Hi
Bambulab Studio 1.6.2.4 does not know how to print counterbore holes!
@ Bambulab team
Please fix this bug!
Regards
Expecting miracles? You need supports or modify design in CAD to include thin layer that you can punch out or drill post print.
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No miracles, no. It should do bridging, where possible. What it does makes no sense at all.
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What do you think is going to hold those central circles up?
Bambu expects their printers to work on Earth, where gravity pulls the softened plastic down.
Bridges are straight lines that are supported at the ends. Break the line to create the smaller hole and there is no support for the bridge.
Counterbored vertical holes need to have the smaller diameter on the bottom, or some sort of support if they are on the top.
Workarounds without sacrificial support material:
I know how gravity works 
If you have many holes in different orientation, you can not always orient each hole the right way.
But why not doing bridging like this:
Thatās the fourth suggestion in the video. Bridges 1 and 2 on one layer, 3 and 4 on another, bridging around the hole. Those separate layers are specified manually in the modeling software, not the slicer.
Iāve never seen mention of any software that does that automatically, so I canāt consider the lack of that function in Studio to be a bug.
Well ok, yes I see, you could model that. But to be honest, that is not something you want to do in the model. This is way too much work to do for each hole. And if you want to do a drawing, you have all those lines which you donāt want to be shown.
If you print an āLā upside down, the printer will print in the air when not using support. I would not call this a bug, since there is no other option (beside activating support).
For the case with the counterbore hole, the slicer could understand how it needs to do briding. You could implement that on the same layer. There is a solution, but the slicer does not know how to do that. Since the slicer does something inappropriate I would rather call it a bug and not a missing feature.
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I think this is a bug as Orca Slicer does not do the same thing. Iāve been using Orca Slicer 1.6.3 and find it to be much more capable than Bambu Studio. Hereās how it slices counterbore holes. This method comes out nice and clean for me.
What you have there looks to me like a blind hole. A counterbore hole sliced upside down (as the op is trying to do it) in orca looks like this:
So no miracles there.
Cura canāt do it properly either:
Not really sure what the op expected to be honest.
Without investigating in detail, I expected the slicer to do what I have drawn by handā¦ Obviously it is not implemented. The question is why? Is it difficult / to much effort, or nobody ever complaint? I use counterbore holes very often.
Thereās a tool in onshape called bridge overhangs, automates the design modifications for this type of problem. You may find it useful.
Itās a known issue, but probably not worth the effort to resolve it on the slicer side when the necessary model adjustments are easy enough to do. Would be cool if BL could do it though.
Iām no software designer but doing what you drew, wouldnāt be what you modeled. The slicer needs to print what we model. If I model a circular feature, I wouldnāt want it to make a hexagon. Who knows, maybe they will add the option to create the extra unmodeled geometry for you, as it is easier on the user, but the slicer canāt make that decision on its own. The problem with enabling an option like that would be, it wouldnāt stop at that one feature. It would need to carry it out all over the model. Having hexagons instead of circles would just cause more problems than itās worth.
Sorry, these are just the limitations of the medium we are using.
Thanks for the hint. I might try onshape in the future, but currently I donāt use it. Even if there is a feature, Iām very sure that this does not belong in to the model. It is part of the printing process and therefore should be done in the firmware of the printer. I might use the models not only for 3D printing but as well for other manufacturing technologies and I donāt want to have two copies of the same part.
@ just4memike
I donāt expect the slicer makes a hexagon if it should actually be a circle. But it could do a different pattern and a different order, as it is done in other situations. My drawing was not fully correct. I would actually do that:
I donāt see why this should not be possible?
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I think you are missing that what you have drawn up is a circle on top of a square. Note that would be multiple layers and not what is modeled.
How could the printer possibly print the half lines in yellow in mid-air without support underneath? Same for the half lines in green? How could it print the fully curved black lines with just a few points to connect to? Not on this earth. Bridged lines have to be straight and attached at both ends.
At best you would end up with a polygon.
For shallow counterbores, I use supports. For deep ones, I add a thin layer in CAD to act as a bridge where the hole reduces in size. I punch it out post print.
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Iām not an expert. If the yellow lines donāt work, you could accept overlapping? Since it is bridging, filament flow is lower and therefore this should not cause big deviations from the model?
Anything is better than printing in the air!
Yould be so simple.
Logic, when I should print something in the air, because the master has not told to do supports, then I will do the best possible solution - - > new smart algorithm
Lets assume you have a large print with many holes in various orientations. You will orient the part according to the overall shape and not according to the holes. Yes I know I can use support. But this is usually the plan B.
And plan A being what? Do nothing and hope for the best?