Printer no longer working  

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frank.w15
(@frank-w15)
New Member

Hey everyone, I'm hoping I can find some help as my Prusa MK3 has recently stopped printing correctly. I've had it for a few months (it came assembled) and has been working perfectly.

2 days ago however I tried to print a fairly basic model and about half way through the print alignment went off, and it started printing the rest of the model about 2cm off from the correct position. I stopped the printer and started again, now nothing seems to print and I end up with blobs and strings of plastic everywhere.

I did some Googling and:

- Made sure the heat bed was clean

- Switched back to using the original PLA supplied with the machine

- Tried increasing the heat of the heat bed

None of this worked so I ran the calibration controls and found they are now failing (they passed when the machine arrived). Doing the XYZ calibration the piece of paper under gets dragged around so I power it off and I'm not sure what to do.

Running the Z calibration resulted in this:

I have no knowledge about how to fix this and have been searching for hours, I would be greatful any help and please excuse my lack of knowledge in this area.

Thank you

- Frank 

Posted : 27/04/2019 9:50 pm
Tim
(@tim-m30)
Illustrious Member

Dirty bed is one of the issues - sorry, but the symptoms fit the issue.

Dragging the paper can be the result of debris on the nozzle. Heat it up and use a paper towel to clean off any plastic ooze.  Probably not a bad idea to unload the filament before running the calibration wizard.

Once the xyz cal is completed, do a hot water wash of the bed using a paper towel to scrub, no dish rags or sponges. Very hot water, rinse well, and do not touch the PEI print surface with your fingers nor use alcohol to clean the bed after a wash. Dry with a fresh paper towel.

Run the internal first layer cal to get the basic level down.  Then print a full test pattern that has enough area to allow on the fly adjustment.

 

Here's the issue: the bed gets dirty, filament stops sticking, you try adjusting layer 1 to compensate, it works a few times, but eventually stops working. Filament now blobs onto the nozzle and drags any stuck filament off the bed. More tweaks are made in an effort to "fix" the problem. 

In the end a full factory reset and calibration is the simplest and safest way to get back to a known condition.  Part of that is knowing the bed really is clean: soap and hot water is what works.  Acetone on an old bed might help AFTER a good wash, since acetone removes oxidized PE that accumulates with heat and time. But you can use acetone BEFORE a wash, too, and be sure you didn't leave oils sucked off your fingers by the acetone.

It is always wise to get more than one opinion......
Posted : 28/04/2019 5:40 am
bobstro
(@bobstro)
Illustrious Member
Posted by: frank.w15

[...] Running the Z calibration resulted in this.

As @tim-m30 says, cleaning the bed is the first and most important step. After doing that if you have not already done so, try using Jeff Jordan's "Life Adjust" procedure for calibrating your Live-Z setting. It is much easier to use and understand than the on-board routine. 

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 : 28/04/2019 7:20 am
toaf
 toaf
(@toaf)
Noble Member

is it still printing 2 cm off?

do the soap and water trick on the plate, and maybe change the nozzle I can see 2 months making a nozzle bigger or dirtier.

I have a Prusa,therefore I research....
Posted : 28/04/2019 7:44 am
Vojtěch
(@vojtech-p6)
Honorable Member

If your XYZ calibration is failing by dragging the paper, there is a simple step needed that's not documented well. 

Lower the P.I.N.D.A probe.

Simply loosen the screw on the probe holder and move the probe down by one or two thread turns. If this is not sufficient, repeat.

It's likely the probe hit the model back when you got your first major failed print and moved up in the mount.

I expect that once the XYZ calibration succeeds, you'll be also able to complete the First Layer calibration successfully. If the probe is positioned correctly (just slightly above the nozzle tip height), you'll get Live Z (First Layer Cal) values between (negative) -0.700 to -1.500. 

This post was modified 1 year ago by Vojtěch
Posted : 28/04/2019 9:13 am
milos.v
(@milos-v)
Reputable Member

I strongly recommend as well the "soap and water trick" it sounds stupid, especially when you are using Aceton or IPA. But I can confirm, it makes a difference. I also lost adhesion, suddenly, one PLA print perfect, 20 minutes after same filament, same settings, nothing stayed on the bed, never ever. Nothing other helped. It is easy and working.

Milos

Posted : 28/04/2019 9:47 am
frank.w15
(@frank-w15)
New Member
Posted by: tim.m30

Dirty bed is one of the issues - sorry, but the symptoms fit the issue.

Dragging the paper can be the result of debris on the nozzle. Heat it up and use a paper towel to clean off any plastic ooze.  Probably not a bad idea to unload the filament before running the calibration wizard.

Once the xyz cal is completed, do a hot water wash of the bed using a paper towel to scrub, no dish rags or sponges. Very hot water, rinse well, and do not touch the PEI print surface with your fingers nor use alcohol to clean the bed after a wash. Dry with a fresh paper towel.

Run the internal first layer cal to get the basic level down.  Then print a full test pattern that has enough area to allow on the fly adjustment.

 

Here's the issue: the bed gets dirty, filament stops sticking, you try adjusting layer 1 to compensate, it works a few times, but eventually stops working. Filament now blobs onto the nozzle and drags any stuck filament off the bed. More tweaks are made in an effort to "fix" the problem. 

In the end a full factory reset and calibration is the simplest and safest way to get back to a known condition.  Part of that is knowing the bed really is clean: soap and hot water is what works.  Acetone on an old bed might help AFTER a good wash, since acetone removes oxidized PE that accumulates with heat and time. But you can use acetone BEFORE a wash, too, and be sure you didn't leave oils sucked off your fingers by the acetone.

Thanks Tim,

Unfortunately this cleaning approach is something I tried, using warm soapy water, a paper towel and then using the supplied cleaning wipe that came in the box afterwards. I don't believe I can get it any cleaner.

