I saw this coolest concept art ever in artstation and wanted to give it a shot.

https://www.artstation.com/artwork/8bZzKR

Modeled in Plasticity, textured in Substance Painter + Blender, rendered in Blender Cycles.

I had the upmost joy in each process, hope you like it! Any feedback is much appreciated!

I renamed my STLtoSTP script to 2STEP-Converter - and added support for 3MF, OBJ, AMF and IGES while I was at it.

A while back I posted a small script called STLtoSTP that batch-converted STL files to proper STEP solids using OpenCASCADE - the same engine FreeCAD uses internally.

Original post: https://www.reddit.com/r/3Dprinting/comments/1t34y2z/free_batch_stl_to_stp_converter_python/

The key difference from online converters was geometry quality: instead of just wrapping the triangle mesh into a STEP container, it actually sews the mesh into a solid, repairs it, and merges co-planar faces back into real flat surfaces.

People liked it, but the requests were always the same - "can it do 3MF?", "what about OBJ?". So I added them. Then AMF. Then IGES. At that point calling it STLtoSTP made no sense, so I renamed it.

The new name is 2STEP-Converter and it has a deliberate double meaning. It reads as "to STEP" - because whatever you throw at it, you always get a clean STEP file out. It also means "two steps" - because that is literally all it takes to use it: drop your files in the folder, double-click the bat. Done.

Supported formats

Input: .stl .3mf .obj .amf .igs .iges

Output: .stp

How it works under the hood

It replicates the FreeCAD Part workbench pipeline exactly:

1. Read the mesh
2. Sew triangles into a watertight solid
3. Repair invalid geometry
4. Merge co-planar faces - this is what makes it actually useful, triangulated flat surfaces become real faces
5. Export STEP AP203

Setup

No manual installation. On first run the bat downloads micromamba and sets up a Python environment with pythonocc-core automatically. About 6 GB on disk, internet needed once. After that it runs fully offline.

Works in batch mode (drop everything in the models\ folder and run) or single file mode from the command line. Tolerance is configurable if you have coarse meshes that fail to sew.

Tested on Windows 11, output verified in Plasticity.

GitHub: https://github.com/yaneony/2STEP-Converter

In case you would like to thank me: https://ko-fi.com/yaneony

TL;DR - I built a free, open-source tool that batch-converts STL/3MF/OBJ/AMF/IGES files into editable STEP solids, because I was tired of doing it manually in FreeCAD every time I downloaded a model.

Hey everyone,

If you're into 3D modelling you've probably grabbed free STL models online and then wanted to tweak them - change a dimension, cut something out, adjust a feature. STL is a dead-end mesh format though, so to edit it properly in a solid modeller like Plasticity you need a STEP file first.

Every single time I found a model I liked and wanted to modify, I had to go through the same manual ritual in FreeCAD: open STL, "Create Shape from Mesh", "Refine Shape", export STP. Over and over. It's only a few clicks but it gets old fast, especially when you have a handful of files to process.

The thing that actually wore me down wasn't the clicking itself, it was the rhythm of it. FreeCAD has to load the file. Then "Create Shape from Mesh" takes a few seconds to think. Then "Refine Shape" thinks again. Then you save, close, open the next file. You can't really do anything else during it because each step needs you to confirm something, but you can't really focus either, because you're just waiting in 10-second bursts. After half an hour of that on a folder of free downloads, you start questioning your life choices.

I looked around for a proper solution but couldn't find anything that just worked - the only reliable option was FreeCAD, and even then it was a manual step-by-step process for every single file. There are a bunch of online converters but most of them just wrap the mesh as-is, so what you get is a STEP file made of thousands of flat triangular faces. Technically a STEP file, but completely useless for actually modifying anything.

So I automated it. This was a fun little project built purely to fill my own need, so there might be some rough edges or edge cases I haven't hit yet - but it works well for me and hopefully for you too.

What it does

You drop your STL / 3MF / OBJ / AMF / IGES files into a folder, run a launcher, and editable STEP files come out the other side. Each result also gets a small preview image so you can glance at a folder of outputs without opening a CAD app for every one.

The bulk of what I use it for is printable models - phone holders, brackets, replacement parts, enclosures, that kind of thing. Stuff that started life in someone's CAD tool and got exported as STL for sharing. Those convert almost perfectly because the source mesh is just a thin tessellated skin over real geometry, and the tool effectively rebuilds that geometry. You import the result into Plasticity (or whatever you use) and it's just there as a proper editable solid, with faces and edges you can select and modify.

Scanned models work too, but you'll get a more approximate solid. Usually good enough to use as a reference body to model on top of, not always good enough to use as the final part. That's not really a tool problem, that's just the nature of going from a noisy point cloud to clean CAD topology.

A few honest caveats

• If your source mesh has holes in it (common with scans or sloppy exports), the result won't be a perfectly closed solid. A quick pass through Blender or MeshLab to patch it tends to fix that.
• Color, materials, and textures aren't preserved. Just the geometry.
• Clean, dense exports come out beautifully editable. Sketchier meshes need a bit of experimentation with the reduction setting, but it's forgiving once you find a sweet spot.
• It doesn't replace your CAD tool. It just removes one annoying step at the front. You'll still do the actual editing wherever you normally would; this just gets you from "STL on Thingiverse/Printables/MakerWorld" to "thing I can work with" without the conversion ritual in between.

Practical stuff

Works on Windows, macOS, and Linux. Free, open source, and there's nothing to install beforehand - the launcher sorts itself out on first run. The first launch takes a little while because it downloads everything it needs, but after that it's instant.

