We Are Learning 3D Printing Through Our Personal Experience…
There are multiple specialized websites that serve as communities for users making 3D models for printing on 3D printers to share their work, some are freely available, and others offer their work for a price and you can even order the model to be printer and sent to you as well. If you are interested in downloading some free STL models for trying out your new 3D printer then you might want to check the following popular websites as a good starting point…
Thingiverse – a large community operated by MakerBot, a manufacturer of 3D printers, where you can find a lot of 3D models shared by users and available for free download in STL format. There are a lot of new 3D models added every day and many of the published models come with instructions and photos of successful prints, though be careful that even if some models may be available for download in STL format they may not be optimized for 3D printing and may need some extra work fixing them, but these are usually not many.
Youmagine is an alternative to Thingiverse, also operated by a 3D Printer maker – Ultimaker. Not as big as the first one, but also a good place to check often as it has some interesting designs and also apparently some of the Thingiverse users have decided to move here. Not as many new models added and users interacting and sharing photos and comments when printing an object, but the place has the potential to grow.
Cubehero is another smaller platform made to help 3D printer users to interact and collaborate on projects they are making. This project is not operated by 3D printer maker and while there are still not that many projects available, you can still find some interesting 3D models, so do check it out.
GrabCAD is not your typical place to just download free STL 3D models for printing, it has many CAD models a lot of which are also available in STL format, but not all are. You can download 3D models in other formats and also try to convert them in STL for 3D printing, but you may experience trouble with more complex ones. Nevertheless many interesting things available so do check the website out.
SketchUp 3D Warehouse is the place for 3D models for the SketchUp software previously owned by Google, but then sold to Trimble. There are a lot of SketchUp models available, though you will need to export them in STL format from the software with the help of an STL Import/Export plugin and then to print them.
TurboSquid is one of the largest 3D model resources, both free and commercial ones. Even though the 3D models available there are not specially designed for 3D printers you should be able to convert many of them into STL format and then print them.
There are other smaller resources available providing some free STL models for 3D printers as well as other 3D models not designed especially to be 3D printed. The good news is that if it is a 3D mode of something you may be able to convert it to an STL file and print it on your 3D printer. This process however could not be as easy as just opening a 3DS, DXF, OBJ or another file format and exporting it as STL model and may require some more extra work, so if you are still new to 3D printing you might want to stick for now to places that have free 3D models available in STL format to make your life easier.