Foldable/Flexible Card-sized Smartphone Stand

How to print

Disclaimer: The stands in the pictures and the 3D models have slight differences, which is because the pictures are of multiple previous iterations of prototypes.

Decide on the version you want to print

Multi- vs single-material:
If you can print with flexible and non-flexible materials at the same time, I recommend you make use of that capability since it will significantly increase the lifetime of the hinges and the ease of use. In case you have a Prusa MK4(S) or a CoreONE with the MMU3, I made this guide, which will allow you to print flexible materials on the MMU3. This is also the setup I used to print my parts.

Corner type:
This is just a cosmetic difference, choose whatever you like more.

Width:
Width of the cutout for your phone. Note that the more play there is, the further the phone will tilt back, and if it tilts back too far, the stand will tip over. If you have more play then you like with the presets I provided, you can also choose a width less than your phone and then use a hobby knife to cut away material and enlarge the cutout.

Printing the chosen version

For both versions, you should be careful when getting the print off the printbed. If your bed adhesion is too strong, just pulling it off by one side can damage the hinges. I recommend pushing something flat and hard, like a credit card or a thick piece of paper, under the part from all sides until it falls off the build plate.

Single-material version:
It's pretty simple, just slice your part with a 0.15mm profile. This is to ensure that the hinges are made up of two layers, where the top one should have the oval cutouts. It's best to choose a material that survives being bent over and over again, like PETG. Brittle materials like PLA will break after a couple of uses.
If you wonder why there are these oval cutouts on the hinges, they are there so that the bend starts to form in the middle of the hinge and not at the edges, which is relevant for alignment and durability.

Multi-material version:
After getting your .stl file in the slicer, right-click it and choose 'Split > To parts'. Now you can assign your flexible material to the part that will form the hinges. For the other parts choose any stiff material you have. I designed interlocking geometry into the parts, so it is not important if the stiff material you chose chemically bonds well with your flexible material. Also choose a layer height of 0.15mm.
The interlocking geometry is designed for a nozzle diameter of 0.4mm, below you can see the design and how it should look after slicing.

Usage

The hinges are designed to be folded 'downwards' (referring to the orientation when you pick it up from the build plate), you can see an example of that in the second picture at the top. It is easiest to first fold down the middle section about 100°, and then fold in both sides at the same time such that the 'T'-shaped ends of the middle section pass through the slits in the sides. Then pull the middle section back out. It should secure in place with a slight 'click'. 

Dimensions:
The dimensions of the stand are 85×54×1.5 mm, so it is 50% thicker than a normal credit card.
The phone rests at an angle of about 15° (the pictures might suggest otherwise, but as said, they are of older prototypes, which had an angle of 20°).

Customization

In case you want to add your own design or get a custom width or angle for your phone, I added a .step for easy customization.
One thing to keep in mind when adjusting the width is that due to the way the stand folds, the distance on the surface of the part is longer than the actual width of the cutout for the phone. Below is an example for phones that are 10mm thick.

Another thing that is easy to overlook is that the distance in the following picture should not be decreased to much, the absolute minimum is 3mm. It is there to make sure the hinge of the middle part has enough space behind the phone when folded.

If you modified the multi-material version and want to export it to your slicer, to make sure the parts are aligned, I would recommend exporting the modified stand as an .stp file and opening this in your slicer. You can then right-click it and choose 'Split > To parts' and everything should be aligned.

Making sure the folding works well and everything is aligned in the end, as well as figuring out geometries for the living hinges for the multi- and single-material versions took some effort. So if you like the model and want to give something back, you could buy me a coffee.  Thank you ^^.