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Hobby Hoarder
(@hobby-hoarder-2)
Trusted Member
Z height varies wildly between prints (pic included)

After printing for a couple of months, I've started to really fine tune my settings and I've been playing around and doing test prints. I'm really getting annoyed with large differences in Z height between prints.

I've added custom G code that lifts the extruder before the heating begins. My thinking was that this should reduce problems with PINDA probe giving out different results based on heat.

Anyway, I've started off with Live adjust Z of -60 (yes, I've played with the PINDA height a long time). It sticked ok, as you can see in the photo below. So then I wanted to do another print with slightly different values, I think it was -70. However, this time around, the print wasn't even sticking at -70. I had to crank it up to -100 before it would even hold. Judging by this, I'd need to bring it down to at least -150 to get the same result as I did the first time with -60.

So my question is, what's causing the Z height to be so different between consecutive prints? I'm ok with a few microns difference here and there, but a 100 difference can easily break my prints.

Should I just leave the PINDA near the bed and let it heat up?

Any and all suggestions much appreciated, thank you.

Napsal : 10/08/2017 3:13 pm
JeffJordan
(@jeffjordan)
Member Moderator
Re: Z height varies wildly between prints (pic included)

as already mentioned inside my thread and a lot of other postings here:

the sensitivity of the probe depends on several "environmental" factors.
first there is the temperature of the probe. inside the actual firmware there is a "calibration" option, where the probe is "heated up" by the heatbed and the change in the height where the probe triggers is measured.
but this calibration is at last not very useful in practice, because the printer can only guess the actual temperature of the probe (there is no sensor that measures the probes temperature). so personally I would recommend not to use this temperature calibration option. instead of it I would assure that the pinda is cooled down to room temperature before starting the 9-point calibration procedure. just "park" the extruder way above the heatbed before starting to print.
the second one is the stability of the supply voltage for the probe. normally there should be no problem with it, but at some rambo boards there is a tiny fluctuation of the voltage (all in between the specification of the voltage regulator).
and last, but not least, if you've got an mk2s, the holder often doesn't fix the probe completely... so it could be slightly moved accidentially (or if it hits a printed part).

dem inscheniör is' nix zu schwör...

Napsal : 10/08/2017 3:29 pm
AJS
 AJS
(@ajs)
Noble Member
Re: Z height varies wildly between prints (pic included)

A few comments.

Your PINDA sensor is much too low. It is nearly at the same level as the nozzle. If a print curls up at all it will catch on the PINDA sensor and ruin the print, and possible damage the PINDA or create a tumor of plastic around the extruder.

It should be between 0.5mm and 1.0mm higher than the nozzle. About the thickness of a credit card.

People have reported variability like this when they start the print (bed heating up) with very low Z-values, and have indicated that ensuring the extruder is well above the print bed when starting a print has reduced this effect. Before you hit "start" have Z up near the mid way point.

There are a number of threads on this topic.

Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage or loss. If you solve your problem, please post the solution…

Napsal : 10/08/2017 3:31 pm
Hobby Hoarder
(@hobby-hoarder-2)
Trusted Member
Topic starter answered:
Re: Z height varies wildly between prints (pic included)


as already mentioned inside my thread and a lot of other postings here:

the sensitivity of the probe depends on several "environmental" factors.
first there is the temperature of the probe. inside the actual firmware there is a "calibration" option, where the probe is "heated up" by the heatbed and the change in the height where the probe triggers is measured.
but this calibration is at last not very useful in practice, because the printer can only guess the actual temperature of the probe (there is no sensor that measures the probes temperature). so personally I would recommend not to use this temperature calibration option. instead of it I would assure that the pinda is cooled down to room temperature before starting the 9-point calibration procedure. just "park" the extruder way above the heatbed before starting to print.
the second one is the stability of the supply voltage for the probe. normally there should be no problem with it, but at some rambo boards there is a tiny fluctuation of the voltage (all in between the specification of the voltage regulator).
and last, but not least, if you've got an mk2s, the holder often doesn't fix the probe completely... so it could be slightly moved accidentially (or if it hits a printed part).

Thank you for a quick reply.

I know about the calibration function, but I've read nothing good about it, so I've never used it.

I'll try and move the extruder even further, it was set to Z100 before it starts heating the bed.

