Degraded bed adherence

K8200 3D Printer K8200 - Issues while printing
1

I have run into an issue with my K8200. When printing the first layer, the PLA’s adherence to the print bed is now quite bad. I get this using both Slic3r’s default start code, as well as Cura’s default start code. For those of you not familiar, Slic3r’s default is to position at 0,0,0 and extrude some amount to prime the nozzle, while Cura’s default is to position at 0,0,15(z) and drag the drip-extruded PLA onto the print bed.

The problem manifests thus: When printing starts, PLA is extruded, but doesn’t adhere right away. Instead, it loops back around to stick to the underside of the nozzle bezel (This is the stock Velleman nozzle, .5 mm). Eventually the extrusion will stick to the print bed, but the nozzle is now dirty and keeps either laying whiskers in addition to the main extrusion, or picks up the previously extruded plastic and ruins the layer.

If I am very diligent in picking off the stuck PLA, and lucky, I can get the skirt to print successfully and things are usually well behaved as long as I’m printing large, simple shapes. However, that’s not what I’m trying to print right now! I’m trying to print out the upgraded Z-axis mount, but when laying the first O-shaped lines for the screw holes, the filament again starts to bind up on the extruder nozzle or nozzle bezel, ruining the layer.

I’ve printed several very similar objects to this (A new fan nozzle and a holder for it). These all have had small round features in the first layer. Really, up until now the printer has been behaving fantastically (Won it in a Christmas raffle, so about 2 months of use). I’ve gone through probably 2 kilos of 3.0 mm PLA.

Here are some more technical details:
This occurs with both the glass plate at 60°C, as well as with painter’s tape at ambient and at 40°C (Yes, I’m cleaning the glass plate with 99% alcohol).
I’m using the latest firmware, but don’t have the upgraded Z-axis installed yet (firmware has been modified to allow this - my Z-axis is calibrated correctly).
Speaking of Z, the bed is level, and the Z-home has been set to achieve perfect positioning when both surfaces are at print temperature.
I get this when printing at both a .25 (.35 first layer) and .20 (.30 first layer) slice.
Temps are always 190°C or 195°C filament, with the print bed either at ambient, 40°C, or 60°C
Filament is MG Chemicals “Gray” 3.0 mm.

Any ideas?

2

You could try putting some cheap hair spray on the glass.

3

I find ccleaning the bed with acetone before printing every time helps

4

RE: Acetone: As stated above, the print bed is cleaned before printing.

So I’m really more interested in why the print performance has degraded over 2 months. Additionally, is filament sticking to the print nozzle something that only occurs with the stock nozzle, or is that an inherent fact of printing? IE will my eventual upgrade to a E3D hotend have the same issues?

5

The fact that curled up filament adheres to the nozzle will happen with all hotend.
It is just due to the fact the nozzle melts the filament and makes it stick.

If you print on the stock heatbed without glass, the PCB might have come to saturation with particles picked up from the printed
objects. Applying hairspray can eventually help there.

I print on a glass plate, with 70°C for PLA and 90°C for ABS.
For ABS objects i coat the glass with hairspray before every print.

cheers,

Christian

6

When was the last time you calibrated the Z axis?
It may have moved away from the bed.

7

[quote=“Wrong Way”]When was the last time you calibrated the Z axis?
It may have moved away from the bed.[/quote]

About 15 minutes before posting this topic :smiley:

Requesting a 0.30 mm Z-height with both the bed and nozzle at printing temperatures results in slight drag on my 0.30 mm feeler gauge.

[quote=“ichbinsnur”]The fact that curled up filament adheres to the nozzle will happen with all hotend.
It is just due to the fact the nozzle melts the filament and makes it stick.

If you print on the stock heatbed without glass, the PCB might have come to saturation with particles picked up from the printed
objects. Applying hairspray can eventually help there.

I print on a glass plate, with 70°C for PLA and 90°C for ABS.
For ABS objects i coat the glass with hairspray before every print.

cheers,

Christian[/quote]

Thanks for the knowlege!

Is it at all possible that the model file could be causing this?

8

Just as a test please try this.

Get a sheet of printer paper fold it so you have 3 layers.
Position the print head in the middle of the bed.
Home the Z axis on the paper now adjust the Z axis until it slightly drags on the paper.
Retry the print.

Please let us know the results.

9

OK, I’ve managed to get things printing. I was able to print the upgraded Z-axis mount by a combination of low initial layer height and 120% over extrusion. It resulted in a first layer that was wider than it should have been, but at least it stuck. Had to trim the edges of excess, but got the upgraded Z-axis holder and K8204 spindle installed.

The issue is by no means fixed, however.

I’m printing at a more reasonable 115% over extrusion on the first layer, but before was able to do 110% without issue. Trying to do 110% now results in a first layer of individual lines of extrusion, not a coherent surface.

Additionally, the first few CM of extrusion are “sausage-like”, bumps connected with thin whiskers, not the continuous smooth tube it used to be. Finally, the real issue seems to be that the extrusion is coming out and wrapping around 270 degrees to hit the side of the nozzle, creating a giant blob of PLA that sweeps any properly extruded material up into it. I’ve taken to watching the first extrusion like a hawk and cleaning off the nozzle with tweezers while it’s extruding the skirt. That usually allows a print, but not always. Also of note, prior to starting, or after the print finishes and the PLA is drip-extruding, it often comes out curved as well, and creates a loop that is attached to the extruder and then hangs down.

10

It looks like your nozzle is partially clogged (possibly by burned filament). It also happens when you switch from ABS to PLA. The PLA temperature is too low to clean the remaining ABS.

11

What’s the recommended method of clearing out the extruder bore?

12

Had the same problem two times and cleaning the nozzle always helped, so raby could be right.
I cleaned the nozzle by burning it out with a blow torch and then polishing with a piece of fabric wrapped around a match.
There are several videos about this point in the internet, e.g. https://www.youtube.com/watch?v=6bTfl35zlHE.

good luck

walo