No extrusion after a few successful layers

[the_keen_bee]

Hello Community,

the HBP printer is my first 3D-Printer but - after reading all the beeverycreative-documentation and video tutorials and the most posting in this forum, I was able to assemble and setup the printer successfully
I set up the end-stops, home-point, the stepping values for the three axis (like described here https://beeverycreative.com/forum/viewt ... ?f=8&t=373 , I leveled the bed several times and so on ...

But unfortunately it was not possible to print the 3DBenchy example, which is recommeded in the HBP manual. I used all software tools (CURA 15.04) and given settings, values and parameter from the user manual. I changed several parameter (print speed, extruder temperature, bed temperarure and so on) I also used the settings from the calibration tutorial (refer link above) ... I changed finally the type and vendor of the PLA - but nothing works.
The results look like this:





My basic settings / setup:

1,75mm PLA
Extruder temperature: 215°C
Bed-temperature 65°C
Printing from SD-Card
G-Code generated from CURA 15.04




After starting the print - everything looks fine (to mee ) ... the skirt and the first layers stick very well on the bed ... all following layer looking very good as well. But after some layers/minutes it seems, the extrusion stops. The print head ist still moving (corresponding to the G-Code) but no PLA came out anymore.


The Z-axis is moving more and more away from the alredy printed part - sometimes the exrusion started later on again and produce "strining" or "lumps" or the printer finished the job without any further extrusion.
Sometime this behavior started with some drops on the last layer (you might see this in this pictures:




Here you can see how the extruder is already slightly above the last successfully printed layer but the extruder dos not support any PLA.
Very suspect is the fact, that the extruder stepper motor ist still moving. The pressure on the roll opposite of the extruder gear is also high enough.



It would be very nice, if somebody can help me with this problem.

Many thanks and best regards,
"the_keen_bee"

[Geoffrey Borny]

Try to decrease the retraction amount. The default settings don't work verry well. Try with a retraction distance off 1.5mm instead of 4.5mm.
It looks like everyone has had this problem in the beginning and by decreasing my retraction amount the problem was solved.

[GVeyron]

Ah I recognize this problem. The big problem is the retraction speed of 40mm/sec. Change this vlaue to 10-15mm/sec. Retraction amount could be 1.5 to 4.5. I recommend 4.0mm, that works for me the best.

The next tip against mid-print stops is lubricate your filament with rapeseed oil (?).

[the_keen_bee]

Many thanks for this hints - with a reduction of the retraction amount and retraction speed it has been printed without interruption.
Finally the 3Dbenchy has been printed



But now, I have some issues with stringing and warping (with an other object).
I will try to play around a little bit with the settings in CURA.

Just one basic question: is it necessary to evaluate, change the parameter and do some test prints for each new object (print job) depending to it's dimensions and geometry?

Kind regards,
t_k_b

[GVeyron]

In the beginning it is. After few weeks/months you know what settings you need for what object.

Stringing is the result of a too low retraction amount and/or too high print temperature.

Warping can have several causes. Even I have sometimes problems with. Tips: Increase bed adhesion with glue stick and reduce the print speed (max. 30-40mm/sec for all parameters!)

[the_keen_bee]

Great ... Thank you for the hints .. ... I'll try it.

There seems to be also a huge difference between the types/vendors of the filaments, isn't it?

The example print (3dbenchy) could be printed (with minor issues) with my blue PLA filament, but it doesn't with my white one
My experience is growing "print" by "print" - but oviously it is a huge effort: changing just one or two paraemter - start print - waiting a couple of hours .. and in case of an unsuccesful print do it again and again (trial and error)

best regards,
t_k_b

[the_keen_bee]

After several fails to print with different PLA, I guess, that I found the reason for the problem.

The PLA (I tried different types and vendors) blocked/clocked in the cold end of the extruder nozzle. I assume the cold end is getting to hot over the time and the PLA is melting in that area and during retraction it will cool down and blocked in the cold end.
The situation apperas always after 30-40min after start. This let's me assume, the cold end needs some time to get hot enough. Print jobs with shorter duration will be printed successfully.
I'll now try to contruct a more efficient cooling for the cold end (and the aluminium block) or I'll replace the cold-end steel nozzle by a PTFE part.

May be there are some other people with similarly behavior, which can share their experience.

Many Thanks,
t_k_b

[GVeyron]

Hello Keen, mostly you are right. The construction/cooling of the extruder is not wrong. The problem are the used and standard parameters in Cura. De retraction parameters are too "agressive". The speed and distance of the retraction are too high. The hot PLA comes into the cold-end and cools down. As a result that the nozzle clogged.

[Wim Adriaens]

That's excactly the same problem that occurs with my prints now. Could it harm to set retraction off?

[MrDoom]

Turning retraction completely off will leave you with stringing between parts the printer head has to move while not printing. Try 1.5mm at 10-15mm/s and a printing temperature between 190-200ºC that's when I have the best results

I also lowered my extruder voltages to about 0.8v