My Spring Steel Smooth sheet has been totally wrecked by inaccurate Live-Z adjustments
 

My Spring Steel Smooth sheet has been totally wrecked by inaccurate Live-Z adjustments  

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g.j.sieben
(@g-j-sieben)
Eminent Member

Hello,

I've had this problem too many times to remember, and it's really frustrated me and "come to a head" today. I will very frequently have an issue where the nozzle is printing the filament a little too high to stick on the first layer. Not too much, but a little bit. So, I'll adjust the Live-Z until the first layer is printing nicely. And the first layer will then continue printing and will look splendid. It looks like a perfect calibration throughout the rest of the first layer and upward. And then, on the very next print, the head will go too low, and will leave either a) a disastrously bad and super low first layer and/or b) a dented/scraped spring sheet.

It came to a head today when I tried printing some board game pegs. The first layer looked beautiful after some slight adjustment, and the rest of the pegs printed very well. I had 16 pegs on the tray, and so I got the height dialed in after the 2nd peg, so the remaining 14 had almost perfectly smooth first layers, and I was happy. I then had to leave for work, but started a second batch just before I left, but didn't have time to watch the first layer. It's all calibrated and dialed in, right? And these pegs are thin and only take about an hour to print, so worst case scenario, there's a bundle of filament tumbleweed somewhere, right? WRONG! It gouged the perfect shape of my pegs into the sheet! So now, well, both sides of my spring steel sheet are damaged. One with peg outlines, the other side with a failed calibration attempt and the shape of a hexagonal part where this happened as well.

Has anyone else had this happen, and if so, what can be done to avoid it? Also, I will be contacting Prusa Support tomorrow about a replacement, because this is (as far as I know) not my own fault and is a design issue. Also, take a look at that scratching!

Failed Calibration Hexagon and Calibration Line problem

 

Posted : 14/02/2020 2:07 am
bobstro
(@bobstro)
Famed Member

It's not formally documented anywhere, but you do need to let the on-board Live-Z calibration complete at least once. My understanding is that this sets a flag in nonvolatile storage indicating it has been calibrated. Until you do so, Live-Z may drift. You need to do this once per selected sheet.

Personally, I run through the on-board routine quickly to meet this requirement, then go with Jeff Jordan's "Life Adjust" procedure for actual Live-Z calibration whenever swapping nozzles thereafter.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 14/02/2020 2:19 am
g.j.sieben
(@g-j-sieben)
Eminent Member
Posted by: @bobstro

It's not formally documented anywhere, but you do need to let the on-board Live-Z calibration complete at least once.

Is this the First-Layer Calibration under the Calibration menu? Because I have not been doing that. I've just been adjusting Live-Z because the UI makes it look like the same thing.

Also, just curious, because this was undocumented, do you think I have a legitimate warranty claim for my wrecked sheet? (The dent in image #2 was actually caused by my first MINDA probe failing during calibration, so that is also somewhat their fault.)

EDIT: I did do a full calibration when I got the printer, but not afterwards.

This post was modified 5 days ago by g.j.sieben
Posted : 14/02/2020 2:23 am
bobstro
(@bobstro)
Famed Member
Posted by: @g-j-sieben\

Is this the First-Layer Calibration under the Calibration menu? Because I have not been doing that. I've just been adjusting Live-Z because the UI makes it look like the same thing.

Just realized you're on a Mini. All the posts bubble up on my 1st page, so missed that. I do believe, though, that it works the same way on the Mini as the Mk3. You need to go under the calibration menu and do Live-Z. Someone with a Mini will have to confirm.

Also, just curious, because this was undocumented, do you think I have a legitimate warranty claim for my wrecked sheet? (The dent in image #2 was actually caused by my first MINDA probe failing during calibration, so that is also somewhat their fault.)

Doubtful, but you can try. I contacted support when my powder-coated textured sheet would not adhere out of the box, and the immediate response was "it's a consumable". 

