Extruder temperature / black burnt spots in prints?

[virtox]

Hi all,

During some of my prints I get black spots of burnt plastic.
I've seen it at 0.4 0.3 and 0.2 mm with varying support settings, but mostly on solid fills.
(no other settings changed)

At first it seemed random, but then it appeared symmetrically on some models, and seems reproducible.

As far as I can see:
It tries to deposit abs for too long in a small area, so it builds up a little to high
It then comes into contact with the extruder, and burns.
I'm not sure if the support builds up to high or if its the filling thats deposited too much.
But it just looks like it's hitting the same spot too often/long.

I will make some pictures and post them later.

But anyone else having this problem? Any idea what could be wrong ?

I was also wondering, what temperature readings do people get on the the extruder?

After a job is send to the printer and you open the maintain dialog, you can see both the bed and the extruder temperature.
When it "starts" it shows (the targets?) 100C for the bed and 260C for the extruder.

Then its switches to the read read values which slowly start to climb.
When the extruder hits 260C the printer beeps and starts the print job.
For a few seconds the temperature is still showing on screen and continues to climb, going over 270C..

On the other hand, the heated bed sometimes has not even reached 50C yet before it starts printing.
So for big builds I use the pre-heat function as a precaution, but seems a bit off.

But are these readings correct ? 260/270 ?
I thought ABS was best at 240 and starts to burn at higher?

Other than that, still amazed by the capabilities of Up!

Cheers,

Virtox

[bophoto]

Virtox,

Same thing here, I did 3 identical prints for shipping today, each had a small black spot on the surface at the same point.

Bo

[TTT험ทดสอบ]

Hi all,

105C for the bed and 270C for the extruder when start print, and the temperature is change when printing.

The black spots often appear at a small area, because the small area is hotter, and often warp.

Support area often warp too. We can't find a solutions. and still work on.

Darkhouse

[Linkreincarnate]

I don't get black spots. I clean my extruded head after each print using the snips that came with the printer.

[virtox]

It's not so much a dirty nozzle problem, I also keep my nozzle very clean.

But It does not happen on all models/prints, usually with shallow overhangs.
With or without support, (small) shallow overhangs tend to curl up on the edges.
Which then get burned by the nozzle when it moves over it.
IT reproducible, two identical print jobs will have the same burns spots.

I do hope it is resolved soon

Would it be possible to stop the curling by adding a very few lines between the support structure and the overhanging surface ?
Something like a "support" web, just a few lines to keep things down.

Code: Select all

MMMM/-/S     

MMM/ /S

MM/-/S

M/ /S

/-/S

M=model, S= support, - = support wire

[josejuako]

When bip the machine clean nozzle many times.
Or we need a new hardware to clean it .
The new software is more better to print.

J

[cyberbadger]

Just a thought - what about coating the outside of the nozzle in some heat insulative material?

Kaptop tape?
Ceramic?
Silicon?
Teflon?

cyberbadger

[-soapy-]

I don't have mine yet, but I don't think it would help if you put extra insulation on the tip, as after hours of heating it would still be hot on the outside. Also, from what I've seen on the RepRap and other forums you get issues if the tip isn't able to cool slightly, as the whole thing gets too hot and then the plastic further up melts and the head jams.