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Need help determining my z height  

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rangertown
(@rangertown)
Active Member
Need help determining my z height

I've had my i3 mk3s+ for a few weeks now and I printed ~5 great prints, all using the presets from prusa and all with glow in the dark filament.  I have read that this is an abrasive material and could be bad on my nozzle.  I have since ordered a few more brass and steel nozzles.

So I changed from the glow in the dark pla to prusament petg and I started having trouble with first layer adhesion.  I then thought it might be a good idea to calibrate the first layer since I switched materials, and by doing so I lost the original z height prusa set.

I am now struggling to get a good print, presumably because of the z order since these are the same prints I already had success with (same g code)

I ran the first layer calibration with a few different numbers, in the ballpark of what I think this bead is supposed to looks like.

are any of these correct

-1.455

 

Posted : 17/01/2022 7:58 pm
rangertown
(@rangertown)
Active Member
Topic starter answered:
RE: Need help determining my z height

more z heights

Posted : 17/01/2022 7:59 pm
Milos V.
(@milos-v)
Prominent Member
RE: Need help determining my z height

First, Z-height is not a constant. Different filament will need to push a bit more or less. Once you have got some experience, you will be able to slightly modifiy Z height during the print of the first line (skirt). 

And now to calibration. These pictures are useless. Print something bigger, 10x10cm at least. Make a foto of the first layer still on the bed. Then you can make a photo after removal, but that is not so important. Use some none transparent filament. You can better see the lines, if these are squiezed to the bet right way, if they nicely connects each other.

Posted : 17/01/2022 9:37 pm
Milos V.
(@milos-v)
Prominent Member
RE: Need help determining my z height

Once you are printing the bigger object, you can simply change the Z height during print. So finally you will nicely calibrate on the fly. That automatic calibration rutine is good for the very start, not for fine tuning.

Posted : 17/01/2022 9:40 pm
Diem
 Diem
(@diem)
Noble Member

Hard to tell once you've removed it, please show us your best calibration print *on* the print sheet.

You are aiming to peel it off in one and fold it without the threads seperating. If it breaks into lines it is too high, not squished enough. If it is a single sheet but with wavy lines or drag marks on it you are too low.

Glow in the dark is abrasive 'though not so harsh as other filaments.  You should be able to print a spool with a brass nozzle but don't expect it to have much life left in it afterwards.

Cheerio.

Posted : 17/01/2022 10:23 pm
rangertown
(@rangertown)
Active Member
Topic starter answered:
RE: Need help determining my z height

I'm working on it.  I'm printing the prusa plaque that comes on the SD.  I have the original that prusa printed and I have 2, -1.450 and a -1.440.  I can see where the -1.440 has a much better bottom, almost perfect.  The top of the letters (last layer) still has the same imperfections, but the original that prusa printed has similar imperfections.

I'll post pics of the prints when I'm done.  

One thing that isn't clear is how much to move the z-axis in between tests.  The answer is probably "it depends" It depends on how bad you are currently printing, if horrible, move a lot.

if I am fine-tuning, I don't know if I should move the axis 1/100th and try again or 1/1000th and try again.  Is there much value in moving 1/1000th (of a millimeter I presume)?

I'm trying in 1/100th increments, once I get close, I am going to try 1/250th increments

so

-1.450

-1.440

looks close

-1.435

Posted : 18/01/2022 2:59 pm
Bob
 Bob
(@bob-2)
Reputable Member
RE: Need help determining my z height

I've run 1+ rolls of glow in the dark filament in mine, don't be overly concerned about nozzle wear, I've read how it's more abrasive but I don't think 1 or 2 rolls is enough to wear out a nozzle.  Still, having a spare nozzle or two isn't a bad idea.

-Bob

Prusa I3 Mk2 kit upgraded to Mk2.5s, Ender3 with many mods, Prusa Mini kit

Posted : 20/01/2022 11:20 pm
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