i have the exact same problem^^
My Extruder clicks/can’t push the filament further.
I guess i have to check if the nozzle is clogged, but i’m not really sure how to do that…
Also it seems to be wired, that it clogs after 5 min of printing with a completely brandnew-printhead. Even settings total standart.
The troubleshooting page isn’t really a help at all, since it is just 3 sentence long explain of “remove and clean the hotend”.
It is frustrating and it seems that i’m not the only one here… 
I made these changes to mine
PLA 190C retraction 4mm retraction speed 110
This helped alot
Hm, i had a very similar problem, the nozzle did stopped to eject filament and the extruder clicked continuously.
Try these steps descriped in my thread (viewtopic.php?f=62&t=14936)
Make sure the nozzle isn’t clogged by the following steps:
I found out, that the extruder pulley accidentally ripped of some material from the filament wire, what caused the non grip on the pulley.
You can find a picture of the ripped of material from the filament wire in the linked thread.
Hope it helps you!
Additionnel to Tuxx report, also have a look at the 70-80 cm you cut off. I observe some part are twisted in accordion WWWWW
It generally append when printing with many retraction. Reducing, retraction distance and speed, as stated before, could help but not sufficient for some prints which need many retraction. Another idea, will be to use ABS and not PLA for those prints.
Is it possible to get a PTFE tube with sligtly bigger diameter to prevent it geting stuck when it have been to many retraction that causes the filament to jam in the PTFE? or is this going to affect the print?
I have very similar problem.
After loading fresh ABS, printer was working perfectly about 50 layers and after that it’s “skipping” some of the filament. Similar to http://3.bp.blogspot.com/-WzIozoUxThs/UWrujlwtIqI/AAAAAAAAAnA/kXg3TKepAjk/s1600/IMG_3952.JPG. It gets worse and in about 100th line barely any filament was extruded. It looks like curly hair or something, as little droppings of filament coming out of the hotend and sticking randomly at any higer point there may be. There’s nothing left of the structure it should be.
It seems that extruder motor feeds about 1cm of the filament into the tube. As it does that I can clearly see tension rising in the tube, it bends a little. Almost nothing comes out of the hotend. While the tension rises and stepper cannot push any further, tension releases by pushing the filament backwards, sliding over the stepper wheel and peeling off some of the material from the filament. It does that on regular basis. Seems like a clog.
I tried to unload the filament, but it didn’t come off. Something at the nozzle was blocking it from coming out. I preheated the hotend and pushed filament manually, little came out from the nozze but it was soft enough to allow me to pull it out. At closer looking I noticed that the tip was little bigger and with a collar-like line on it. This explained me why it didn’t came out.
After re-loading prints started off well. Perfect, I’d say.
After abou 50 layers all my problems came back. This has happened 4 times in a row now.
May the problem be in my nozzle? Maybe I’ve gave it a hit with buildtak plate little too hard.
If that may be the case - where to get spare nozzle? I’d like to test my theory.
i had these problems with mine aswell, with using both PLA and ABS.
i took the extruder apart and found alot of clogged plastic in the nozzle and isolator (had to put in a new piece of PTFE tubing aswell)
took it all to the toolshed, heated up the nozzle with a blowtorch and cleaned it out with a 0,35mm wire.
then it worked fine for a couple of days, and it was back
i then reduced the print temp to 187 for PLA (renkforce 190 for velleman) and 225 for ABS.
since that i havent had a single clogged nozzle 
Cut the PTFE tube with some filament in it that way you can cut cleaner.
Also I had problems with bad quality filament (grey color) the pigments that give the color were so big they got stuck in the nozzle every 5-10 minutes of printing.
Just another answer to add to the knowledgebase: check your filament thickness. I bought filament from a maker right in town (support your local economy, yada yada) and one spool varied widely in thickness. When it got a little thicker than normal, it overran the flow rate and built up backpressure until it oozed between the hotend PTFE tubing and the nozzle. When it got thicker still, it just plain got stuck in the tube leading to the printhead, stopping flow altogether. So don’t go cheap!
I can add some results, too.
It seems to be a heat problem. Backpressure is not the reason, it’s the result.
Push some filament manually through preheated printhead. Remove PTFE tube from the printhead and push, you should see and feel smooth liquid flow through nozzle. Apply constant pressure, I let the weight of my hand and gravity do the job. If you cannot get constant flow or you see that filament flow is lower or it looks like a pearl neckless rather than a fishing wire, add heat 10% and retry.
If the problem disappears or seems to go better, retry until you find the temperature that opts-out the problem. If that is the case - your temp sensor may be faulty or assembled badly. Try a spare and compare temperatures with third device.
If you cannot get smooth fishing wire alike result, use a guitar string to push through printhead from top through bottom and gently pull it out. I had some plastic-alike pieces in there too. It seems that at some moment some of the filament had crystallised and formed a thin layer around PTFE tube’s inner wall, letting some of the soft filament flow through.
Low temp might be reason for the dust to accumulate and form hard pieces in nozzle that at some point clog the printhead. They wont block it (as my case), they just cause random semi-clogs randomly at any time while printing.
That’s why replacing filament works for few hours - if you pull out old wire you cut the previous end that had some of the pieces hardened at the tip.
I’ve been having the same problem. I thought it may be the PTFE tube since only the right nozzle seems to block, but I think changing the settings should help. My filament has been destroyed in the extruder due to rapid, successive retractions. I’ll post my findings.
In my opinion the main problem is that filament is getting too hot in the isolator guide(s).
