Looks very practical to me.
From the “installed” image it looks like the holder is glued to the counter top. ?
I can see that you are enyoing your 3D printer, 
I used Tesa powerstrips to install it, so that I can remove it easily in the future if necessary.
How many parts to print a new caravan?
How big and do you want it and do you want wheels to turn . . and what do you have for 3D printer and how big . .What are you using for Slic3r ( G-Code maker ) I use Prusa version 1.3.9 of Slic3r and what is it your using for running the 3D printer ? I use Repetier-Host 1.6.2 never misses a beat . . Oh yeah and your definition of a CARAVAN ! 1 or many LOL ?
A holder for the kitchen scales in the caravan…
Starting a set of dust collection adapters (who knows why all manufacturers make incompatible ones?)…
Seems your not the only one who has to or ends up making a part to fit the Job . . Like the Ideals you had there . . NICE WORK !. . What threading Extension did you use for the hose ?
I’ve modeled the threads without a specialized extension.
Cotty’s The Man!!!
I’ve followed Daves tutorial 
Out of curiosity, have you modeled and printed internal threads for machine screws or bolts? If so, how is the fit when you insert the screw?
perfectly matched color 
Not until now, this one (for the dust collection hose) is only very rough and does not have to fit very precisely. I would probably use metal inserts for reliable screw connections…
Have you looked at adding metal threaded inserts during printing?
No, some time ago I watched this interesting video and decided to try this one day, bit I didn’t have to print something with threads until today. Have you used that technique already?
Edit: forgot to insert the link 
I haven’t used it yet but there’s some parts I’d like to do for the robot that could benefit from having threaded inserts.
Now that sounds good. . Maybe you should write a Extension for that kind of thread …close to a LAG screw settings . . Can you give me a Ideal as to how you made these Screw in threads ?
I’m using the technique explained by Dave in this tutorial: