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David
(@david-30)
Active Member
Blob print

Hello, I'm still fairly new to printing. I just switched out my nozzel from a .4 to a .25. I had one very successful print that took just over two days, then tried to print shortly after and had spaghetti print (never had this problem with my .4 nozzel). Then cleaned and tried printing again with the .25 and my print out looked like the attached image. Can anyone help explain why I would have printed a spaghetti mess and then this? I did set my prints to fit the .25 nozzels. Thank you in advance.

Posted : 05/08/2019 1:03 pm
bobstro
(@bobstro)
Illustrious Member
RE: Blob print

The printer doesn't really "print a blob" or "print spaghetti". The mechanism is rigid and doesn't start wildly swinging around for unknown reasons. The printer moves as it's being told to according to the gcode. What is happening is that your part is either coming partially loose, causing it to wobble around as the printer continues to extrude (creating the blob), or completely loose, leaving the printer extruding in free air (creating the spaghetti). Your underlying issue is bed adhesion. This is a common problem that can be caused or aggravated by two factors that need to work together well for successful prints. Here's mama's tried and true copypasta recipe to get you going...

You are having bed adhesion issues. Filament should lay down cleanly on the PEI print surface and hold throughout the print. There are 2 main causes of bed adhesion issues. Even if you're dubious that these are the cause of your problems, they're 2 fundamental troubleshooting steps that you need to complete to rule out the basics:
 
  • A dirty PEI print surface. Even if you don't think this is the cause, it's always a good idea to make sure your PEI surface is clean before trying any other fixes. If it's a smooth PEI sheet, take it to the kitchen sink and give it a good dunk with Dawn (original formula, no vinegar or hand softener variants) dishwashing soap or your local equivalent (e.g. Fairy in UK). Use a clean paper towel to clean it off, and another to dry it. Avoid using any sponge or cloth that has been in contact with grease. Above all else, avoid touching the PEI print surface. Once it's good and clean, you should be able to use 91%+ isopropyl alcohol between prints, 100% acetone when that fails , and another dunk when acetone fails. Worst-case, use a 3M 7445 ScotchBrite pad or equivalent on smooth PEI to give it a very light buff, but only infrequently. If you've got a textured powder-coated PEI print surface, the official instructions are to use 91%+ isopropyl alcohol on it only. Rumors persist that some tribes deep in the jungle have had good luck getting started with these sheets by giving them a wipe with 100% acetone and a dunk with Dawn. Either way, there's no real warranty on these sheets. YMMV.
  • If you have not already done so, try using Jeff Jordan's "Life Adjust" procedure for calibrating your Live-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.    
And above all else, avoid touching the PEI print surface.
 
Try those 2 steps. If you're uncertain of the Live-Z results, post pics here of the 75x75 print bottom and you'll get quick help. If you want more detail, I've consolidated my notes on Prusa PEI adhesion, bed cleaning, and Live-Z calibration. I've done a brain dump on nozzle sizes as well.
My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 05/08/2019 2:26 pm
David
(@david-30)
Active Member
Topic starter answered:
RE: Blob print

@bobstro

I'm sorry for the delay in getting back to you. I went on a short vacation and wasn't home to test things. I will work with what you mentioned and see how they work out. 

Posted : 07/08/2019 1:00 am
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