Raspberry Pi 4 Experimental Resin 3D Printer -- Episode 414

Hello! retyping my thoughts from my youtube comment:

I recommend you make a build tank out of solvent welded acrylic, and a base of thin plastic film. This will allow you to see how thick your gap liquid layer is from the side of the tank. a tub with rounded edges makes this impossible and has too thick a base. You want as little distance from pixels-to-resin as possible which means the gap liquid+plastic film needs to be as thin as possible.

As for bubbles, I pour the resin in the tank and then give it like 10 minutes to settle, then i use the build plate motor to stir it up and down but under the surface so you don't introduce further bubbles. maybe add the gap liquid only after the resin is well stirred & de-bubbled.

It seems like for this method to work you really have to avoid agitating the gap liquid which probably means running the thing super slow. as the build plate moves up there will be a strong suction force inward which will disturb the uniformity of the gap liquid. perforating the build plate should reduce this force in the early layers. also using a physically smaller build plate, like just the size of one benchy for starters, because the smaller the build plate the less it disturbs the fluid.

It will maybe also be necessary to glue down the plastic sheet to the display surface (like with a light dusting of contact adhesive like super77) to prevent it from pulling away from the display under the forces.

I'm not a chemist, I'd love to hear from one on how to increase the separating forces between the liquids, like maybe if the resin is less dense and gap liquid more dense then they will want to more strongly separate. If density is part of what makes the gap liquid fall and the resin float, then you should measure the densities of various resins and use the lightest one, and figure out how to increase the density of the gap liquid. I think i'm talking about the buoyant forces like what makes oil float on water.

Another maybe useful idea is to put a sort of plastic mesh or fine netting material against the display and putting enough gap liquid to *just* cover up the mesh material. it'd act as a baffle keeping the gap liquid mostly in place, in the case where the suction forces are disturbing the interface too strongly.

alright, that's all I can think of right now. Cant wait to see more experiments

Hello! retyping my thoughts from my youtube comment:

I recommend you make a build tank out of solvent welded acrylic, and a base of thin plastic film. This will allow you to see how thick your gap liquid layer is from the side of the tank. a tub with rounded edges makes this impossible and has too thick a base. You want as little distance from pixels-to-resin as possible which means the gap liquid+plastic film needs to be as thin as possible.

As for bubbles, I pour the resin in the tank and then give it like 10 minutes to settle, then i use the build plate motor to stir it up and down but under the surface so you don't introduce further bubbles. maybe add the gap liquid only after the resin is well stirred & de-bubbled.

It seems like for this method to work you really have to avoid agitating the gap liquid which probably means running the thing super slow. as the build plate moves up there will be a strong suction force inward which will disturb the uniformity of the gap liquid. perforating the build plate should reduce this force in the early layers. also using a physically smaller build plate, like just the size of one benchy for starters, because the smaller the build plate the less it disturbs the fluid.

It will maybe also be necessary to glue down the plastic sheet to the display surface (like with a light dusting of contact adhesive like super77) to prevent it from pulling away from the display under the forces.

I'm not a chemist, I'd love to hear from one on how to increase the separating forces between the liquids, like maybe if the resin is less dense and gap liquid more dense then they will want to more strongly separate. If density is part of what makes the gap liquid fall and the resin float, then you should measure the densities of various resins and use the lightest one, and figure out how to increase the density of the gap liquid. I think i'm talking about the buoyant forces like what makes oil float on water.

Another maybe useful idea is to put a sort of plastic mesh or fine netting material against the display and putting enough gap liquid to *just* cover up the mesh material. it'd act as a baffle keeping the gap liquid mostly in place, in the case where the suction forces are disturbing the interface too strongly.

alright, that's all I can think of right now. Cant wait to see more experiments

Hi, thanks for sharing your ideas here. I will add some of them for the Q&A when I finally get to the second iteration.
O nthe separation forces: density of course is a factor, but the resin does not seem to be always at the same density from batch to batch and also behaves differently at different temperatures, over the course of a print it warms up a bit. For floating it was crucial to have unbroken surface tension. so I increased the density of the liquid but also had to make sure the surface would not get broken. which made removing air bubles areal pain.

to avoid having to deal with it the current plan for C.L.E.M. iteration 2 is to put it on its head and have avery deep floating liquid that supports a bigger amount of resin and the topmost layer wil lget cured not the layer at the seperation zone of the two liquids.
this avoids having to make sure for a perfectly clean separation and only needs it to be a uniform layer of resin that levels itself by gravity.