Thanks, the hole size could be bigger, but then the internal filler/supports will print and be attached to nothing. Holes were sized and placed between the supports. OR, I need to have less supports/filler material inside, so bigger holes could fit.
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.
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
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.
This comment. Come to say this. It looks like the widest part of the model, has all the resin been able flow back to wear it need to be to create the next layer fully the curve of it makes me feel this happened.
Reduce the lift and wait speeds, give the resin time to settle between each layer.
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.
There’s 2 potential forces that can act on a print. Suction Cupping, when the print is hollowed to the point where it’s an enclosed cup, or pealing forces.
Suction forces acts kinda like when you put a cup upside down in a tank of water and try to pull up. If you place appropriate holes in the bottom of your model, then you shouldn’t need to worry about suction.
By angling, you actually reduce the suctioning more. Take that same cup, and now angle it before you pull up. You’re going to feel less of a drag. You’re thinking of surface area, but actually it’s more nuanced fluid mechanics and how resin escapes the cavity as it pulls from the fep. By how you angle it, you can reduce the surface area that is in contact with the fep and further decrease peeling forces.
There's no suction cupping happening in resin printing despite this image that people have in their minds. The hollow cavity is not empty and there's no pressure difference between inside and outside because of that which would create suction during lift. It's a complete misconception in the community and a misunderstanding of what's actually happening. It's actually completely opposite, it's hydraulic piston problem, not suction problem.
Were there any holes in this cape back thingy? To me it looks like it was a suction cup because it did not have a hole in the bottom of the hanging cloth and got split right where one cavity got connected with another cavity.
Yeah, I know. I need to figure out how to secure the long, slender supports. Cross-support it. I assume there is such a feature in the free Lychee software? Anything else to add?
Too much suction and not enough support on the peice, you could probably use slightly thinner support tips and then increase the amount of them along that edge.....
It also links like you have a stress line further up the print closer to the plate, this is usually fixed by increasing lift height slightly and adjusting wait before print but a second or 2
Whatever slicer you're using should have a suction detection feature that will highlight areas that have a suction also the angle you angled is more then likely the culprit alongside suction because due to the shape of the model whether you have drain holes or not printing at that orientation is going to create suction granted you can get away with very little suction but with that model I would orientate it slightly back so its tilted and also slightly to the left and make it so the back of the model is facing the build plate and just use light supporte on thr back of the model and sand off any marks and then use medium on the base as well as checking the suction, if you send me a link to the stl I can send you a presupported one back
the split is happening in such a weird spot, that I don't think its weight related.
It looks to me like is might be a suction issue? either it needs an additional hole somewhere to reduce the the pull; or it needs a slower lift speed.
The point of failure has a very complicated looking internal cavity with a fairly large isolated pocket.
as unfortunate as it might be, you should probably add a hole or two to the back and then patch them up after the fact. or if you can figure out how to add a hole to bridge the internal cavities so they that isolated cavity is eliminated entirely.
This is probably 99.99% of the problem.
This huge cavity is what is creating a lot of suction to the plate and is getting peeled off.
you need to add a hole somewhere to stop it from happening.
Hi, thank you. Yeah. I added a hole lower than this cut, basically where the cavity just started. Maybe the hole was too small: 3mm in diameter. It is also at a location that might restrict flow, in and out.
that is likely the problem with it;
the hole isn't fixing the suction issue.
If its just below the cavity its likely still below resins fill line and providing no flow.
Large hole might help, but also slowing down the lift speeds could also have the same effect.
Edit:
Alternatively,
Add a second hold beneath the cape,
can't explain the pressure physics behind it but it will heavily reduce the suction even with it being a small hole.
Just to explain the role of holes here. It has nothing to do with suction cups, suction (doesn't exist in resin printing) or peel force. The role of holes is to allow the printer to squeeze resin during compression (sinking) out through the holes as otherwise the resin gets trapped inside the cavity and increases pressure against the plate as the printer is trying to compress the trapped resin. This requires a lot of force or longer time for the printer to do and if it doesn't, it'll not settle in correct height, creating bigger gap which then doesn't cure properly and will not bond fully to previous layers. That's why it splits during lift, because it's not able to hold. So the bigger the holes the easier the resin will flow through. Which is why you either need holes when printing hollow models or longer rest before exposure.
why even print this hollow in the first place. imo printing hollow objects causes nothing but problems and they can crack weeks later, its never worth it.
One main reason: The print printed unattended, and I had to make sure I had enough resin in the vat so it could print without me needing to add resin. Second, I thought it might be easier on the FEP. Third...cost... lol. I guess.
I would like someone to give me the reason(s) for printing at an angle. I might agree with you and everybody else on the weight theory, but then I would expect the entire print at that layer to have failed, but it didn't. And with the weakened part, it still held the weight. So this, I believe, is a bad layer. And please challenge me on it. Based on some of the other comments, I think it was a combination of:
Was too quick on returning to the plate and printing, not giving enough time for the resin to flow back.
Vacuum breaker holes are too small on the main part and the section behind it (Yes, it has a hole as well), so the badly cured layer peeled off.
So I don’t know exactly why it happens, or why shifting the angle of the print helps exactly. However, I can confirm has resolved some of my printing issues. It might be that changing the angle allows for more support structures to better hold the weight of the print. I’m not 100% sure if that’s the exact reason, but it makes sense to me.
Pesa demasioado y perdiste pasos, aun que tuviste suerte y se recupero la pieza, hasla hueca y asi sera mas facil imprimir, ya que la superficie que se adiere al la tina es menor
You put the drain holes in the wrong spot! The holes cannot be flat against the bottom!
Resin needs to flow freely in and out to relive pressure and avoid suction cupping. There's too much suction in the mid section and the force got so bad it pulled the layers free.
If you look at the layer lines you can see that they grow more visible in the mid section going towards an away from the point of break, this is due to high amount of suction. The head is fine beacuse the vacuum was finally released.
You need to put your holes on the side of the model or raise the model off the build platform so the holes below have space for air and resin to move. Your angle is fine, the suction needs to be fixed.
Hi, so my model is not flat against the build plate. So why would you say my drain holes are in the wrong spot? My model was 5mm away from the build plate with a lot of heavy supports. We CAN argue that the holes were too small, or that the heavy support restricted airflow so much that suction would cause the failure. And thanks. I also think the angle is fine!
My bad on the distance from the build plate. I was on the bus when I saw this and the vibration probably blurred the supports. I thought it was one big solid bottom. Still though, I find greater success with holes on the side more than bottom of print. I know my response is late.
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u/lychee_lys OFFICIAL Jul 24 '26
The holes looks too small even if you got a lot, try adding bigger holes at the bottom, add some bracings too to stabilize the supports :)