Rough Benchy and zits after extruder rebuild
The long story of how I got here can be found here: https://forum.prusa3d.com/forum/original-prusa-i3-mmu2s-mmu2-hardware-firmware-and-software-help/rebuilt-extruder-and-now-having-load-and-extrusion-issues/
At this time I am running as a MK3S, but with the MMU tower still installed.
It's been a pain to get this far, but I was finally able to print some tests tonight, but the Benchies I ran off have me scratching my head a bit and I don't know if it's tuning I need, I overstepped in my slice, or there is something still wrong.
I ran 2 Benchies in one print using the standard Generic PLA profile using Natural Inland PLA. One Benchy was set to 0.2mm layers and I set the other to 0.1mm, which is something that I've never tried before.
The 0.2 version was actually pretty good for the most part with very little stringing though it did have some zits on it (mostly around where it would jump to the other Benchy. By zits I mean little bits that simply rub off with my thumb. Prior to the Benchies I ran off a 20x20x20 at 0.2 cube and it too had a few zits that I've not had before.
The 0.1 Benchy looked ok other than being covered in zits, but when I rub my finger on the hill (especially the bow) it is exceptionally rough.
I'm happy with my Live Z, but there was signs of lifting on the bottoms of both boats though both were stuck good when I removed them. It's been awhile since I have the plate a good cleaning though and it's been mostly gathering dust for the last month. So I gave it a good cleaning and acetone bath tonight and expect that should cure the lifting. I only mention that in the event it may be relevant to the other issues.
So, what causes zits and what might make the hull so rough?
RE: Rough Benchy and zits after extruder rebuild
Pictures?
More often than not, zits are ooze from wet filament or insufficient retractions. I suspect it also gets worse in the summer as the ambient temperature is higher and the filament doesn't cool as quickly after extrusion.
RE: Rough Benchy and zits after extruder rebuild
No pics. The zits rubbed off and as it's natural PLA the roughness is hard to see even in person.
Ambient temp shouldn't be an issue as we keep that pretty consistent year round. Wet filament could be an issue though. That spool has been open for awhile and my "dry" box doesn't want to go below 20%...
RE: Rough Benchy and zits after extruder rebuild
Yeah, I've noticed the spools I have out on my MMU getting worse over time and in need of a good drying; the stringing is giving issues with the bucket mechanism... 😉
RE: Rough Benchy and zits after extruder rebuild
I have a couple spools of Prusa sold filament - matte beige and white - that give matte finished parts that look like they were extruded too cold, and have a lumpy texture that is rough feeling; yet, under a microscope look like they were printed too hot. Very glossy, hard to see layers, and little bits here and there, but these don't brush off.
So obvious question is have you tried a different spool of three?
RE: Rough Benchy and zits after extruder rebuild
So obvious question is have you tried a different spool of three?
Not yet as I'm running low on suitable scrap filament to use for such testing (read cheap, open, and/or not already ear marked for other projects once I get the damn thing printing again). The other scrap spool I have is definitely going to be a moisture risk as it sat out much of the last month while the printer has been down.
If I can get a break at work (morning not going as planned) I'll upgrade the printer firmware (still on 3.7.0) and I have a re-slice of the Benchies to print them cooler as that was my first guess (210/200 vs the default 215/210). If that still doesn't help I'll throw those spools in the oven and see if drying them helps at all.
RE: Rough Benchy and zits after extruder rebuild
So running the print at 210/200 vs 215/210 appears to have cleared up the zit issue. About halfway through and both models are clean while on the 215/210 print the majority of the zits were already present.
The 0.1mm layer height boat is still rough though. I didn't really pay attention until I looked at it again this morning, but both last night's and today's print has the rough area on the side facing the rear of the plate (they are positioned facing with the X axis, so it's the left side of the boat that is rough) and the roughness appears to stop at the level where the decking begins. That also coincides with where it stops having to infill, but I've never had issues with gyroid before even at a 0.5mm height.
RE: Rough Benchy and zits after extruder rebuild
If I recall right, there were some early complaints of the MK3S performance downwind of the print fan, and that repositioning it a little seemed to help. Vague memory - so for what it's worth.
RE: Rough Benchy and zits after extruder rebuild
If I recall right, there were some early complaints of the MK3S performance downwind of the print fan, and that repositioning it a little seemed to help. Vague memory - so for what it's worth.
Any more info on this Tim? What should I try adjusting? The fan? The shroud? The part?
I've tried fiddling a bit, but my 0.1 prints continue to experience this issue.
RE: Rough Benchy and zits after extruder rebuild
My memory plays tricks on me - wide association span. But if I recall right, a couple folk said they had success reorienting the fan shroud to point in a more downward direction. It was affecting nozzle thermal recovery and causing artifacts on the rear face of the part. Seems like some of the images showed the heater block also wasn't aligned well, rotated off at an angle so air flow was weird. I'll try to find time to google the problem (well, forum search it - lol),
RE: Rough Benchy and zits after extruder rebuild
The 0.1mm layer height boat is still rough though.
One other thought, have you done an extrusion calibration since all your work? If the driven Bondtech gear moved sideways, even a fraction, your extrusion rate will be different. 2% is 2%... and may be just enough different. A random filament click from the extruder is my cue my gear is off center (filament starts twisting).
RE: Rough Benchy and zits after extruder rebuild
I suspect the fan more than the extrusion since the roughness isn't consistently spread. It is only on the back side and only where there is an extended area of overhang. Also my 20x20x20 test cube is consistent with my other test cubes as well.
RE: Rough Benchy and zits after extruder rebuild
Often fuzzy memory like mine is a good thing for finding odd problems, but once in a while it is a beast. I did a search - and came up empty handed. Similar references but nothing that is directly related to what you are seeing or what I recall reading. Most of the positional issues were the shroud scratching the first layer off the bed. And the one fan related print issue that fits your case was the back side looking better that the front - just the opposite of your concern - but with no answer or resolution provided: I'm thinking he downgraded back to a MK3.
But here's a few anecdotal threads on the MK3S design - for when you get bored.
RE: Rough Benchy and zits after extruder rebuild
Your issue doesn't look like this does it?
Head was printed nose forward. Chin shows a similar effect, but to a much smaller degree than the cranial base.
RE: Rough Benchy and zits after extruder rebuild
Yeah actually that does look a lot like how this feels.
The other weird part here for me is that it only seems to bother the 0.1 prints. The 0.2 prints are nice and smooth like I expect.
Funny thing is I wouldn't know of this yet as all my normal tests are at 0.2. Don't even remember why I threw the extra test in this time...
RE: Rough Benchy and zits after extruder rebuild
My head print is showing an overhang issue. Something about how the filament extruding downwind is somehow deformed or affected such that it does not lay down smoothly. On the chin, you can see obvious bridged perimeter artifacts, but unlike the rear of the part, they are smooth and consistent. But I haven't found a good solution to the artifacts, yet (I'm still working on it).
RE: Rough Benchy and zits after extruder rebuild
0.05 can make it particularly noticeable