Bridging quality - what is necessary?

Hey people,

Exactly how good do the small bridges on the flexure need to be? I’m wondering how far I need to push the envelope to get perfect bridges on my prints, or what is “good enough”. If the first layer sags a bit on the just_leg_test test print, do I need to fix that first?

Edit: and what slicers are people using? I’ve been trying prusaslicer, but it seems to have a known bug where it changes extrusion settings mid-air in a print, and it doesn’t take any steps to improve anchoring of a bridge, it simply does a 90 degree turn from the external perimeter into the unsupported bridge. I see cura tries a little bit harder by starting a bit farther in, giving the plastic a bit more chance to anchor properly. But I’d be interested to hear what everyone else has got working.

Welcome to the Forum @kefir

A little bit of sagging is to be expected but as long as the bridges on the leg test look pretty flat it should be fine.

We slice the microscope in Cura for our Ultimaker 2+, and we slice it in PrusaSlicer fro our Prusa i3. It is worth noting that when printing the main body using PrusaSlicer you need to be careful about how it handles the smart brim, we have some docs on this.

Prusa Mini with Prusa Slicer and Prusament. Works also pretty good. There is some sagging in the first layers, but in practice it’s near to perfect.

There’s some discussion and photos here:

So long as the thin parts of the bridges are relatively thin, a bit of sagging in the middle should not be a problem. The photos here are less good than we typically see on our Prusa i3 or Ultimaker 2+, but I would still expect them to work fine, and I’ve definitely built microscopes that looked worse! The maker in question was not happy with the print quality, but did say that it moved as expected when he manually flexed it.