Look for settings referencing “chord height,” “angle tolerance,” or “deviation.” These set how nicely the mesh follows the surfacing of your model. Lowering the chord height and angle tolerance, and reducing deviation will up the number of triangles, giving you the smoother surfaces you want.

Packages like Blender, Fusion 360, or SolidWorks have their ways of inputting the same stuff. In Blender, you’d look at the export settings and adjust the resolution there. In Fusion 360, it’s under the “Mesh” workspace. In SolidWorks, you can adjust the linear and angular resolutions under the “Options” when saving.

Maybe some background might help, to know why this happens. When STL files were first introduced, file size limitations were a big concern. Email and storage media had way less capacity, so the resolutions of STL files had to be kept low to manage file sizes.

Back then, manageable file sizes were a big deal, really limited by the tools at the time. Higher resolutions have created files too large to handle effectively. I remember fighting with 10mb email attachment limits. Now file sizes don’t matter, so we can afford to use much higher resolutions and get smoother, more detailed models.

Yep, and one more thought: check the capabilities of your 3D printer. Some printers are more limited and can’t take advantage of extreme-resolution files, so it’s about finding that sweet spot for your specific setup or your supplier’s capability limits.