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random under extrusion

Posted by Gamemaker 
random under extrusion
May 17, 2019 02:36PM
Hi,
Since a few weeks i have randomly ampiering under extrusion (sometimes the first 2-5cm look perfekt before it starts and then it gets Bader with every layer).
Mostly after trying to print after Leaving the printer turned of for a day it`s more likely to have no under extrusion in the first few layers.


What I`ve tried:
-PID tuning
-changing driver current
-new stepper driver (after changing to a new one it worked for a single spiral vase print before starting again)
-changing temperature ( currently 210 C for PLA)
-testing different PLA filaments
-changing retraction
-cleaning the nozzle
-changing the flow rate
-tride to print with the second extruder (separate hotted) => still inconsistent extrusion

Thank you very much for your answers in advance,
Gamemaker

Edited 4 time(s). Last edit at 05/18/2019 10:56AM by Gamemaker.
Re: random under extrusion
May 18, 2019 12:54PM
I'd first go through the whole mechanical build and use a zero assumption strategy.
- is the hobbed bolt or gear slipping?
- is the tensioner too tight or too loose? Is the filament idler bearing still ok?
- extruder motor getting hot, skipping steps, makking loud noises?
- is the filament new, clean and the path clear of debris?
- is the step stick overheating?
- is the temperature of the hotend accurate? Did you check with a thermocouple? Is the temperature stable?
- is the diameter of the filament consistent?
- feel the filament motion during extruding, notice any jerkiness? Push or pull the cold end extruded filament, is it tight and consistent?
- put some filament in the hot end manually, is it easy to push it through?
- pull out the filament when heating up, this usually clears any debris blocking the nozzle.

- check anything that could come loose and remove any pkay or compliance in both extruder and z axis.
- print a 20x20 by 100mm high cube with varying temperatures from 150 to 215 degrees in steps of 5 to 10 degrees every 5 to 10 mm and see what prints most consistently.

After all that check the settings like max. Velocity, acceleration, jerk? Use really slow settings then bump it up until things start to get worse, then back it up a bit. Is the calculated steps per mm matching with actual settings?

Did you upgrade or downgrade the firmware and reset the eeprom configuration?


--
Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]
Re: random under extrusion
May 18, 2019 01:27PM
Hi,
Many thanks for the answer.
I double checked both extruders and hotends. Everything looks fine.
The second extruder and hotend i tried had been completely new an still the same problem (also i’ve used different pins on the rumba board).
The Extruder motors don’t skip any steps and don’t get hotter then normally.
The stepperdriver dosen’t even get warm (already replaced them but nothing changed).
Stepps per mm are perfect.
I’ll try out another software on and an calibration cube (but in my opinion the problem must be something else.
Thats because somethimes i get 8h spiralvasemode prints with perfect extrusion and then the next ame print is complete
trash)
Many thanks,
gamemaker

Edited 1 time(s). Last edit at 05/18/2019 01:28PM by Gamemaker.
Re: random under extrusion
May 19, 2019 04:36AM
Did you try a different psu? Maybe it's on its way out.

What about the coldbreak fan, the filament might get stuck if it's not spinning or not moving enough air through it.

What type of stepper driver are you using? The drv8825 has some trouble at low rpms for example, which can cause problems when using it as extruder driver.


--
Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]
Re: random under extrusion
May 19, 2019 05:03AM
Hi,
I’ll try a new Psu. The coldbreak fans are working normally and the coldbreak dosent get warm.
Currently I’m running DRV8825 stepper drivers. I already replaced my old ones with brand new ones but it only worked fine
For a 10h spiralvasemode print after that the problems came back. Infact of this I consider the motionboard to be damaged.
That’s because the problems first showed up after shipping the printer on bumpy roads. And like you suggested i tried tifferent extrudrr temperatures but there had been no visual difference between the 170C and 220C (on both extruders nothing changed).
Tomorrow I’ll get S3D and test it out (but GCodes which worked fine before underextrusion won’t work now tho it can’t be infact of an bad slicer).
Another thing i tried out yesterday where the new Software (updatet Marlin) but no difference.
Thank you very much,
Gamemaker
Re: random under extrusion
May 19, 2019 05:22AM
Quote
Gamemaker
Hi,
I’ll try a new Psu. The coldbreak fans are working normally and the coldbreak dosent get warm.
Currently I’m running DRV8825 stepper drivers. I already replaced my old ones with brand new ones but it only worked fine
For a 10h spiralvasemode print after that the problems came back. Infact of this I consider the motionboard to be damaged.
That’s because the problems first showed up after shipping the printer on bumpy roads. And like you suggested i tried tifferent extrudrr temperatures but there had been no visual difference between the 170C and 220C (on both extruders nothing changed).
Tomorrow I’ll get S3D and test it out (but GCodes which worked fine before underextrusion won’t work now tho it can’t be infact of an bad slicer).
Another thing i tried out yesterday where the new Software (updatet Marlin) but no difference.
Thank you very much,
Gamemaker

When using the DRV8825 steppers I've understood that there can be issues in many cases when used in 3D-printers. If the problems persist you could try out the diode-fix. [forum.vellemanprojects.eu]

I ordered 5 premade boards from Aliexpress last week to try and see if they can fix the DRV8825's behavior, as I tried them out last week and wasn't happy with the performance. Maybe those could be a solution for you as well. Or you can make the diode board yourself. Even though I don't think we need a board for this and the diode fix can also be integrated into the cables.

Anyway, if your new PSU doesn't solve the problem, maybe try out the diode fix as I've understood it can fix a whole host of problems when it comes to the DRV8825's.


http://www.marinusdebeer.nl/
Re: random under extrusion
May 19, 2019 05:42AM
Hi,
Thank you for your answer. I had a quick look on that diode fix and I might try it out if the new PSU doesn’t work.
But in my opinion the problem must be the Rumba motionboard or the PSU because everything worked quite fine till the shipping.
And after replacing the stepperdriver after shipping and only an better result for 8h and than starting to underextrude again.
Therefore i think its the rumba board kinda killing the stepperdrivers.
But i definitely try a new PSU tomorrow.
Sincerely,
Gamemaker
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