Nice video. I like to make the holes 5mm where I can. Kind of large, but this way, I can fit a UV LED up inside the model to cure the inside space as well once I'm finished draining the resin out. Especially useful for dark, solid builds.
Very helpful. I was printing a Minecraft Ghast. Essentially a giant cube. I hollowed it out, and during the printing I could hear the suction every time it was time for a new layer. It was still a successful print, just don't know how long my luck will last
With the orientation flat on the build plate, would it make a difference (in terms of suction forces) if you put a large hole in the bottom of the model where it sticks to the build plate? Also, I don't really see how the cross section significantly decreases by tilting the model. It does decrease at the start and end, but halfway through the print, the cross section seems about equally large as when the model is oriented straight up, correct...?
@@readywhen I'll try answer these as best I can: -If you would hollow the model, keep it flat on the plate and put a hole on the surface that's touching with the plate, you wouldn't be achieving anything with regards to venting the model during the print. You'd still have the issue that the model acts like a suction cup and you'd be getting a different pressures inside and outside of the hollow potentially causing a print failure or surface defects. There's a great post on reddit that showed how important venting is: cutt.ly/tjuwKwr. So if you'd want to print it flat on the plate, you'd want to then put the venting hole on the side at the lowest point of the hollow section to avoid issues. -The tilting is more of an orientation optimization thins. You are absolutely right that the minimum cross section will be at the bottom and top of the print, and the middle is going to be a little larger, but I was trying to say that the cross sectional advantage was better relative to a non-hollowed model. -For your follow up, I'm going to be doing a video explaining orientation and why we angle things very soon so I'll ping you when that's out, but the TL;DR is: we want to try avoid having the "first surface that prints at the tip of supports" to be large flat areas. That includes bases, and long flat edges. The reason for this is that once that part starts printing on the support tips, you're looking at a 0.05mm (or less) thin single layer. Just with the peel, it might rip in places if it's under supported and if it survives the peel, it then has to survive traveling 10mm through the resin (5mm up and 5mm down) at whatever your lift and retract speeds are. That's why you see a lot of models that are printed with a flat parallel to the LCD on supports with a horrible surface finish on that face. Hopefully that's helped!
@@3DExtra Thanks for your elaborate reply! The reason I care so much about this topic, is that for the objects I want to print, printing parallel to the build plate would allow the model to go almost suportless, whereas a slight tilt would introduce many islands. Everything you explain makes sense. But there seem to be inconsistencies in all the opinions I find on the internet. Consider this youtube comment I came across and I'd appreciate it a lot if you could share your thoughts on it: "There is effectively no suction being created inside the hollow because no resin nor air has been removed from the hollow after it was sealed. In fact, the air inside is VERY, VERY slightly compressed by the hollow model dipping into the resin. (You can see this in action by taking a drinking glass, turning it upside down, then lowering it into a bath tub or swimming pool. The deeper you go, the more the water will compress the air in the glass and you'll see the water level rise up inside the glass similar to what happens in a diving bell.) For a resin model the hollow cavity has a ~0.05-0.01 gap between the FEP and the model until the light source turns on, so up to that point, the cavity isn't sealed and pressure can equalize. For LCD printers, the resin perimeter will harden, but it will just hold the resin inside and outside now - it doesn't remove any material, so still no suction. When the model starts to lift, there is still no air or resin being removed from the cavity, so that side of the FEP is stable. At the same time as the model lifts, the underside of the FEP is open to the air, so there is no force pulling down on the inside of the hollow. All the force is on the outside perimeter of the model as the FEP is pulled between the edge of the model and the edge of the vat. Once the FEP peels away from the outer perimeter far enough to reach the inside of the hollow, then there is now a hole between the inside and the outside, so air and resin can flow an no vacuum can form to create suction. The only way for significant vacuum to form would be if the entire model stretched more than the depth of the resin in the hollow. At that point, the volume of the interior would have grown by more than the volume of the resin trapped air, and a vacuum would start to form. A flex resin could do this, but standard miniature resins are too rigid.
