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cdduncan
(@cdduncan)
Active Member
Extrusion problems?

Hello

I just finished assembly of an MK3s yesterday and am having a hard time getting the bugs out. 

The most common problem I am having is what appears to be missing layers or poor extrusion. 

I have been trying to print the Prusa logo from the SD card as I figure it is simple and doesn't introduce mistakes from me in slicing. 

The two blue prints were made without any adjustments. The print quality is ok every few prints but is mostly bad. 

I have changed the extruder tension screw several times. At this point I'm just leaving the head flush with the body per the instructions. 

I have tightened the y-axis belt. 

I have adjusted the PINDA higher and reran the calibration wizard (live z is now -1.2). 

I did a cold pull in case there is a clog. 

The z-axis looks fine. The smooth rods are solidly in the end caps. I do get a forced z-axis calibration every few prints. Also, crash detection has happened a few times. It isn't able to recover and the nozzle just digs into the print. 

I have used two different filaments. Both PLA. Both Prusament. 

The first layer looks ok to me. It rarely has a problem with the first layer. It is usually when the z-axis gets above 1 that problems occur. 

Any more troubleshooting tips would be appreciated!

 

 

Posted : 21/07/2019 4:22 pm
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(@)
Illustrious Member
RE: Extrusion problems?

Power off - do the x and y axis move freely without any drag?  If you tilt the printer, the bed should slide forwards or backwards on its own.  The extruder takes a bit more tilt, but should also move freely side to side.

If any stiction is felt - catches or points of drag, you have an assembly problem.  Also, did you lubricate the bearings before installing them? Did you over tighten the bed bearing U=bolts? Have you tried loosening the extruder house screws that clamp the bearings?

Are both X and Y drive gears attached flat first?  

Posted : 21/07/2019 5:31 pm
cdduncan
(@cdduncan)
Active Member
Topic starter answered:
RE: Extrusion problems?

I also checked the alignment of the filament to the gears and made sure the screw was tight on the flat part of the motor axle. 

Posted : 21/07/2019 5:32 pm
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(@)
Illustrious Member
RE: Extrusion problems?

If these are gcodes from the SD card, and not something you have sliced, it is a build problem or a defective part.

PLA not adhering to prior layers (what photo 1 looks like) is either layer height or temperature.  What does the screen show for extruder temp as thi sis happening?  Should be 210 to 215c.  Might also be friction stalling the X motor.

...

If these are parts you sliced, which slicer and profiles did you use?

 

This post was modified 2 years ago by --
Posted : 21/07/2019 5:37 pm
cdduncan
(@cdduncan)
Active Member
Topic starter answered:
RE: Extrusion problems?

The temp is set at 215 and seems to stay there. 

The y-axis moves freely when tilted. The x-axis can be manually moved but will not move when tilted. 

I did not lubricate the bearings because I thought the came lubricated. They have left a thin film of grease on the smooth z rails. 

 

Posted : 21/07/2019 5:44 pm
cdduncan
(@cdduncan)
Active Member
Topic starter answered:
RE: Extrusion problems?

These are the gcode from Prusa pre-loaded on the SD card. 

Posted : 21/07/2019 5:45 pm
cdduncan
(@cdduncan)
Active Member
Topic starter answered:
RE: Extrusion problems?

The problem seems to consistently occur after the first few layers. Does that suggest a problem with the z-axis?  I loosened the motor covers and went through the calibration again. 

Thanks

Posted : 21/07/2019 6:24 pm
cdduncan
(@cdduncan)
Active Member
Topic starter answered:
RE: Extrusion problems?

Sorry for all of the posts but trying to check off all of the possible problems.  After loosening the motor covers on the z-axis, I went through calibration again.  When I ran the first layer calibration, the nozzle was too close to the print bed (first picture / link).  I ran the calibration again without changing any settings and it came out fine.