EDIT: I did do a full calibration when I got the printer, but not afterwards.

That should have set the flag. Does the Mini have support for multiple sheets? If so, you need to do it for each sheet. (Note that this is all subject to change with each firmware release. Also, if you update firmware, it's often worth recalibrating.)

 

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 14/02/2020 3:06 am
g.j.sieben
(@g-j-sieben)
Eminent Member

@bobstro

Yep, I am on the Mini.

The main problem I have is that I did Live-Z adjustment. It was printing beautiful first layers. Then I print again, and boom - it's an overly low scraper mess. I didn't change the Live-Z. I didn't recalibrate from the last print. It was printing beautifully, and then on the very next print, it wrecked the plate. That can't be right. I did not change sheets or flip the sheet. 

And by beautifully, it was truly an amazing first layer. Something you'd post on reddit. Perfect adhesion, perfect corners, not too low or high, just awesome. It was crushing to see the ruined plate returning home after the very next print. I'm almost going to blame the firmware, but stuff like this has happened on all releases so far.

This post was modified 5 days ago 2 times by g.j.sieben
Posted : 14/02/2020 4:09 am
bobstro
(@bobstro)
Famed Member

I'd contact support to see what's up. Live-Z should not be drifting!

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 14/02/2020 6:35 am
michalrakowiecki
(@michalrakowiecki)
Active Member

I have exact same problem with z offset. I will dial it perfect for one print write the numbers down. Next print it will print really bad like it would be to high and I will adjust live z to compensate. Next print after this one nozzle is to low and I will go back to the previous figures that I have written down and they will be spot on. Weird almost like Minda probe would measure it wrong every second print. This is why they have to give us the ability to stop bed leveling with every print. 

Posted : 14/02/2020 8:01 am
PJR
 pjr
(@pjr)
Antient Member Moderator

As the probe does not have temperature sensing, you need to be consistent when starting a print.

I auto-home then preheat the bed for 5 minutes with the probe in the centre before I start a print which does really help with preventing Live-Z drift.

 

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…...
Posted : 14/02/2020 8:53 am
Strankler
(@strankler)
Active Member

We had this problem, too. No only once. Also, a lot of others MINI owners were struggling with this. Just take a look here in the forum, you will find several threats about this. One of a few examples: Z Height Calibration Seems to not hold between prints

 

Mostly the problem is caused by a not proper working MINDA, at least in our cases this was the reason. Problem was always gone after replacing the MINDA - until the MINDA, in particular the cable broke again... We are currently running on MINDA No. 4.

 

The confusing thing is, that the MINDA cables doesn't brake completely, but only some braids of the wire. This gives inconsistent results in probing, but anyhow it gives results, which are interpreted as valid results for the printer software.

My belief is the braids of the cable are made of a very soft copper alloy, which tend to brake very easily.

Prusa already designed new parts for guiding the MINDA cable, which avoids too much bending, and with these parts our printer didn't brake the current MINDA cable - for now.

 

So contact Prusa support and describe your problem. I belief they will assume a broken MIDA cable, too and send you a new one. Also mention the damaged sheet, they will probably send a replacement, too.

 

Bob

Posted : 14/02/2020 1:01 pm
g.j.sieben
(@g-j-sieben)
Eminent Member

Hello!

A quick update: Prusa agreed to send another new MINDA probe and a new steel sheet, which is about the best possible outcome this could have.

On a side note, I just began trying to print on a textured sheet I recently bought, and was watching that Live-Z like a hawk. I had to begin the print at -1.100 adjustment, which is insane because it needed to be printed at -1.845 the night earlier! Can't wait to get the new probe...

Posted : 15/02/2020 4:12 am
crawlerin
(@crawlerin)
Reputable Member

@g-j-sieben

Wow, your Z jumps around like bowling ball on a trampoline. And I complain when I have to set it by  0.0x mm when it's warm between prints LOL.

Hopefully new set sorts it for you.

Posted : 15/02/2020 1:40 pm
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