Heat from nozzle and heater block(s) rises up to isolator guide and melts the filament in the PTFE tube.
2 “problems” can come together here:
If one of this happens and the flow increases at that time of print then you compress the melted material in the PTFE tube from 1.75mm diameter to a diameter of slightly over 2mm (inner diameter ot the tube) and then every little step (for example from PTFE tube to nozzle) will block the flow
I came to this conclusions as I sometimes had problems in unloading filament. Retraction the first few millimeters was no problem but if there was a thicker part of filament in the PTFE tube it sometimes stopped suddenly at upper end of isolatorguide (small step from PTFE to PEEK or from PEEK to under side of the coupler)
Since I increased the cooling of the isolator guides, added a “heatshield” between heater blocks and isolator guides and separated the two fans in function (different mainboard outputs for printhead cooling and print cooling) I got problems with stucking filament very rarely.
Thank you for this in-depth explanation. Knowing what’s wrong is half the battle. Can you be more specific about the alterations you made, and perhaps provide pictures?
How did you increase the cooling of the isolator guides?
How did you separate the two fan speeds?
The make sure, is the glued in centrifugal fan on top the printhead cooling, and the 40mm one the print cooling?
Hello DanielDC88!
http://forum.velleman.eu/viewtopic.php?f=58&t=15344
Here you can find further explanation and some pics.
The truth is nozzle is not 0,35 but 0,335. When you change it in slic3r it will be ok. By setting nozzle hole to 0,35mm you are giving folse information that printer can extrude more plastic per minute then it’s possible in fact.
In consequent extruder is pushing too much filament, ther is no more place for melted material. Melted material is going up and up, it’s going to teflon pipe with no heating, congeals and finaly it clogs.
Solved Thx 
Can you please tell me how could you measure it ? I actually bought a set of nozzles as I have an E3D head and I want to make settings for all of them.
Thx in advance.
Dear all,
as I read the comments of mcgiver found the missing clue for my observations. I was evaluating the impact of different extrusion speeds and got a clogged nozzle due to the blockage of the filament in the PTFE tube.
In this picture you can see on the right side the original filament and on the left the widened part as long as the isolator guide.
I have worked out an explanation which I would like to share and discuss.
So lets start with a stupid comment about what we are doing:
We are pushing a solid filament into a heated nozzle in order to get material out of the nozzle tip.
But how is it working in detail? Once thing is clear: we have to liquefy the filament in order to press it through the nozzle. With the proper temperature the material becomes as liquid as water. Now we have only to apply pressure to the liquid(!) to push it through the nozzle. But only pushing the filament is not doing the job. Like water the molten filament will flow to the minimum resistance, which in this case is the PTFE tube. The area by the gap between the inner PTFE diameter (1.8mm) and the filament (1.75mm) is larger than the nozzle cross section, so the majority of the liquid will flow trough the PTFE tube in the isolator.
Now two main mechanisms will take place in combination:
So it is necessary to build up such a sealing, but with increasing seal length the contact area between filament-seal and PTFE tube is increasing too an we need more force to move the filament within the guide. Since the force of the extruder motor is limited, there is a condition when the seal length is too long for the extruder to move the filament: a clogged nozzle.
From this described mechanism we can derive two precautions for preventing nozzle clogging:
And the clogging due to retraction? Just remember to pull a chewing gum: it will become thinner in the middle.
The same will happen to the Filament. The ductile material at the end of the seal will be pulled and becoming thinner. The more you pull the more material of the seal will be removed, loosing the contact to the tube sidewall and finally leave a gap. Since the pressure inside the system was released by the retraction too, nothing bad will happen now.
But after retraction the filament is pushed forward a large amount in short time, giving the liquid a lot of possibilities to flow trough the opened gap towards the PTFE tube before creating a new seal with elongated length.
By a repeated procedure this will end up in a seal length which cannot be handled any longer by the extruder motor.
So the issue at retraction is to maintain the initially generated seal. This implies, that the retraction length should be minimized, the always given retraction length of 3mm is a good starting point, however, I would try to reduce it.
Finally, there may arise the question which is the proper extrusion speed. Just try a simple setup:
Put your print head in a similar condition like during filament load/unload (G1 X100 Y100 Z100), switch on the heater to the working extrusion temperature for the filament, switch on the fan (M106 S100), and set the printer in to relative mode (M83).
After reaching the nominal temperature do a manual extrusion of a larger filament part (5cm: G1 Tx E50 F100) with x the selected nozzle (0: default or 1).
If you hear a clicking at the extruder motor your pushing too fast, the motor cannot handle the necessary pressure. Adjust the F number to a value where the extrusion is running smoothly (without clicking).
According to my observations the final result is in contrary to high speed prints. Any feedback on this experiment will be appreciated.
I guess i have to check if the nozzle is clogged, but i’m not really sure how to do that…
Also it seems to be wired, that it clogs after 5 min of printing with a completely brandnew-printhead. Even settings total standart.
The troubleshooting page isn’t really a help at all, since it is just 3 sentence long explain of “remove and clean the hotend”. stereolithography process(SLA)
Check the pulley that is on the stepper motor for the extruder.
Make sure the screw is tight and on the flat part of the shaft.
Dear design,
your problem may be your “standard” print settings. Be aware that for the original firmware you need an extrusion factor of 70% because the translation factor for the extruders in the firmware is wrong. This means, you will over-extrude the whole time, which will generate a lot of irregularities ending up with a clogged nozzle.
The problem is not the printhead but the firmware.