I may be suspecting the wrong culprit (this is my first 3D printer) but the z-axis may be the most likely culprit?  When I get a z-axis calibration enforced error, it seems that the right motor is consistently lower by just a tad.  I only get this enforced calibration occasionally.  The z-axis seem to turn fine by hand.  I took them off the lower mount to loosen the covers and they seem to be installed fine.  The smooth rods with the bearings are tight in the brackets.  I have run the calibration wizard about four times now and haven't had any problems.

https://photos.app.goo.gl/EDSmzMQXryreLnkK7

First Layer Calibration #1

 

https://photos.app.goo.gl/YheL2XmtjbdCdYcB6

 

First Layer Calibration #2

 

 

Posted : 21/07/2019 7:02 pm
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(@)
Illustrious Member
RE: Extrusion problems?

The X-axis does look like it is stalling - making too short a movement both directions. You should be able to move the extruder side to side with little effort. And it should not have any sticky points along the full path.  Try loosening the extruder screws near the bearings. Just enough to hold the extruder from wobbling, but so they aren't torquing down on the bearings.

....

The way to calibrate Z is to move the extruder up until it jams into the top stops long enough both motors are stalling.  If assembled right, this ensures the X-Axis is level with the bed.  It sounds bad when it is happening, but it is intentional.

If one motor is turning and the other stalling after a top calibration, it is usually the dust nut or a bad T-nut. Dust nuts should be well above the motor.  T-nuts are easily damaged when people bolt them to the brackets then try to put the X-Axis on to the z-screws ... they cross-thread and are damaged.

 

Posted : 21/07/2019 9:02 pm
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(@)
Illustrious Member
RE: Extrusion problems?

I can add there was a recent defect in the firmware that is similar to what you are describing.  Supposedly fixed, but hey - it's open source and anyone's guess.  

But that thread suggested doing another Calibration:Calibrate Z Axis from the menus to see if that has any effect.

Posted : 21/07/2019 9:10 pm
cdduncan
(@cdduncan)
Active Member
Topic starter answered:
RE: Extrusion problems?

Tim, thanks for taking the time to help me troubleshoot.

I had a crash detection where it looked like the extruder was rotating on the x-axis when it was hitting the bed, so I tightened the screws up some.  I'll back them off a little.

I have calibrated the z-axis through the menu a few times and it hasn't had an impact.  I started another print (triceratops with Prusa supplied gcode).  It started fine and then around the z-axis ~2.0 it started 'skipping' lines.  I was watching it and it looked like material was still coming out of the extruder but the nozzle was too high for it to bond to the previous layer.  It would string across the bed and eventually adhere.  This happened in a couple of layers and then it seemed to fix itself.  After another 15 mins or so, it started doing it again.  I included pictures throughout this failed build, a video of the z-axis calibration and a video of me tilting the printer with the power off.

I loosened the dust caps about ~1-2mm above the z-axis motors with no effect.  The t-bolts went on pretty smoothly for me but I'll check them again.  When the z-axis does its calibration, both motors do stall at the top but the left one seems to get to the top before the right one by a few mm.  Thanks again.

Pictures and video:

https://photos.app.goo.gl/ibLJ1MNnEMeqd1kQ9

 

Posted : 21/07/2019 10:25 pm
cdduncan
(@cdduncan)
Active Member
Topic starter answered:
RE: Extrusion problems?

Took the t-bolts off.  They were fine - unscrewed from the z-axis smoothly.  Raised the dust caps more.  With the t-bolts off, I raised and lowered the extruder x-rail by hand.  Felt smooth the entire length of the z-axis.  Loosened the bolts holding the extruder on the x-axis slightly.  Went through the wizard and calibrated the first layer.  No luck.  Still skipping lines.

Posted : 22/07/2019 1:09 am
cdduncan
(@cdduncan)
Active Member
Topic starter answered:
RE: Extrusion problems?

During a print the printer went into a forced z-axis calibration. It took several attempts for it to get the rail to the top for calibration. I took a video of it and out it in the album of printing problems. With the t-bolts removed the rail moved smoothly by hand. I'm not sure what to check next. 

https://photos.app.goo.gl/ibLJ1MNnEMeqd1kQ9

 

Posted : 22/07/2019 2:41 am
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(@)
Illustrious Member
RE: Extrusion problems?

It may not hurt to loosen the screws holding the top Z-axis brackets and see if they are properly fitting the rods and screws and not binding.  But it's a bit odd that the first issue seems to be X-Axis binding ... that may account for the bad layers, but it doesn't account for the Z-axis failure to move to the top. 

