NEW Subsurface Non-Planer FFF
There's inherent problems with FFF's layer adhesion in functional applications and here I'm trying to provide some solution.
It's common knowledge that injection moulding offers parts with, sometimes significantly, higher tensile strength over 3D printing. Annealing can help but is yet another step in the process and may be difficult to control the distortion of parts. From my experience with wood working joints, it's clear, as many of you know the wood joint is only as good as your surface area is large. This is the same issue we have with FFF. Essentially we are creating constant layers of "butt joints" and lending the parts vulnerable to the characteristics of grain with in-line fractures under stress.
We can increase layer adhesion and remove this grain like effect exhibited by 3D printing if we change our joint, increasing surface area. We can increase tensile strength by changing the layer geometry. Below I have a diagram showing an example of subsurface non-planer layer adhesion, take a look. If you were to remove one of those wavy layers and flatten it - it would expand to be about 17% larger than a normal planer layer. Effectively increasing surface area and therefore layer adhesion and tensile strength.
-Planer_FFF