Editing .stl files

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sky1911
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Editing .stl files

Post by sky1911 »

Ola,

I am currently considering buying a 3D model meant for 3D printing and editing it for an art project. However, the file is only available as an .STL file. And I have no clue what to use to edit those. My idea is to take the file, load it in a suitable software and then try and slice it in such a fashion that I get contour lines. Something akin to the gridlike patterns used to fabricate the metal bodywork over.
So far I have never worked with .STL files, so I have no idea if they are something like an object made of vertices, lines, polygons or just a fine cloud of points. I just would like to know prior to purchase if that is an editable too. If so, what would be a suitable tool to do the job?
Cheers,
Roman

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Re: Editing .stl files

Post by jaykay »

Hi Roman

STLs are made of triangles.
They are the standard for 3D printers but not really meant to be worked on.
Some softwares can work with them, like cutting them into smallert segments, closing holes, scaling them etc.
It's not really possible to convert them back into the "clever" surfaces they originally were.
It is possible to make sections from them and build a body buck model from them with the right software.
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Re: Editing .stl files

Post by indycals »

What Jaykay said. You know how 2d images have bitmap (made up of individual dots) and vector files? STL files are the bitmap images of the 3d world.
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Re: Editing .stl files

Post by sky1911 »

Yea, that's kind of what I was expecting / dreading. Damn.
I might give it a shot anyway - in the end I will print it regardless, but for my project I just need a few very thin slice, actually just the outline of those thin slices.
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Roman
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Re: Editing .stl files

Post by MoFo »

Err... is should be doable and *may* be relatively easy.

It sounds like, basically, you want to make a body buck:

Image

The first thing you'd need is your STL file. Here's a F1-ish one you can experiment with: https://www.myminifactory.com/object/3d ... 1-car-8416

Next, you'll need a way to create cross-sections of your model. You could do this with something like Meshmixer: https://www.meshmixer.com/ to directly modify the STL file**, but IMO it would be easier to take another, more software-heavy tack.

Download Chitubox here: https://www.chitubox.com/en/download/chitubox-free

You don't need to set up for a specific printer, really, but it's probably easiest to pick one of the defaults. I'd probably pick something like the Elegoo Saturn, as it will give you a larger image output. Anything that says "4K" would also be a good choice.
Next, import your STL. The slicer will output horizontal cross sections, so you'll want to orient the model in the correct direction for whatever slices you'll need; for a traditional body buck, you'll need to run through this process once in profile, once in plan view, and once head-on. You can re-scale the STL so if fills the build area, but you'll want to make sure you scale it the same amount for each view.
Next, you'll have to configure the thickness of each cross section. Click on 'Settings', then 'Resin', and change 'Layer Height'. It will probably be around 0.05 mm by default, which is higher than you'll need. The lower this number, the more cross sections you'll have; a bigger number means fewer cross sections. You can calculate a specific number based on the height of the STL and the number of cross sections you want, or just trial-and-error to figure out what works. When you click out of settings, there's a slider on the right side of the main window that will let you scroll through the layers to see if they fall where you want them to. If they don't, go back and play with the layer height some more; if they do, you can...
Click 'Slice' to actually create the slices, then 'Save' to save the file. This file includes a bit of data to tell the printer what settings to use, and an image for each individual layer it will display, to cure the resin. Those images are your cross-sections, but you'll need to extract them from the print file.
So next, you'll need to download BulgeBuster: https://nerdtronic3d.com/bulgebuster/ (there are a bunch of ways to do this, but BulgeBuster is just a small, lightweight piece of software that'll work on any system).
Open your print file in BulgeBuster, then click the 'Unpack Images' button. This will save each layer image as a PNG file. VERY IMPORTANT: Navigate to the folder the images were saved in, then copy and paste them somewhere else BEFORE you close Bulge Buster, as it deletes them when you close the program.
So now, finally, you've got your cross sections, in PNG format. You can open them in an image editor or illustration program to edit them as you need. They'll be black and white, so it's easy to invert, or trace the outlines if you want to do a layered 2D image, or print something you can cut out.




**Meshmixer can do this within the software itself, but you'll have to cut each cross section individually, so it would be more labour intensive. It might be a better option if you need irregular spacing or fewer sections, though. Do a search for 'Meshmixer cross section' to find some tutorials.
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Re: Editing .stl files

Post by sky1911 »

Hi MoFo,

thanks for the elaborate reply. It's a bit more than I had hoped for :). On the topic of printing - I already have an Photon, so for the time being I'm good there.
However, this project is more of an art project of mine. I want to get a 3D model of a figurine and take the head to turn into something vaguely familiar to the photo you have posted. I want to slice the head in such a way that I have several slices of its profile. Of those profiles I only need the contour line (forward part, nose, eyes, etc.) and will then layer those contours in a perspective. The attached photo was the inspiration for this. But this is a flat piece directly from the side, I want it at an angle, to have a 3D-ish effect.
stuff.jpg
On the modelling aspect with the guides and all that - thank you very much for your insight into that and the tool recommendations. I will give it a go - probably with something easy like the body of a 908/3 :)
Cheers,
Roman
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Re: Editing .stl files

Post by MoFo »

I think you mis-understood me.

You're only using the slicer to generate the cross-sections you need for your art project. Once you extract them from Bulge Buster, you can do whatever you want with them - print them as templates, open them in a drawing program to manipulate them or trace the contours, open them in CAD to stack and model... It's just a simple, straightforward way to slice it to generate the cross-sections you want.

Image
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Re: Editing .stl files

Post by capri-schorsch »

Hello,
i also made my first steps with 3d printing and converting files from a racing game to printable files.

This is the project i am working on right now.

Image

A Ford Escort Mk1 in the Zakspeed racing livery.

Image

I started with the front grill and tested 2 different versions. This was the first time i used my own stuff instead of finished files from the net. Worked very well.

Image

And here are the part after the curing with UV light.

Image
Also bought a new filament printer because my old Anycubic made problems and i was not able to fix that.
Now its an Creality3D CR-6 SE and i was amazed how big the difference was to the first one.
Much finer,faster and not so loud than the first one.And he got auto-leveling of the heatbed.Very nice!
I still have a lot to learn but the first small steps are done.

Great hobby!

regards Christian
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Porsche 962 in 1/8 Scale IMSA & Shorttail New!

http://mezzo-mix-models.jimdo.com
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Re: Editing .stl files

Post by sky1911 »

MoFo wrote: Wed Apr 14, 2021 3:28 pm I think you mis-understood me.

You're only using the slicer to generate the cross-sections you need for your art project. Once you extract them from Bulge Buster, you can do whatever you want with them - print them as templates, open them in a drawing program to manipulate them or trace the contours, open them in CAD to stack and model... It's just a simple, straightforward way to slice it to generate the cross-sections you want.

Image
Guilty as charged!
I have read your explanation - several times - always with the pic in your post in mind and always got sidetracked into thinking "but that's not what I want". After having re-read it again just now AND downloading & installing the software as per your text and running it and performing the actions you have described, I have to say "I am an idiot" for that is exactly what I wanted to do. So sorry about that and a huge thank you for taking the time to write it down and bearing with this idiot right here ;)

Awesome!

Oh and while we're on the topic of unexpected revelations. I found out today that fusion 360 can actually legally be used for free for a year and that apparently can be extended on a yearly basis. I only saw the prices and thought, "ok pass".
With that said, I am going to dive right in as I have been using sketchup ;) for most of my projects (mostly wood working stuff (cabinets, shelves, my sim cockpit))...
Cheers,
Roman
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Re: Editing .stl files

Post by MoFo »

Glad it worked! :D
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