Bridging Failure
I've been printing tall, detailed objects cheerfully in [rigid.ink] ASA for several months now but, for some reason, over the weekend one object has begun failing to print cleanly. It's printed cleanly before, I've changed nothing (consciously) and very similar constructions still print fine so I'm looking for advice on how to fix it. The problem is with bridging across a set of manually-added supports (adding supports automatically is way too messy for this complex shape):
My ASA print settings are the standard ABS settings but with bed temperature at 120 C for improved adhesion (even with a brim). I'm using "0.15 mm quality" printer settings (which I've always used). Crash detect is off. Another very similar object prints fine (see below) and, as I say, this object printed fine when I last printed it a few weeks ago. In repeated attempts to get a successful print the faults always occur in the same areas.
The .blend file can be found here and the .stl file here.
Here's a picture of a very similar object which printed absolutely fine with the same settings a day or two ago:
Re: Bridging Failure
I've taken the time to tune my bridging settings for this particular ASA, so I know bridging works reasonably well from test prints but the problem shown is still occurring. I was kinda hoping someone might say "ah, you've got so-and-so problem, I had that, what you need to do is..." but it would seem not 😕 .
Re: Bridging Failure
When was the part cooling fan last serviced?
Re: Bridging Failure
The printer was only assembled last October (upgrading from a MK2S) and the fan is, visually at least, working during bridging.
I've just tried an experiment: I've cut the object in Slic3r so that I am printing just one of the sections showing the problem and printed this once; this is the lower part in the picture below where the problem is clearly visible in the left-hand side of the bridge. Then I rotated the part by 90 degrees around the Z axis in Slic3r and printed it again; this is the upper part in the picture below: the problem is barely visible, if at all. So I have a kind of workaround.
I also took a fuzzy YouTube video of the printing when the problem is occurring but I wasn't able to get the camera really into position so I don't think it helps:
RE: Bridging Failure
FYI, this problem went away so I ignored it but I recently had to change nozzles and, within a few prints, the problem came back again: you can see the transition between prints (each took about 12 hours) in the attached file where it suddenly goes haywire in (3).
What fixed it was to run PI Tune from the calibration menu, which I should have done when changing nozzles anyway. This allows the printer to reassess what it needs to do to keep the nozzle at exactly the right temperature. I'm guessing that some manoeuvre or other that Slic3r asks the printer to perform on some of my manually created bridges is rather sensitive to nozzle temperature.
RE: Bridging Failure
Most likely it is the fan kicking on that causes the nozzle temperature to fluctuate.