In the print: The round holes come out oval, and the hexagonal ones for bolts are slightly off. The thickness of the model is correct, so the issue is only with the holes.
The area you are concerned with is bridging (shown in blue).
It is designed to span a distance without any material underneath, as such there is nothing to stop any sagging.
You should enable supports and if automatic supports do not generate for these areas, use the PAINT SUPPORT option and change the support type to PAINT
Wow, based on the forums and various discussions, it’s clear that a lot of people are struggling with the same issue. And so far, the only real solution seems to be either using a non-Bambu Lab printer or printing vertically.
I’ve tried every recommended setting tweak—nothing worked. In the end, I had to resort to printing parts vertically, and the difference is night and day. It’s frustrating that this is the workaround instead of having an actual fix.
Like Jon said, it’s just how FDM works. When using support you can tweak how close the slicer will bring support to the model surface. The closer you bring support (the smaller the gap) the more sticking you’ll have between model and support but the model surface will be closer to the desired position.
There are water soluble supports that you can also use, or dissimilar plastics that don’t stick, where you can cut the support spacing to zero and still be able to remove it.
It’s not a problem with Bambu printers. It’s just a limitation of how FDM works. There are solutions, though. Water soluble support and dissimilar plastics can get you better accuracy in your prints but add time, cost, and effort.
if this is your design, you can add a “tear drop” cut to the top of the circle, which will mitigate, below a photo of how i did this in one of my designs:
In other words the ‘fix’ is to design with the FDM process and print orientation in mind.
Whether you are designing for printing, milling, injection molding, you have to optimize the design for the process. Modern printers have done a great job presenting 3D printing as an anything goes option but it just isn’t. It’s just another way to manufacture stuff with it’s own limitations and possibilities.
The design you made could easily be printed without supports on its side like you want but the small design choices you made make it so it needs support and will still come out slightly disappointing. Easiest rule is to give bridges a bit of extra tolerance and avoid any overhangs steeper than 45 degrees
next time i need it i’ll give it a go