Live Z Adjust Constantly Decreasing  

Re: Live Z Adjust Constantly Decreasing

This is indeed an extremely frustrating issue that a number of people have reported, but the actual cause has not proven to be consistent yet. There has been some speculation that it may be related to heating of the PINDA probe by the heatbed. As an experiment, try pre-heating your beat with the nozzle raised up so that the probe doesn't heat up during pre-heat, and see if you get better results.

Re: Live Z Adjust Constantly Decreasing

I have the same issue. Many prints are good, and then Z adjust needs lowering again !!!! To achieve first layer adhesion performance again. I rerun V2Calibrate gcode and original Z adjust is good, Until the next print. Consistancy has gone again.

Re: Live Z Adjust Constantly Decreasing

Same problem here (I3 MK2). Need to (re)adjust Z every new print.
Everything else works perfectly!

Re: Live Z Adjust Constantly Decreasing

This is indeed an extremely frustrating issue that a number of people have reported, but the actual cause has not proven to be consistent yet. There has been some speculation that it may be related to heating of the PINDA probe by the heatbed. As an experiment, try pre-heating your beat with the nozzle raised up so that the probe doesn't heat up during pre-heat, and see if you get better results.

Wow. I would never have thought about that. I had the same issue at the beginning but it went away and I could not tell why. Now it could be because I have modified the end g-code to raise the extruder after finishing or cancelling a print.

Re: Live Z Adjust Constantly Decreasing

Hi,

I have the same problem.
When printing V2calibration Gcode several times in a row, I each time need to lower the nozzle height.
If I keep the last Live Z calibration setting when the printer has cooled-down, the nozzle crashes in the print bed.

Very frustrating 😡

Some findings I already shared with the support team:

Re: Live Z Adjust Constantly Decreasing

Hi,

I have the same problem.
When printing V2calibration Gcode several times in a row, I each time need to lower the nozzle height.
If I keep the last Live Z calibration setting when the printer has cooled-down, the nozzle crashes in the print bed.

Very frustrating 😡

Some findings I already shared with the support team:

Nope. My probe is from June and it's quite sensitive. I really wish PR would formally acknowledge this and comment on the subject.

Re: Live Z Adjust Constantly Decreasing

Same thing happens here too
i have to lower the z almost every new print 🙁
it started about 3 weeks ago suddenly
i update the firmware to 3.0.9 but nothing change 🙁

Re: Live Z Adjust Constantly Decreasing

Nope. My probe is from June and it's quite sensitive. I really wish PR would formally acknowledge this and comment on the subject.

Ok Omikron. Thanks for your input.

I just used cura 2.1.99 with its original prusa i3 mk2 settings, and figured out that the start Gcode makes the nozzle go to "home" before heating both the nozzle and the bed up, so

I don't like the idea of doing the mesh bed leveling before heating it up so much, but it gives some workaround ideas.

Re: Live Z Adjust Constantly Decreasing

I don't like the idea of doing the mesh bed leveling before heating it up so much, but it gives some workaround ideas.

No, you should not do that. There may be a bit of plastic on the end of the nozzle which will push the bed down slightly and give incorrect probing.

Heat the nozzle to 170 degrees before homing and mesh calibration.

M140 S<BED> ; Heat the bed
M104 S170 ; Warm extruder up to calib temp
G28 W ; Home all (no calibration)
M109 S170 ; Warm it up to calib temp, and wait till it's warm
G80 ; mesh bed levelling
M109 S<TEMP> ; Warm it up to print temp, and wait till it's warm


Peter

Re: Live Z Adjust Constantly Decreasing

Hi All, I have been struggling with this as well. I have been trying different scenarios. First print live adjust Z to -0.535, (printer not turned off or any other adjustments, next print set to -0.950, I kept doing this until I had an live adjust z of around 2.5mm. Seemed to be chasing my tail.
I then tried resetting the live adjust z to 0 before starting a print which has fairly consistently resulted in a live adjust z of -0.535.
My suspicion is that once you have the live adjust z at a value then do a new print the mesh level calibration is taking the live adjust z into account so it is then adding this to the mesh calibration figures which then moves the bed further away which then needs a larger live adjust z.

Re: Live Z Adjust Constantly Decreasing

I just started having a similar issue since today.

I've been tinkering with the MK2 since over a month on a daily basis, and this behaviour is new, sudden and constant.

I installed the 3.0.9 firmware today and have had the problem ever since.

However, I am also using a .gcode file that was created with the new Prusa Slic3r in Windows, previously I was using Slic3r in Ubuntu.

I am printing a large based object, almost the entire plate, so live z-adjust can be used for almost an hour to get it just right. Tiny holes left in the corners, lower z a bit more; if waves start forming, raise it a bit.

First print attempt:
live z-adjust fine-tuned to -0.445, then print stopped manually.

I stopped the print and restarted a new one straight away, no time for big temperature changes of PINDA probe.

2nd print:
Live adjust z:
Initially left at -0.445 despite some waves in first layer, but they turned out to be quite severe..
-0.425: still waves
-0.350: to stop waves
-0.400 after waves had stopped; waves start again
-0.35: waves stop
-0.375: mild waves
-0.36: mild waves
-0.35 this looks good, keep and restart print.