I do have Mk2S, but I think I've tightened the probe quite well. I'm guessing that if this was the case, the probe would move slightly, I'd readjust the Z height and it would stay consistent afterwards. The third print I did after the above two was at -90, so I had to lower it a bit further again. Maybe the only option left is to put the printer in an enclosure where I can ensure much more stable temperatures.

Napsal : 10/08/2017 3:48 pm
Hobby Hoarder
(@hobby-hoarder-2)
Trusted Member
Topic starter answered:
Re: Z height varies wildly between prints (pic included)


A few comments.

Your PINDA sensor is much too low. It is nearly at the same level as the nozzle. If a print curls up at all it will catch on the PINDA sensor and ruin the print, and possible damage the PINDA or create a tumor of plastic around the extruder.

It should be between 0.5mm and 1.0mm higher than the nozzle. About the thickness of a credit card.

People have reported variability like this when they start the print (bed heating up) with very low Z-values, and have indicated that ensuring the extruder is well above the print bed when starting a print has reduced this effect. Before you hit "start" have Z up near the mid way point.

There are a number of threads on this topic.

Thank you for replying so quickly.

Maybe I wasn't clear enough, but the -60/-100 isn't the distance between the PINDA and nozzle. They are quite far apart in my case, I'd say about 1.5mm, so there's plenty of space between the probe and the printed part. I was talking about the Live-Z adjust values, which only compensate for the PINDA measurements and have nothing to do with the height difference between the nozzle and the probe.

As I've mentioned, I'm lifting the extruder to Z100 before heating the bed. I'll try and move it even further up, which will hopefully eliminate any heat from the bed.

Napsal : 10/08/2017 3:56 pm
AJS
 AJS
(@ajs)
Noble Member
Re: Z height varies wildly between prints (pic included)



A few comments.

Your PINDA sensor is much too low. It is nearly at the same level as the nozzle. If a print curls up at all it will catch on the PINDA sensor and ruin the print, and possible damage the PINDA or create a tumor of plastic around the extruder.

It should be between 0.5mm and 1.0mm higher than the nozzle. About the thickness of a credit card.

People have reported variability like this when they start the print (bed heating up) with very low Z-values, and have indicated that ensuring the extruder is well above the print bed when starting a print has reduced this effect. Before you hit "start" have Z up near the mid way point.

There are a number of threads on this topic.

Thank you for replying so quickly.

Maybe I wasn't clear enough, but the -60/-100 isn't the distance between the PINDA and nozzle. They are quite far apart in my case, I'd say about 1.5mm, so there's plenty of space between the probe and the printed part. I was talking about the Live-Z adjust values, which only compensate for the PINDA measurements and have nothing to do with the height difference between the nozzle and the probe.

As I've mentioned, I'm lifting the extruder to Z100 before heating the bed. I'll try and move it even further up, which will hopefully eliminate any heat from the bed.

I am quite confused. Your Live-Z value, IS the distance from nozzle tip to the PINDA. At 1.5mm, I am surprised you can do an XYZ Calibration. Maybe photos would help. Also, have you adjusted other parameters to get the filament to stick during the calibration?

Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage or loss. If you solve your problem, please post the solution…

Napsal : 10/08/2017 4:26 pm
Hobby Hoarder
(@hobby-hoarder-2)
Trusted Member
Topic starter answered:
Re: Z height varies wildly between prints (pic included)




A few comments.

Your PINDA sensor is much too low. It is nearly at the same level as the nozzle. If a print curls up at all it will catch on the PINDA sensor and ruin the print, and possible damage the PINDA or create a tumor of plastic around the extruder.

It should be between 0.5mm and 1.0mm higher than the nozzle. About the thickness of a credit card.

People have reported variability like this when they start the print (bed heating up) with very low Z-values, and have indicated that ensuring the extruder is well above the print bed when starting a print has reduced this effect. Before you hit "start" have Z up near the mid way point.

There are a number of threads on this topic.

Thank you for replying so quickly.

Maybe I wasn't clear enough, but the -60/-100 isn't the distance between the PINDA and nozzle. They are quite far apart in my case, I'd say about 1.5mm, so there's plenty of space between the probe and the printed part. I was talking about the Live-Z adjust values, which only compensate for the PINDA measurements and have nothing to do with the height difference between the nozzle and the probe.

As I've mentioned, I'm lifting the extruder to Z100 before heating the bed. I'll try and move it even further up, which will hopefully eliminate any heat from the bed.

