Extrusion error in fiirmware 1.4

I have build up a new K8400 and installed the firmware V1.4 for two nozzles from the very beginning.

I was wondering, why I need extreme low extrusion factors in the range of 0.7, until I did a calibration of the extrusion length.

I found a default value for the extrusion setting of 200 steps/mm, which gave 6.5mm filament pushing when programming 5mm.

With a correction down to 153 steps/mm the extrusion length is the same as commanded, the extrusion factor maintains around 1.

From hardware geometry the default value would be calculated to 156 steps/mm.

Unfortunately with this correct setting the filament loading/unloading isn’t work properly any longer. at loading the pushing is not long enough, the filament is not reaching the print head; during unloading the approx. 15 cm of filament remains in the guide tube.

Please review and update the firmware.

1 Like

There exist a user fix for this that some of us have put in varius previus posts and dealings of the firmware.

I have put a 1.4 version in a thread with a corrected stepper setting and load and unload functions along with other tweeks and changes in it.

viewtopic.php?f=61&t=15451

// Marlark

Thank you for the prompt feedback, I will check your update.

By the way, I would have expected that Velleman provide this bugfix in their official download link. Its definitely a task they are resposible for, it’s related to their hardware.

Was surpriced it didnt make it into the 1.4 version. I do agree with you.

// Marlark

just for completeness;

the extrusion setting in your firmware mod for the extrusion steps is 148.7.

I checked the drawings for the filament pulley, they gave an inner radius of 6.68 mm, which would end up in an extrusion step value of 152,48.

I would propose to use this value, since it is the target value and small variations will come from production tolerances.

For some unexpected reason this was found to be the setting for my printer (153).

Dont know how they came upp with that value actually i just used it based on previus info and it works.

// Marlark

Thnx for the info,
for not reaching the extruder you could manually push the filament in the nozzle

Best Regards,
VEL337

I’ve updated my firmware with the E calibration value of 152.48. After that I was horrified by the print results.

Finally It became obvious, that all !!! calibration values were different in your mod.

The problem was with the Z calibration: your new value was 3% higher than the original from Vellemann.

As a consequence the layer height was too high, too few material was extruded and it looked terrible. By the way, the final hight of the test part was 3% too high.

Since Vellemann is using a threaded bar with an inclination of 1.5mm/rot for the z move, there can be not so much difference from the theoretical value of 4266,66 steps/mm.

I don’t kwon where you got your values from, but at least I would strongly recommmend to use the target values from the “old” firrnware revision 1.4 and change only the E value!

Restoring the old Z-calibration ended up with the former print results.

the E calibration value was someone in a old thread that came upp (dont remember who came upp with the value) a couple of months ago with that i reused and then the other settings is values for XYZ is calibration values i have done for my own printer as a followup. However sins you picked upp that the E calibration wish i initialy thought was correct without actually double checking it i do agree maybe time to redo that part and get the value correct if it is wrong. and redo the calibration on XYZ again after to get them correct based on the altered E value.

// Marlark

Just did the calibration for it hoh61 and nope 148.7 is the correct one for this printer if you use your setting it over extrude by about 2 mm and to my printer the xyz setting gives a perfect box in term of the dimensions and thickness with that e value. However i can imagine that there is slight differences to this between different builds.

// Marlark

Hello Marlark,

thank you for this reply. To make it clear: I’m using a K8400, which I assembled some weeks ago.

The only reasons for these differences can be that there are different revisions of hardware for this 3D printer. Otherwise I cannot understand these deviations.

The values I gave were calculated from the hardware design which I found for the K8400, and for my printer they fit quite good (except the E-Value).

Maybe Vellemann can solve this issue.

P.S: I got an Idea for that:
I noticed that the filament was not aligned properly in the extruder. When loading the filament it was pushed sidewards by the extruder pulley, making it a little bit complicated to meet the upper hole at loading.
In this configuration the filament is pressed against the sidewall of the trench in the pulley, therefore the effective radius for the transport becomes larger, the E calibration value smaller.
I did a re-adjustement of the extruder pulley to achieve an alignment between lower through hole, pulley trench and upper through hole in the extruder. By this alignment the filament is pushed in the middle of the pulley trench using the design radius.