@@readywhen The term "suction" gets used for a bunch of things interchangeably and the community is not really willing to decide on one specific thing. Suction should only specifically refer to the added force created while peeling an un-vented hollow object from the FEP. There is no suction during regular peeling, that's just a peel and there's no suction between the LCD and FEP since that's a completely open system. -The comment from the very start has no substance to it since there's no air trapped inside the hollow of the model unless your lift height takes the print above the resin line and in most cases that I've seen, the vats are full enough and the lift height is small enough for that not to happen. So while the diving bell analogy works to demonstrate that air is a compressible fluid it is completely invalid for explaining suction forces on hollow resin prints. The right test for this demonstration is: fill your sink up, take a glass, put it under the water and fill it up completely. Turn it bottom side up and try to remove it out of the water. Once the mouth of the glass comes close to the water line, you're going to start feeling some resistance on being able to pull it out of the water and that resistance is equivalent to the suction force on an un-vented model. It's most often not going to cause a catastrophic failure but it might result in a pretty big layer shift and if the model is big enough and the supports aren't quite right, it can result in the model tearing away and staying on the FEP. This graphic (not super accurate but brings the point across) might help with visualising it imgur.com/1M4W5iu. -While there is a small gap there to theoretically be able to "normalise pressure" you're not going to be able to do that once the print builds up past the resin line in the vat, since there's no way for resin to drain out of it and as you keep building up the print, you're left with . As far as things go, that gap might be too small to be able to let things normalise and since the print is always at the lowest point in the vat, there's no way to let air move into it without a vent hole at the highest point of the model. Plus resin is viscous and 0.05 is a super small gap.
Is it normal if there’s supports inside the figure, I placed the supports but I realized there are supports inside the figure and I can’t print bc I think it’s not right, please help me ;((.
Yeah, supports inside are perfectly normal. In most cases, you really even want supports inside because you will be getting geometries such as islands that can happen inside the hollow of a print.
Think I finally understand why my hollow prints fail in some manner now, thanks!
Nice video. I like to make the holes 5mm where I can. Kind of large, but this way, I can fit a UV LED up inside the model to cure the inside space as well once I'm finished draining the resin out. Especially useful for dark, solid builds.
good
Very helpful. I was printing a Minecraft Ghast. Essentially a giant cube. I hollowed it out, and during the printing I could hear the suction every time it was time for a new layer. It was still a successful print, just don't know how long my luck will last
nice explanation, thanks
Thanks for your explanation!! great and very helpful
this is very helpful tutorial thank you so much
Thanks for the great video! Helped alot!
Great video!
Very informative, thanks.
Great video!
So the inner supports can break off and rattle inside driving me crazy?
So why do some models that are hollowed out, not allow me to add holes? I have had this issue many times on differnt models.
Enjoyed your channel, shame you stopped after 3 videos :(
Give me download link pls
Thxn you
Hy man, do you know why my Chitubox doesn't place supports inside the shell?
P.s Great video 😀
With the orientation flat on the build plate, would it make a difference (in terms of suction forces) if you put a large hole in the bottom of the model where it sticks to the build plate? Also, I don't really see how the cross section significantly decreases by tilting the model. It does decrease at the start and end, but halfway through the print, the cross section seems about equally large as when the model is oriented straight up, correct...?
And a follow up: would it make a difference (in terms to suction forces and sticking to the build plate) if I place the non-tilted model on supports?
@@readywhen I'll try answer these as best I can:
-If you would hollow the model, keep it flat on the plate and put a hole on the surface that's touching with the plate, you wouldn't be achieving anything with regards to venting the model during the print. You'd still have the issue that the model acts like a suction cup and you'd be getting a different pressures inside and outside of the hollow potentially causing a print failure or surface defects. There's a great post on reddit that showed how important venting is: cutt.ly/tjuwKwr. So if you'd want to print it flat on the plate, you'd want to then put the venting hole on the side at the lowest point of the hollow section to avoid issues.
-The tilting is more of an orientation optimization thins. You are absolutely right that the minimum cross section will be at the bottom and top of the print, and the middle is going to be a little larger, but I was trying to say that the cross sectional advantage was better relative to a non-hollowed model.
-For your follow up, I'm going to be doing a video explaining orientation and why we angle things very soon so I'll ping you when that's out, but the TL;DR is: we want to try avoid having the "first surface that prints at the tip of supports" to be large flat areas. That includes bases, and long flat edges. The reason for this is that once that part starts printing on the support tips, you're looking at a 0.05mm (or less) thin single layer. Just with the peel, it might rip in places if it's under supported and if it survives the peel, it then has to survive traveling 10mm through the resin (5mm up and 5mm down) at whatever your lift and retract speeds are. That's why you see a lot of models that are printed with a flat parallel to the LCD on supports with a horrible surface finish on that face.
