In the off-chance that you also own one of these extremely rare Chinese watch phones, you may have discovered that the detachable wrist strap is made from a poor quality plastic that becomes brittle and cracks over time. Spare parts are impossible to get, the model is no longer being manufactured and I doubt whether it can still be bought.
The photos show the original cradle at the right, which I have repeatedly repaired with epoxy glue and tape, but it was nearing the point where it became impossible to fix. One of the main reasons why I bought a 3D printer was to be able to print my own spares for cases like this. I finally got around to model and print one of the very first things that I thought I would be using my printer for.
The model is a very close replica of the original F80 cradle, only without all the weak points. The useless hole is gone and the base is slightly thicker. It provides a good snap mount without being overly tight. I printed it in ABS, but PLA will probably do fine too. You can detach the push pins from your original cradle with an xacto knife, or if it is unusable anyway, just break it…
Update 2017/01/14: a while later, the rubber strap itself also started to disintegrate, so I printed a replacement for it as well!
Update 2017/02/02: because the first version was a bit sloppy and the phone would move around in it, I created a new version v2 which has a better design, with a tab that sits tight against the phone, and two tiny spherical notches to further keep the phone secure. I printed this one with a support included in the model, and painted the underside with the same ABS filament dissolved in ABS, for a smooth underside without tiny gaps that could accumulate bacteria.
Update 2017/05/11: I completely destroyed my v2 print in an attempt to anneal it, so I took the opportunity to further improve the model before printing a replacement. Next to some small details, I added a few protruding tabs that provide ‘click’ action when pushing the watch in the cradle, so it takes a bit of force to release it. This should avoid that it shifts in the cradle when bumping against something or being subjected to shocks.
It is essential to print this vertically (like in the model file) to provide maximum strength for the groove in which to mount the phone. This is also pretty much the only possible orientation to print it anyway.
The contact surface with the bed is extremely small, therefore it is also essential to use both a brim of at least 2 mm, and of course support material. For the first version I just let Slic3r do its job with pillar supports and it did the job well, I only tweaked the contact Z distance to be only 0.1 mm (one layer) to ensure good adhesion.
The print may become a bit wobbly in the topmost layers, but if the supports and brim are well-configured, this should not cause problems.
The downside of printing the model in this orientation is that layer adhesion is crucial to prevent the cradle from cracking in the same way as the original. Print this slowly and hot for maximum strength.
I printed the second and third versions in pretty much the same way, only with the fan speed reduced to 50%, because there was a small crack in the first version print due to too much cooling. The cooling is essential however to obtain an accurate and smooth print.