Until I adopt a final solution for the Z-Axis banding problem (which I hope will be an upgrade option purchased from Velleman), I have a temporary improvement.
By changing my layer width to 0.4 mm from 0.25 mm, I get much much smoother vertical surfaces on things like the electronics enclosure. I know, I know…a finer layer SHOULD give a smoother surface. But, because of the Z-Axis banding problem, the surfaces are smoother with a thicker layer. That’s because the thicker layer is not as sensitive to the innacuracies of the Z-Axis position. This pretty much puts the lie to the theory that the banding is caused by Z-Axis wobble. It is actually caused by variations in the pitch of the threaded rod. It must be replaced with a more accurate lead screw to solve the banding problem.
As Wally explained, a compressed layer becomes “fatter” in the X-Y plane because the volume of material is constant. The material that does not go into a vertical direction squirts out into a “fatter” horizontal layer. These “fat” layers appear as bands at regular intervals because the inaccuracies in the threaded rod pitch are regular and cyclical. We have all observed that the spacing of the Z-Axis bands corresponds to the pitch of the threaded rod.
In the interim, before replacing the Z-Axis threaded rod, using 0.4mm layers instead of 0.25 mm layers is a good compromise. A smooth 0.4 mm layer surface has a better appearance than a banded .24mm surface. Once the Z-axis threaded rod is replaced, then I will move back to thinner layers.
There will always be some striations visible on vertical surfaces. Only with the impossible layer height of 0 mm would a perfectly smooth surface be realized. That’s ust a limitation of FFF technology. For perfectly smooth surfaces, one option is to buy a commercial grade laser powder sintering printer for 20,000 pounds.
Art Cominio