I am quite confused. Your Live-Z value, IS the distance from nozzle tip to the PINDA. At 1.5mm, I am surprised you can do an XYZ Calibration. Maybe photos would help. Also, have you adjusted other parameters to get the filament to stick during the calibration?

Not exactly. The Live-Z allows you to fine-tune the distance between the nozzle and the bed. If what you are saying were true, then adjusting the Live-Z value would change the physical distance between the nozzle and the PINDA, which of course it doesn't, because both the nozzle and the PINDA are firmly fixed in their place.

Bed and nozzle temperatures are fine for the filament that I'm using. I don't see what else I could adjust and I'm using fairly standard Prusa settings (layer height, width etc.).

Napsal : 10/08/2017 4:33 pm
AJS
 AJS
(@ajs)
Noble Member
Re: Z height varies wildly between prints (pic included)



Thank you for replying so quickly.

Maybe I wasn't clear enough, but the -60/-100 isn't the distance between the PINDA and nozzle. They are quite far apart in my case, I'd say about 1.5mm, so there's plenty of space between the probe and the printed part. I was talking about the Live-Z adjust values, which only compensate for the PINDA measurements and have nothing to do with the height difference between the nozzle and the probe.

As I've mentioned, I'm lifting the extruder to Z100 before heating the bed. I'll try and move it even further up, which will hopefully eliminate any heat from the bed.

I am quite confused. Your Live-Z value, IS the distance from nozzle tip to the PINDA. At 1.5mm, I am surprised you can do an XYZ Calibration. Maybe photos would help. Also, have you adjusted other parameters to get the filament to stick during the calibration?

Not exactly. The Live-Z allows you to fine-tune the distance between the nozzle and the bed. If what you are saying were true, then adjusting the Live-Z value would change the physical distance between the nozzle and the PINDA, which of course it doesn't, because both the nozzle and the PINDA are firmly fixed in their place.

Bed and nozzle temperatures are fine for the filament that I'm using. I don't see what else I could adjust and I'm using fairly standard Prusa settings (layer height, width etc.).

No. I am saying that the printer has no way of knowing what the distance is between your PINDA sensor and the nozzle, and no way of moving it, so you SET this value by setting Live-Z, informing the electronics where the nozzle is relative to the PINDA sensor (which can measure where it is relative to the build plate. Typical Live-Z values are between -0.500mm and -1.00mm, depending on how you have positioned your PINDA sensor. Values outside of that are an indication of a problem.

This, if set correctly, the Live-Z is the distance from your PINDA to nozzle. Since you feel those two values are differing by more than a 1mm I think something is wrong.

You may want to try the step startup-steps I have listed below.

--

Here is my starter advice for getting your printer going well, and avoiding some of the common frustration inducing issues.

0) Make sure the belts are tight, and all of the axises are free to move smoothly. Make sure the wire bundle coming out the back of the extruder is held high and does not droop down where it will hit the print when the extruder is at any height. Make sure the X and Y axis are as perpendicular as you can judge by eye.

1) Run the Self Test from the menu. Make sure everything is connected correctly.

2) Make sure PINDA is above nozzle tip by <1mm but above the nozzle. About 0.6mm is a good starting point (but anything between 0.5mm and 1.0mm is fine), which is about the thickness of a credit card. Place a sheet of paper on the bed, and run the XYZ Calibration from the menu. Stay with the machine, and watch it. As it hunts for the calibration points, watch if the paper moves. If it does, STOP THE PRINTER. That means the nozzle is dragging and the PINDA sensor is a bit too high, lower it and try again, but make sure it is still higher than the nozzle tip. Repeat until you have a good XYZ Calibration. (Note the instructions on the XYZ calibration, and make sure the nozzle tip is clean.)

3) Set your Live Adjust Z roughly correct.
a) Set Live adjust Z = 0.00. (XYZ Cal does this).
b) Do a Calibrate Z. (Head must be clean of drips and lumps).
c) Do a Home. This leaves the head at Z=0.15mm. DON’T SKIP THIS STEP.
d) Use Setting -> Move Axis X and Y to get in the approx center of the print space. DON’T TOUCH Z.
e) Put a piece of printer paper under the head. Printer paper is approx 0.1mm
f) Wiggle the paper while adjusting "Live Adjust Z" (in settings) until the paper just starts to drag on the paper.
g) Back off a bit (50) on the “Live Adjust Z"
NOTE: If your Live Adjust Z value is >1mm something is wrong. It should be approx the distance from the PINDA probe to the nozzle. Anything between 0.4mm and 1.0 should be fine. (Less than 0.4 means the PINDA probe might catch on some print that curles up a bit, greater than 1.0 means either you did something wrong, or are just barely in the PINDA’s detection range.}
Now you have set the nozzle approximately 0.15mm (paper +0.05mm) above the bed while the printer’s electronics think the Z is at 0.15mm.

