What is the best way to learn about first level calibration?
 

What is the best way to learn about first level calibration?  

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peter.c20
(@peter-c20)
Reputable Member

Hi, I have read the guide: https://help.prusa3d.com/en/article/first-layer-calibration_112364 and some youtube videos. However, I don't think I am good at it. In the guide, there are some confusions:

Under both Smooth Sheet and Textured sheet, Good and Low photos look the same to me. What is the different?

Under Have a look at the nozzle, sometimes I see filament between the nozzle and the sheet but sometimes I don't even I turn the knob in both directions. How come?

In 1-2 youtube videos, they suggested using a finger to lightly touch the filament to see if it sticks to the build plate. If not, need to lower the extruder more. They mentioned about pressing the dial knob once a suitable level is found. However, in the guide, there is no such mention. Who is right? 

My printer always makes a thick line of filament on the front at the beginning of the calibration and printing. Why this line is always thick (more filament extruded?) than the rest?

What is the best source to learn about First Layer Calibration? 

This topic was modified 2 months ago 2 times by peter.c20
Posted : 13/08/2020 6:50 pm
bobstro
(@bobstro)
Illustrious Member

It sounds simplistic, but simply working through the process a few times is your best way to master it.

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. 
 
Don't worry so much about adherence to a rigid process as understanding what is going on and what impact changes you make have. It took a few passes before it clicked for me, and I can usually get my Live-Z very close after observing a few lines of a test print go down.
 
Also, be aware that having your print surface properly and thoroughly cleaned is essential to getting good Live-Z results. A tiny bit of grease can really screw up your adhesion on the PEI print surfaces.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 owners 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.
 
I've put together my own notes on calibrating Live-Z for the Prusa i3 Mk3 here that may (or may not) be more helpful. 
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 : 13/08/2020 7:04 pm
jsw
 jsw
(@jsw)
Prominent Member
Posted by: @peter-c20

My printer always makes a thick line of filament on the front at the beginning of the calibration and printing. Why this line is always thick (more filament extruded?) than the rest?

What is the best source to learn about First Layer Calibration? 

The comments in the stock gcode call this the 'intro line' and I've heard people call this the 'prime line' as well.  I've always assumed it's to prime the extruder and get it flowing and stable, as the flow on this line does not always start in the same location.

I agree that the only way of learning the first layer calibration is doing it.  I use that 3x3 square pattern and I'll do it as a sanity check if I ever suspect things may be off a bit.  Surprisingly, once I got things dialed in it's been very consistent.  When I added the MMU2S it did not change at all, even though there was some major surgery on the extruder.  Ditto with changing the fan shroud a couple of weeks ago.

Posted : 13/08/2020 7:26 pm
peter.c20
(@peter-c20)
Reputable Member

Thanks. Few weeks ago I posted a thread about ugly bottom. Somebody mentioned that the first layer calibration was not good. I tried to calibrate for a few times but same thing. Now I got another model. As you can see, the lines on the top half of the model seem to merge better than the bottom half. If the first level calibration were bad, why not the entire bottom looks bad?

Also, is there any way that I can set the perimeter of holes independently from other parts of the models. Here both the edge of the model and the holes have perimeter 5. I would prefer to have smooth looking bottom.

The model was made using Prusament PLA and textured sheet.

Posted : 13/08/2020 7:33 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: @peter-c20

Thanks. Few weeks ago I posted a thread about ugly bottom.

That is very close. You want to close up those small gaps between extrusion lines. Lower (make more negative) your Live-Z by 0.04mm to start (using Jeff Jordan's "Life Adjust" print) and lower it by 0.02mm until they close up.

The rough edge at left looks to be caused at least partially by a fillet, a curved surface. On undersides, these print as severe overhangs for the 1st few layers which can cause rough finish. Troubleshoot that problem separately.

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 : 13/08/2020 7:42 pm
peter.c20
(@peter-c20)
Reputable Member

Thanks. How can I make the top surface looks smooth? Like some kind of top cover to hide the internals.  As you see, there are ugly looking lines and some gaps on the top surface. I had Horizontal shells->Solid layers->Top set to 7 already.

This post was modified 2 months ago 4 times by peter.c20
Posted : 14/08/2020 4:35 pm
peter.c20
(@peter-c20)
Reputable Member

It seems that PrusaSlicer does not make a cover to hide the internals automatically. Is there a way to make it print a top cover to hide those ugly lines?

Posted : 14/08/2020 4:41 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: @peter-c20

Thanks. How can I make the top surface looks smooth? Like some kind of top cover to hide the internals.  As you see, there are ugly looking lines and some gaps on the top surface. I had Horizontal shells->Solid layers->Top set to 7 already.

Using something besides concentric infill may help.

 

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 : 14/08/2020 4:42 pm
peter.c20
(@peter-c20)
Reputable Member

@bobstro

I have: 

Fill pattern: Gyroid 30%

Top and Bottom fill pattern: Rectilinear

Do you have any good suggestion?

Posted : 14/08/2020 4:51 pm
Neophyl
(@neophyl)
Noble Member

There are so many perimeters on that part that there is no room for infill So it doesn’t matter what infill pattern is selected.  It’s basically solid and in that orientation it will always be like that. 

Posted : 14/08/2020 5:23 pm
peter.c20
(@peter-c20)
Reputable Member

@neophyl

Thanks. Actually what does "Horizontal shells->Solid layers->Top" do? I thought it were to set the number of layers to make the top cover to cover up the internals but obviously I am wrong.

Posted : 14/08/2020 5:25 pm
Neophyl
(@neophyl)
Noble Member

It does create the top infill, however it creates the top infill in between the perimeters. If there perimeters take up all the area then it can’t create it. Just as an experiment reduce your perimeters to 1 and reslice then check the preview. You should then start to see the top infill (and actual infill inside your part). Then increase the perimeter count by 1 and slice again and again check the preview. You will see what it’s doing then. 

Posted : 14/08/2020 5:35 pm
bobstro
(@bobstro)
Illustrious Member

Try reducing your external perimeter count to 2 and see how it looks.

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 : 14/08/2020 6:00 pm
peter.c20
(@peter-c20)
Reputable Member

I only see one perimeter setting under Layer and Perimeters->Vertical Shells->Perimeters

Is there one for external and possibly another one for internal perimeters?

Posted : 14/08/2020 7:15 pm
bobstro
(@bobstro)
Illustrious Member

That's it. Sorry for the confusion. You just want 2 "shells" with some infill in between to compare.

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 : 14/08/2020 7:16 pm
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