STL to any useful format

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david merten

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Mar 4, 2026, 8:33:57 PMMar 4
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Does anyone know of a usable free program to convert stl files to something usable like step,3mf...  I have tried some crappy online ones with poor results. The actual files I want to translate are not mine, so I have to be careful with them.
The old pictures below are not 3D printed, so forgive this part of the message for bieng off topic.

           David
20230220_081322.jpg
20230220_081331.jpg

markni...@gmail.com

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Mar 4, 2026, 8:42:59 PMMar 4
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I'm pretty sure that the free version of Fusion 360 lets you read in files and save them in other formats, but I use the paid version, so I'm not sure.

david merten

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Mar 4, 2026, 8:50:32 PMMar 4
to markni...@gmail.com, 3D Printing Tips and Tricks
Unfortunately it doesn't ( the maker version ),  I installed it a couple hours ago. I used my 30 day trial run back in 2017, It told me so and showed the models I made back then. They keep good records. 
   David

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Kurt The 3D Printer GUY!!

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Mar 4, 2026, 9:01:05 PMMar 4
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I looked into this a While ago David - and the idea is problematic at Best!

WHY???

If you look thru prior posts - and it may be HARD to find - there was a Prior discussion - and, problem is - the resultant model WILL have Layer lines & Stair Stepping built into it - thus its NOT Very Useful!!!

-K

Kurt The 3D Printer GUY!!

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Mar 4, 2026, 9:02:19 PMMar 4
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After I sent last reply - I got to see  your pics - and that IS INSANELY WILD!!!!!!!!!!

Was that a Pet of  yours???

-K

On Wednesday, March 4, 2026 at 8:33:57 PM UTC-5 david merten wrote:

david merten

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Mar 4, 2026, 9:23:50 PMMar 4
to Kurt The 3D Printer GUY!!, 3D Printing Tips and Tricks
Many years ago a family member bought a lion cub from the classified adds in a newspaper.  It was supposed to be a female, but turned out male. Declawed but with all teeth. They then bought the Kenworth show truck ( semi ) and went out on the road, leaving me to raise it in their house ( a really dumb idea, DON'T DO THIS  AT HOME ) I loved that cat and he loved me. BUT he destroyed their house. His tongue was like a power sander, he could lick the skin off you. I would be bruised n battered playing with him. He never bit me! He reached 450 lbs in the basement eating raw chickens ( I couldn't eat chicken for years after). They finally found a animal rescue farm that took him. He had a good life for a wild animal,  that could have been worse. Nowadays there are a lot more laws to stop things like this from happening. While it was a dumb thing to happen to a wild animal,  It was an amazing experience for me and I have a whole photo album of crazy pictures of lion that was just a big kitty.

       David

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Bryan Eckert

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Mar 5, 2026, 9:08:11 AMMar 5
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Have you tried Meshlab?

3MF is just a .zip container file, the model data inside is usually STL. Just download any .3mf file and change the name to end in .zip, open it and you can see what I mean.

Alternatively, you can try FreeCAD and the PartShapeFromMesh operand:
https://wiki.freecad.org/Part_ShapeFromMesh

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Kurt

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Mar 5, 2026, 3:25:36 PMMar 5
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David - completely IGNORE this last message reply of mine. I was thinking Wrong!!

In fact, I could take that STL from you and convert it. But, keep in mind - a STEP file is from a True CAD program - and a true CAD file is something that can be edited in a CAD program. If you have an STL - it's essentially a Mesh file - and not something easily editable! Like - if you have a screw hole in a part - it will only be polys - you will NOT have the CAD data in the file which would allow you to change screw hole diameter, screw threads - or even shift the screw hole. 

I hope this makes sense. So - yeah - I could convert the STL file for you - to another format - but, it will Probably NOT be in a format that would allow you to easily edit the file. 

You may need to give us further info. on your request - as to what you are really looking for. And - your mention of converting STL to 3MF - it's kinda senseless - since a 3MF already essentially has an STL within it. 

-Kurt

david merten

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Mar 5, 2026, 4:42:06 PMMar 5
to Kurt, 3D Printing Tips and Tricks
I wasn't the one mentioning 3mf as I knew that wouldn't do me any good.
I have been studying the stl format to understand why conversion back to something useful is so hard when you are able to print  accurate models from the stl. I understand now. Its similar to a vector drawing vs a bitmap. They can both show the same thing, but the data to work with it is gone. Expand your bitmap and it gets blocky because all the math is gone.
Thanks for offering to convert files for me but they are not my files. It is a cool rc drone/plane that I want to print and there are several special modifications I would like to make experiment with. I have tried contacting the creator to see if I can buy the step files. But no luck yet.
           David

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Joseph Larson

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Mar 5, 2026, 6:44:41 PMMar 5
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Your first message said "something usable like step,3mf".

You're gonna have to explain why STL isn't usable. What are you trying to do that can't be done with STL?

I may be about to blow your mind. In slicers STEP gets converted back to STL for slicing. 3MF contains STL data. There is literally nothing I can think of that can't be done with an STL. I think you've been listening to the wrong people about what STL files are for. There's a reason STL has been the standard since 1984 when it was invented. It gets the job done.

And, even more, if you did convert it from the mesh data of an STL into a STEP file, isn't gonna be mesh data in a STEP file. The only way to make your STL into a STEP file is to load the STL into your CAD program of choice and create a new object around the STL. There is no automated tool that can do that because what's it gonna do when someone feeds it a warhammer 4k mini or some other shape that can't be adequately expressed in STEP files? What you are asking for not only does not exist but, I don't think, can exist.

Just use the STL.

Here's some additional viewing for you:
3MF has been abused by bambu to the point that it's worthless. https://www.youtube.com/watch?v=PlK74r4QM8U
And STEP files provide very little benefit for the limitations they impose. https://www.youtube.com/watch?v=FLCr7ehLZ_A

Gary Myles

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Mar 8, 2026, 11:43:49 AM (14 days ago) Mar 8
to Joseph Larson, 3D Printing Tips and Tricks
STL is a stupid format, many attempts to change the status quo to even, 3mf, have failed

STEP is not a free standard, but doesn't typically use triangles. But rather as NURBS, Non Uniform Regular Bezier Splines, Ie curves
Slicers have no idea how to slice such a surface, and would be extremely difficult to implement. 

A free software that can easily switch between a faceted standard, and a NURBS standard, would be, FreeCAD 

Kurt The 3D Printer GUY!!

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Mar 8, 2026, 12:04:33 PM (14 days ago) Mar 8
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David - look at your original post again - since you specifically wrote:  "... a usable free program to convert stl files to something usable like step,3mf...  "

Just sayin'...

-K
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