4) Load some filament.
a) Make sure the tension screws are about 14mm from the body with no filament in the extruder. (This is looser than is intuitive for most people. Too tight or too loose will cause issues.)
b) Heat the extruder. You can do this with pre-heat or settings->temperature.
c) Use Load Filament from the menu. Continue until you have a nice thin strand coming from the extruder.
d) Cool it back down.

5) Make sure the bed is very clean.
a) Wipe with as pure an isopropyl alcohol (IPA) as you can find. The little toweletts are not enough in my opinion. Use (and re-use) a paper towel and a good squirt of IPA.
b) (If really dirty, you can use Windex followed by Acetone followed by IPA, but that should only happen if you had used glue stick or other things on the bed and want to really clean it off). I do this if I am changing materials.

6) Get your Live Adjust Z dialed in real well.
a) Print using "Calibration_surface_PLA_75x75@200um_v4.gcode" found in Jeff's "Life Adjust My Way" Thread (Read through page 7 or so till you see the .v4 code. Look at the pictures.)
http://shop.prusa3d.com/forum/prusa-i3-kit-building-calibrating-first-print-main-f6/life-adjust-z-my-way-t2981-s150.html
b) Repeat until you have a nice test print - all stuck together and one nice clean sheet.

7) Do the PID calibrations for the bed and the extruder from the calibration menu. Note: Some users don’t like the PID calibration and feel it has caused problems. Others have had great luck with it.

8) Print a few of the included gcode files. Start with the Prusa logo. The gears are a great test and fun thing to have.

9) Start with a few things on Thingiverse that are easy. Learn how to use the slicer of your choice (I like Slic3r, but there are many options and opinions and all have pros and cons). Start with things that don’t need supports. Trust me, supports should come in after you have good confidence in your printer and yourself. I suggest a Benchy as a great test print to make sure your printer is dialed in correctly. https://www.thingiverse.com/thing:763622

10) Start designing your own things. Learn supports settings. Try different filament types.

Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage or loss. If you solve your problem, please post the solution…

Napsal : 10/08/2017 4:43 pm
Hobby Hoarder
(@hobby-hoarder-2)
Trusted Member
Topic starter answered:
Re: Z height varies wildly between prints (pic included)



I am quite confused. Your Live-Z value, IS the distance from nozzle tip to the PINDA. At 1.5mm, I am surprised you can do an XYZ Calibration. Maybe photos would help. Also, have you adjusted other parameters to get the filament to stick during the calibration?

Not exactly. The Live-Z allows you to fine-tune the distance between the nozzle and the bed. If what you are saying were true, then adjusting the Live-Z value would change the physical distance between the nozzle and the PINDA, which of course it doesn't, because both the nozzle and the PINDA are firmly fixed in their place.

Bed and nozzle temperatures are fine for the filament that I'm using. I don't see what else I could adjust and I'm using fairly standard Prusa settings (layer height, width etc.).

No. I am saying that the printer has no way of knowing what the distance is between your PINDA sensor and the nozzle, and no way of moving it, so you SET this value by setting Live-Z, informing the electronics where the nozzle is relative to the PINDA sensor (which can measure where it is relative to the build plate. Typical Live-Z values are between -0.500mm and -1.00mm, depending on how you have positioned your PINDA sensor. Values outside of that are an indication of a problem.

This, if set correctly, the Live-Z is the distance from your PINDA to nozzle. Since you feel those two values are differing by more than a 1mm I think something is wrong.

You may want to try the step startup-steps I have listed below.

--

Here is my starter advice for getting your printer going well, and avoiding some of the common frustration inducing issues.

0) Make sure the belts are tight, and all of the axises are free to move smoothly. Make sure the wire bundle coming out the back of the extruder is held high and does not droop down where it will hit the print when the extruder is at any height. Make sure the X and Y axis are as perpendicular as you can judge by eye.

