This phone stand can change with hold the hinge angle by spring tension.

Print Settings:

• Material: “PhoneStand_Spring.stl” should be printed with PETG. Other parts, PLA will work fine.
• Layer height: 0.2mm
• Supports: Yes, “PhoneStand_Plate.stl" need support.
• Perimeters: 2

Assembly: 

Place the spring and gear in the case as shown in the image. Make sure that the spring and wheel are engaged before attaching the other side of the case. 

Finally, it is inserted into the base part to complete the process. Use glue if necessary.

Enjoy!