Hopefully that's helped!
@@3DExtra Thanks for your elaborate reply! The reason I care so much about this topic, is that for the objects I want to print, printing parallel to the build plate would allow the model to go almost suportless, whereas a slight tilt would introduce many islands. Everything you explain makes sense. But there seem to be inconsistencies in all the opinions I find on the internet. Consider this youtube comment I came across and I'd appreciate it a lot if you could share your thoughts on it:
"There is effectively no suction being created inside the hollow because no resin nor air has been removed from the hollow after it was sealed. In fact, the air inside is VERY, VERY slightly compressed by the hollow model dipping into the resin. (You can see this in action by taking a drinking glass, turning it upside down, then lowering it into a bath tub or swimming pool. The deeper you go, the more the water will compress the air in the glass and you'll see the water level rise up inside the glass similar to what happens in a diving bell.) For a resin model the hollow cavity has a ~0.05-0.01 gap between the FEP and the model until the light source turns on, so up to that point, the cavity isn't sealed and pressure can equalize. For LCD printers, the resin perimeter will harden, but it will just hold the resin inside and outside now - it doesn't remove any material, so still no suction. When the model starts to lift, there is still no air or resin being removed from the cavity, so that side of the FEP is stable. At the same time as the model lifts, the underside of the FEP is open to the air, so there is no force pulling down on the inside of the hollow. All the force is on the outside perimeter of the model as the FEP is pulled between the edge of the model and the edge of the vat. Once the FEP peels away from the outer perimeter far enough to reach the inside of the hollow, then there is now a hole between the inside and the outside, so air and resin can flow an no vacuum can form to create suction. The only way for significant vacuum to form would be if the entire model stretched more than the depth of the resin in the hollow. At that point, the volume of the interior would have grown by more than the volume of the resin trapped air, and a vacuum would start to form. A flex resin could do this, but standard miniature resins are too rigid.
Looking forward to your upcoming video!
@@readywhen The term "suction" gets used for a bunch of things interchangeably and the community is not really willing to decide on one specific thing. Suction should only specifically refer to the added force created while peeling an un-vented hollow object from the FEP. There is no suction during regular peeling, that's just a peel and there's no suction between the LCD and FEP since that's a completely open system.
-The comment from the very start has no substance to it since there's no air trapped inside the hollow of the model unless your lift height takes the print above the resin line and in most cases that I've seen, the vats are full enough and the lift height is small enough for that not to happen. So while the diving bell analogy works to demonstrate that air is a compressible fluid it is completely invalid for explaining suction forces on hollow resin prints. The right test for this demonstration is: fill your sink up, take a glass, put it under the water and fill it up completely. Turn it bottom side up and try to remove it out of the water. Once the mouth of the glass comes close to the water line, you're going to start feeling some resistance on being able to pull it out of the water and that resistance is equivalent to the suction force on an un-vented model. It's most often not going to cause a catastrophic failure but it might result in a pretty big layer shift and if the model is big enough and the supports aren't quite right, it can result in the model tearing away and staying on the FEP. This graphic (not super accurate but brings the point across) might help with visualising it imgur.com/1M4W5iu.
-While there is a small gap there to theoretically be able to "normalise pressure" you're not going to be able to do that once the print builds up past the resin line in the vat, since there's no way for resin to drain out of it and as you keep building up the print, you're left with . As far as things go, that gap might be too small to be able to let things normalise and since the print is always at the lowest point in the vat, there's no way to let air move into it without a vent hole at the highest point of the model. Plus resin is viscous and 0.05 is a super small gap.
Is it normal if there’s supports inside the figure, I placed the supports but I realized there are supports inside the figure and I can’t print bc I think it’s not right, please help me ;((.
Yeah, supports inside are perfectly normal. In most cases, you really even want supports inside because you will be getting geometries such as islands that can happen inside the hollow of a print.
@@3DExtra I was going to print a Hollow Totoro
If I drain the inside of the figure with alcohol to drain the resin, are the supports going to come off and stay there?
@@ivankas52 Supports are going to stay there, but you don't need to remove them. You can just leave them there and everything will be fine.
@@3DExtra Thank you so much ☺️☺️