After all this I ran the factory reset and went through the steps to calibrate, but get to the point where the paper is dragged around by the machine.

At this point I'm wondering whether the paper is meant to be dragged around? It's not being ripped or folding, it simply moves around with the nozzle so I switch the printer off as instructed. Should I just allow it to continue and forcibly hold the paper still?

 

 

Posted : 29/04/2019 9:10 am
frank.w15
(@frank-w15)
New Member
Posted by: bobstro
Posted by: frank.w15

[...] Running the Z calibration resulted in this.

As @tim-m30 says, cleaning the bed is the first and most important step. After doing that if you have not already done so, try using Jeff Jordan's "Life Adjust" procedure for calibrating your Live-Z setting. It is much easier to use and understand than the on-board routine. 

This seems useful, but I've know idea how to "change the life Z adjustment level in the middle of the print" as it requires?

Posted : 29/04/2019 9:12 am
frank.w15
(@frank-w15)
New Member
Posted by: toaf

is it still printing 2 cm off?

do the soap and water trick on the plate, and maybe change the nozzle I can see 2 months making a nozzle bigger or dirtier.

It only did that once (the first time) and I've not been able to get it to print anything long enough since to see the issue again.

Posted : 29/04/2019 9:13 am
toaf
 toaf
(@toaf)
Noble Member

the paper should not be dragged around. if you are holding it.

can you run the Z all the way to the top, and make sure it's level? I forget what calibration that one is. off hand.

it should goto top and try to move up more then it physically can.

also maybe heat it up and try to run filament by just moving the extruder motor. see if its running even, or if there is a clog.

I have a Prusa,therefore I research....
Posted : 29/04/2019 9:30 am
Tim
(@tim-m30)
Illustrious Member

In the LCD menus there is a line called Live-Z Adjust ... you start a print, and as the printer is laying down Layer 1, you select that menu, and you get to the Z-Offset value and can adjust it.

The idea is you are doing a sacrificial print, something with a large area layer 1, so you have time to make a good adjustment, see the results, and still have time for more adjusts.  Much better than trying to do an adjustment on a single line you can barely see.

Suggest you read the entire post ... most folk who follow that guide are pretty happy they did.

It is always wise to get more than one opinion......
Posted : 29/04/2019 9:34 am
Vojtěch
(@vojtech-p6)
Honorable Member
Posted by: frank.w15

This seems useful, but I've know idea how to "change the life Z adjustment level in the middle of the print" as it requires?

Click button, go to Tune -> Live Z Adjust.

Posted : 29/04/2019 9:50 am
Vojtěch
(@vojtech-p6)
Honorable Member
Posted by: frank.w15

At this point I'm wondering whether the paper is meant to be dragged around? It's not being ripped or folding, it simply moves around with the nozzle so I switch the printer off as instructed. Should I just allow it to continue and forcibly hold the paper still?

The paper is there to protect the heatbed from getting scratched. If it's moved around, it means the nozzle tip is dangerously close. You can proceed, but the risk of a scratch is there. To fix this, simply move the PINDA probe a bit lower (0.5mm) in the mount - there will be no paper movement the next time you do the calibration.

The reason is that the printer needs to find the calibration spots using the probe. If the probe is too high, it will not 'see' the points until the nozzle tip is way too close. Making the vertical difference between the nozzle tip and the probe smaller fixes the problem. If it's too small, however, or if the probe is lower than the tip, it'll hit the model during printing. So a good balance is needed.

Posted : 29/04/2019 9:54 am
Tim
(@tim-m30)
Illustrious Member
Posted by: frank.w15

Thanks Tim,

Unfortunately this cleaning approach is something I tried, using warm soapy water, a paper towel and then using the supplied cleaning wipe that came in the box afterwards. I don't believe I can get it any cleaner.

After all this I ran the factory reset and went through the steps to calibrate, but get to the point where the paper is dragged around by the machine.

At this point I'm wondering whether the paper is meant to be dragged around? It's not being ripped or folding, it simply moves around with the nozzle so I switch the printer off as instructed. Should I just allow it to continue and forcibly hold the paper still?

The cleaning wipe just added muck to the bed ... especially true if alcohol based.   Wash in soap and water and dry with a paper towel, do not touch the bed surface with fingers or anything else.  You almost need to be OCD about this.  After a while, you'll start to realize just how sensitive PLA is to contamination.  Alcohol and acetone are useful, but not needed often, and they are not useful for getting fingerprints and common dirt off the bed.

The paper is a guide to let you know you have clearance. I can hold the paper and it doesn't move or tear.  I have had a nipple of plastic form on the nozzle that did tear the paper, but I immediately stopped the cal and found the problem and cleaned off the nozzle. If your nozzle is clean, and it still wants to drag the paper or tear it, the PINDA is too high and should be adjusted. I always refer folk to the assembly manual - you don't want to take short cuts here - the nozzle can dig into the fiberglass and cut the heating layer. 

 

This post was modified 1 year ago by Tim
It is always wise to get more than one opinion......
Posted : 29/04/2019 10:19 am
Tim
(@tim-m30)
Illustrious Member

And to follow up with what Voj is saying: there are four metal disks embedded in the heat bed fiberglass at precise spacings. The printer uses the PINDA probe to home in on each spot, and records the steps from 0,0,0 (home) to precisely calibrate the X and Y axis.  You can print a 25 mm cube and it will be 25 mm on X and Y with really good accuracy. Z axis is good, but not so much.  Z depends on the lead screw turns and trapezoid nut backlash can cause a small error. It's common to see as much as a half mm error in part height.

It is always wise to get more than one opinion......
Posted : 29/04/2019 10:30 am
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