All the actual CAD heavy lifting is done by the OpenCASCADE team - the same engine that powers FreeCAD. I didn't write any of the conversion math; I just made it easier to run on a folder of files and added a few quality-of-life things like previews and ETA estimates. Genuine thanks to that whole ecosystem - without them this would've been a years-long project instead of a weekend one.

Everything else (install steps, options, troubleshooting) is on the GitHub page:

github.com/yaneony/2STEP-Converter

One last thing

I'm treating this as the final stable release. I've been working on it solidly for about a week and it's at the point where it does everything I set out for. There won't be big new features from here on, just bugfixes if someone runs into something that breaks. I'd rather ship a small finished tool than a sprawling half-finished one, and this comfortably falls into the "small and finished" category. Last release, but not a least one - it's done because it works, not because I'm walking away from it.

That said, if you do try it, I'd genuinely love to hear how it went - especially if you find a mesh that breaks it, because that's exactly the kind of thing a bugfix patch could address. Even just a "this saved me an hour" comment goes a long way when you've spent a week on something for your own use and put it out there hoping it helps someone else too.

And if it ends up genuinely useful to you and you feel like throwing a coffee my way, I have a Ko-fi here: ko-fi.com/yaneony. Any support is hugely appreciated, but absolutely zero pressure - the tool is free and always will be, and a comment in this thread means just as much.

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THIS VERSION IS OUTDATED. PLEASE CHECK THE LATEST RELEASE HERE:: https://www.reddit.com/r/3Dprinting/comments/1tbj4np/2stepconverter_v200_last_but_not_least/

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Hey everyone! I've been working on a bunch of improvements to 2STEP-Converter, my open-source tool that converts STL, 3MF, OBJ, AMF and IGES files into clean STEP solids using OpenCASCADE - the same engine that powers FreeCAD.

Previous post: https://www.reddit.com/r/3Dprinting/comments/1t9bdku/2step_converter_formerly_stl2stp_free_opensource/

What's new?

✨ Mesh simplification

The biggest new feature. Before converting, you can now reduce the triangle count of your mesh by any percentage - great for large scans or overly dense models that produce bloated STEP files.

• --simplify 25 removes 25% of triangles before converting
• Set DEFAULT_SIMPLIFY in config to always apply a reduction automatically
• Enable SIMPLIFY_INTERACTIVE in config to get a per-file prompt that shows you the triangle count and lets you decide on the spot
• In batch mode, prefix your input with ! (e.g. !25) to lock that value for all remaining files

🧠 Self-learning time estimation

The converter now tracks how long each conversion takes and uses that history to predict how long the next one will take - before it starts the slow steps. It fits a quadratic model to your past runs, so estimates improve the more you use it. The confidence percentage tells you how reliable the prediction is.

📦 Multi-file CLI & watch mode

You can now pass multiple files directly on the command line without using the models/ folder:

2STEP-Converter.bat model1.stl model2.obj model3.3mf

And with --watch, the converter stays running after a batch and automatically converts any new files you drop into the folder. Ctrl+C to stop.

⚙️ New options

Flag	What it does
--simplify / -s	Reduce mesh before converting
--format	Choose STEP schema: ap203, ap214, ap242
--output-dir / -d	Write outputs to a specific folder
--force / -f	Re-convert even if output is up to date
--dry-run	Preview what would be converted
--watch / -w	Auto-convert new files as they appear

🗂 Config overhaul

Settings moved from config.py to data/config.json - easier to edit, no Python knowledge needed. Invalid values are caught at startup with a warning instead of crashing.

🔗 Links

• GitHub: https://github.com/yaneony/2STEP-Converter
• No installation required - everything downloads automatically on first run
• Works on Windows, macOS and Linux

If this tool saves you time, consider buying me a coffee: https://ko-fi.com/yaneony

Feedback, bug reports and PRs are always welcome!

This is the first model after the plasticity study, I hope you like it!!!

Done in 4.5 hours, a quick design ready to be textured.

Concept art found from artstation
https://www.artstation.com/artwork/8bZzKR

Exercise with plasticity I hope you like it🔥🔥🔥

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p.s. Obviously it's a WIP

Hey everyone, just wanted to share a sci-fi model I made for practice. Based off of this image on Pinterest https://pin.it/6yhOx1yx2. It took me about an hour and a half.

Just need to print it out now and make a static chassis for it while I design the RC chassis.

Thanks for reading.

I've created a custom radio trim piece for my car in plasticity. I've been fighting it for 5 hours today. My elegoo CC prints all other stl junk from online just fine. But with my model it prints the purge line fine and then fails immediately. Under extrusion, blobs, no adhesion. I had a similar problem today printing a trash can, and I thought it was the new update to elegoo slicer so I downloaded orca and it fixed the issue....for the trash can.

I've tried countless bed leveling, different exporting file types, checking the hot end a million times, testing all other parts....and nothing. It fails immediately.

What I've learned so far....

1. Only my custom part fails. All other parts from online work great.

2. I have dragged the part into a sliced file with the same settings as a part that I know works fine, and it still fails immediately after the purge line

3. Purge line always comes out perfect no matter what

4. I've messed with the z offset and I can get it up in the air, or scrape the bed....no difference. Still blobbing up.

5. I've "fixed" the part in the slicer, changed bed types, temp settings, speed, nothing works.

Maybe the part is floating? Or the slicer isn't orienting the part correctly? Or maybe my model is broken and I need to start all over again....

Thanks for the help. I've given up at this point 🫠🫠🫠

Lately I’ve been working on my designing skills and I am so proud of how far I’ve come with this. What do you think?