So the number of issues makes me wonder if something else isn't going on. Bad CPU, power supply, etc. At this point I suggest you log in to the Prusa store and open a chat session; see if the Prusa techs can give you a clue.

Posted : 22/07/2019 7:08 am
cdduncan
(@cdduncan)
Active Member
Topic starter answered:
RE: Extrusion problems?

Thanks.  I sent them an email.  I couldn't find a link to start a chat.  I'll circle back with my solution if that ever happens.  Thanks again!

Posted : 22/07/2019 2:09 pm
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(@)
Illustrious Member
RE: Extrusion problems?

You'll be waiting for weeks with email. CHAT is the best option. And you MUST be logged in to see the tab.

Posted : 22/07/2019 2:26 pm
cdduncan
(@cdduncan)
Active Member
Topic starter answered:
RE: Extrusion problems?

Thanks, I wasn't logged in.  We didn't solve it in the first chat session so now I am relegated to email as we troubleshoot.  A factory reset and firmware flash seemed to make the problem worse.

I'll follow up with what the ultimate solution is in case that helps anyone else.  Their support seems to be pretty busy right now.

Trying to calibrate the z-axis after a factory reset and firmware install:

https://photos.app.goo.gl/7K8rmosxrw62cK1m8

A couple of videos showing some of the assembly in case I messed up:

https://photos.app.goo.gl/V4gAivnqxjvxxA8SA

https://photos.app.goo.gl/ZdQbQ5cTmxsVk7Wy7

 

Posted : 25/07/2019 4:03 am
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(@)
Illustrious Member
RE: Extrusion problems?

It looks pretty obvious from the video your X-Axis is skewed which will jam Z-Axis.  That and/or your Y-Axis rods aren't set in the holders properly so the bed is canted off the frame (hard to say, just something to check). It also looks like the pressures you are applying to move the axis are very high, and both X and Y are binding in places.  Axes should move freely with very little pressure.  And your Z motor dust covers look like they are too close to the motors.  They should be a mm or two above the motor - definitely NOT touching.  The up side is you have some of the smoothest T-nuts I have seen. Wish mine spun that easily.

And it appears your rods and bearings are devoid of grease. You should add that to the list of to-dos.

Measure the height the left and right X-axis brackets are off the motors (blue), and the height the X-axis rods are off the bed (gray).  They should be equal, any delta between sides shows a skew that needs to be addressed.  Normally, when Z is "calibrated" the motors move the axis to the top and hammer on it for a bit forcing the two sides to into level (top brackets are crucial). 

If all else fails, find an old copy of 3.4 - 3.6  firmware and flash it to the printer, do the EEPROM clearing All Data factory reset and run through the wizard again.  I have no knowledge of known issues, but I have a growing suspicion there are ghosts in v3.7.x firmware.

And let's hope someone else comes along with better observational skills and sees something obvious.

Posted : 25/07/2019 7:43 pm
Dave Avery
(@dave-avery)
Honorable Member
RE: Extrusion problems?

my test for X axis tram is to raise the X axis above the bed until i can slide something rigid between the X rail and the bed( i use a CD case). the gap between the bed and the rail should be the same from side to side. if not either the bed is not level to the frame or the Z top ends are not the same height above the frame

Posted : 25/07/2019 7:50 pm
cdduncan
(@cdduncan)
Active Member
Topic starter answered:
RE: Extrusion problems?

Thanks.  I will look into those suggestions.  I had moved the dust caps off the motors but it is hard to see in the picture.  I'll double-check the level of the x-axis and loosen the belts a little.  When I was first troubleshooting, I saw advice that the moving the y-axis should cause the lcd screen to flicker.  Mine did not at first, so I tightened the belt a little.  The belt numbers in the support menu are within range but if the x-axis is supposed to move just by tilting the machine, mine is too tight.

Prusa support had me check the PINDA and do report the 7x7 array from mesh bed leveling.  Both of those checked out fine based on their guidelines.

When I was performing the bed leveling, it would always fail at one of the points and force a z calibration.  I did not have the PEI sheet on the heatbed.  Once I put the PEI sheet on it did the bed leveling with no problems.  Is that normal?

Posted : 25/07/2019 7:57 pm
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