[Solved] Is this cold pull OK?  

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Peter M
(@peter-m)
Noble Member

Reassembled the hotend, and did a few cold pulls.

Is this OK, see picture.

Posted : 16/05/2021 9:35 am
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(@)
Illustrious Member

The nozzle end looks okay. The heat break end is showing what looks like the classic 2.2 mm bulge typical of a heat break that is in the process of jamming the filament and causing underextrusion or even full stop jams.

Posted : 16/05/2021 9:49 am
Peter M
(@peter-m)
Noble Member

I have a e3d heatbrake ! Without the 2.2mm.

The thicker part at bottom of picture m where is this in the hotend?

I measured the thick part, it is 1.65 mm.

This post was modified 4 weeks ago by Peter M
Posted : 16/05/2021 10:21 am
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(@)
Illustrious Member

Usually in cold pulls there are these steps:

  1. the nozzle end: a cone shape
  2. the heat break to nozzle join: a thick spike in the middle of the pull
  3. the heat break end: a thick section that thins to 1.75 mm

Measure the diameter of the filament at this thick area, if only 2.0 mm, then it's normal.  It looks larger, but the photo may be deceiving.

Posted : 16/05/2021 10:36 am
Peter M
(@peter-m)
Noble Member

I measured it again.

Posted : 16/05/2021 11:07 am
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(@)
Illustrious Member

@peter-m

It just looked large, and 2.02 is good - it's the diameter of the bore down through the heat break and nozzle. Thanks for measuring. 

Peter - were you trying to fix something with the cold pull, or just doing a double check it was normal?

Posted : 16/05/2021 5:04 pm
Peter M
(@peter-m)
Noble Member

Both.

A few weeks ago I had the grub screw loose from the extruder gears. That is fixed.

At the same time I had , the filament stopping extruding for a long time in the print(print went on), then it starts again, printing.(if I was by the printer i could push the filament in the extruder then it would work again).(the extruder makes a lower then normal clicking noise).

At the same time I had the filament stopping, printing went on. After stopping the print, sometimes the unload filament does not work, extruder motor does not turn, after pulling and doing a few times unload it works again.

At the moment I am playing with the springs of my mk3, If adjust the springs to hard the gears/motor locks up, loose is better.

I have rebuild the hotend with a new heatbrake and new paste, and wanted to now if the cold pull is ok.

I am doing some more testing, but I now something is wrong.

How can I check if the extruder gears are working OK, and not damage because it was loose?

Possible I will rebuild to a mk3s in a few weeks.

Thanks for the help.

Posted : 16/05/2021 5:37 pm
ssill2
(@ssill2)
Honorable Member

@peter-m

you can always open the extruder and visually inspect the gears. as long as they are clean and no broken teeth, I'd think you're fine.  I checked mine a couple weeks ago troubleshooting an issue with the MMU.

Posted : 16/05/2021 6:42 pm
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(@)
Illustrious Member

@peter-m

Any Bondtech skipping is bad and needs addressing. Generally it's too little tension or a clog. The latest firmware has some new settings that reduce motor drive current and temps. You might read about that and see if switching to a higher current has any effect.

It's hard to damage the gears unless printing very hard filament. Glow in the dark will wear out the teeth if you print enough. The teeth also are subject to normal wear, but it takes a lot of filament to do that. More often, they just fill with debris and don't grip as well as they should.

Take a stiff fine bristle brush and clean out the gear teeth. It's also a good time to place an even dab of lithium grease on the idler feed gears. You might also check the idler shaft to make sure it is still centered in the door dogs.  If off to one side the axle falls out and the idler gets flimsy. 

If you have some Prusament filament, you might want to print the Prusa belt tension tool - supposedly an easy way to verify belts are at the correct tension. I just printed one and will post my thoughts elsewhere.

 

Posted : 16/05/2021 6:48 pm
Peter M
(@peter-m)
Noble Member

Extruder gears I did clean, so they look like new, and put new grease on them.

 

Could the extruder motor be stopping and starting after a little while, I have to check , if no cable is loose in the board.

Firmware I will try.

Posted : 17/05/2021 3:42 pm
Peter M
(@peter-m)
Noble Member

I broke some cables of extruder.

I am gonna rebuild  the mk3 to mk3s, with all new cables.

Thanks for the help.

Posted : 17/05/2021 10:37 pm
cwbullet
(@cwbullet)
Illustrious Member

@peter-m

That is really common during a rebuild.  Some of the cables are very delicate.  Don't beat yourself up.  

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Chuck H
3D Printer Review Blog...
Posted : 18/05/2021 12:12 am
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