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some thoughts and a problem  

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xt550
(@xt550)
Active Member
some thoughts and a problem

So i have been fiddling about whit my new mk3s and what i found out is that it's hard to fin info about the first layer issues, i could not find anything more specific about first layer calibration so if you are running the first layer calibration the square at the end of the test print should hold together without any see threw holes, try pulling it apart it should not rip. (as usual i probably missed this info some-ware)

And i have a first layer issue, when the extruder is making short stokes it makes blobs what to do?  (photo)

 

 

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Posted : 16/05/2019 7:47 pm
bobstro
(@bobstro)
Illustrious Member
RE: some thoughts and a problem

Here's what the little square should look like:

Here's some copypasta...

Adhesion issues are usually caused by 2 main problems:
  • 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. 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 to give it a very light buff, but only infrequently.
  • 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 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. 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 it's right, you should be able to gently rub it without it coming loose. Then start lowering (more negative) the level until there are no gaps between layers. 
The good news is that a good dunk with Dawn should restore both sides to like-new condition. If you want more detail, I've dumped everything I know about Prusa PEI adhesion here, bed cleaning here and Live-Z calibration here.
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 : 16/05/2019 8:07 pm
xt550
(@xt550)
Active Member
Topic starter answered:
RE: some thoughts and a problem

thank you for the fast answer.

but it seams like the first layer is connecting with the print surface for what i can understand i got a problem whit blobs and on layer 2 the nosle hits the blob and loosens of the first layer some.

so what can be happening when the printer makes these blobs ? the only seams to start appearing when the nosle makes short movments, the other part of the print seams OK

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Posted : 18/05/2019 5:31 am
bobstro
(@bobstro)
Illustrious Member
RE: some thoughts and a problem

The blobs can form if the nozzle is scraping the 1st layer due to being too close on your Live-Z. Bits fall of and accumulate on the next layer. Parts of the 1st layer appear to have been pulled up by your nozzle in the 2nd pic. That's why I emphasize the importance of getting adhesion and Live-Z right. 

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 : 18/05/2019 5:56 am
xt550
(@xt550)
Active Member
Topic starter answered:
RE: some thoughts and a problem

Here is as see through i think its a quite even until the travel distance get shorter

 

(by the way its PLA and first layer is set to -0,75 first test string is about 1,4mm wide and 0,5 high )

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Posted : 18/05/2019 7:26 am
bobstro
(@bobstro)
Illustrious Member
RE: some thoughts and a problem

What happened when you tried Jeff Jordan's "Life Adjust" Live-Z calibration? Have you tried it yet?

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 : 18/05/2019 5:52 pm
xt550
(@xt550)
Active Member
Topic starter answered:
RE: some thoughts and a problem

Just did that, raised the z to -0.5 the first 1/3 of the square and got some blobs -0,6 still some blobs (and the strings was not attached to another) got down to-0,75 and the string were glued back together

Still blobs

Posted : 18/05/2019 9:15 pm
bobstro
(@bobstro)
Illustrious Member
RE: some thoughts and a problem

If you are going from -0.5 to -0.7, you are lowering the nozzle further. I would raise (go less negative) by a significant amount until the filament is not sticking, then come down in increments of 0.2mm until it starts sticking. At that point, you should see gaps between the lines, but they'll adhere. Keep lowering until the gaps close up and you're good.

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 : 19/05/2019 3:41 am
xt550
(@xt550)
Active Member
Topic starter answered:
RE: some thoughts and a problem

i tried, still getting blobs and i have to go below -0.6 for the gaps to disappear but it is still blobbing at - 0.5

 

Posted : 19/05/2019 7:00 am
bobstro
(@bobstro)
Illustrious Member
RE: some thoughts and a problem

Any chance you have filament built up on your heater block or nozzle that is coming loose and falling into your print? Are you using a silicone sock? Are there odd bits of filament on your bed? Have you changed nozzles or other extruder work? 

Take at look at the hotend to see if you have filament oozing out in odd places. If Live-Z is correct, you may have bits of filament getting into your print for some reason. 

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 : 19/05/2019 12:02 pm
xt550
(@xt550)
Active Member
Topic starter answered:
RE: some thoughts and a problem

I changed the nozzle to 0,6 and increased bed and nozzle temperature by 10C and it seams to have fix it

Posted : 01/06/2019 4:40 am
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