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I have a Printrbot Simple Metal. The extruder is getting clogged all the time. I went through the process demonstrated here multiple times already. Heatting the extruder and pushing different tools all the way through to make sure it is completely clear. Every time I get a clear flow of PLA, and after a few minutes the extruder motor starts clicking again. At that point, it is even hard to push in the filament by hand.
I replaced the tip already, but this didn't make any difference. I also tried few different filaments, all of them worked perfectly before.
It feels like stopping the flow even for about 30 seconds would cause it to jam.

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    $\begingroup$ Hi, Ron. Could you be using a too long retraction settings? To long retraction can make the hot filament cool down and fasten too far up inside the hotend when either not printing or printing an area with frequent retractions. $\endgroup$ Feb 20 '16 at 23:44
  • $\begingroup$ @TormodHaugene This happens even with no retraction at all. I just extrude (from the control in OctoPrint) then stop for about 30 seconds and try again and it will be stuck already $\endgroup$
    – Ron Harlev
    Feb 21 '16 at 4:03
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    $\begingroup$ Which version of the Ubis hot end do you have? Do you have a fan blowing at the heat sink? Assuming you have a version with a PTFE tube, have you checked the condition of the PTFE tube? $\endgroup$ Feb 21 '16 at 4:05
  • $\begingroup$ What temperature is your hotend at? $\endgroup$ Feb 21 '16 at 14:51
  • $\begingroup$ @TomvanderZanden I was experimenting with 195-210C $\endgroup$
    – Ron Harlev
    Feb 21 '16 at 18:13
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I had a similar issue on my Printrbot Simple Metal. I believe my problem was initially caused by clogged nozzle which I replaced, however the jamming persisted. I can't say for sure that it was acting exactly as you describe but I think it may have been similar. I noticed that the little red insulating sleeve was pushed up higher than it was when I got it from Printrbot. When I lowered this my problem seemed to go away.

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I'm not sure if this is particularly the issue for you right now, but I have encountered the tension on my drive gear being too high.

Before I upgraded my extruder to the spring loaded mechanism, my extruder used a Delrin plunger to provide tension against the filament towards the drive gear. This plunger used copper washers to help adjust the tension required. Many people ended up upgrading their assemblies to the spring loaded mechanism as the plunger would either put too much or too little tension against the drive gear. Too little and the filament will not be driven into the hotend. Too much and the filament will grind against the drive gear and the drive gear may begin to "eat" away at the filament (especially when the filament becomes hotter). Obviously, if the drive gear is no longer able to catch on the filament, the nozzle will get clogged.

However, even with a spring mechanism, your tension can become too high. Most of these mechanisms allow you to adjust the tension by tightening/loosening the screw holding down the spring. The "sweet spot" for me is just past when the filament can be successfully driven into the hotend. You can test this if you have control over your extrusion motor by removing the extrusion motor from its mount, leaving the spring mechanism installed on the face of the motor. Then, turn your motor on and try feeding the filament through the mechanism. Starting with no tension on the spring, begin slowly increasing tension by tightening the screw on your mechanism until the drive gear is successfully able to guide the filament through. I might even complete another half turn on the screw to account for varying diameters and plasticity states of the filament as it becomes hot.

Hopefully this helps and please keep us updated on anything else you find.

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  • $\begingroup$ Thanks for the info. But this is not the issue I have. As I mentioned, the filament will flow just fine, until it has a short while (about 30 seconds) to be idle. Then it will get stuck again $\endgroup$
    – Ron Harlev
    Feb 21 '16 at 4:00
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This used to happen to me and my Simple Metal often. The jam was always caused by one of the following:

  • Feed rate too high (especially on solid layers or long lines)
  • Temperature too low
  • Nozzle pushing into previous layer, causing back pressure
  • Variance in filament diameter

Personally, I have never printed at 195c. I'm always about 225 or 230. That may seem high for PLA, but then I have stopped having the issues after slowing the print and raising the temperature from 200.

You want to strike the right balance between speed and temp. The slower the feed rate, the lower you can afford to lower the temperature. I think you should start by raising the temperature to 215 and slightly lowering the feedrate.

Also, I have directed a fan at my extruder motor and filament as it enters the nozzle. Keeps the motor very cool and stops the filament softening too early.

Is there a foreign object blocking the nozzle, or does it seem like the filament isn't heating up enough?

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  • $\begingroup$ I replaced the nozzle tip with a new one, which didn't help. So it is probably not the problem. I also put a metal object under the detector when the print started, to make sure it is working "in free air" and not pushing into the surface, while I was testing it. I will try the temp/speed idea and will let you know. Thanks! $\endgroup$
    – Ron Harlev
    Feb 22 '16 at 18:57
  • $\begingroup$ Taking the temp to 230 seemed to help at first, as the filament was flowing easier at the first few moments. But then when I stopped the extrusion for a few seconds it got stuck again :( $\endgroup$
    – Ron Harlev
    Feb 23 '16 at 19:49
  • $\begingroup$ I actually had a jam yesterday after moving my printer. Long story short, I accidentally reversed the extruder motor connector and pulled out all the filament from the nozzle because the motor was reversed. I didn't notice at first and the nozzle jammed because a small string of plastic was left being charred in the chamber. $\endgroup$
    – ArkTekniK
    Mar 1 '16 at 10:50
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I found a solution to my problem, which is very similar to your!

Ok, so first, this clog has nothing to do with the flow rate! speed, retraction, or acceleration!

why? because if it under extrusion or over extrusion, the nozzle would spill more or less filament, but it would not make the extruder clog. To make it clog, there must be something that block the path which make the step driver couldn't push the filament through right? even using your hand.

This problem is call "heat creep", especially if you print small detail things. This is because small details make the filament stay inside the nozzle longer, which the heat eventually make the filament swole up and block the path.

To find out if your problem is cause by "heat creep" or not, try to print something small but tall and print something large overall. If it is heat creep, then the small but tall print would immediately clog your nozzle and make the step driver create click sound. If both print ( small and big ) take the same amount of time to clog your nozzle, then it may not cause by "heat creep".

SO HERE the solution for "heat creep." First and the most important, replace your thermal barrier tube. Second, lower the temperature. Third, check the filament guide components such as the drive gear, bearing, and spring. For example, check the drive gear if it securely screw into the stepper motor. Lastly, check the fan, if it possible, install another fan to cool down the thermal barrier tube. In conclusion, replace your thermal barrier before doing anything else.

I hope this help for you and for many other people!

Alopicaso!

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  • $\begingroup$ Thanks for info. For flexible filament is this still the advice regarding cooling? IE I read I thought for flexible it is better to turn the fan off? Having said that I'm having hot end blockages with flexible... $\endgroup$
    – Greg
    Jan 22 '19 at 1:35

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