1) Run the Self Test from the menu. Make sure everything is connected correctly.

2) Make sure PINDA is above nozzle tip by <1mm but above the nozzle. About 0.6mm is a good starting point (but anything between 0.5mm and 1.0mm is fine), which is about the thickness of a credit card. Place a sheet of paper on the bed, and run the XYZ Calibration from the menu. Stay with the machine, and watch it. As it hunts for the calibration points, watch if the paper moves. If it does, STOP THE PRINTER. That means the nozzle is dragging and the PINDA sensor is a bit too high, lower it and try again, but make sure it is still higher than the nozzle tip. Repeat until you have a good XYZ Calibration. (Note the instructions on the XYZ calibration, and make sure the nozzle tip is clean.)

3) Set your Live Adjust Z roughly correct.
a) Set Live adjust Z = 0.00. (XYZ Cal does this).
b) Do a Calibrate Z. (Head must be clean of drips and lumps).
c) Do a Home. This leaves the head at Z=0.15mm. DON’T SKIP THIS STEP.
d) Use Setting -> Move Axis X and Y to get in the approx center of the print space. DON’T TOUCH Z.
e) Put a piece of printer paper under the head. Printer paper is approx 0.1mm
f) Wiggle the paper while adjusting "Live Adjust Z" (in settings) until the paper just starts to drag on the paper.
g) Back off a bit (50) on the “Live Adjust Z"
NOTE: If your Live Adjust Z value is >1mm something is wrong. It should be approx the distance from the PINDA probe to the nozzle. Anything between 0.4mm and 1.0 should be fine. (Less than 0.4 means the PINDA probe might catch on some print that curles up a bit, greater than 1.0 means either you did something wrong, or are just barely in the PINDA’s detection range.}
Now you have set the nozzle approximately 0.15mm (paper +0.05mm) above the bed while the printer’s electronics think the Z is at 0.15mm.

4) Load some filament.
a) Make sure the tension screws are about 14mm from the body with no filament in the extruder. (This is looser than is intuitive for most people. Too tight or too loose will cause issues.)
b) Heat the extruder. You can do this with pre-heat or settings->temperature.
c) Use Load Filament from the menu. Continue until you have a nice thin strand coming from the extruder.
d) Cool it back down.

5) Make sure the bed is very clean.
a) Wipe with as pure an isopropyl alcohol (IPA) as you can find. The little toweletts are not enough in my opinion. Use (and re-use) a paper towel and a good squirt of IPA.
b) (If really dirty, you can use Windex followed by Acetone followed by IPA, but that should only happen if you had used glue stick or other things on the bed and want to really clean it off). I do this if I am changing materials.

6) Get your Live Adjust Z dialed in real well.
a) Print using "Calibration_surface_PLA_75x75@200um_v4.gcode" found in Jeff's "Life Adjust My Way" Thread (Read through page 7 or so till you see the .v4 code. Look at the pictures.)
http://shop.prusa3d.com/forum/prusa-i3-kit-building-calibrating-first-print-main-f6/life-adjust-z-my-way-t2981-s150.html
b) Repeat until you have a nice test print - all stuck together and one nice clean sheet.

7) Do the PID calibrations for the bed and the extruder from the calibration menu. Note: Some users don’t like the PID calibration and feel it has caused problems. Others have had great luck with it.

8) Print a few of the included gcode files. Start with the Prusa logo. The gears are a great test and fun thing to have.

9) Start with a few things on Thingiverse that are easy. Learn how to use the slicer of your choice (I like Slic3r, but there are many options and opinions and all have pros and cons). Start with things that don’t need supports. Trust me, supports should come in after you have good confidence in your printer and yourself. I suggest a Benchy as a great test print to make sure your printer is dialed in correctly. https://www.thingiverse.com/thing:763622

10) Start designing your own things. Learn supports settings. Try different filament types.

Thank you for your list of tips and suggestions.

I haven't read enough technical specs to argue your point, but I have a different understanding. I think that the PINDA probe detects the distance, but it's not accurate enough to be useful for printing. You then use the Live-Z to micro-adjust the distance between the nozzle and the bed, so that you get a nice sticky line. Maybe we're talking about the same thing from a different point of view.

In any case, I'm currently doing a print, so I couldn't put a tape measure behind, but you can see that the distance between the nozzle and the PINDA is set properly. Yet I still only need a Live-Z of around -0.100 for it to stick nicely. Maybe I'm doing something wrong here, but it seems to work and I've printed tons with this setting.

