First layer test : impossible to obtain acceptable results after some maintenance  

Re: First layer test : impossible to obtain acceptable results after some maintenance

Had today the same issues!
MK2 worked for one year and some 1.300hrs without problem!
After Re working of Hotend,lheatbed leveling was strange.
seems, that the pinda probe does not work correctly any more.
Have ordered new probe, new heatbed and new extruder assy.

hope this will work...

Re: First layer test : impossible to obtain acceptable results after some maintenance

It's perfectly fine to have a Live-Z value of -800 or even -1500. Does your print results have changed after the rebuild?

Re: First layer test : impossible to obtain acceptable results after some maintenance

- Thanks to both of you,

- harald.m2 you propose , in some way, to come back one year ago when you got your brand- new printer but excepted the hotend, I changed PTFE tube and nozzle ( tightened at ~250° ) and a few month before the Pinda probe. It is true that the PLA does not not sticks much in the corners ( I clean the heatbed with isopropylic alcool ) but it cannot, I think, explain the non uniformity of the first layer..

- nikolai.r : Yes, before rebuilt, I had an acceptable first layer ( in terms of homogeneity, flatness, each line melting nicely with the previous one …) and changing Live Z from -330 to -350 or -320 was modifying the results in terms of surface quality.
Now the surface is not regular,( as if the nozzle was cloggled), lines are almost separeted even with -800. Sometimes some PLA remains and sticks on the nozzle tip etc. and jumping from -800 to -900 microns doen't change much the results.

You said that Live-Z values can reach -1500. I do not remenber where, but I read in Prusa documentation, that -1000 microns has to be considered as a max value otherwise there is a problem. So trying to remain in that limit I get a first layer not sufficiently squished explaining may be these poor results ?
Could please say a bit more concerning the possibility to have an upper limit of -1500, the nozzle should be close to be in contact with the heatbed ?

Re: First layer test : impossible to obtain acceptable results after some maintenance

Hi chester, if your Live 'Z' is over 1000, it might be time to re adjust your pinda height.
your new nozzle is probably a touch shorter than the original.

If you raise the pinda a little, the Live 'Z' size will reduce

regards Joan

Re: First layer test : impossible to obtain acceptable results after some maintenance

Thanks Joan,

- Once the nozzle tip / Pinda distance is adjusted ( ~ 0,6 mm in my case) and if I suppose that Pinda can detect in good condition ( with respect to its sensitivity ) my only degree of freedom is to play with Live Z adjustment to approach the heatbed sufficiently enough to the nozzle tip in order to get a nice print.
note : my Z calibration is apparently fine, Pinda probe shall work in not so bad conditions.
However If the new nozzle is shorter than the original. (although a Prusa model too ) I can imagine that the Live Z value will be different from the one I am used to and could explain the remark of nikolai.r ( -1500 microns ) ?

- What I don't quite understand is once nozzle tip / Pinda distance is adjusted to any right value, and with a live Z value = 0, what is the standard distance nozzle / heated bed. I would guess a distance such that the print is slightly squished and can be improved with negative values of the Live Z , but is that true ?

Re: First layer test : impossible to obtain acceptable results after some maintenance

Hi Chester, there is no absolute best value, as the Pinda probes all have slightly different sensing ranges, all printers are built from an assembly of disparate parts, which, even if within tollerances, may still be slightly different sizes...and we all estimate perfect squish, slightly differently,

I always try and get my Live 'Z' for PLA between 0.3 and 0.6mm, this then allows me to reduce it a little for PETG or TPU prints... currently I am using
about 0.450 for PLA Prints, and 0.333 for PETG prints...
If i change my nozzle, there should be enough room for adjustment without having to re adjust the Pinda

I have successfully used 1.30 when the printer was initially built, but I then readjusted the pinda once everything was proved to be working...
(I didn't want to risk an error on my behalf, damaging the PEI. )

regards Joan

Re: First layer test : impossible to obtain acceptable results after some maintenance

Hello Chester. The optimum z-height range is based on two factors.
1. If your probe is placed too low ( >0 ), the probe might touch the object during printing. It will be on the same height or even lower then the nozzle.
2. If your probe is placed too high ( highly depends on the probe. less then -1200 is safe value), the probe will not be able to catch the magnet before the nozzle hit the build surface. But as already mentioned it might be -1000, -1200, -1500 or even -2000 based on your probe.
The optimum range of -0.3 ... -.8 is because it helps to have a buffer to raise or lower the z-height based on your material and outside temperature. It may vary all the time.

I would recommend you to forget about numbers at first. Just adjust the z-height as mentioned in the calibration guidelines until you have a nice looking first layer. Once you have that, you can physically move the probe down or up to hit the optimum range.
Try to understand that z-height of -1000 and -200 might both produce ideal first layer and perfectly fine print.

Re: First layer test : impossible to obtain acceptable results after some maintenance

Thanks again to Joan and nikolai.r.

- Indeed when a year ago I started to use my i3 MK2 everything worked fine, so I didn't pay much attention to the relations between all parameters. Now after having this problem I asked your support and to be sure of a correct understanding, I wrote a little note ( see annex). If you have any comments don't hesitate...

- I redo all calibrations tests and made several measurements on the PINDA probe ( Zp /threshold versus voltage supply ) to be sure that the probe is OK, results were better but not satisfactory. Now when I replaced PLA ( Futura form) by PLA from Prusa I had a big improvement and I am not so far from what I had a long time ago.
I read in the forum” the z-live adjust value should be the same for all filaments” , I don't verify this statement...

- Still two questions related to a better quality of the first print (and all prints in general I guess ):

Q1:I read too that an extruder calibration shall be done. I use Cura and using the flow rate parameter, I shall correct this filament flow if necessary ? This correction c ould explain may be what I noted between two different PLA?
Q2 :There is a PID calibration on firmware 3.1.0 . I don't understand the effect on quality if the bed and nozzle temperatures are always very stable and constant ( is-it a first order effect )?

annex : First layer and print parameters