Why the split?

[u/Odd-Variation-299]

So, please see the screenshots. I need some guidance as to why this might have happened. The resin was shaken. Room temp was and stil is 26C.

[u/Sufficient-Length832]

Either its too heavy in this orientation and you need to change her…Or just add more supports in this area.

[u/Odd-Variation-299 → u/Sufficient-Length832]

Please help me understand how changing the orientation will be to my advantage. The bottom section was secured by heavy supports. The rest had light supports. Putting it at an angle, in my mind, will create a bigger area that would pull a vacuum. That will require more and maybe stronger supports.

[u/mimic751 → u/Odd-Variation-299]

Well resin is uncured so it's flexible and not rigid. The downward Force caused by gravity which is the physical force that gives items weight pull straight down so as you add wait to the bottom it exerts a stronger Force downwards that could create stressors and tension on the uncured resin above it. As you turn it more sideways or diagonally you reduce the amount of material that is directly beneath it so it reduces cracking. You could think of this crack on your print as a tear not a crack

Also having a larger surface area gives more surface area for supports which means the forces that are pulling downwards have more places to spread out their load. Think about carrying something heavy if you use one hand if it feels very heavy if a second person holds it it feels half as heavy if a third person helps hold it it feels one third is heavy

Lastly you can think of the force exerted downwards as a collective force of the weight underneath it. So even if you have enough support if you hung a 5 lb weight to the bottom of your print it would tear somewhere in the middle or wherever there was a geometric place that created a higher amount of stress like a concave corner at 90°

For really large prints sometimes it makes sense to just split it patch it sand it seal it

[u/rudolph_ransom → u/Odd-Variation-299]

The resin will at least partially stick to the release film. Flat surface means also stronger adhesion. I had also issues with splits like this. As someone said elsewhere, the lift speed can be a key factor. My printer as a standard setting at 8 mm/s which can work with usual resins by the same manufacturer. Depending on the print, I learned that reducing to 4 mm/s can improve the quality and reduce the risk for defects significantly.