I am trying to design and 3D a custom snap in fastener, and I am having a hard time figuring out what cross section it needs to have so that it does not break when compressed, but also isn't so that it is not too hard to compress to push in the clip.
This illustration shows the over all device, including a "cylinder" (gray with white line) that is inserted into the blue "clamp" component. The green "e-clip" is supposed to snap onto the blue clamp, as shown. With this clip in place, the center section of the e-clip should push the cylinder tightly against the blue clamp to impede both rotational movement of the cylinder and radial (in/out) movement.
Finally this entire assembly is pushed into a cylindrical hole in a panel to hold the assembly in place. on either side of the part that is inserted there are fingers with a nub at the end. When inserting these will need to be compressed to fit through the hole, and once they reach the other side of the panel they should spring back out, and the nub prevents the assembly from slipping back out.
I am having two problems that are causing 3d printed versions of this design from being reliable.
The first problem is with the e-clip. If the center part of the clip isn't long enough, it won't push the cylinder tightly to the other side, and the cylinder easily turns.
If the center clip is long enough, and too strong and stiff, it may actually make it impossibly hard to get the clips on the prongs to open enough to slip all the way past the retaining edges of the blue clamp.
If the center key is not strong and stiff enough it can snap off.
If the prongs are not thin enough to flex open to go around the retention part of the clamp they can't be pushed over the retaining edges. And if they are too thin, the ends of the prongs break off.
The second problem is with the clamp itself. It also has two fingers to hold the clamp in place. These will need to be thin and flexible enough to compress and allow the assembly to be pushed into a hole, but they also can't be too thin so that they fracture when compressed.
What I have tried:
I have tried 3d printing using a number of different materials including PLA, PETG, ABS and Nylon.
I have tried to increase the thickness of the parts that fracture, and to decrease the thickness of those that are too rigid to compress or expand enough.
I don't seem to be dialing into a workable solution through this trial and error method. How can I determine thickness/cross section needed to prevent fracturing during insertion, but still be bendable enough to "snap" in place.