I’m slicing a model that I can’t share unfortunately but I will add as much information as possible. The model is fairly complex, and it includes two hinges for a lid. I modeled the hinges myself as a solid cylinder inside another hollow cylinder with the caps as cones so that it prints in place and it can’t be dismantled. A section through the middle of the hinge would look something like this:
< <=> >
The gap between the two parts (cylinders) of the hinge is 0.3mm. When slicing the model in Bambu Studio, it does not add any support of the bottom of the inner cylinder, but considers it overhang. I attached screenshots of the print steps on those layers.
The thing is, I already printed just the hinge and it works as intended, to me that’s black magic, as I don’t understand how the printer started the bottom of the inner cylinder. I’m guessing it printed in mid-air and the filament fell down two layers on the outer cylinder and somehow kept doing that. It did need a “pop” after printing as it was obviously stuck, but nothing major. Looking at the printed part, it’s hard to see anything inside that area as the gap is so small.
What I would like to do is to add a bit of support on the model between the two cylinders so that the spacing between them at the bottom is correct and smooth after breaking the small supports. I tried drawing support in Bambu Studio but it won’t add support there and keeps the layer type as overhang (blue) as you can see in the slicing screenshot.
EDIT: Added some information about the printer and support settings.
You basically have it right. The filament printed and fell down to the bottom and built up enough to support the upper layers, letting the print complete. For me at least, this is something I rely upon when making print in place hinges or sockets. That bit of filament that droops down basically creates a weak support that breaks away when you move the joint for the first time. I’ve never seen a need to add additional support here, as that’s adding additional filament I don’t want in the cavity.
Thanks for confirming, I let it print like that and the hinge works perfectly. It’s good to better understand the physics of printing in these situations.
There was no “floating region” error given out when slicing?
Just for curiosity, I type “Can Banbu Studio print a part inside a model that is hanging in mid air if the gap is suffiently small“ into Google and got the following AI overview:
**
AI Overview**
Yes, Bambu Studio can print a part inside another model while it is suspended in mid-air, provided the gap is very small and leverages bridging techniques. The software is often used to create “print-in-place” mechanisms, such as trapped, moving parts within a cage or casing, where the inner part bridges across the void.
How it works in Bambu Studio:
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Bridging & Small Gaps: If the gap is small (typically around 0.2mm to 0.4mm, or up to 5mm depending on printer capability), the printer can bridge from one side of the surrounding model to the other, essentially printing a flat surface in the air that forms the bottom of the internal part.
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Support Settings: You can set the “Top Z Distance” to 0 in the support settings to force the part to print directly on top of a lower layer, acting as a support.
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Print Order: To ensure success, ensure the print order is set to print inner walls first, which provides a more stable anchor for the bridging.
Limitations and Tips:
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Risk of Drooping: If the gap is too large, the filament will sag, creating a messy, unsupported surface.
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Required Clearance: While it can print in air, for a functional, moving, print-in-place part, you still need a small, defined gap (e.g., 0.3mm or 0.4mm) to prevent the two parts from fusing together.
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Slicer Behavior: Sometimes, Bambu Studio may struggle and generate “floating supports.” It is crucial to check the sliced preview (layer-by-layer) to see if it’s attempting to print in the air.
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Increase Walls: If the bridge is failing, increasing the number of wall loops (e.g., to 3 or more) can help the slicer properly bridge the gap.
No, there was. I message, but I was not entirely surprised. It did create supports in other areas much bigger so I knew it was looking for such cases but for this particular case it would not accept support even if I tried to draw them manually.
The giveaway that it knew it was something fishy there was that it always marked the inner cylinder with dark blue lines which mean overhang.
As for gapping voids, I successfully tested (by mistake) printing over a round 7.5 mm hole. First layer over the hole sagged a bit but from the second one it recovered and you would not be able to tell that there is a void inside there.
Funny enough I searched something similar and GPT gave me a nearly identical answer.
Problem in this case was that there is no support around that point. The whole inner cylinder is completely disconnected from the outer cylinder so it can move. The AI response still assumes there is some kind of supporting structures on the side and what you’re asking is how big of a gap it can span.
Not really. What the AI says is that Bambu Studio will create a bridge first and then the inside suspended part will be printed on top of this bridge. In your case, a bridge is made across the walls of the outer cylinder to form the bottom of the inner cylinder. Because of this bridge, the inner cylinder is no longer printed mid-air.
“the printer can bridge from one side of the surrounding model to the other, essentially printing a flat surface in the air that forms the bottom of the internal part.”
What is not clear from the AI response is whether this bridge is automatically created in Bambu Studio without needing any input from the user. Or maybe the bridge is created only when support is enabled.
AI can be wrong though. At the moment I don’t have a model with an inner part that is suspended mid-air to test what the AI says.
Ah, yes, I see what you mean. That would make sense.
Looking at the sliced model, I don’t see any bridge created (see screenshots above) but maybe there is an option somewhere to do just that. I can confirm at this point that my original guess was correct in that it simply prints in mid air and lets the filament fall on the layer below. It’s a 0.4mm fall which I can clearly see on the printed part.
I whipped out a simple model to do a test. I think AI is making up stuff about what Bambu Studio (BS) does in this case.
Here is the cross-section of the model. I set the gap between the two parts to 0.8mm to make it easier to see inside BS.
First I didn’t enable support and BS threw out an error about “floating region” and asked me to re-orient the object or enable support generation
So I enabled support and left all default settings as they were. BS generated the support interface (the green pattern in the center of the 1st image below), and then the overhang wall and a bridge layer (in blue and grey in the 2nd image) on top of the support interface, before proceeding to print the inside part (3rd image).
So BS does make a bridge layer but it is on top of the support structure, not across the walls of the outer cylinder at the base layer of the inner part as described by the AI overview. The AI is either smart enough to make the inference because that bridge would have worked, or it read about that kind of bridge being done on some other slicers and infers that BS would do the same.
Edit: If the gap is smaller, such as <=0.5 mm, then enabling the support will not create the support interface. It will only create the overhand wall layer and use that as the support. This makes sense because the gap is too small to fit in both the support interface layer and the overhang wall layer.
In my case the gap was 0.2 all around and it did cross my mind that this might be the reason why it was refusing to create supports.
I did some testing too with an object closer to my original design: a tube completely enclosed inside another tube. Playing with the gap value between the two tubes, at 0.2 and 0.3 BS won’t suggest or create when enabled supports for the bottom of the inner tube. At 0.4 it warns that there are unsupported parts. Since I’m working with a 0.2mm layer height, for a gap of 0.2 between the cylinders, BS will have a single empty layer under the inner cylinder (obviously). And at 0.3mm gap, it will have two empty layers under the part.
I was only curious about how Bambu Studio handles supports in tight spaces. In practice, there can be ways to avoid getting into the situation. The model that I whipped out above doesn’t have to be. For example, it can be done like this, or some other way depending on the design, to avoid having the hinge suspended mid-air.
