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Kevlar
(@kevlar)
Eminent Member
live Z adjust

My first layer has been pulling away from the bed and/or not adhering to it so I decided to try and run the live Z adjust. I can't get it to succeed no matter what I do! I reset it to zero and it fails. I try putting it at -.200mm or greater and it fails by the plastic bunching out coming out of the nozzle. So I figure -.200mm is too low, so I lower the value below -.200mm towards 0 and it won't stay on the bed, and then bunches up again at the nozzle. 

I've cleaned the bed sheet with 91% ipa.

I've tried turning the sheet over to the side that I've never used. 

Please help with some suggestions. 

Thank you,

Kevin

Posted : 31/12/2019 3:56 am
bobstro
(@bobstro)
Illustrious Member
RE: live Z adjust
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. 
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 rinsisng 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 break down the bacterial cell walls. 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

Posted : 31/12/2019 6:22 am
JBinFL
(@jbinfl)
Reputable Member
RE: live Z adjust
Posted by: @maincityimp

 I try putting it at -.200mm or greater and it fails by the plastic bunching out coming out of the nozzle. So I figure -.200mm is too low, so I lower the value below -.200mm towards 0 and it won't stay on the bed, and then bunches up again at the nozzle. 

Well,  per your info above, you are going the wrong way in the values as they are reversed.  A larger negative number is closer to the bed and a smaller negative number is further away from the bed.  If it is too high at -.200mm, you need to go further like -.300mm or -.400mm instead of to zero.

Do what Bobstro suggests, then try again with the live z value starting at -200 and dial it in more negative until it sticks...

My PEI is at -0.258mm and my Powder coated sheets are at -0.425mm or so, that was after i moved the pinda probe further from the bed, when i started out, my live z was -1.400...

 

Strange women, laying in ponds, distributing swords, is hardly a basis for a system of governance!

Posted : 01/01/2020 12:22 am
Kevlar
(@kevlar)
Eminent Member
Topic starter answered:
RE: live Z adjust

@bobstro

Thank you both. I will try these during this week. Hopefully, things work out. 🙂

 

 

Posted : 01/01/2020 10:38 pm
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