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Jonathan
(@jonathan-5)
Active Member
Stepper noise (extruder?)

Hello there,

 

I recently upgraded my old mk2 to a fresh new mk2.5s (without superpinda because it has been out of stock for 2 months now).

But since I improved the dampening around the printer and it became a lot less noisy (even without the 24v trinamics), I suddenly noticed a sound that I knew was there with the mk2 but it is much more noticeable now. I've attached a video with sound and if you listen closely you can hear a quick soft knocking noise that almost sounds like purring from a cat but also like a dampened rollercoaster lift system. It appears to be relatively random but there are frequency patterns in the noise.

 

Is my extruder stepper end of life? Or did the software change the stepper driver behavior? (I'm running 3.9.1 since I don't have the superpinda yet) The printer prints pretty normal as far as I can see. Perhaps a little under extrusion during infill with flex. The bondtec drive is properly lubricated and the grip on the filament is excellent. Also I don't see any thermal runaway or temperature drops during printing.

Does anyone recognise the knocking sound?

 

Thanks!

 

Kind regards,

 

Jebs

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Posted : 01/04/2021 5:23 pm
Diem
 Diem
(@diem)
Noble Member
RE: Stepper noise (extruder?)

Change the infill pattern: do you get the same noise now?

Cheerio,

Posted : 01/04/2021 6:25 pm
Jonathan
(@jonathan-5)
Active Member
Topic starter answered:
RE: Stepper noise (extruder?)

@diem

Interesting proposal! I will try it tomorrow and get back to you.

Thanks!

Jebs

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Posted : 01/04/2021 6:32 pm
Jonathan
(@jonathan-5)
Active Member
Topic starter answered:
RE: Stepper noise (extruder?)

@diem

I changed the infill pattern and the sound definitely changed. But it is still there. I also noticed it when the printer was doing the first layers. It seems to be directly related to the speed of extrusion I think. It's not that noticeable if you don't focus on it but when you do it becomes like an old door that slowly opens in the distance.

Could it be the stepper motor skipping steps internally? Or could it actually be the normal operation of the steppermotor since it's operating at such a low rpm? I have always wondered why the extruder stepper didn't use a hefty reduction, since you don't need that much rotation to extrude/retract.

Any thoughts? 

I mean as long as it prints fine, I am happy. The machine has gone from causing massive vibrations and high pitched noises to being there in the room without preventing normal conversation. But better is always desirable of course 🙂

 

Perhaps this can only be solved with microstepping and or 24V steppers, which means that this mk2.5s will receive a mk4 brother when it comes out.

 

Thanks!

 

Kind regards,

 

Jebs

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Posted : 03/04/2021 10:58 am
Chicago Keri
(@chicago-keri)
Trusted Member
RE: Stepper noise (extruder?)

A knocking noise from the extruder stepper is usually the extruder  stepper motor "skipping" steps.

This can be made to happen on the first layer if the first layer calibration is set too low.  The cause is usually for some reason, the extruder is trying to force too much plastic through too small of a nozzle or the plastic is too cold.  This can be on the first layer that the nozzle is too close to the bed, as above, or it can be a clogged nozzle, too small of a nozzle for the print settings,  high friction in the filament path, too low of a temperature for the plastic being used or possibly the extruder stepper motor not operating properly possibly caused by a broken wire, a poor connection or a fault with the driver board (MiniRAMBO). 

Easy things to check-

Make sure that your Slicer settings match the nozzle size, and the nozzle temp is high enough for the filament being used

You checked the Bondtech gears for lubrication, but also check to see that they line up with the filament path. While checking, make sure the filament path is not obstructed, distorted or blocked.  For example, a binding filament sensor arm or ball, or a crushed PTFE tube in the Hotend

Double - check the wiring by checking that the Extruder connector is fully plugged in, then try wiggling it at various points while the printer is printing. See if the noise gets worse or stops when the wires are moved.

By the way, Firmware 3.9.3 and up defaults to "SuperPinda OFF" , and there is a screen accessible setting to toggle  SuperPinda ON and OFF, so don't let that stop you from upgrading.

Happy Printing!

¡no entiendo Español!
Nein! Nicht Versteh!
Я немного говорю по-русски но не очень хорошо, и...
I'm not very good at English either! Maybe someday I'll find a language I'm good at?...
Posted : 03/04/2021 9:46 pm
Jonathan
(@jonathan-5)
Active Member
Topic starter answered:
RE: Stepper noise (extruder?)

@chicago-keri

Thanks for the advice! Much appreciated!

Seeing as this sound is pretty much present during the whole printing process, I don't think it's a first layer issue. But I mentioned the first layer because the printing speed is much lower and therefore the motors are producing less high pitched vibration sounds, thus making the noise more noticeable. It would've made sense if it only occured at the first layer, though!

