Several Issues in print quality

K8200 3D Printer K8200 - Issues while printing
1

Hello,

now, after a quite bumpy assembly with some strange problems I finally get my printer working. Yeah!

But after several test prints I´m very disappointed about the really poor quality of my prints. There are several problems, some which I could get managed in some way, others where I have no idea, what may cause these. I´m using a stock K8200 with the z-axis-improvement offert by velleman. I´m very new to 3d printing and there I need some help to get my baby running… there are my issues, please help me solving them.

  1. Prints did not stuck to the plattform. I solved this so far by using an 2.3 mm glass panel I found in my workshop, and added the blue painter tape mentioned in some threads here. After adding the panel, heating up the printbed needs up to about 23-25 minutes to get 50 degree, very long time I think. Do I need a better psu?

  2. In some prints the layers did not stuck to the lower layers and the object was very brittle. I have releveled the heatbed, the lower layers are quite good now, but with more building height, the problem increases, so about 3 or 4 cm, the layers are brittle again. No Idea what to do here.

  3. The precision of the test prints was very poor. Object created in CAD with a messure of 61.5 mm i x dimension get printed between 60.8 and 62.3 mm. y axis has also deviantions about 0.1 to 0.3 mm. Investigating this issue, I found that the pulleys may cause this, the holes for the motor axis are not centered correct, so the pulleys wobble. This may also cause another issue I got, slipping of the ribbons when printing larger objects, ruining the job completely.

By the extreme mass of the printbed, the T5 ribbons are not that good choice I think, maybe better change them to GT2 to get more traction? I this step I could change the pulleys too, which should result in better quality, or not?

  1. Filament feeding… in 2 of 5 prints filament breaks while printing, I have always to be in sight of the printer, in order to reload the filement to the extruder when it was broken to keep the job running. Sometimes the filement breaks directly from the spool when I try to reload it. I´ve added a small alu pipe to the spool holder to get it easier to rotate, but this seems not to be the cause, nothing has changed since I added it. I using black PLA from velleman for my prints.

Ok, the K8200 is a nice simple and cheap 3d printer, and I know that I could not expect results like from a mendel90 or so. But when I see, what others have printed with the K8200 so far, I really disappointed that my one seems to have some really strange problems. Maybe I´ve done something wrong, but after checking the assembly guide again, I would say, I´ve done it right so far.

So, please give me some advise what I can do to get these nice prints I can see in the “compare your prints” gallery. Thank you very much!

2

To get reasonable Heating it’s a good idea to run the Heatbed off a 24V Power supply.
This would need a bit of electronics to control the 24V via the heater output of the Control board.
You can find circuits for a power expander or a simple relay circuit here on the forum.
It’s also agood idea to put thermal compound between the heatbed pcb and the glass, to get evely heating.

[quote=“juhu”]
2) In some prints the layers did not stuck to the lower layers and the object was very brittle. I have releveled the heatbed, the lower layers are quite good now, but with more building height, the problem increases, so about 3 or 4 cm, the layers are brittle again. No Idea what to do here.[/quote]
This can be a combination of underextrusion and too low printing temperature.
Try calibrating your extrusion length first. If you got that right, try slightly higher temperatures.

[quote=“juhu”]
3) The precision of the test prints was very poor. Object created in CAD with a messure of 61.5 mm i x dimension get printed between 60.8 and 62.3 mm. y axis has also deviantions about 0.1 to 0.3 mm. Investigating this issue, I found that the pulleys may cause this, the holes for the motor axis are not centered correct, so the pulleys wobble. This may also cause another issue I got, slipping of the ribbons when printing larger objects, ruining the job completely.

By the extreme mass of the printbed, the T5 ribbons are not that good choice I think, maybe better change them to GT2 to get more traction? I this step I could change the pulleys too, which should result in better quality, or not?[/quote]
I’d suggest to go for GT2 Belts and 10 teeth pulleys. That increases accuracy a lot.
You can also request properly made GT5 Pulleys as a replacement from velleman, if you don’t want to mod to GT2 at once.

[quote=“juhu”]
4) Filament feeding… in 2 of 5 prints filament breaks while printing, I have always to be in sight of the printer, in order to reload the filement to the extruder when it was broken to keep the job running. Sometimes the filement breaks directly from the spool when I try to reload it. I´ve added a small alu pipe to the spool holder to get it easier to rotate, but this seems not to be the cause, nothing has changed since I added it. I using black PLA from velleman for my prints.[/quote]

That sounds your filament is quite brittle at all, possibly because of wrong storage.
Is may help to “bake” the filament in an oven at about 100°C for 2 hours, to dry any humidity out of the filament.

