Nothing sticks to the bed anymore
I have a stock Ender 3 Pro. The only upgrade was a BL Touch (from Creality) and I was using Creality's firmware (I'm also using Octoprint with a Pi4). I'm using the stock magnetic mat and I've never used glue or anything on it. I've used a few different brands of PLA, but the last was Amazon Basics. The printer was working wonderfully. I could print just about anything and never had a problem.
That all changed one day when a left a big print overnight. When I returned to it in the morning, the filament had run out and the printer head was about an inch over the last layer printed, still going like it was printing.
I had to order more PLA, and once it came in, I restarted that same print. Only this time, it didn't stick to the bed. It ended up a stringy mess that stuck to the nozzle. I tried a few other small prints and it did the same thing. I had bought Overture PLA this time and thought that might be the problem, so I ordered another spool of Amazon Basics, but it did the same thing. I had made no changes to the printer or in Cura since all my prints that came out beautifully.
Since then I have replaced the main board with a Creality v4.2.7, replaced the (stock) fans, nozzle, silicone sock, all metal extruder and Capricorn tubing, and of course recompiled Marlin firmware. My printer is much quieter, but still makes a stringy mess.
This almost seems like a Z offset issue to me, even though nothing changed when I bought the replacement spool of filament. I've been using Teaching Tech's First Layer GCode to try to get my Z offset perfect. On the left side of the bed, the prints are "Too close", while the rest are "Too far". So, I'm looking at getting a glass plate. I see some made of borosilicate glass and others of "carbon and silicone" and not sure what's best.
Has the BLTouch still got the pin in it? May seem like a silly question but a friend has this on his homebrew printer and when that spaghetti'ed it broke the pin off and was consequently way out of Z alignment. He sent me pictures and we BOTH missed the bleeding obvious, that there wasn't a pin in the Z probe any more...
@kevinp Have you tried manually leveling the bed and then do your BLTouch stuff (don't have one and don't know how they are set)? If you can print a calibration cube. Measure the Z height and whatever your off by take that as a percentage of 20mm, then take that percentage and multiple it by 400, that will give you about the mms you should increase or decrease your Z axis by. If the cube is below the 20mm you will increase your Z offset and if it's more then vice versa.
The BL Touch pin was bent, but was still there. I straightened it out and it seems fine. Not sure if it just snaps in or what. Maybe it's not fully seated in whatever holds it?
Yes, I have tried manually leveling the bed several times. I bought stiffer (supposedly) springs. I'll try putting them in and leveling the bed once again.
@kevinp There should be a spare part for the Bl-touch probe. If the pin was bent, then now sure that the whether the structure inside is fine.
Yes, I have that spare part. I took another look at the probe and it seemed to be fine.
So, I replaced the springs and releveled the bed. So far, I've printed four of the things that I couldn't print before and every one has turned out perfect with no problems. I don't understand what the difference is. The BL Touch is supposed to compensate for the bed being a little off. I'm pretty sure it wasn't originally that far off. Either way, looks like I'm back in business.
One thing - did you "save" the settings for the BLTouch after you got things set? And then you powered down?
Did you have an SDCard in the slot? If you're like me with the Octopi, figured "why have an SD card" - well, the settings for the z-offset (and other things) get saved in the EEPROM.dat file on that card. The stock firmware from Creality does NOT save settings to the board.
Once I put an SD card in, and saved - after resetting things - been fine ever since. I still need to get around to using the z-offset setting in the gcode put into Cura/Prusa - just haven't gotten there yet. Trying to see if the setting goes "off" after a period of time and many prints or not.
So - make sure an SD card is in the slot on the printer, then "save" - keep the card in there and then when it boots again, it'll read the settings off the card....