Hi,
I’ve beeing encountering this issue since I bought my Vertex 3D on last february (8 months), but I’ve succeeded at least to identify it : the filament gets stuck in the top of the printhead : yes, in the space between the tube fitting and the isolator guide. It is more frequent when there are a lot of retarction work to perform.
In this area the filament seems to be hot enought to become larger than 1.75mm under the feeder pressure & retraction go/back effect. But cool enought to definitelly get stuck.
Here a picture of the last one I’ve just extracted, the top is the side from the feeder, the bottom is the side that goes to the printhead. You can see the “enlarged” portion of the filament that causes it to stop printing :
Each time it happens I need to remove the tube fitting, extract the filament then screw it again.
It seems also to happen “some times” randomly and also seems linked to the PLA brand.
Some - maybe - useful details :
. Material : PLA (always)
. Printing at : 190°C
. Retraction speed : 110mm/s
. Retraction length : 9mm
. Feeding at : 65% (sometimes at 70%)
For the moment the most effective solution I’ve found is to disable retraction, but as you can expect, it has some unwanted “side effects”…
It is an issue very time and PLA wasting. Maybe some one knows some kind of “hack” to avoid it ?
so, using a 4mm retraction length makes it behave as well as when disabling retraction : same unwanted side effects… (!?)
In other words it acts like retraction has no retracting effect. But it is well enabled : I hear it.
when I see your response I’m thinking about your picture you presented in the initial post. In comparison to my last stucked filament it indicates that within the PTFE tube the PLA is still liquid.
This leads to the assumption that the temperature in the hotend is too high, which will also explain your side effects. Normally 190°C is a commonly published extrusion temperature, but as I explained, you can give a damn on this value due to the weakness of temperature control of the K8400 hotend design (see this post: http://forum.velleman.eu/viewtopic.php?f=62&t=18021). In my well controlled hotend design (approx. ± 3°C absolute accuracy) I’m printing PLA with temperature between 205 and 220°C, depending on brand and color.
So the next thought is to review your temperature sensor assembly and ensure a proper thermal contact.
I tried to show: proper thermal control is essential for reproducible print results!
hoh61, thank you for your reply.
So, if I understand well, it will not work better without modifications as you suggested in your blog, at least the temperature sensor…
I’ll analyse it more closely to see if it is in my knowledge range of “can do” or “can learn how to do”.
Thank you.
That’s what I’ve done and ok, in the last print I did not get the filament stuck but I had the same “unwanted” effects than when printing without retraction. I mean there are a lot of “little over printings” around the borders of the printed objects, following the printhead path…
[quote=“Wrong Way”]Not trying to offend.
Did you save the settings after you changed them?[/quote]
No problem, I’m not easily “offendable” : yes, the settings have been saved after every change and before a new slicing & print.
Regarding my problem : With the 4mm retraction set I’ve already printed two objects without that “stuck” issue, but the result is as bad as when disabling the retraction. That’s the reason why I’ve previously set the retraction to 9mm, because by setting less, there are “filament remains” that pollute my printed objects…
As promised, here is a picture of the result I get when using no retraction, or 4mm retraction which is the same. The piece in the picture has been made using 4mm retraction :
As you can see, it is a little “hairy” down there…
If you are printing with PLA it looks like the temp is still too high.
Check the thermistor for proper placement.
If it is outside of the heater block you will get incorrect readings and the temp will be too high.
[quote=“Wrong Way”]If you are printing with PLA it looks like the temp is still too high.
Check the thermistor for proper placement.
If it is outside of the heater block you will get incorrect readings and the temp will be too high.[/quote]
Yes, it is PLA. The thermistor seems to be at the right place : i’ve already replaced it several times without any change…
If you take a closer look, the top of my piece is printed like the extruder was partially obstructed : there is not enough PLA to make a full contour lines (opposing to the bottom part that is OK, despite of the “hairs”).
Sorry, but I did not get “the procedure” : your topic shows how to determine the viscosity of the melted filament, ok. But wich viscosity is the best for printing ?
the best viscosity it the one for the highest temperatur (with some margin), when no graviational flow will take place. I did an update of my page showing the final selection step. I hope this makes it more clear.
thankyou hoh61, it is a bit more clear now. I’m giving it some tries, for the moment no more successfull than the one shown before…
But I think there may be another problem, directly comming from the way the filament is feeded to the printhead : the stepper mottor “pushing” the filament is arround 70cm from the head, so it creates some kind of “pressure” effect due to the elasticity of the feeding tube and the gaps inside it. So, even if the head is not too hot to make the PLA “fall” by gravity, it may continue getting out only because of that pressure…
