Completly unreliable prusa

I have been trying for the last while to get the printer to work reliably. however it seems to fail a lot of prints. the problem is that it will print perfect for a while and then nothing will come out of the extruder and it will begin to fail, sometimes it will start up again and extrude plastic by its self, or if i push the filament manually it will extrude again?

there have many things i have looked at,
i checked the temps and they seem prity good
I looked at the hobbed bolt and it does clogg a little but this may be because of screws being too tight, i have tightened and losened them and it makes little difference.
The filament is tight in the idler and i could not pull it out by hand so i dont think its that
there was a leak in the j head which i think is now fixed as i wrapped the threads with ptfe tape and secured the ptfe tube
the main thing that made a big difference is when i turned off the fan that was pointed at the hot end/print and this reduced the fail a good bit. however it does still jam sometimes
I have several rolls of different coloured plastic from the same source, each one gives the same problem. Could it be bad plastic?
there doesnt seem to be a huge ammount of heat traveling up the peek to the cold end, the print could fail at the start or the end so it could have little to do with too much heat.
the extruder motor is not greatly hot either and as it can fail at the start just as much as the end i doubt it has much to do with heat as there would not be much heat at the start.

Its a very strange problem and very hard to pin down? does anyone know what to do or check or has anyone had any experiance with this kind of problem? Im really just starting to think its the plastic but i would doubt the shop i bought it off would sell bad plastic
Thanks

seems like your extruder is clogging. This causes the above to happen. Also make sure to remove and clean your hobbled bolt, possibly with a wire brush. I bet it has plastic in between the teeth. Once it is completely clean and free from plastic gunk, then look at power to the stepper driver for e axis.



Also I think it is more important now, since people are extruding at higher speeds to know that setting the extruder stepper driver to power enough to stall just before it slips is important. It allows for a set back pressure, and does not strip the feedstock.


setting the power to the e axis to where it stalls before it strips feedstock has saved me from a lot of bad prints.

yes it is getting jammed, but only some times. mid print if it stops extruding i will push it down manually until it starts extruding again. I have removed and cleaned the hot end and the bolt a few times.
What do you mean look at the power to the e stepper? what could be going wrong there?
do you think its the plastic?

I dont understand what you mean power enough to stall just before it slips?

thanks for your help

how close to the target temp does the temp stay?, depending on the hotend pretty good may not be close enough, ideally you don't was anymore than 2c variation in temperature,

also what kind of hotend are you using ?

---

-=( blog )=- -=( thingiverse )=- -=( 3Dindustries )=- -=( Aluhotend - mostly metal hotend)=--=( Facebook )=-

im using a jhead, the original 100k thermister broke for the hotend so i took the 100k glass bead thermister out of the heat bed and replace it. i dont think its the thermister because the problem existed before i changed it. there doesnt seem to be any huge variation in the temp its prity much at the 190 all the time.

right now there is no fan on atal during the print, and it seems to be slightly more reliable. I used to have the fan pointed at the hot end does this cause problems?

i am going to print a fan duct to point it more towards the cold end.
however the prints are still extruding fine one second then missing a patch then back to normal, on and off every print.

Try setting the temperature to about 100C (I assume from your temps you're printing pla?), then pulling the plastic out. That way the plastic just about will come out, but will pull any detritus from your extruder. I do this every month or so, and always get a huge clump of crap from the cheap plastic I'm using. As to reducing the power so it slips before strips, basically you want to reduce the power to the stepper (with the potentiometer on the stepper driver), so that you have only just enough power to extrude, and any extra friction causes the motor to stall. This sounds counterintuitive, but a stalled motor is much better than stripping the plastic and needing an extruder cleanout.

ok yes i will try pulling out the filament at 100, is there any reason why this problem gets worse with the fan blowing on the hotend?
thanks

Well it'll probably cool down the hotend a bit which will increase friction a little. You might not be able to measure this temperature drop with the thermistor, since usually the thermistor is closer to the heater than the tip is.

fredted1234 Wrote:
-------------------------------------------------------
> ok yes i will try pulling out the filament at 100,
> is there any reason why this problem gets worse
> with the fan blowing on the hotend?
> thanks


because the fan cools the hotend down, what you'll find is that the thermister reading is out, so if the temp reading is 190 the actual temperature could be a lot less

---

-=( blog )=- -=( thingiverse )=- -=( 3Dindustries )=- -=( Aluhotend - mostly metal hotend)=--=( Facebook )=-

ok i have tried nearly everything i can think of and is sudjested and there seems to be no improvement, the extruder will print fine one minute and the clogg and not extrude untill i put pressure on the filament manually. or with luck sometimes it will start going again. this can happen several times throughout the print? does anyone have any other suggestions i could look at?
thanks for the help so

Slipping pulley? Idler block too loose? E motor skipping steps (does it vibrate loudly when it stops printing?).

it could also be the hobbed bolt itself, as well,

---

-=( blog )=- -=( thingiverse )=- -=( 3Dindustries )=- -=( Aluhotend - mostly metal hotend)=--=( Facebook )=-

I once had an issue with the power connection at the hotend. after it would get to a certain height the wire would bend a bit and lose connection and would do what you describe.

Also maybe the plastic is not good, is it from a good supplier or is it maybe an off brand (China) where the quality is not consistent?

'-I dont understand what you mean power enough to stall just before it slips? '

lower the current to stepper driver that controls e. you want the motor to not have enough power to strip the feedstock. it will solve the most frustrating issue you have currently : the feedstock keeps stripping. it is actually ok to every once and a while have the e stepper driver skip. what happens otherwise is your feedstock starts to strip. if the stepper skips it can push the nonstrip feedstock when back pressure lowers a bit. also the teeth of the hobbed bolt remain clean!