How to clear nozzle when it's jammed

zhangxueyou
Posts: 1405
Joined: Fri Feb 06, 2015 1:33 pm

How to clear nozzle when it's jammed

Post by zhangxueyou » Fri May 22, 2015 3:50 pm

MK8:
https://www.youtube.com/watch?v=3iS8YU_TNEw
J-head:
https://www.youtube.com/watch?v=OQG97plWXl0
If you can't remove the nozzle at room temp, please heat the hotend and then do it, be careful and you don't have to heat it to a very high temperature.

akos
Posts: 9
Joined: Tue Jun 30, 2015 5:53 am

Re: How to clear nozzle when it's jammed

Post by akos » Tue Jun 30, 2015 6:13 am

hello

i just bought and assembled an Acrylic Reprap Prusa I3 Pro B. When i first tried to print the pla got clogged in the nozzle. I followed the instructions and cleaned it and tried again. I set the temperature to 195C but it got clogged again. I tried on 200C with same result. Once it's clogged the extruder motor starts ticking because it cannot feed the cable but until that point it's feeding the pla ok so i know that it works. If i heat up the extruder to 240C as i see in the video and push the pla manually or with the cleaning rod the stuff comes through the nozzle.
I'm new to this machine and 3D printing so i don't know if i do something wrongly or there can be a problem with something in the system. software or hardware settings.
please help
thank you

zhangxueyou
Posts: 1405
Joined: Fri Feb 06, 2015 1:33 pm

Re: How to clear nozzle when it's jammed

Post by zhangxueyou » Tue Jun 30, 2015 10:14 am

akos wrote:hello

i just bought and assembled an Acrylic Reprap Prusa I3 Pro B. When i first tried to print the pla got clogged in the nozzle. I followed the instructions and cleaned it and tried again. I set the temperature to 195C but it got clogged again. I tried on 200C with same result. Once it's clogged the extruder motor starts ticking because it cannot feed the cable but until that point it's feeding the pla ok so i know that it works. If i heat up the extruder to 240C as i see in the video and push the pla manually or with the cleaning rod the stuff comes through the nozzle.
I'm new to this machine and 3D printing so i don't know if i do something wrongly or there can be a problem with something in the system. software or hardware settings.
please help
thank you
Can you extrude the filament by you hand when it's jammed? If you can, I think it's not jammed actually, you can refer to this page to solve the issue:
http://www.geeetech.com/forum/viewtopic ... 19&t=16575

akos
Posts: 9
Joined: Tue Jun 30, 2015 5:53 am

Re: How to clear nozzle when it's jammed

Post by akos » Wed Jul 01, 2015 5:13 am

i can extrude the pla by hand but after a few seconds it jams. I used the metal rod to clear the jam then tried again extruding by hand but jammed again.
when i push down the rod it feels like there is some pla stuck in the screw that i cannot clean.
Is the screw narrower inside at certain points? When it first jammed and cleaned it i felt something inside that i thought was plastic so i took a drill but when i started drilling it felt it was no plastic so i stopped drilling.
If you extrude the pla by hand could you extrude it as long as you want? for example could you extrude the pla for a few minutes with no stop?
what is the recommended temperature for this operation? for cleaning and for normal use?
thanks

zhangxueyou
Posts: 1405
Joined: Fri Feb 06, 2015 1:33 pm

Re: How to clear nozzle when it's jammed

Post by zhangxueyou » Wed Jul 01, 2015 9:17 am

If the nozzle is not jammed, you can extrude the filament by hand all the time.
If you are using PLA, I suggest you can raise the temperature slightly to 210 degrees (usually 200 degrees is high enough).

akos
Posts: 9
Joined: Tue Jun 30, 2015 5:53 am

Re: How to clear nozzle when it's jammed

Post by akos » Thu Jul 02, 2015 5:26 am

it seems to me that it's not jammed in the nozzle but it jams in the screw.
it looks like that the melted plastic is not just going through the hole in the nozzle but it's coming backwards up in the screw as the filament is pushing it because the resistance is smaller than through the hole. This is not desired but inevitable. It also explains what i asked in my previous message about the narrowed diameter in the screw. In my opinion the narrower section is supposed to prevent the melted plastic to flow upwards and fill in the screw because it can clog the screw. In my opinion there is a transition layer in the screw between fluid and solid state. If the melted plastic comes higher up and fills in the screw the top of the plastic will cool down and becomes solid. As soon as this happens that solid layer will catch the filament which in turn stops moving.
The conclusion and question is that is it ok for the melted plastic to come up?
Is it possible that filaments with different diameter need different screws? For instance a 1.75mm filament uses x mm inner diameter screw and a 3mm filament an y mm inner diameter screw. What if i got the screw for 3mm filament but i have a 1.75mm pla filament?
Is this possible? How can i test it?
thanks

zhangxueyou
Posts: 1405
Joined: Fri Feb 06, 2015 1:33 pm

Re: How to clear nozzle when it's jammed

Post by zhangxueyou » Thu Jul 02, 2015 1:54 pm

The diameter of the "screw" you say must be equaled to filament diameter.

akos
Posts: 9
Joined: Tue Jun 30, 2015 5:53 am

Re: How to clear nozzle when it's jammed

Post by akos » Fri Jul 03, 2015 5:10 am

I measured the diameter in the screw on the nozzle side and it's somewhere between 2 and 2.1mm
I made a simple calculation to compare the area of nozzle and area of the gap in the screw. The area of nozzle with 0.3mm nozzle is 0.28 square millimeter whereas the area of gap calculating with 2.05mm is 3.58 square millimeter which is 10 times greater than the nozzle area. this explains why the melted plastic likes going up in the screw rather than going through the nozzle.
Is my calculation correct or is this 2-2.1 mm ok for the screw inner diameter?
is it worth trying a 0.5mm nozzle? the area is almost 3 times greater than the 0.3mm, so i see a bigger chance that the plastic will go through the nozzle?
what are the pros and cons of using a 0.5mm nozzle to using 0.3mm nozzle?
Also could you send me please slicer settings for pla? I have only found for abs in this forum.
i guess i'd better order a new screw and nozzle maybe the heater too. Should i contact customer support and refer to you or can you arrange this for me?
Thank you

zhangxueyou
Posts: 1405
Joined: Fri Feb 06, 2015 1:33 pm

Re: How to clear nozzle when it's jammed

Post by zhangxueyou » Fri Jul 03, 2015 3:36 pm

It is normal that the diameter is bigger than the filament filament. Think about it, how can you feed the filament when the screw diameter is exactly equaled to the filament diameter.

akos
Posts: 9
Joined: Tue Jun 30, 2015 5:53 am

Re: How to clear nozzle when it's jammed

Post by akos » Fri Jul 03, 2015 4:50 pm

yes i know there should be some tolerance but i'm still looking for the answer what causes the problem for me and so far this is the only answer i could think of.
I have ordered the hotend parts with the 0.5mm nozzle so i will see if it improves anything for me.

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