Benchy Crash
Solution: Use the stock part cooler duct..
My Benchy has crashed into a piling!
I've previously printed near perfect Benchies, but after a few seemingly innocuous changes to my setup, I got the above Benchy. I installed squash ball feet [1]. I installed PrusaSlicer 2.7.4, then I got this Benchy :-(.
I sliced Benchy again with 2.7.2 and printed a new one but alas, it looks like it ran into the same piling. Go back to 2.7.4.
I guess I may have to take the squash ball feet [1] off and go back to the original feet and print again (what a pain).
Yikes! Back on the original feet, and the same defect. I'm running out of stuff to try.
I guess another recent mod was swapping in a new part cooling fan duct [3] and shield for the heatbreak fan [4]. Let's put back the original fan duct. Somewhere in there I also printed up dust covers [2] for each Z axis, might as well take them off too (they just sit there, they aren't screwed in or anything).
With the printer now back to pretty much absolute stock, it no longer crashes into the piling:
That blip that looks like some kind of Z seam is there in the old benchies I've printed as well, so it isn't new.
Now I want to figure out which mod causes the crash. I'm printing again with the Z axis covers [2] back in place (seems impossible for this to be the culprit, but I've given up trying to understand what is going on.)
OK, the Z axis covers made no difference. The Benchy printed fine with the covers on the Z axis. Added just the heatbreak fan shield [4] back and I'm printing yet another Benchy.
Another perfect Benchy. I guess that only leaves the new part cooler fan [3] as the culprit. I want to try putting back the squash ball feet [1] before putting back the fan just to make sure there really is nothing wrong with the feet.
One more Benchy in progress now with the squash ball feet [1] back on the machine, but the stock part cooler fan duct.
It finished and printed fine (and was quieter!). Looks like the culprit is the cooling fan duct [3]. Just need to put it back on and see if the crash comes back.
Yep, with the cooler fan duct [3] back on in place of the original duct, the dented hull comes back again. Confirms that the fan duct is the cause. Why just in that one spot, I'll never understand.
There is a wider [5] cooler fan on printables that is derived from the fan I used, but extended a bit. The creator says it works better by getting the air coming out a bit farther away. I should try printing one and see if it works better for me.
But wait! Before I print a new fan duct, let's try taking off the heat block sock. It might be large enough to affect the air flow.
Nope. Same damaged bow on the Benchy. But now I see the improved fan duct [3] I've been blaming has had an update published since I originally printed it to provide more uniform air flow. Let's get setup to print PCCF and print that improved version.
Somewhat different character defect, but still defective:
I have to conclude that I should go back to the stock part cooler duct. Maybe some completely different model would work better with the new duct [3], but all my evidence says stock is better. I don't think I'll do any more experiments any time soon.
P.S. All these prints used the standard 0.2mm SPEED profile, Generic PLA, and MK4 Input Shaper 0.4 nozzle. The Benchy STL I've been using is oriented to print like it is sailing from left to right across the print bed.
Parts mentioned in this page: