When I use my 3D printer, I'm recording the printing process. A Raspberry Pi, with a Camera module, takes a picture every second. These pictures are saved and later imported to Blender.

First I need to switch to the Video Editor part of Blender:

Blender animation

Then the images needs to be imported.

Blender animation

Then I use the command:

ffmpeg -start_number 1 -i %04d.png -vcodec libx264 outputfile.mp4

If the render is has a framerate of 60 FPS then I add -r "60"

This combines all the .PNG files into one .MP4 file.