Fwoomp: The Saga Continues
So I had more fwoomping today, and yes that is the technical term. It was another case of the machine generating a big gob of melted filament which clung to the extruder like some kind of unholy wasp's nest. I don't get it. The nozzle was clear and I'd just wiped the build surface down with isoprophyl alcohol. We've been having to calibrate the Z axis a lot lately: could that be the cause? The thing is we can't seem to figure out what level the Z Axis should start at in order to avoid fwoomp.
If anyone has any ideas that'd be great.
RE: Fwoomp: The Saga Continues
Why the double post?
And - just like it was explained in the last post - alcohol does NOT clean the bed of fingerprint oils. Soap and water is the recommended method if you actually expect to use your printer.
ps: oh well, it's your time and effort and frustration ... lol. If you don't want to wash the bed properly, then try sandpaper. I hear 400 grit works wonders (again, not something I'd do, but people who don't like soap and water often resort to it).
RE: Fwoomp: The Saga Continues
Why? Well, I deal with things that stress me by adding levity. Or trying to, anyway. In addition I saw the print surface wiped down with the same alcohol and everything printed just fine. This seems to be an issue beyond just soap and water.
RE: Fwoomp: The Saga Continues
[...] I saw the print surface wiped down with the same alcohol and everything printed just fine. This seems to be an issue beyond just soap and water.
Well... maybe. Soap and water addresses adhesion. Adhesion keeps parts securely on the bed. If a part comes loose due to poor adhesion, it's going to go somewhere, usually towards whatever's hot, and that's likely to result in exactly the blob you've described. Or to think about it differently, given the construction of the printer, it's impossible for the nozzle to suddenly print your wasp's nest on its own. The "Blob of Doom" usually relates to a part lifting, snagging the nozzle or hotend, and eventually wrapping around the hot bits. Do check the nozzle and hotend to make sure there's no filament leaking from above, but other than that, it's all about adhesion.
I've tried to summarize everything in my "mystery of adhesion" notes, but simply put: There's nothing you're going to be able to apply to the bed that will approach the volume of good old dish soap and water under a running sink. Alcohol, acetone an other measures do break grease up, but in direct proportion to the concentration of the solvent and the volume of solvent to grease. They also don't make it disappear, so while you can try to wipe thoroughly, some will always be left. There's simply no way any sort of wiping is going to approach the effectiveness of an actual rinse. Believe me, I didn't buy into this at the start until I spent some time working through it.
In extreme cases, you can try scuffing up the PEI surface, but I would never use anything much more abrasive than a 3M 7445 Scotch-Brite pad (the version used for polishing chrome) to do so.
If you are convinced your bed is clean, the next most important aspect to adhesion is getting a good Live-Z setting. If you need Live-Z calibration, try using Jeff Jordan's "Life Adjust" procedure for calibrating your Z setting. It is much easier to use and understand than the on-board routine. It's much easier to make mid-print adjustments accurately with. In general, start high (less negative) and work lower (more negative) in large increments (e.g. 0.1mm) until the filament starts to stick on its own. When you've got your Live-Z setting adjusted properly, you should be able to gently rub the extruded lines on the PEI surface without dislodging them. Then start lowering (more negative) the level until there are no gaps between layers.
Good luck with it.