Newbie - Inconsistent 75mmx75mm calibration test  

RE: Newbie - Inconsistent 75mmx75mm calibration test

Posted by: @jungerle

Hello,

I'm a newbie (3 days old)!  I stumbled across the "film" calibration test and it has been a wonderful help, however, I can't get my Prusa 3d mini to print the whole film correctly.  From the bottom right to about the half-way diagonal, it prints well, then it becomes striated.  I can crank my z depth down further, but that produced thin results on the bottom right.

 

Any idea what is causing this?

Thanks for your help.

 

Hello and welcome to the Prusaforum!

You must make sure that the geometry of the axes fits and that the printing bed is flat. When assembling and tightening the screws of the Z-axis (too tight or too loose), axis errors of up to 1mm and more can occur.

A lot has been written about this topic: https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-assembly-and-first-prints-troubleshooting/life-adjust-z-my-way/

RE: Newbie - Inconsistent 75mmx75mm calibration test

Posted by: @jungerle

I'm a newbie (3 days old)!  I stumbled across the "film" calibration test and it has been a wonderful help, however, I can't get my Prusa 3d mini to print the whole film correctly.

I haven't heard of this test, do you have a link?

Getting the Mini bed levelled is a tricky business, and the mesh bed levelling doesn't seem to always do a great job. Clearly if you have loose strands, you need to lower the Z. You may have to accept lower height than desired in other parts of the bed, unless you get into shimming the frame or bed levelling mods, e.g. https://forum.prusa3d.com/forum/user-mods-octoprint-enclosures-nozzles/prusa-mini-silicone-bed-leveling-mod/

RE: Newbie - Inconsistent 75mmx75mm calibration test

@bobcousins

@karl-herbert posted the link to the film calibration test in the post above (but it's buried at the bottom of the first post S3D_calibration_surfaces_75x75@200um_v6.1.zip).  Based on his answer, I **think** he meant to post what you posted. 

Thanks for your help.

RE: Newbie - Inconsistent 75mmx75mm calibration test

Hello everyone,

I've had my Prusa Mini (the first 3D printer ever) for a week now and I'm currently still working on First Layer Calibration. The ideal value for me was -0.975/-0.985, but I was not 100% satisfied with it and I experimented a bit. Among others with the "life adjust Z - my way".

But the print is very strange. The problem occurs with the original Prusament PETG. I have already tried both heating plates (smooth and textured), the same result.

Can anyone give me a hint what this is due to and I (have to) look for? 🙁

Thanks a lot!

Regards
Marcel

RE: Newbie - Inconsistent 75mmx75mm calibration test

Your Live-Z value is too low (too negative). The nozzle is so low to the print surface that it is having a hard time extruding. When it does, the surface is rough from the nozzle gouging the filament just laid down. It is interesting that it appears to get better as it moves to the left, which might indicate a leveling problem, but for now, I'd just raise (make less negative) your Live-Z by 0.06-0.08mm until the 1st part of the print comes out as a nice even sheet. When complete, you should be able to peel it up without it tearing apart, and the top should be even.

If you still see a lot of variation across the print, you may have other leveling issues.

RE: Newbie - Inconsistent 75mmx75mm calibration test

To add to Bobstro's post, yes, your live z is clearly too low and it looks like a level issue too.

There have been reports of the MINDA on the MINI being much more effected by heat and causing wandering Live Z values.  That can be a cause too.  there are threads on it.  something to do with heat breaks and screws not being tight....

On my Mini I was going crazy trying to get a stable Live Z value and I ended up following a knowledge base article and adjusting the MINDA height ... 

https://help.prusa3d.com/en/article/first-layer-calibration_112364/              <=Pictures of first layer showing your issue.

https://help.prusa3d.com/en/guide/troubleshooting-the-mini-assembly_7848    <=Section on Minda adjustment.

https://help.prusa3d.com/en/article/xz-axis-skew-correction-mini_158518      <Mini XZ axis Adj.

Definitely, more tweaking necessary than the MK3 which has never given me such problems...