3rd print:
z way too high when left unchanged since last attempt at z-0.350; very poor cohesion, no bed aherence.
z-0.450: leaves tiny holes, no waves.
z-0.500: miniscule holes in corners
-0.525: no holes, but waves starting
-0.515: no holes, no waves
keep this
pause print
stop print
turn printer off
turn printer back on
restart print immediately.

4th print:
Live adjust-z is still at -0.515, but marked waves appear everywhere in the first layer again.

So unlike many other above reports, I do not have to continuously increase the live z-adjust in the same direction, but in opposite directions between each new print. It seems like the printer tries to over-compensate for whatever change I make to the live z-adjust: Next time, I have to move it in the opposite direction.

I'll try this next: Adjust it not quite enough, maybe to (515 + 350) / 2 = 432.5 .

I have to abort this print again, the waves are now starting to 'break'. Totally unacceptable. The printer is not useable in this condition.

Re: Live Z Adjust Constantly Decreasing

Another new behaviour since I installed the 3.0.9 firmware is that the printer misbehaves when i cancel a print. It slams into the extreme x-axis points, prints outside of the bed area, and the stepper motors make loud noises when it tries to keep going although it is at the edge of the print bed.

Re: Live Z Adjust Constantly Decreasing

My next printing attempt was again made after carefully adjusting live z-adjust, to z -0.450 in this case.

The I turned thr printer off for about an hour and started up 'cold' again in about 24C environment.

Same result, z was way too low, causing waves to form immediately.

So I decided to run the full self-test and xyz calibration. I got 'slightly skewed axis' result for the first time, probably because I was mucking around figuring out what all the noisy resonating bits on the printer are, greasing x and y axis while it was running, not recommended. 😉

So I ran the xyz calibration a second time and interfered less and got the 'axes perpendicular. Congratulations!' result.

Then V2 calibration: The live adjust z value was 0.000 to start, I adjusted it to -0.400 .

I re-sliced the thing that I'm trying to print so that it has a 7mm brim, giving me time to adjust the live z-adjust before the actual print starts.

During the brim printing, I adjusted the live z to -0.375 and the first layer of the print continued to go well.

This could be coincidence, and maybe the next print will be requiring live-z adjustment again, but maybe it is fixed.

It will be a couple of days before I can try this again, because I'm intending to do the 'impossible' and 'print silicone'. I'm printing a very thin PLA mould (my latest attempt to beat warping) and I will leave it on the printbed and then pour silicone resin into it. Hope there are no leaks, that's why I really needed the bottom layers perfect. That will take a day to set while it's occupying the print bed.

Anyway, if your printer suffers this z-axis shifting, then repeat the full calibration and see if it fixes it.

If not, add a generous brim and do live adjust z before each print until someone figures out what causes this most annoying problem.

Re: Live Z Adjust Constantly Decreasing

The problem continues despite of the successful full xyz calibration.

On the next print, I had to change z from -0.375 to -0.325 to get rid of waves, then I paused, waited and then stopped the print (that way, no nasty noises and banging into the boundaries).

On the next print attempt, I had to change z to -0.450 because it was practically printing the first layer in the air.

So the z-adjustment of my Prusa i3 MK2 suddenly bounces around by 50 micron to 125micron (at least) between prints. Not changing in the same direction, but (so far) always alternating between up and down between prints.

It never did this in the first months of daily printing since I had it.

Any ideas what has changed and how to fix this?

Re: Live Z Adjust Constantly Decreasing

I'm glad I found this thread. This is exactly what is happening to me. I've found I need to reprint V2Calibration before every print multiple times before I can then print a successful print. Even then the print can lift off the bed.

I feel this problem may relate to the ramp up in demand for the printer from all the positive reviews. I've created an expanded version of the V2Calibration file that fills the entire bed allow you more time to adjust Live Z and test bed levelling.

https://dl.dropboxusercontent.com/u/7799729/3Dprint/V3CalibrationSlic3r.gcode

Re: Live Z Adjust Constantly Decreasing

+1.
I have the same problem after the probe's mount broke off.
I glued the probe back again but since then I have to check and manually adjust the "Z" before every print. I think I might have damaged the probe.

Re: Live Z Adjust Constantly Decreasing

I also have this problem. And when I read other posts, I can see a lot of people having the same problem, but this is explained differently. I wonder if there is another solution than checking and readjusting live Z adjust before each print. Some of my prints completely failed because I didnt check live Z adjust, and the print detached from the bed before the end of the print.

Re: Live Z Adjust Constantly Decreasing

Stephen, Daniel and Cyrille,

what exactly is the problem with your printers?

A few somewhat different scenarios have been described above, for example that the live-z-adjust needs to be changed in the same direction every time, or that it changes up or down, alternatingly, or maybe at random.

Re: Live Z Adjust Constantly Decreasing

Hi

Mine needs to be readjusted after every print, either up or down. I have to reprint the Calibration print before every print. Sometimes it can be as much as 0.2mm difference in Z Adjust. This is even if I don't change filament. I am not moving the Z axis by hand or knocking it.

In this state, the printer is far harder to calibrate than my FlashForge and far less reliable. On that, I only had to check the calibration once a week with a piece of paper. The big selling point for me of this printer was the auto bed levelling and Z probe.

If the probe is two low, the bottom layer gets strange marks and patterns appearing in it. If it is too high, the print ends up lifting from the bed part way through. My success rate for prints is about 30% currently.