Current simulations

My mental simulations suggest that the current roller solution would be unreliable, and it's likely the reason why my modelling speed has slowed this week; the roller assembly moves other assemblies around. I'm thinking that the resin may stick to the roller, but there is a probability that some resin is further pushed down along the edge of the part. 

The simulation assumes that the top of the exposed area is fully cured, thus the only location for uncured resin is the boundary between solid and liquid parts. It should be possible to roll the X axis over the section to be printed to prevent the resin being compressed between the LCD and another material in the same layer, though this requires 2 applications on the PET. For a single application, it might be possible to move to press on the part, roll off to expose a different part of the layer and then roll back, pushing out the resin.

The simulation is using 0.2mm layers because I want to be able to draft print if possible and the higher the layer height, the harder it is to clean.

Possible solutions

The ideal solution is one that obtains a result similar to a cookie cutout of dough, whereby everything exposed sticks to the part and everything else sticks to the film. Additionally, the LED strip is ommitted, instead making use of the hight powered UV lamp that already exists overhead.

Since the LCD is light, thin, and for this printer, small, it shouldn't be too much of an ask to install it on a trapdoor.

For non-conductive materials, I'm thinking of electrically charged resin and something on the screen-side of the PET attracting the resin. Something like a toner printer maybe?

Wait... things are getting real close to a laser printer now. The differences is that the laser step is ommited and the "fuse" (read: expose) step comes before the transfer (back to the film) step.

For conductive resins, I'm thinking of adding ferrous powder and having magnets on the screen-side of the film. I have a better feeling that this would work (magnetic putty is just an extremely viscous liquid, right), but the bigger question is making affordable and highly conductive resins. I still believe that liquid deposition into channels would be for the best. Silver paste may be expensive, but only a 1 layer (40um) thick trace would need to be deposited and would still exceed conductivity of 2oz copper traces, and the silver is only deposited where it's needed. I don't have to worry about reclaiming excess paste or the metal particles reflecting most of the UV light if it was in a UV curable resin.

Compute conclusions

Both solutions may allow the "every single drop makes it to the print" ideal that BCN3D and those 2021 researchers talked about. It should also be more gentle on small features, since there shouldn't be any contact (and if there is, very lightly).

As the X axis may now be responsible for cleaning and curing, the application rollers may be brought back for speed improvements, but right now I need a minimum viable product not a max velocity printer. Thus, this solution should remove: 

• 4 stepper motors 
  • (so all the cleaning roller related motors and 1 motor is repurposed to move the LCD instead of the cleaning thread)
• 2 stepper drivers
• UV LED strips
• Most bearings and pullety from the design, as well as some 2GT belt
• The cleaning roller and the hand-cut aluminium channels 
• Long strands of thread as a consumable, and the associated maintinance downtime
  • This was one of the things holding up a compute. The problem was being able to get the thread into position and how the thread bowden would get to/leave from the roller assembly.
• 2 linear rails

Additionally, the Z height is likely to increase by 20mm.

Now I need to research how to negatively charge liquids and what voltages would be needed for the anode.