Napsal : 10/08/2017 5:20 pm
PJR
 PJR
(@pjr)
Antient Member Moderator
Re: Z height varies wildly between prints (pic included)

OK, so "Live Z Adjustment" is used to correct the probe setting in relation to the nozzle and it will be differ based on the responsiveness of the probe.

The "ideal" live Z adjustment is Zero. This would be the point where the probe triggers at exactly the point where the nozzle is 0.15mm above the bed.

But because probe responses differ and probe positions differ, Live Z is used to effectively correct both those things.

With earlier firmware, I used to be able to adjust my probes to get Live Z = Zero, but the later firmwares have changed and that is no longer possible. I do, however work with my probes set as high as possible and consistently passing XYZ calibrations.

My Current Live Z values are -250 on one printer and -400 on the other.

Peter

Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…

Napsal : 10/08/2017 6:40 pm
Hobby Hoarder
(@hobby-hoarder-2)
Trusted Member
Topic starter answered:
Re: Z height varies wildly between prints (pic included)


OK, so "Live Z Adjustment" is used to correct the probe setting in relation to the nozzle and it will be differ based on the responsiveness of the probe.

The "ideal" live Z adjustment is Zero. This would be the point where the probe triggers at exactly the point where the nozzle is 0.15mm above the bed.

But because probe responses differ and probe positions differ, Live Z is used to effectively correct both those things.

With earlier firmware, I used to be able to adjust my probes to get Live Z = Zero, but the later firmwares have changed and that is no longer possible. I do, however work with my probes set as high as possible and consistently passing XYZ calibrations.

My Current Live Z values are -250 on one printer and -400 on the other.

Peter

Thank you Peter for clearing things up. What you say confirms my thinking, I just couldn't explain it as elegantly.

I've resorted to simply waiting 15 minutes between prints, so that the PINDA probe cools down completely. I think this is having the best effect out of everything so far and the Live-Z is much more consistent now (+- 40).

PS:
It's great to see a fellow countrymen on the forum, thank you for all the help you're providing here.

Napsal : 11/08/2017 1:03 pm
PJR
 PJR
(@pjr)
Antient Member Moderator
Re: Z height varies wildly between prints (pic included)


Thank you Peter for clearing things up. What you say confirms my thinking, I just couldn't explain it as elegantly.

I've resorted to simply waiting 15 minutes between prints, so that the PINDA probe cools down completely. I think this is having the best effect out of everything so far and the Live-Z is much more consistent now (+- 40).

PS:
It's great to see a fellow countrymen on the forum, thank you for all the help you're providing here.

Petra

I don't have to wait between prints and I don't think it is particularly necessary. Only thing I would say that my printers are currently running in my office (basement) which is pretty much a constant 33 degrees.

Are you also from Slovenija? We shall be exhibiting our prints and demonstrating the printer in Tuš centre, BTC, LJ 17th to 19th of this month (I will be there on the 19th and after 18:00 on the other days).

Peter

Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…

Napsal : 11/08/2017 1:49 pm
Hackinistrator
(@hackinistrator)
Trusted Member
Re: Z height varies wildly between prints (pic included)

set your pinda height so your live z adjust is around 600-800 .
once you do that , lets see if your issue continues .
until you do that , there is no point to discuss how temperature or god knows what effects your pinda or whatever .
fact is , most users have same pinda probes , same beds and most get consistent prints with same z level adjust values (me also) .

Napsal : 11/08/2017 6:09 pm
Hobby Hoarder
(@hobby-hoarder-2)
Trusted Member
Topic starter answered:
Re: Z height varies wildly between prints (pic included)


set your pinda height so your live z adjust is around 600-800 .
once you do that , lets see if your issue continues .
until you do that , there is no point to discuss how temperature or god knows what effects your pinda or whatever .
fact is , most users have same pinda probes , same beds and most get consistent prints with same z level adjust values (me also) .

Hey Sergey, thanks for replying.

Could you please elaborate your thinking on why a higher Live-Z adjust would make a difference? 800 is almost at the upper limit. As I've mentioned in my previous response, the Live-Z is much more stable if I let the printer cool down vs. printing as soon as the last print is finished, so the temperature seems to have at least some effect.

