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MortenA
(@mortena)
New Member
First layer issue

My Prusa has been giving me problems with first layers doing large prints.

If I life adjust Z so that the filament sticks in the low left, low right and top right, the nozzle becomes too high at top left side, and it doesn't stick/clogs around the nozzle.

If I adjust it so that I get it to stick top left, it gets so thin in top right corner that there's only an extremely thin film or nothing at all there.

 

Should I try to loosen the screws and re-tighten the heat bed to try to get a better level, throw away the PEI sheet, or what? I am blank, don't know what to try next, and annoyed 🙁

 

Any tips would be appreciated.

 

Kind regards

 

Morten

Respondido : 29/07/2020 9:30 am
MortenA
(@mortena)
New Member
Topic starter answered:
RE: First layer issue

Here's some pictures from the first layer first printer:

 

Any idea what to do? Any advice appreciated....

Respondido : 29/07/2020 11:28 am
bobstro
(@bobstro)
Illustrious Member
RE: First layer issue

I'm going to give you the full info dump. This should help you get going with bed cleaning and live-z calibration...

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. 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 and 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. You should not be able to peel the lines apart after printing, but the top should be regular. 
Remember that the effectiveness of a solvent such as isopropyl alcohol is going to depend on concentration and volume relative to the amount of grease you're trying to remove. 71% pads work... on very tiny amounts of grease. A squirt of 91% works better, but if there's a lot of grease, you need a lot more alcohol. This is why the wash under the sink with Dawn is so effective: There's a much larger volume of Dawn-and-water rinsing stuff away instead of just moving the broken-down grease molecules around.
  
And above all else, avoid touching the PEI print surface.
 
Glue stick is NOT necessary for PLA on the PEI print surface. You paid the big bucks for a Prusa with a removable spring still sheet with PEI, so clean it up and take advantage of it. Save the glue stick for printing sticky stuff like PETG that might adhere too well. Even then, I only find I need glue stick when printing high-temp PETG at 260C+ temps.
 
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
 
A bit of trivia - The reason higher concentrations of alcohol seem to be harder to find is that isopropyl alcohol is most effective against bacteria at roughly a 71% concentration. A bit of distilled water helps slow evaporation, making the alcohol more effective. If you're looking in pharmacies, that's why 91% and higher seem to be hard to find.
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

Respondido : 29/07/2020 3:31 pm
MortenA
(@mortena)
New Member
Topic starter answered:
RE: First layer issue

@bobstro

Thank you so much for the tips.

I did manage to get it pretty much perfect now by adjusting the bed level corrections, but I do believe the tips about cleaning helped too; that print is so big - it gets so far out to the edges that it's easy to touch the plate after cleaning...

I also used my finger to feel the tool lines and around the prints; when I'm getting close to the right settings I found it easier to "feel" when the lines were sufficiently pressed down - when it's no longer round nor flat 🙂

Respondido : 29/07/2020 8:35 pm
Peter M
(@peter-m)
Noble Member
RE: First layer issue

In the 3d printer settings, set the calibration to 7x7 for bed leveling.

Movie with a good zoom in,

Respondido : 31/07/2020 5:07 am
bobstro
(@bobstro)
Illustrious Member
RE: First layer issue
Posted by: @mortmath

[...] I also used my finger to feel the tool lines and around the prints; when I'm getting close to the right settings I found it easier to "feel" when the lines were sufficiently pressed down - when it's no longer round nor flat 🙂

You don't want to touch too much, but when the 1st layer is going down, you should be able to poke an extrusion without it popping loose. I've also noticed that there's a feeling of slight dragging when rubbing a paper towel on the PEI while washing in the sink. A few things in 3D printing are tactile.

 

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

Respondido : 31/07/2020 2:46 pm
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