K8203 direct extruder kit - not working / bad documentation

K8200 3D Printer K8200 - Assembly and user manual
1

I already spent several hours to get the K8203 extruder working … without success.
The documentation (if it’s allowed to name it documentation) is really terrible.

Missing in documentation:

  1. When mounting the extruder as discribed on the right hand side then the FW needs to manually adapted viewtopic.php?f=50&t=14977#p68782 otherwise the extrusion is reversed
  2. In the document it’s described that 7cm PTFE tube is needed later on. Anyhow the whole document does not provide any information what to do with this 7cm tube.
  3. Description about … How to load the filament?
  4. Description about … How to change the filament?
  5. Bed leveling: With old extruder it was 0,2mm offset. With K8203 … is it still the same?
    6. Calibration of new stepper driver: Original driver was adjusted to 0.425V. Same value for new stepper driver or other value???

Currently i have the problem that the extrusion is not fluent. The extrusion is sometimes getting stuck for few steps.
I already increased the temperature (210 for PLA) but this does not help. Same also with reduced extrusion speed.
Anybody here who can help???

2

Hello,

I have also purchased a K8203 direct extruder kit in the hope to improve print quality.
I have also spend a lot of hours to get this kit working… without success.
It seems that the guys who had written the documentation, could not terminate their job… a lot of important things are missing.

The actual main problem is that the extrusion is not fluent. The PLA temperature is 200°.
It seems that the motor is not strong enough to push the filament. And this one is stopped.
I have disassembled and reassembled it a lot of times without improvement.

Does someone has also encoutered this problem and solved it ?

Thanks for your time.

3

This sounds like you didn’t change the driver card for the Extruder.

4

Hello Wrong Way,

Thanks for your reply.

I have changed the driver card furnished with the kit.

It seems that the spring is too strong. I tried to release the spring and it works better but the print quality is bad.

5

Are you sure the screw that holds the pulley on the motor is tight?
Also is the pulley aligned correctly?

6

Hello Wrong Way
I have checked the screws and the pulley’s alignement.
Everything seems to be ok.

Is the file Slic3r_175_pla_config.ini can be used as downloaded from Velleman site without modification ?

Thanks

7

Did you check the reference voltage for the driver card?
It should be the same as the K8400 0.89 -> 0.925
The rest should be 0.55

Yes that should be good but you will need to use a higher version of Repetier

8

Hello Wrong Way,

I have checked the voltages of the drivers
Z 0.434 changed to 0.558
Y 0.443 changed to 0.550
X 0.439 changed to 0.549

Extruder 0.5 changed to 0.91

Repetier 1.6.1

I do not see difference in the print. Very bad quality is still there.
It seems that the little temperature sensor on the extruder is perhaps positioned to close from the printing surface. it is difficult to push it up.
I’m not a specialist but this extruder seems to be not very well designed.
Do you know if this extruder could be replaced by a better quality model ?

9

After a lot of tests, I finally get a better quality.
I have modified the lower part of the extruder so the sensor can be placed without being to close to the print surface.

But the top of the printed part is not flat.
The honeycomb is not filled.

http://www.verticam.be/FR/PGPHO.php

Does someone has an idea of what I can do to obtain a better result ?

Thanks for your help.

10

I don’t understand what you mean by the sensor being to close to the print bed.
Could you post a picture of your modification?

11

Hello I have enlarged the hole containing the temperature sensor.
I could take a photo but I prefer not to disassemble it again as it seems to work now :slight_smile:

But the top of the printed part is not flat.
The honeycomb is not filled.

verticam.be/FR/PGPHO.php

Is it a parameter in the Slicer file ?

12

All,

A few weeks ago I decided to upgrade my belt driven extruder (upgraded with an E3D hot-end) by the direct drive extruder as offered in the Velleman K8203 kit. I did not install the included hot-end but modified the angular mount to fit the E3D hot-end.

Before:

98hljl.jpg1600×1200

After:

309jz1i.jpg1600×1200

In the past I printed magnificent pieces and since the upgrade the quality of the printed parts went heavily backwards. It looks like the extruder steppermotor was missing steps and has not enough torque to turn smoothly. As a result the extrusion looks like a cobblestone path.

The force required to push 1.75mm PLA through a 0.35mm hotend at 190° Celsius is between 15 N = 1.5 kg (slow) or 25 N = 2.5 kg (fast). The Nema17 steppermotor is able to produce 30 N, so there should be something else wrong.

I’ve spent at least 3 nights browsing the web to find a solution and another 3 nights with trial and error:

[ul]- steppermotor driver set to 0,75 - 0,80 - 0,85 - 0,90 volt

  • multiple adjustments to align the filament pulley
  • PLA extrusion temperature set to 170° - 175° - 180° - 185° - 190° - 195° - 200° - 205° - 210° - 215° - 220° - 225° - 230°[/ul]

Nothing helped !

After some more sleepless nights, I noted the following facts:

First of all it feels the driver spring is way too strong and pushed the filament too hard between the bearing and the filament pulley. I could barely push the filament by hand. As a result the Nema 17 steppermotor floats betweens microsteps and nervy skips.

This issue was easily handled: I grinded off one resolution of the spring.

After reading an in depth description how steppermotors works, I concluded the 1/32 step modus as default set on the high power DRV8824 driver wil not do the job. As test I replaced the DRV8824 driver by the original A4988 board with default 1/16 step modus and guess what: the extrusion was as soft as a baby’s skin !

Of course the A4988 driver is not able to deliver enough current as needed in direct drive modus for a long time without getting extremely hot, so this solution was only a temporary one for test purposes. Next I cutted the M1 and M2 traces on the backside of the controller board and inserted the high power DRV8824 driver over again. Cutting M1 and M2 forces the DRV8824 in 1/16 step modus with the same extrusion result as with the A4988 board, but now able to work for a longer time.

Sorry for the double post, but perhaps this is also useful for you…