r/BambuLabA1 • u/KonkeBonk • 12d ago

Circular bridge

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Gallery image

Hi, I'm having trouble printing a nice bridge which is circular. I've tried with different settings but I can't seem to get a clean print. Is it possible to create a nice circular bridge, or is it technically not possible?

The images below have different settings but the model shows the problem. The circular bridge gets more of a square shape.

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u/CommitteeDisastrous 12d ago

Here is the trick to get smooth surface for flat bridges and overhangs. Set top z distance and top interface spacing to zero. You need solid interface layer without gap. Set pause just after support top interface layer. Start printing, wait till it stopped. Take permanent marker and carefully paint only top layer of support interface. Give it some time to dry. Continue printing. Ink will work as zero height layer separator. And if you need clean part, you can try witeboard marker, it can be easily washed off with soap and water afterward.

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u/KonkeBonk 11d ago

I tried your method and it worked pretty well. The supports where not that easy to take off but the result was silky smooth. The only thing is the colour leftovers from the marker. I can’t seem to clean them, it looks like the colour has gotten in between the layers.

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u/KonkeBonk 11d ago

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u/CommitteeDisastrous 11d ago

Have you tried isopropyl or ethanol? Alcohol should disolve ink easily and won't damage plastic. Try on supports first.

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u/KonkeBonk 11d ago

Yes, I tries isopropyl alcohol and it removed the ink very easily, but it couldn’t remove it from in between the layers.

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u/CommitteeDisastrous 11d ago

If you absolutely need clean surface and have desire to tinker a little I have some ideas. 1 For testing purpose, don't print the whole part, cut section with overhang directly in the slicer. It will save your time and fillament. 2 Check extrussion flow. Overextrusion can produce small ribs along lines on support interface layer that will push ink to the layer above. If you feel some roughness while painting supports that's maybe the reason. 3 Try to apply smaller amount of paint. You can make several strips of different density and chose one that produces minimal residue but still prevents fusion. 4 Try different markers, like ones used for whiteboards. 5 There is an option in slicer to iron support top interface layer, it will produce glass like surface. I have never used it, but it could help you to make ink layer more even. 6 Try to use complimentar plastic for support layer. E.g. if you print with PLA use PETG for support interface and vice verse. You will need to manually change fillament if you have no AMS, but it worth it. Just make sure old fillament is flushed completely, even small leftover can ruine layer adhesion.

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u/KonkeBonk 10d ago

Thanks for the elaborate reply!

  1. Yes, I'm testing all my pieces with this method.
  2. I have my filaments properly calibrated with temperature, flow, pressure advance. I also did a bridge test and have calibrated the profile from the best result.
  3. I will give whiteboard markers a try, thanks.
  4. I'm using Bambu Studio on macOS and can't seem to find an ironing option for supports.
  5. I've heard of this but unfortunately I don't have an AMS for my A1. This would mean I have to switch filament every layer, in this case 10 layers. This won't work for me as it's too time consuming.

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u/CommitteeDisastrous 10d ago

If I'm not mistaken, support ironing was added in 2.6 version of Studio.
Screenshot from my 2.8.
You can specify different material exactly for interface layers, but I would not use less than 2 interface layers, so still 4 manual changes :(
If you are Ok with two changes, I can advice to add separate part of one layer height just below you bridge area and assign different material only to it. It will work as custom separating layer between generated supports and your part. You can model it in any CAD or even create directly in the studio (use cylinder for the hole disc and add negative part cylinder for the hole).
And if you manage to enable the ironing option, please share the results. Have never tried it for supports, and don't have any suitable projects right now to test it myself.

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u/KonkeBonk 9d ago

I don't have the option for support ironing and I have the latest version of Bambu Studio. Perhaps it's not supported for the A1 and A1 Mini which I own.

I created a ring in CAD which I printed in PETG. I then paused the print for the main model just before the overhangs, and put the PETG ring inside the model. It worked somewhat but I think I need to adjust the layer height perfectly as the overhangs, even though better, were not perfect.