extruder skipping up after printing for about 20 minutes

As of late the extruder motor on my prusa i3 has began to click from time to time when it prints continuously for more than about 20 minutes. ive been trying to figure out what it might be.in troubleshooting its of importance i think to note that it only begins after a about 20 minutes. the only thing which comes to mind is that the radiator on the hotend is not losing heat fast enough so the filament is buckling and causing the extruder trouble. ive no idea why this might happen all of a sudden as i dont think ive changed anything on my setup.
can anyone hazard a guess as to what might be causing this? its very frustrating as i cant do any long prints any more(major under extruding).
thanks.

What type of extruder ?
Does the motor feel like its getting too hot ?
Mk8 direct drive extruders have been known for the pressure roller to come loose.

Typically if something starts to fail after time, it's due to heating/cooling issues... you might have been living on the edge of this problem without realising it. You could try slowing down your print speed... that might improve things, or help you diagnose?

Also check the driver chips to make sure they're not getting too hot. And check your temperature graph for changes approaching the 20 minute mark... maybe at a certain nozzle position, a wire to the heater is disconnecting or shorting out?

Quote

What type of extruder ?

this is my printer. ive been using it frequently since i bought it about 2 years ago so its done some miles. its been suprisingly good to me considering the price.

Quote

Does the motor feel like its getting too hot ?

ive felt the motor and it doesnt feel hot to the touch.

Quote

Mk8 direct drive extruders have been known for the pressure roller to come loose.

my pressure roller(the clamp which pins the filament to the gear?) has been jerry rigged with duct tape to put it back in place. ive ordered another one but this is the situation currently. i believe it works and itsnt the cause of the issue because it is merely misaligned and the tape pulls it back.

Quote

Typically if something starts to fail after time, it's due to heating/cooling issues... you might have been living on the edge of this problem without realising it. You could try slowing down your print speed... that might improve things, or help you diagnose?

i have experienced this in the past but it was always when i was printing at 0.3 height at too fast a speed. this is now doing it at 0.2 at a moderate speed. slowing down may help but its finding out what has caused this to happen all of a sudden which i would like to do.

Quote

Also check the driver chips to make sure they're not getting too hot.

i'll check the driver chips but this would be a symptom of some other problem would it not, rather than the root problem?

Quote

And check your temperature graph for changes approaching the 20 minute mark... maybe at a certain nozzle position, a wire to the heater is disconnecting or shorting out?

i will see if there are any abnormalities when it starts misbehaving.

do the stepper motors themselves have a very good life span? ie, would buying a new motor be a wasteful solution? Thanks for the replys guys.

You don't say what material you are using but the other common issue with PLA is a combination of temperature and retraction. Seems you have a Bowden so retraction should be a significant value.
A smaller layer height and a lower speed reduces the flow rate that means there is more time for heat to soak up the filament so if its temperature related it could make the issue worse.

Hmmm... the duct-taped roller sounds dubious. Inconsistent feed rate due to inconsistent pressure due (I assume) to changes in alignment could cause your problem, especially in combination with other factors. Could you perhaps print something in less than 20 minutes to make a more consistent fix?.

Stepper motors generally last forever... I wouldn't think about replacing one unless there was some obvious reason to.

As per @MCcarman... Retraction exacerbates heat soak in that it pulls warmer, softer filament back up into the cold part of the hot-end, where it may jam. You could try reducing or disabling retraction... this may cause stringing and maybe other issues, but it may help diagnose.

Hot driver chips may just mean they don't have adequate heatsinks (try adding a fan), but may be due to too much current to the corresponding stepper(s). (Insufficient current can also cause problems through missed steps). Record the stepper driver settings before you fiddle!

Identifying the root cause can be difficult; you may have been on the verge of this issue for some time, and something small and seemingly insignificant has pushed you over the edge. There are a lot of interacting factors that can cause filament jams, so the usual approach of changing one thing at a time may not work in getting things going again.

Maybe the air temperature in your house/garage has increased? Or decreased?

Maybe you've changed filament colour or manufacturer recently? Some filament (e.g. black) conducts heat better than others. Have you tried changing your extrusion temperature? 5 degrees more or less may solve it?

Maybe your filament diameter has changed and it is now slightly thicker than it used to be? This kind of thing happens mostly on cheap Chinese filament, but I don't think the "quality" brands are immune. Thicker filament means more material is fed than you expect, which increases the back pressure in the nozzle. So try measuring your filament with digital calipers, or try reducing the Flow Rate by 10%.

Another diagnostic thing you could try is to print for about 15 minutes, then pause (keeping the nozzle heater on) for 10 minutes, then resume printing. If it immediately jams, then it's probably heat-related in your hot-end. If it jams after another 5 minutes, then it's probably not heat-related. Perhaps something to do with the physical position? If it jams in another 20 minutes, then it's probably something to do with the extruder stepper heating up; but, on the plus side, you can print larger items so long as you pause for 10 minutes every 15 minutes.

There's also a chance that some kind of mechanical thing has changed (e.g. a bit more slack in the Z axis) which therefore causes the hot-end to sag just a bit more, which increases back pressure inside the nozzle, which causes the filament to eventually jam.I think it's good practice to regularly check all the screws and belts are tight and nothing is cracked or distorted and all moving parts are lubed. Redo that check when things aren't working as expected. Perhaps also disassemble the hot-end, examine the PTFE liner, and put it together again properly, in case something has loosened in there.

Are you trying to print the same object each time? Or does the jam happen after 20 minutes no matter what shape object you're printing?