Nozzle cleaning

A few minutes after finishing a print job, the filament is solidified in the nozzle and the nozzle-throat. When I start another print job a while later, the filament is not sufficiently melted and the nozzle is obstructed. Do I need to clean the nozzle after every print job ? or is there a practical method to overcome this difficulty ?

Instead of repeating yourself endlessly and expecting a different result... how about actually providing some useful information?

What temperatures are you printing at?
What material?
What sort of hotend?
What wattage heater cartage?
What voltage?
What type of extruder?
What sort of hotend/part cooling do you have?
What size filament do you use?
If this a home built machine or a commercially sold printer?

Pictures of your extruder and hotend?

This is not normal extruder/hotend behavior

Edited 2 time(s). Last edit at 08/28/2019 06:36AM by Dust.

I don't know why your nozzles are clogging, but I have clogs about once every year or two.
Nozzles cost about $2 each. I don't bother cleaning them- just replace.

In your case, I'd figure out what the problem is and fix it, then buy a handful of spare nozzles that should last for the next few years.

80% of clogs are thermal problems with the hot-end or the way you are using it. There should be a cooling fan running on the hot-end whenever the block is hot. If you don't have a fan on it, or you're not running it for some reason, that's the first thing to fix. The fan should not blow on the heater block or the print, just the heatsink fins. A print cooling fan is a whole different thing and will not keep the cool side of the hot-end cool - it's not supposed to.

10% of clogs are due to insufficient torque to push the filament through the hot-end. Geared extruders are much less susceptible to such problems. You can also have this problem is you're trying to print too fast with a tiny nozzle or not printing at a high enough temperature.

The other 10% of clogs are due to people not setting the pinch roller tension high enough. If the extruder is chewing divots in the filament, this is at least one of your problems. If the tension isn't set high enough, the drive gear teeth will chew a divot into the filament and then lose grip. The teeth of the drive gear should bite deeply into the filament so that they can't slip and chew a divot.

Edited 1 time(s). Last edit at 08/29/2019 08:21AM by the_digital_dentist.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

If the filament melts in the throat the cooling is insufficient. It should only melt below the heatbrake.

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[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

Here are my answers :

What temperatures are you printing at? : 220°C
What material? : PLA
What sort of hotend? : Ordinary one, bought in 3D shop.
What wattage heater cartage? : 360 W
What voltage? : 12 V
What type of extruder? : Bowden
What sort of hotend/part cooling do you have? : Extruder fan that helps cool the extruder drive mechanism
What size filament do you use? 1.75 mm PLA
If this a home built machine or a commercially sold printer? Home built

Srek says "If the filament melts in the throat the cooling is insufficient. It should only melt below the heatbrake."

Right, I think the filament melts in the throat and re-heating of the hotend cannot melt this solidified filament. Cooling is done by the fan blowing to heatsink fins and this fan comes together with the hotend; I suppose the manufacturer has made necessary calculations for it to be sufficient.

The throat I am using has no teflon lining inside; I will try to use one with teflon and hope this will avoid melting and sticking of the filament.

All metal hotends, which sounds like what you have, are better suited for the higher temperature plastics like ABS. Also removing the filament right after the print finishes and before the hot end cools down helps. I add a snippet of gcode that retracts the filament about a 100 mms at the end of each print. Just enough to clear the hot end but not enough to suck the hot plastic into the Bowden tube.

Edited 1 time(s). Last edit at 08/29/2019 05:33AM by Shank man.

Quote
Seapeace


Right, I think the filament melts in the throat and re-heating of the hotend cannot melt this solidified filament. Cooling is done by the fan blowing to heatsink fins and this fan comes together with the hotend; I suppose the manufacturer has made necessary calculations for it to be sufficient.

The throat I am using has no teflon lining inside; I will try to use one with teflon and hope this will avoid melting and sticking of the filament.

NEVER "suppose" when dealing with cheap stuff from China, even sometimes from the West ! ALWAYS SUSPECT ! Yes, usually there is a fan but blowing how and where ? BTW, the fan must always be ON !

And of course, there is the heatbreak .... Certainly the most screwed up thing in the cheap stuff.


So, what about a picture ? A vendor ref ?

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

Quote
MKSA
So, what about a picture ? A vendor ref ?

Its like squeezing blood out of a stone to get information out of this one...

Is your hot end cooling fan wired to be always on?

I had lots of problems at first, only because I cut power to the machine after finishing a print and not letting the hot end cool down first.

Your fan needs to be on until the hot end is 50C or lower.

Edited 1 time(s). Last edit at 09/17/2019 02:23AM by CountZero.

Any progress on this issue?
I read that PLA has issues with heat creep and expansion. 220C seems high to me for PLA. Bowden extruder so typically you will have a couple of mm retraction set. Probably all adding to the problem.
A workaround may be to put in the end code after the heaters are turned off and homed away from the print, extrude a couple of mm filament. This will push the hot filament out the throat before it solidifies, may not work completely as the fresh filament will still be heated by the residual heat in the hot end. You could however do this extrusion at a slow speed.