[quote=“juhu”]
Ok, the K8200 is a nice simple and cheap 3d printer, and I know that I could not expect results like from a mendel90 or so. But when I see, what others have printed with the K8200 so far, I really disappointed that my one seems to have some really strange problems. Maybe I´ve done something wrong, but after checking the assembly guide again, I would say, I´ve done it right so far.[/quote]

Well, the design of the K8200/3drag is quite old, so it surely isn’t cutting edge open source tec.h :wink:
But with some mods, you can get really amazing prints out of it.

cheers,

Christian

3

[quote=“ichbinsnur”]To get reasonable Heating it’s a good idea to run the Heatbed off a 24V Power supply.
This would need a bit of electronics to control the 24V via the heater output of the Control board.
You can find circuits for a power expander or a simple relay circuit here on the forum.
It’s also agood idea to put thermal compound between the heatbed pcb and the glass, to get evely heating.[/quote]
Ok, I´ve seen some topics about this in the forum, will check these and find out, which one would fit to my plans. I saw a nice solution with a 24V and a 15V supply somewhere here…

[quote=“ichbinsnur”]
This can be a combination of underextrusion and too low printing temperature.
Try calibrating your extrusion length first. If you got that right, try slightly higher temperatures.[/quote]
The extrusion length is set in repetier, I´m right? Will try to do so, maybe need some help, but I will write here, if needed.
Temperature of the extruder is set to 190 degree, but varies while printing between 182 and 190 degree, where 190 it hold only for a few seconds.

[quote=“ichbinsnur”]
I’d suggest to go for GT2 Belts and 10 teeth pulleys. That increases accuracy a lot.
You can also request properly made GT5 Pulleys as a replacement from velleman, if you don’t want to mod to GT2 at once.[/quote]
I think I will change these to GT2, but I can find only pulleys with 20 teeth for it. Will this make a great difference? Or where to get them?

[quote=“ichbinsnur”]
That sounds your filament is quite brittle at all, possibly because of wrong storage.
Is may help to “bake” the filament in an oven at about 100°C for 2 hours, to dry any humidity out of the filament.[/quote]
Hm, this may be caused by a greater leakage we got about two weeks ago, which flooded some rooms. You can still smell and feel the wetness in some corners, so the conditions may be very bad for storage of PLA.

I think it is not a good idea to “bake” the filament in our oven, my wife wouldn´t have much understanding for this and I don´t like to sleep in the doghouse for a week or longer. But I´ve got a big bag of selica pellets, so I will put the PLA into the bag for some days.

[quote=“ichbinsnur”]
Well, the design of the K8200/3drag is quite old, so it surely isn’t cutting edge open source tec.h :wink:
But with some mods, you can get really amazing prints out of it.[/quote]
Well, if I could get an acceptable print quality just with making some mods, that will be ok. Learning by doing and see, what effects a mod will have to the prints can help a lot understanding these interrelations of mechanics, settings, material, etc.

I will make some investigation in the forum to build a list of mods, I´ve seen some also on thingiverse, which may be interesting. Will come back with my “list of improvements” soon to hear your opinion.

Best regards,
Jürgen

4

Hi juhu.

The 20 teeth GT2 pulleys will have better grip, whereas the 16 teeth ones will also give you mor precision and torque,
cause they have a much smaller diameter.
I don’t know where you live, but here is where i got my Pulleys in germany : youprintin3d.de/hardware/riemen … aehne.html

cheers,

Christian

5

[quote=“juhu”]Hello,

now, after a quite bumpy assembly with some strange problems I finally get my printer working. Yeah!

But after several test prints I´m very disappointed about the really poor quality of my prints. There are several problems, some which I could get managed in some way, others where I have no idea, what may cause these. I´m using a stock K8200 with the z-axis-improvement offert by velleman. I´m very new to 3d printing and there I need some help to get my baby running… there are my issues, please help me solving them.

  1. Prints did not stuck to the plattform. I solved this so far by using an 2.3 mm glass panel I found in my workshop, and added the blue painter tape mentioned in some threads here. After adding the panel, heating up the printbed needs up to about 23-25 minutes to get 50 degree, very long time I think. Do I need a better psu?

  2. In some prints the layers did not stuck to the lower layers and the object was very brittle. I have releveled the heatbed, the lower layers are quite good now, but with more building height, the problem increases, so about 3 or 4 cm, the layers are brittle again. No Idea what to do here.

  3. The precision of the test prints was very poor. Object created in CAD with a messure of 61.5 mm i x dimension get printed between 60.8 and 62.3 mm. y axis has also deviantions about 0.1 to 0.3 mm. Investigating this issue, I found that the pulleys may cause this, the holes for the motor axis are not centered correct, so the pulleys wobble. This may also cause another issue I got, slipping of the ribbons when printing larger objects, ruining the job completely.

By the extreme mass of the printbed, the T5 ribbons are not that good choice I think, maybe better change them to GT2 to get more traction? I this step I could change the pulleys too, which should result in better quality, or not?

  1. Filament feeding… in 2 of 5 prints filament breaks while printing, I have always to be in sight of the printer, in order to reload the filement to the extruder when it was broken to keep the job running. Sometimes the filement breaks directly from the spool when I try to reload it. I´ve added a small alu pipe to the spool holder to get it easier to rotate, but this seems not to be the cause, nothing has changed since I added it. I using black PLA from velleman for my prints.

Ok, the K8200 is a nice simple and cheap 3d printer, and I know that I could not expect results like from a mendel90 or so. But when I see, what others have printed with the K8200 so far, I really disappointed that my one seems to have some really strange problems. Maybe I´ve done something wrong, but after checking the assembly guide again, I would say, I´ve done it right so far.

So, please give me some advise what I can do to get these nice prints I can see in the “compare your prints” gallery. Thank you very much![/quote]

Don’t expect perfect prints directly after assembly.
It needs lots of calibrating and adjusting.
That’s the fun of this cheap printer.
Keep reading the forum and the quality will improve!