Recurring hot end clog

[RodimusPrime98]

Help. Before diving further into troubleshooting this recurring Voron 2.4 Rapido HF hot end clog on my own I thought I would reach out here for help and guidance on what to check. I have been printing well for hundreds of hours with this setup and just recently I have had 3 prints fail after printing well for several hours. I am printing PETG at 235C hot end and 80C bed temps. When I find the failed print is is still trying to print but clogged and several layers above the last deposition. After canceling the print and heating up the hotend I am able to use a thin metal tool to push the filament out. I replaced the nozzle after the second fail print and clog. I printed a few good prints with the new nozzle and then I got another clog that I am now struggling to clear. I am wondering if there is an issue with my hotend fan but I am not sure how to troubleshoot much without just replacing it. Any ideas? This possibility of fan issues makes me wonder if Klipper/Fluidd/Mainsail could have a monitor to alert if fans aren’t running as set or expected? Is there any log I could review to get an idea of what happened at the time of failure? What should I look for?

[Simon2.4]

I have dogs and cats. Any dust (fine cat hair) that makes it to your nozzle, carried by the filament, has a chance to cause a blockage, partial or complete. Ask me how I know..  ; ) 

This is a possible cause for your failure. dust on the filament.

To clean my nozzles, I use a plumber's torch to heat them hot enough to burn off all plastic (and shiest), then I use a sharp toothpick that I push in and turn until I see it sticking out the nozzle. That picks up the soot and polishes the inside. I've had good success with this method. An electric heat gun works too but takes longer to burn.

[mvdveer]

6 hours ago, RodimusPrime98 said:

What should I look for?

As @Simon2.4 said. I have had this happen by moving the printers into the garage where there is obviously more dust than in the house.

I printed a filament cleaner for all the printers and problem has been solved.

Here is a list of what I refer to - choose the one you think would suit your setup. I just went for the simple model and it seems to work,

[VoronManiac]

Dust filter could be a fix. 

Is the issue limited to one roll or brand of filament?  Debris quality control on off brands is not always the best.

If possible, the first question to answer is the filament jamming at the heat break or is debris clogging the nozzle orifice.   Try releasing the extruder drive gears and heat the extruder to 180C or so.  If you have a heat break jam this low of a temperature would tend not to be able to clear the jam while trying to remove the filament.

Measure the fan motor current.  Would expect at least 40mA.  Sleeve bearing fans can fail where the bearings start to bind, dropping the fan speed.  Pull the fan apart and add a drop of oil, or better get a dual BB fan.

I use 0.30mm stainless steel wire that is available on eBay to clear clogs. Search for "Stainless Steel Dental Wire Orthodontic". Insert the wire into the nozzle orifice while hot and pass a few feet through the extruder filament intake.  The contents of the melt zone will stick to the wire.  After puling the wire all the way through, refill with filament and run the wire again.  Repeat a number of times.  Goal is to purge the melt chamber.  Cold pulls are also a good option.

Cooking a nozzle with a torch should be a last resort because it will create carbon deposits that can flake off at a later time. I'd prefer to switch to ABS and use a solvent like carb cleaner to soak the nozzle to free debris.

While extruding high above the bed in air, observe the angle that the filament comes out of the nozzle.  It should come straight out of the nozzle.  It is shoots to one side, there is a deposit or partial blockage in the nozzle.

 

 

[RodimusPrime98]

So to follow up… I thought I resolved the issue when I found the hotend fan connector on the Octopus board had a lose pin. I fixed that and printed another ~2kg with no issues. Last night I put a brand new spool of Sunlu PETG on to print a 600g flower pot. Wake up this morning 10hrs in the 15hr print to find it had a level shift at about 1” off the bed and then was continuing to print fine to where I found it and cancelled it. Before leaving for work I started a different unopened spool of Sunlu PETG to come home to find I had both a level shift (this time at ~1cm from the bed AND another blockage in the hotend, up and out the top of the Rapidio cooling fins. So, I disassembled the tool head and checked all the motion and all seems smooth with no catches. I did notice where the belts pass on the pulleys on the XY joints look more warn. These belts are only a few months old. 

[claudermilk]

On my Trident I did Nero's trick and made bearing stacks instead of the toothed idlers. After I swapped to the pin front idlers like you have there I found you have to very carefully tighten them to be certain that they are not angled. If they are, they will push the belts to rub at the top or bottom and start wearing. I'd double check that.