Hi all,
As a beginner, I’d love your advice and suggestion on the result I get.
I’m using a velleman k8400 and velleman PLA.
Sliced with Cura at 0.1 layers, 50 MM/s.
6 Likes
Bon, je pense que tu parles français, mais on va quand même continuer en anglais! 
First of all, welcome here. Let me introduce myself: Dominique Vienne, owner of Gloomy Spark (a hub and a colorFabb reseller in Switzerland).
It seems that your Marvin had some troubles between layer X and Y. It could be the filament or the printer. I really do not think that the settings are involved (bad news).
The first thing I’ll do would be simply to print another Marvin using the same gcode. After that you’ll be able to compare if the problem is the same or not.
If the problem has disappeared, I would bet that the quality of the filament was not that good (air or water bubbles or filament diameter).
If the problem is still there, we’ll troubleshoot step by step.
By the way, I also own a K8400 which I have a LOT of problems to calibrate. Was it the same for you? How did you do?
Have you had missing parts in your kit? How many? Was the support prompt to send the parts?
Thanks
J’avoue être plus à l’aise en français oui 
Hi Dominique, tanks for your answer.
I agree the problem seems to be physical and not the settings as i’ve made 4 tests with differents settings (speed, temperature…) and the result is still not as good as i want.
I’m not sure the velleman filament is the best but it’s for now the only one i have (colorfab pools are coming soon).
The vertex seems a good printer but your’re right, calibration and tuning is difficult. I was unable to print circles because of bad belt tighteness. It’s been corrected but maybe to tight now. I will try to release it a bit.
I’d had no missing parts (au contraire ;)) and didn’t ask for support.
Z calibration seems to be the whorse part of building. And i’ve found a printable stabilizer for z axis (wich was printed quite perfectly !)
Here is the lineup of all my tests with Marvin
Inbeso
4
Hello,
I’ve a K8400 as well and mine was delivered without a front plate. Velleman was very fast in sending me this missing part.
Spare parts is a completely other story (especially nozzles)…
Did you go through all the steps of checking the amount of steps for the motors to turn for X,Y,Z,E?
I think you extrude a bit too much.
The thing in Marvins’ neck is something that I still struggle with. It seems that only when all settings are perfect this is rather OK.
Have you installed an improved ventilation?
Davy
Sketch
5
Not bad… your Marvin looks quite good.
The design has overhangs, for example at the eyebrows and ears. I found my trial Marvin had problems with these overhangs.
(like with the ears of your Marvin) Increasing layer thickness from 0,05 to 0,1 helped. So your layer thickness should be allright.
(the printed material tends to sack less if the extruded cylinder is thicker)
Put the fans at 100%…
Perhaps you can play with the speed some more. My Vertex can work at 100 mm/s quite nicely.
The extruder head will then have less time to transfer heat to a product area, and do better at overhangs…
Best regards
@PrinterBob seems to be right… I would also check the Marvin settings and further the flow rate.
The Z stabilizer that you’re talking about is this one? Vertex K8400 z-axis stabilizer by h60 - Thingiverse
Did you use those? Velleman Vertex K8400 XY carriage alignment helper by h60 - Thingiverse
Just wondering… How did you change the belt tightness? By playing with the clamps?
My problem is that X and Y movements are not smooth by using the motors… it is smooth using hands. The result is simple: squares are rectangles, circles are… ?, volumes are shifted.
Want to switch in French? Do not hesitate.
It won’t pass the 3DHubs tests… Look at the back of the Marvin…
It looks really nice! Nice job! Success in the future
Hi Davy,
K8400 kits seems to be strangley packed 
Mine was shipped with all the parts, plus a quite complete set of corners connectors, plus the plastics part for the second extruder…
Didn’t check the steppers settings, I’ve seen the extruder one is badly missetted originally but thought hte new firmware fixed it.
I put it on my to do list !
No improved ventilation yet, do you think it’s usefull ?
100 mm/s ?
How did you tune everything to obtain such a speed ?
I’ll try to push it when i’m sure the belt are all OK.
Thanks, Sketch
Thanks,
I hope succes, but it will be many hours of tuning before it.
Continuons en anglais, pour rester en communauté mondiale
The Z stabilizer is the one you mentionned, not sure it’s so usefull than it means but i’m now sure not to suffer z wobbling.
The pulley where aligned using the self printed alignment tool, usefull (why didn’t velleman provide it !).
The belt wich where under tightned was the ones between the motors and the shafts. Just unscrewed a bit and pull it down. The movements are visibly smooth, by hand and motor. I think about redrawing the motors support to include a screw for belt tithening…
I’ll check flow rate. Cura asks for 90% but i’m not really sure the gcode contains this value.
By the way, as a Mac user, i’m really sad about bad support from velleman when not using windows/repetier host…
Sketch
13
Apart from the belts, cooling of the stepper drivers is also very important. (under the machine) .
If the drivers overheat, layers shift. So make sure air flows nicely over your circuit board. (Possibly with the housing I designed (newsketch.nl) or use an other design from the Velleman forum.
As long as you don’t have shifting layers, you should be ok with 100 mm/s. I had a lot of problems with the drivers (returning them etc) but never with the belts.
I havent seen a shifted layer since I installed the housing many prints ago.
What a great housing !
I’ll try to print it, thanks for the tip.
Sketch
15
tnx! be careful with the positioning…(print a small skirt for checking) as it only just fits. I wonder how it works out! Gr.
Inbeso
16
I did receive two bottem plates instead :-). Received like you some spare parts as well for the second extruder. You do need these if you would like to install a second extruder.
I have seen some influence with air flow that comes from all sides. Many people have developed special ventilation nozzles so probably it is worth investigating this.
With great surprise the test passed…
Ah… un peu étonné quand même… Tes clients risquent de te mettre des mauvaises reviews si tu n’améliores pas ta qualité d’impression, selon moi.
Ce n’est pas un jugement de valeur… ma K8400 me fait de bien plus grandes misères encore! 
Etonné aussi !
Je fais un dernier test actuellement avec toutes les corrections suggérées, c’est le jour et la nuit. Je vous poste ça demain en anglais
Hi all,
Thanks a lot and a lot for all your precious advices !
Lots of improvements have been made to my Marvin…
First test: untightening the X and Y motor belt (2 images on the left)
A big big forward step !
Also tried to cooldown mainboard using a print found on thingiverse (Vertex K8400 Bottom Fan Duct by Hest - Thingiverse) but no improvement. I sure it will help in the future.
Next test: calibrating E stepper… Velleman firmware says 200 steps/mm, the real good value is about 150 steps/mm. Change it and , miracle, no more over extrusion (under extrusion to be honnest) (center image)
Last Marvin (i begin to hate him :)) resliced with 100% extrusion flow and I now think I’m done with physical issues. (right image)
Of course it’s still not perfect but I’ll try to improve it more by changing Cura settings.
Thanks again million times for your help, this community is really great.
