. I’m sure I’ll have more questions in 2021 :slight_smile:

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Nomad is a great program to for modeling.
I’ve been using it to design for 3D printing also.

Two things that really help learning what the tools can do are Stephan’s manual:
There is a beginner’s course that helps a ton and was recently offered from SouthernGFX that can be found in the YouTube description and at the end of the the video here.

There are other YouTubers making tutes. It’s helped me a ton.