Napsal : 11/08/2017 9:20 pm
Hackinistrator
(@hackinistrator)
Trusted Member
Re: Z height varies wildly between prints (pic included)


Hey Sergey, thanks for replying.

Could you please elaborate your thinking on why a higher Live-Z adjust would make a difference? 800 is almost at the upper limit. As I've mentioned in my previous response, the Live-Z is much more stable if I let the printer cool down vs. printing as soon as the last print is finished, so the temperature seems to have at least some effect.

your live z should be between -0.5 to -1mm , this will keep it above nozzle height , and not too far up .
you dont need too cool down the printer , the whole point of LIVE Z is to adjust it LIVE = when the printer is printing and hot .
the difference between hot or cold pinda reading is much smaller then the bed deformation from heating , so you should adjust your live z at the same bed temp level as your print .

are you doing your tests at the same spot on the bed?
if not , then all this is irrelevant . bed might have high and low spots that wont be detected by the sensor .

did you check if the pinda probe is centered right above the marked circle on the bed when homed ?

Napsal : 11/08/2017 11:03 pm
Hobby Hoarder
(@hobby-hoarder-2)
Trusted Member
Topic starter answered:
Re: Z height varies wildly between prints (pic included)



Hey Sergey, thanks for replying.

Could you please elaborate your thinking on why a higher Live-Z adjust would make a difference? 800 is almost at the upper limit. As I've mentioned in my previous response, the Live-Z is much more stable if I let the printer cool down vs. printing as soon as the last print is finished, so the temperature seems to have at least some effect.

your live z should be between -0.5 to -1mm , this will keep it above nozzle height , and not too far up .
you dont need too cool down the printer , the whole point of LIVE Z is to adjust it LIVE = when the printer is printing and hot .
the difference between hot or cold pinda reading is much smaller then the bed deformation from heating , so you should adjust your live z at the same bed temp level as your print .

are you doing your tests at the same spot on the bed?
if not , then all this is irrelevant . bed might have high and low spots that wont be detected by the sensor .

did you check if the pinda probe is centred right above the marked circle on the bed when homed ?

There seems to be some confusion about the Live-Z on the forums; it doesn't mean the height difference between the nozzle and the probe. If you'll look at my photo on previous page, you can clearly see that I have enough clearance between the nozzle and the PINDA probe (~1mm), yet my Live-Z is set to -0.110mm.

Yes, you do adjust the Live-Z when the printer is running, but it shouldn't have to be a repeat process at the start of every print. I am of course adjusting the Live-Z when the bed is hot. I don't think there's any other way, because the print doesn't actually start until it reaches a set temperature.

My test square is always in the centre, 50x50mm.

I've been reading a lot on similar issues and cooling down the probe seems to help in some cases.

Napsal : 12/08/2017 10:49 am
PJR
 PJR
(@pjr)
Antient Member Moderator
Re: Z height varies wildly between prints (pic included)

Your probe height seems to be correct.

Did you turn on the probe temperature calibration?

Peter

Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…

Napsal : 12/08/2017 11:48 am
Hobby Hoarder
(@hobby-hoarder-2)
Trusted Member
Topic starter answered:
Re: Z height varies wildly between prints (pic included)


Your probe height seems to be correct.

Did you turn on the probe temperature calibration?

Peter

No, I've never used that option and I've been reading opinions against it.

The only temperature calibration I did was of the nozzle.

Napsal : 12/08/2017 12:59 pm
AJS
 AJS
(@ajs)
Noble Member
Re: Z height varies wildly between prints (pic included)

I recall a discussion of having the heat break cooling fan pull rather than push air being a factor as it blow hot air (that flows past the heat break) against the PINDA probe.

Might be worth a try. Easy to test - just mount the fan backwards. I had mine mounted backwards for months with no issues.

Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage or loss. If you solve your problem, please post the solution…

Napsal : 12/08/2017 3:03 pm
PJR
 PJR
(@pjr)
Antient Member Moderator
Re: Z height varies wildly between prints (pic included)


I recall a discussion of having the heat break cooling fan pull rather than push air being a factor as it blow hot air (that flows past the heat break) against the PINDA probe.

Might be worth a try. Easy to test - just mount the fan backwards. I had mine mounted backwards for months with no issues.

There was a user on here who had accidentally mounted the extruder fan so that it was sucking. He was experiencing lots of blockages.

Peter

Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…

Napsal : 12/08/2017 4:50 pm
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