My prints suddenly go brittle  

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irwinpks
(@irwinpks)
New Member
MK3S with firmware 3.9.3. I'm having this issue where my prints suddenly become brittle. After printing a few Cable Chain links in PLA-SILK...they look good, but when you slightly depress it, they crumble. I figured it could be the filament having moisture. Note that I've printed several dozen cable chain links with same roll of PLA-SILK and gcode previously months before. Anyway, I grabbed a new roll of regular PLA and printed...same result. Then ran PETG, the problem escalated and looks similar to what you see in the stringy pic.
 
Time to tear apart the hot end. I replaced the following; nozzle, heat block, heat cartridge, thermistor, heat break, heat sink, and PTFE tube with new Prusa parts. It was just time for most of those to come out after several hundred hours of printing. Plus a new blower fan as the mounting points were cracked since I was already in surgery. The result is that first print with stringing all over the place. Generally no change in my situation.
 
While I was loading and unloading filament, I did notice having to press the button additional times to feed and unload filament. I looked at the Bondtech drive gears and they seemed in place with nothing visually worn or broken. Cleaned that area out too with a brush and shot compressed air to loosen any other junk. The tensioner was also tightened or loosened several times to see if the filament was slipping. When it was tight, you could see the teeth marks on the filament.
 
With all that said, I thought the assembly is proper (i've replaced all those parts before several times previously when needed) and it seemed like that filament is not feeding right. What if I increased the flow? So I did to 300...and then BAM...I got it printing again. See non-stringy pic. Aside from the skirt being ruffled at the bottom right edge, CHEP's bed level printed out. It was more dense than it should be due to the heavy flow.
 
I checked the nozzle to heat block for molten filament build up and heat block to heat break for the same...there is none.
 
Could my extruder stepper motor be dying?
 
Posted : 05/02/2021 3:33 am
cwbullet
(@cwbullet)
Illustrious Member

How long has gthe PETG been out of the bag?  It could be hydrated.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 05/02/2021 10:55 am
irwinpks
(@irwinpks)
New Member

@cwbullet

When done, I place the roll back in the bag along with desiccant and then seal. I do that to all my filament.

The problem exists on 3 different rolls, that I've described in my post.  These same rolls print on 2 of my Ender 3 Pros...and that was to make sure hydration wasn't an issue.

This particular Sunlu Black PETG was out of the box for 30 minutes before using it to run the CHEP print.  My original issue is with the PLA-SILK filament.  I used the PETG because its a good filament but not one of my premium colors.

Posted : 05/02/2021 11:00 am
cwbullet
(@cwbullet)
Illustrious Member

@irwinpks

It is not always this issue, but when prints change suddenly, I always think about hydration.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 05/02/2021 11:03 am
irwinpks
(@irwinpks)
New Member
Posted by: @cwbullet

@irwinpks

It is not always this issue, but when prints change suddenly, I always think about hydration.  

Understood.  Though I'm leaning towards the Extruder stepper motor...out of step.  Instead of bumping up the flow on the printer control to 300, I went into the Prusaslicer 2.3.0 and set the Extrusion Multiplier to 3 (instead of the default 1)...its almost the equivalent to 300...and then the CHEP print came out pretty solid.  It was actually "dense" and heavy due to the extra flow of filament.  There was no stringing then.

Posted : 05/02/2021 11:09 am
irwinpks
(@irwinpks)
New Member
I'm back in business! Thank you for chiming in. I had to retrace my steps back to the last thing I was doing...which was printing out chain links. In the Custom GCODE for my Ender 3 Pros within Prusa Slicer the following lines were added.
 
M92 E136.87 ; Set E Steps to 136
M301 P29.79 I3.37 D65.88 ; Sets Hotend PID Tuning
M500     ; Store Settings
 
On all my Ender 3 Pros I have a Micro Swiss Dual Drive All Metal Head Extruder. The E-steps for that is in M92. The default E Steps for the MK3S is 280.
 
I made the mistake of using the wrong GCODE...instead of the export for the MKS3, I used the Ender 3 Pro. That's where everything went south.
 
GRRR...chalk this one up towards experience.
Posted : 09/02/2021 8:09 am
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