Two spring mountings of my couch were broken. So it was time for a repair. Here is what I did:
First I put my couch up side down.
I designed a new 3D part at tinkercad.com.
(You can view, modify, download and print the 3d design.)
Next I printed the part on my Printrbot:
Here is the comparison of the CAD model and the printed part:
The new mountings were fixed with a metal band: