On a comment on “A little bit about UV Curable resins…” post, Traumflug shared some really amazing information that I thought deserved to be blogged on its own, for future easy reference when people start trying some UV curing of they own:
“Here I can talk a bit about my experience as an operator of a 3D Systems stereolithography system. Early SLA resins were all clear, and they produced quite even layer thicknesses. So, coloring the resin isn’t essential at all.
When you expose UV-curable resin to light, it starts hardening at the top (where “top” = “closer to the light source”) and the more light you bring in, the thicker this layer gets. However, the exposure has to be above some threshold to work at all. Not enough light and no hardening takes place.
To find out the relation between exposure and layer thickness, simply expose just one layer, then take this single layer out, postprocess (wash) it as normal, and you can measure the thickness. The minimum layer thickness is very low, like 0.01 mm. Much lower than you can reasonably handle.
Minimum layer thickness also isn’t essential to build accuracy or layer thickness. It’s no problem to advance in 0.1 mm steps, but to expose for 0.2 or 0.3 mm. This way, parts of the resin get exposed twice or three times, wich doesn’t hurt at all.
After all, the SLA slicing algorithm makes the bottom layer (here the top layer) intentionally extra thick, to achieve better build accuracy. More accuracy, because the first layer is more mechanically stable (think of overhangs). The drawback is, this introduces some complications in the slicing algorithm to compensate for this extra thickness. In other words, you have more fun creating a good slicing software.”
Thanks again for sharing this, Traumflug!!!