First of all I would like to thank you for the awesome K8200 3D printer. In last few months I have successfully created a lot of prototypes and just finished my first kg (roll) of the filament.
This might be irrelevant to the problem but as the filament was about to run out it had a tendency to break and I had to disassemble the extruder assembly quite a few times.
Now there is a new roll of filament loaded and I am having some issues. See the images of a sample single wall print below.
My first guess was that the filament is slipping but after closer examination it seems that it still is pulled in with a good force.
Then I thought that maybe the thermal sensor is not fully touching the heater and filament is heated too much/boiled. If that would be the case then it should improve after reducing the heater temperature. I tried it but the material extrusion stopped completely. So I concluded that the heater is heated to the correct 190 degrees.
I have been optimising only with infill, wall thickness and similar settings depending on the design being printed. All speeds and feeds are still set to the default values.
Now I am posting a question here as the last resort as I am out of the ideas of what could be the problem.
There are several problems that might cause inconsistent extrusion. I suggest to check for mechanical issues first:
is the small gear of the extruder fittet tight to the axis if the extruder motor or does it slip?
is the small gear not to close to the big one ? It happen oftens that the two gears are to close to each other, which will cose the gearwheels to block.
has the spring enough tension to press the filament against the hubbed bolt?
are the two screws of the bearing clamp grinded down, so that the clamp can move freely?
Of course the temperature of the hot end is important as well. If you have the feeling, that the thermistor has no good contact to the heating block, you can attach a piece of heat resistant tape (for example Kapton or teflon).
Then you have to calibrate your e-steps. Do a forum search, there are some postings how to do this, or search youtube, there are some good videos about this as well.
You can try and raise the voltage of the stepper driver for the e-motor to 0.55 V.
Well, I’m happy with an E3D V5 here, if there is something wrong with the filament feeder a good hot end will not be able do compensate. The K8200 with the stock hot end can do better as the pictures show, there must be something wrong.
Let’s see if Valdis can find the troublemaker.
The filament feeding mechanism seems to be fine. Any suggestion on how to remove a broken filament? It usually gets stuck when I am trying to pull it out and I have to partially disassemble the mechanism.
I put some heat sink thermal compound on the thermistor but nothing changed.
The sample on the left has a perfectly printed band in it. The sample on the right was almost perfect for a while. The sample in the middle shows a weird cyclic pattern which starts for an unknown reason. Well there is not enough material extruded at that point at least. And I still can not find the cause of the issue. As I mentioned before I have printed 1 roll of filament with no issues until this started to happen recently.
Regarding e-steps, I shall try to adjust them but as you can see the part on the right seems perfectly fine until the issue started again.
Also it is not consistent. Sometimes it starts instantly while other times later on.
When I first put the printer together I had some fun time troubleshooting what turned out to be faulty motor controllers.
Has anybody heard of motor controller failing later on? Huh, yes, I shall try to swap the extruder motor controller with X or Y one, that will show me if the controller is faulty.
Any suggestions are welcome and I will let you know how the controller swapping will go.
Regarding hotends, I might get one in future if you say it would improve the print quality. However I don’t believe that the current issue is related to the hotend.
I can conclude that the melting temperature of PLA filament is changing over time.
When I first got my 3D printer the filament did not break when left on the dedicated threaded rod for long periods of time. The prints were perfect at 190C.
Now the filament is breaking when left on the dedicated threaded rod overnight. Now to get perfect prints the temperature must be 181C.
The only other alternative explanation is that the thermal sensor is reading higher values. For example, the head is heated to 200C while the sensor reads it as 190C. That would fit in my current numbers as the true temperature being 190C while the sensor is reading it as 181C. I borrowed a professional visual IR thermometer to check that but the highest value I managed to read on the surface of the extruder was 160C while the sensor was reading it as 200C. So that test did not help much.
Had a problem with printing as well, was fine in the beginning.
I thought a bow-den type feed would be better and solve most of my problems with feed rates so I stripped the extruder feed unit to see how I could modify it. On checking the parts in the extruder feed, [ drive unit feed unit (( the bolt with splines on it driven by the gears and motor )) I found them to be clogged up with somewhat ground up PLA dust which I cleaned up including the framework parts. Then decided to check the BEARING TYPE: 608. Found that these were also jamming slightly on the drive shaft and the tension adjustment bearing. I found this bearing to be completely clogged up with dust and not able to turn at all, cleaned up all the bearings. PITY THEY WERE NOT THE TYPES THAT HAVE DUST COVERS ON. SURELY velleman COULD HAVE PROVIDED BEARINGS WITH DUST COVERS WHICH ARE 608ZZ TYPES, so I have ordered 3 new bearings with rubber dust covers from eBay.
This caused the extruder to give me low feed rates [ mostly lack of feed at times ] causing many a failed printed project to be scrapped. I had spent many hours trying to find this fault, even replaced the extruder with a V6 extruder unit with cooling fan.
BTW The extruder feed unit can be separated from the nozzle by fitting it with bow-den type tubing and mounting the drive unit on the upright just above the CPU Board and remaking the brackets for the extruder unit [if you using a extruder head similar to the V6 unit] being careful to only use the 6mm type fittings and carefully tap out the entrance and exit points for the filament, also turn the spool mounting post to allow the filament to feed directly to the extruder drive unit. This also makes the feeder bar lighter and easier for the z axis motor to rotate easier.
velleman should have provided the extruder with 608 ZZ bearings I’m not saying this is your problem but might help
[quote=“Valdis”]
Next step - calibration of e-steps. Do e-steps become inaccurate over time?[/quote]
Normally the e-steps can’t get inaccurate over time.
Whereas the filament diameter changes with every spool and also within one spool.
So tuning an even extrusion rate can be tricky, especially with uneven diameter filament.
I found it to be a good solution to leave the set filament diameter at 3.0mm and then
to print a thin object and tune the extrusion rate to get smooth wall thickness every time
i change to a new spool of filament.
Also the hobbed bolt often slips, so i “sharpened” the teeth with a dremel.
That way i managed to reduce it slipping on the filament to alost zero.