Support attention  

Re: Support attention

Hi Amelia,

I feel your pain...

we all have very different experiences

one of the most annoying aspects of the Mk2, is Pinda Sensitivity

as the Pinda changes temperature, it changes sensitivity

if on one occasion, you start with your extruder say 60mm above the build plate(because that is where it was after the last print, and
on another occasion you start with the extruder only just above the build plate, because that's where the last calibration attempt ended,
your pinda probe will be cooler on the first occasion than on the second occasion...

and as a result, the sensitivity is likely to be different,
net result is that your next attempt at a good first layer may be messed up, because the live Z height seems to have changed...

and you end up chasing your tail...

So...

assuming you are using PLA
and assuming you have completed XYZ calibration,

Please gently wash your build plate, again, using soap and water, and dry with Clean, un scented, basic tissue paper... say kitchen roll
then wipe the build plate with IPA and clean basic tissue paper. do not use Windex at this time

you should have a clean build plate...

turn the printer on.
when on main menu,
using the LCD Menu click and hold the button for a couple of seconds, and you should have the option to raise the Z axis.

Raise the Z axis until the extruder is 60mm above the build plate
then re run your favourite Z axis test / adjustment file,
adjusting Live Z to the best of your ability.

when complete, remove the print, carefully, without getting finger prints on the bed.

now use the LCD Controls to move the Z axis back up to 60mm and try the same file again...

I suspect, in the past, this will have given you a bad second print...

this time I hope it gives you a good second print...

the reason, (if I am correct), is that in the past, you have finished your test print, cleaned the bed, and started heating the printer, with the extruder only just above bed height, as the heatbed heats up, it heats the Pinda Probe, (altering it's sensitivity) with the result that next time the printer does Mesh bed levelling, the pinda actually miscalculates the bed position, due to it's altered sensitivity... and your next print first layer, is rubbish...

here's the kicker... if you re run your live Z with the extruder near the heatbed... and then run a successful print, with the newly adjusted live Z settings... it is likely that your print will be successful... so let's say you printed the tree frog...

at the end of that print the extruder will be say 30mm to 50mm above the print bed... ok, in a fit of jubilence... let's assume that you clear the tree frog off the bed, and immediately print another tree frog, from the same gcode, and the chances are, your first layer will be rubbish...(because the Pinda didn't heat up as much, and the sensitivity was different,...)

So.........
you stop the print, pull some more of your hair out... Aaaaannnndddd...
you re do, your live Z. again, whilst mutteing and cursing...

but , having just failed the last first layer... your extruder is again very low... so this time your pinda heats up more than last time... and continues the cycle of print problems...

of course I could be totally wrong... 😮

long story short...

until you get happy with your results,
please consider raising the extruder to the same sort of height before starting heating for the next print!
hopefully this will remove one additional variable...

Good Luck,

regards Joan

Re: Support attention

Once I started doing what Joan explained above I have had very consistent prints. I found with my MK2s(bought fully assembled) that it likes to be approx 100mm off the bed while heating and since then have not had to play with the live Z all the time( only a touch here and there depending on filament used) .After every print finishes I move the Z to 100 mm off the bed so its good to go for the next print. one day I'll learn how to incorporate this into my G-code so it does it automatically at the start up.

Re: Support attention

Once I started doing what Joan explained above I have had very consistent prints. I found with my MK2s(bought fully assembled) that it likes to be approx 100mm off the bed while heating and since then have not had to play with the live Z all the time( only a touch here and there depending on filament used) .After every print finishes I move the Z to 100 mm off the bed so its good to go for the next print. one day I'll learn how to incorporate this into my G-code so it does it automatically at the start up.

Just put
G90 ; use absolute coordinates
G28 X0 ; home X axis
G1 Y195 ; move Y axis to end position
G1 Z100 F5000 ; lift nozzle by 100mm
in your ending script (Simplify3d, other slicers might have a place for scripts as well...)
and your extruder will be lifted after every print away from the bed.
For me this has been working pretty well for a long time, now.
Just check on very tall prints, that it does not collide with the part when it goes to absolute 100mm after homing....

Re: Support attention

Once I started doing what Joan explained above I have had very consistent prints. I found with my MK2s(bought fully assembled) that it likes to be approx 100mm off the bed while heating and since then have not had to play with the live Z all the time( only a touch here and there depending on filament used) .After every print finishes I move the Z to 100 mm off the bed so its good to go for the next print. one day I'll learn how to incorporate this into my G-code so it does it automatically at the start up.

Just put
G90 ; use absolute coordinates
G28 X0 ; home X axis
G1 Y195 ; move Y axis to end position
G1 Z100 F5000 ; lift nozzle by 100mm
in your ending script (Simplify3d, other slicers might have a place for scripts as well...)
and your extruder will be lifted after every print away from the bed.
For me this has been working pretty well for a long time, now.
Just check on very tall prints, that it does not collide with the part when it goes to absolute 100mm after homing....

I will have to give this a try, I'm not very good with coding but trying to learn. Thank you.

Re: Support attention

do you have the temperature calibration turned on in the calibration menu?
have you also run a pinda calibration?

the temp cal forces the printer on print start up to set the extruder about 30mm from the bed and hold after the extruder and bed have reached temperature. It sits with the pinda near the bed for 120 seconds. the idea is get everything to tempature then run the 9 point bed height calibration.
the idea being a more consistent Live Z.

the pinda calibration helps but you have to figure out the most likely temperature you might run at most of the time. i think the default is like 210-215. i run mine at 240C and left it.

Some other stuff.. the LIVE Z can be really flakey especially after a firmware upgrade on the mk2s.

some strangeness i have experienced in the past:

Firmware update or somekind of reset involving XYZ Cal. then loaded a LIVE Z test shape through the SD or USB. noted on each test the live Z was changing. the machine ONLY seemed to lock in the baseline LIVE Z when running the First layer setup.

Ok so from then on i changed the way i ran the machine after a reset.

when i reset the XYZ Cal i would run a tempature cal, then a pinda cal, make sure those were enabled on the settings or calibration menu.
next run a first layer calibration from the Firmware. confirm the layer was sticking to the PEI sheet and looked decent.
run the same wizard again just to confirm it ran the same.
then run a external LIVE Z STL test from my slicer, don't use prepared Gcodes because those were prepared from way older generations of Firmware revisions, so with my slicer settings on the live Z test i would then run and Fine tune the Live Z

all that seemed to lock it in. now the reason i set the PINDA temp cal to 240 and not around 210 for PLA is because i change from PLA to Nylon and PET etc. and those run at higher temps so the idea is i set the PINDA higher knowing that it will calibrate at that higher temp and i run at a lower temp and try to squeeze the live Z more. usually i have to increase live Z a little more when i switch filaments but it stays in a range.
like you i had Live Zs all over the place and what made it worse was running live Z tests over and over Verse a cold start. the cold starts were accurate while the warmed up ones were all over the place. so having the temp cal with the 120 second warm up evened it out.

again also make sure you run the Prusa first layer setup no matter what don't skip that as the machine acts like it ignores your manual input live z before you run that. and next make sure when you make your 100mm live Z test shape that you do not use pre-made Gcodes, use ones you made with the newest slicer and all that. and make sure all the calibrations for pinda and temp are set and turned on.

as a warning this extra time to start a print usually results in extra oozing so preheat the extruder and let it sit for while until the extruder de-pressurizes and oozes out, clean the nozzle then start the print.

the extruder will re-pressurize on the first movement outside of the bed area.