The nozzle, heatbreak, heatblock, thermistor, ptfe tube and heat cartridge are all new, so I definitely hope that there isn't a clog already built up haha! Though, the temperature setting is a very interesting one. I usually only print at the pre-loaded profile temps (prusament standard), but it could be that those temps are fine-tuned to Mk3s+'s that have a 24V system which is much more powerful in the heat power delivery department. I don't see thermal runaway issues, though (only when the part cooling fan kicks in, the temps can drop like 7 degrees and then you can see the printer trying to compensate, it's like a tug of war between the pid and the fan haha). But I will definitely try bumping up the temperature from my standard profiles by about 10 degrees to see if the knocking sound goes away. 10 degrees higher ought to make the plastic less viscous I'd say?

I'll also recheck the wiring! It's an old motor that has been running since the release of the Mk2, so it has endured some punishment during the years.

And I will definitely update to 3.9.3 then! The Prusa agent in the store chat advised me to stick to 3.9.1 because I didn't have the SuperPinda probe yet. I'll patch the firmware and disable the superpinda in the settings.

 

Thank you so much for the insight! Hopefully I can fix or reduce the noise and make my old beast even better!

 

Kind regards,

 

Jebs

...
Posted : 04/04/2021 8:11 am
Chicago Keri
(@chicago-keri)
Trusted Member
RE: Stepper noise (extruder?)

@jonathan-5

Hi Jonathan

Say, the MK3 series really doesn't have any additional heater power... it still has a 40w heater element, though the 24v system allows it to use half the current in Amps to accomplish the same heating effect.  If one were to use a 12v heater in a MK3, it would draw 80w and probably would't last very long. Likewise, a 24v heater in a MK2 series would draw 20w and would take a very long time to heat, possibly failing on Thermal Runaway.

If you wanted to increase the wattage of the heater, I can speak for the Slice Engineering 50w heater. It is available for 12v and 24v systems, and fits an E3D heater block.  As the wiring it comes with is far too long for a PRUSA, you would want to get some ferrules to terminate the ends with and a ferrule crimping tool, both available at very low cost.

I still advise checking the filament path for alignment and obstructions... the PRUSA assembly guide has some good tips.  This section seems the most relevant : https://help.prusa3d.com/en/guide/3-e-axis-assembly_59936

¡no entiendo Español!
Nein! Nicht Versteh!
Я немного говорю по-русски но не очень хорошо, и...
I'm not very good at English either! Maybe someday I'll find a language I'm good at?...
Posted : 04/04/2021 1:28 pm
Diem
 Diem
(@diem)
Noble Member
RE: Stepper noise (extruder?)

@jonathan-5

I changed the infill pattern and the sound definitely changed. But it is still there. I also noticed it when the printer was doing the first layers. It seems to be directly related to the speed of extrusion I think.

I think I heard two noises in the video.  One, I think, was the sound of the nozzle touching the infill - I suspect you were using one of the infil patterns where the filament crosses in the same layer.  Something like gyroid or cubic should not make this noise.

The other was a fizzing that might have been caused by damp filament. Drying might be in order As a check, a brand new freshly opened spool should not make this sound.

Could it be the stepper motor skipping steps internally?

I can't rule it out but I would expect you to be complaining about print quality if this were the case.

Cheerio,

 

Posted : 05/04/2021 2:01 pm
Jonathan
(@jonathan-5)
Active Member
Topic starter answered:
RE: Stepper noise (extruder?)

@chicago-keri

Aaah okay, my apologies. I thought I remembered back when the mk3 launched that one of the perks of switching to 24V was that the printer could dump more power in the head and bed without raising the current draw. I will recheck the filament path, just in case. Thank you!

 

@diem

Right, that is a good point, there are crossing infills of course and moving faster over such bridges could change the frequency of the hit bumps. But that wouldn't explain the same noise during the first layer placement. The filament used in the video was an old TPU filament that I tried to dry off in my oven at 50 degrees for 4 hours. I might needed to put it in there for longer to really get all the fizzing pops out of there. TPU is apparantly very hygroscopic haha, well maybe not as bad as PVA, but that aside.

 

The increase in temperature seems the most prominent solution at the moment since I was very meticulous when aligning the filament path with the bondtech system.

I will get back to this post with the results, I still have a few parts to print!

 

Thank you all for your thoughts and solutions!

 

Kind regards,

 

Jebs

This post was modified 7 months ago by Jonathan
...
Posted : 05/04/2021 2:14 pm
Jonathan
(@jonathan-5)
Active Member
Topic starter answered:
RE: Stepper noise (extruder?)

It's been a while, but I've finally managed to get back to my printer and try the suggestions that you have provided.

 

I have increased the printing temperature quite drastically, updated the printer to 3.10 and switched to a non-crossing infill pattern. I can sadly still hear the "purring". I'm starting to think that either this noise is either normal or my stepper is getting older.

Once the Super pinda's are back in stock (it has literally been 5 months now, I fear that they will never get back in stock haha) I will look into getting a new extruder stepper as well as one of those satin sheets. I have a smooth and textured sheet but that satin one really looks interesting for the more exotic materials.

 

Thanks for the help guys! I really appreciate it!

Kind regards,

 

Jebo

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Posted : 13/05/2021 8:37 am
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