It started as a naive project and ended in my daily-use frame. Printed with PLA it lasts about 4 months up to a year until it breaks. Given the costs of a few cents i wouldn't care if it break once a month.

Probably its a good start point if you want to design your own frame. Be aware that this frame, even not noticeable, is on purpose slightly asymmetrical. My lenses do not have the exact same shape. The straight sides need to be gently adjusted with patience and a hot air gun at low temperature.

• see also FreeCad project file on GitHub: glasses.FCStd

Materials:

I tried with 

• PLA, 
• PLA+ 
• carbon PLA and 
• PETG. 

No-name PLA is robust enough; even the beige with wood finish that tend to be softer is okay.

Settings:

• layer height 0.1-0.12mm
• 3 walls, inner-outer-inner, wall engine: Arachne
• infill 40% adaptive cubic
• top / bottom shells: 5/4
• support normal, style Snug, support wall loops 0
• raft: 2
• cooling: 
  • sides: not required
  • frame: 100% - maximum the machine can give (cooling chamber fan etc…)

Issues i had:

• poor layer adhesion if with 0.08mm or lesser layer height
• slight under extrusion on the frame around the hinges: slightly mitigated by extrusion rate smoothing (60mm³/s², segment length 1mm), otherwise reduce print speed or increase layer height
• poor finish in between frame and support interface: i use a SMD hot air soldering station to melt the plastic that became white when ripping off interface/support
• i used to polish the front (don't care so much now): use wet sanding paper and water on a plane surface