Electronhacks made this video to show production process of the 3d printed fan duct. However it is also excellent demonstration of friction welding plastic with filament inserted into Dremel. The friction produced makes a strong welded bond.
Video by ElectronHacks
Here are 3d printable rivets that you can use:
Here is another post about DIY ultrasonic and soldering iron plastic welding:
here is a video with same friction welding technique with PLA plastic.