With all the hype Carbon3d has gotten lately about how it has revolutionized 3d printing with its continuous printing system, I started to ask myself what was stopping me from doing the same thing?
The standard layer cycle for top down machines is to expose the layer, lower the print into the vat, let the resin flow over the print, raise the print back up to the position for the next layer, wait for the resin to flow out evenly, expose the next layer and repeat. This may be faster than the peel cycle of a bottom up printer, but it still isn’t as fast as it could be. With the right resin and a good DLP projector the exposure time can be as little as a second or two, yet the whole cycle can take as long as 8-10 seconds. Now we are only talking seconds here, but an 8 second layer cycle takes 4 times as long to print as a 2 second layer cycle. That’s the difference between a 1 hour print and a 4 hour print. What if we could trim out the extra time so we are exposing resin for the entire layer cycle? It turns out it isn’t that hard to do. Creation Workshop gives you enough control over the program that it is quite easy to make your machine print continuous layers. You set the Z-lift distance to 0mm and the lift and sequence time to 0sec. The machine exposes a layer then drops to the next layer and exposes it with only a brief flicker of the projector as it changes layer. You will probably have to tweak the exposure time and layer height to optimize things, but it is pretty easy.
There are a few problems with the continuous printing system. First the initial layers on the build plate sometimes have trouble because there isn’t enough resin on the surface until the build plate is well submerged. A perforated build plate helps, but isn’t a perfect solution. The second problem is that the resin doesn’t flow out as quickly as we would like. The perfect resin would be water thin and would level out instantly. It doesn’t exist (yet). As print slowly submerges in the vat it sometimes takes too long for the resign to flow in and be exposed. This results in defects and sometimes entirely failed prints. My next project is to heat my resin vat to try to reduce its viscosity.