Blobs everywhere!

[Lmecano]

Hello,

I’m facing an annoying problem, may be two but I think they are linked.
1- The top layer of my part is ugly. There are strings everywhere and mainly, the plastic is pushed by the extruder like if there was too much plastic extruded… Even in some locations, I can see the nozzle trajectory in the plastic

I though that the problem was linked to the parameter in Slicer: “Top infill” in advanced parameters. However, I have tried the range 0.1-0.4 without success. Here is a picture of an example:

And then, on a 2nd example, a little cylinder, the last layers are completely crazy, the plastic is pushed outside the perimeter. Here is a picture:

For that, I have tried to disable “Retract only when crossing perimeter” in Slicer without a change. I tried that because this plastic blob is appearing exactly when the extruder is retracting.

Finally, I think these two problems are related because fundamentally, it’s like extruding too much plastic just on the last layers !
Do you have some ideas to solve that ?

Thank you for your time !

My config:
3d printer: K8200 with homemade extruder + E3D V6 3mm
Plastic: green PLA (really old)
Slicer: Slic3r 1.1.7
Software: Repetier 1.0.6

[ichbinsnur]

It’s not just the last layers.
You extrude too much material at all.

Try calibrating your extrusion rate and possibly lower the temp a bit, to prevent the small part from melting and deforming.
Also try setting your retraction to 2-3mm and at least 500mm/s retraction speed.
That will give less stringing.

But the Stock hotend is not very good anyway.

[Lmecano]

You’re right, I got a problem with the Estep calibration. I have corrected that. I have less than 1mm extrusion uncertainty on 100mm extruded.

Do you have an idea to improve the Estep calibration ? It is acceptable as a 1st calibration but it could be improved ! May be by printing test parts ?

I have also improved the retraction, I’m not sure that my motor and the plastic wire tension system will handle 500mm/s or more.
Now: 2mm and 300mm/s
Before: 2mm and 30mm/s

Anyway, the problems on the top layer and the blob on the cylinder have been reduced but they are still there ! My major concern is that even the perimeter borders are affected. There are some blobs appearing at specific locations !

My running temperature is 207°C for green PLA. The adviced range is 190-220°C, written on the plastic spool.

May be my Estep isn’t calibrated enough for that kind of small part ?

Thank you

[Tag]

Hy,
After PID correction, I print PLA with E3D V6 from 190 to 195 max depending of filament, with Retract 1mm for 50ms speed
Maybe 207 degrees are too much ?
Good luck

[ichbinsnur]

[quote=“Tag”]Hy,
After PID correction, I print PLA with E3D V6 from 190 to 195 max depending of filament, with Retract 1mm for 50ms speed
Maybe 207 degrees are too much ?
Good luck[/quote]

I think so too.
Lower your printong temp in 5°C steps to find the lowest acceptable value.

btw : 1mm of 100 makes an error of 1%, that is quite good for extrusion length calibration

I also calibrated my extrusion length best possible.
When i now change nozzles (i use an e3d V6, it is way better!) or change filament i set the extrusion multiplier to 1.0 in the config.
Then i fine tune the extrusion by printing a test part with thin walls and tweaking the extrusion multiplier (manual control) till i get smooth walls.
Then i use that new value and put it in the config to replace the extrusion multiplier.

[Lmecano]

I’m back with some investigations !

[quote=“Tag”]Hy,
After PID correction, I print PLA with E3D V6 from 190 to 195 max depending of filament, with Retract 1mm for 50ms speed
Maybe 207 degrees are too much ?
Good luck[/quote]

I have defined this temperature to maximise the bonding force. I can print at 190°C but from a mechanical point of view, it’s not that good.
Anyway, I have tried to print it at 195°C and nothing changed unfortunately.
About the retractation speed, I think I’m going to keep 300mm/s, it is generating more whiskers but I just need to put my part in hot water to remove them so it’s better.

[quote=“ichbinsnur”]I think so too.
Lower your printing temp in 5°C steps to find the lowest acceptable value.

btw : 1mm of 100 makes an error of 1%, that is quite good for extrusion length calibration

I also calibrated my extrusion length best possible.
When i now change nozzles (i use an e3d V6, it is way better!) or change filament i set the extrusion multiplier to 1.0 in the config.
Then i fine tune the extrusion by printing a test part with thin walls and tweaking the extrusion multiplier (manual control) till i get smooth walls.
Then i use that new value and put it in the config to replace the extrusion multiplier.[/quote]

Yeah but if you print a part which require 7meters of plastic wire. The last layers could be awful. I’m thinking about a tool to improve that. But on small parts, it’s fine, I agree.
Agree also with the E3D V6, a beautiful part !

What do you mean by smooth walls ? I have calibrated the extrusion width only to get 0.5mm walls with the according test part. I never touched the extrusion multiplier.
I have some “wobbles” on one wall where the extruder is finishing the layer and goes up to the next layer. But I think it’s due to frame vibrations.

I have also tried a range of Estep value (399-410 by step of 2) without improvement. The only thing which improved the part quality (perimeters and top layers) was to slow down the printing at 40% its normal value.

But I think that the problem is mainly the part itself… My printer isn’t perfectly calibrated but I don’t have any problem to print cubes/mechanical parts, even Yoda is pretty good !

Cube:

Mechanical part:

Yoda:

Thank you for your time