I have gone through quite a bit of PLA to get to a Crazyflie frame design that I am happy with.
Here is a list of some of the designs I have been through.
Crazyflie frame v1.0 to 1.2
A simplistic frame concept, simple configuration and easy to fix to the flie arms using dual sided adhesive foam. Strong frame but offers only protection in the XY plane. Weight 2.5g.
Crazyflie frame v1.3
Start of the motor mount attachment method as a means of attaching the frame and to use the frame as the battery cradle. Frame was very weak and flimsy and counted on parts deformation and release so as to dissipate the collision energy. Frame made up of 4 separate parts fixed to the side of the stock motor mounts. Weight 4 x 0.35g.
Crazyflie frame v1.4
Same as v1.3
Frame was very weak and flimsy and counted on parts deformation and release so as to dissipate the collision energy. Frame made up of 4 separate parts fixed to the side of the stock motor mounts. Weight 4 x 0.26g.
Crazyflie frame v1.5
Motor mount attachment joined together as a means of attaching the frame to the flie. The frame itself has a battery cradle underneath the flie that allows the battery to be attached to the frame rather than to the flie board so as to improve flight stability.Frame was very weak and flimsy and counted on parts deformation so as to dissipate the collision energy. Weight 1.72g.
Crazyflie frame v1.6
Integral loops around the rotor so as to improve protection. Frame was very weak and flimsy and counted on parts deformation so as to dissipate the collision energy. Weight 1.51g.
Crazyflie frame v1.6.5
Based on the experience from the community, frame thickness was increased from 0.6mm to 1mm.
Loop around rotors kept and reinforced with extra side bars.
Frame is more rigid than previous versions and relies on increased stiffness as protection, top of rotors remain unprotected. Frame provides additional stability to the quad because it allows for the battery to be mounted underneath the quad. Weight 2.76g.
Crazyflie frame v1.6.6
Same as v1.6.5 with modified clamping method to the flie stock motor mounts. Loop lateral bar reinforcements thickened from 0.6mm to 1mm. Weight 3.23g.
Test flight: https://www.youtube.com/watch?v=CoaYm2FEYzY
Crazyflie frame v1.7
Major redesign from previous versions of the frames.
Attempt to provide an improved protection on the Z plane as well the XY plane.
Frame is too heavy and the thick wake of the struts on top of the rotors decreases the aerodynamic efficiency of the props. Weight 8.085g.
Crazyflie frame v1.7.1 (loopless)
Same as v1.7 but without the rotor loops. Decrease in XY plane protection to the flie. Weight 4.885g.
Based on v1.7 frame without the struts upstream of the rotors, hence better aerodynamic efficiency.
In order to keep the frame weight down the protection loops have been made quite thin and somewhat fragile but it is one of the best frames I have flown.
Crazyflie frame v1.8.5 (TBD)
Weight reduced version of v1.8
Frame weight history
Now I am selling a few of these frames in ebay to feed my 3D print addiction.