Holes in prints/under extrusion

[KHMusicMan]

Hello,

I have been using filament I purchased on ebay. It was printing perfectly before, but now all of my prints are getting "holes" in them and feel like a sponge and bouncy when I touch them. I read online this has to do with "under extrusion" - where not enough filament is not coming out. I think It has to do with the clicking noise I hear on the motor. The filament never gets stripped. It seems to be pushing out the filament just fine, and it purges nice and consistently. I dont undersand why this is happening. Can someone please shed some light on this?

Thank you in advanced, here are some pictures of my prints:

1)

2)

3)

4)


(the PBJECTES in the picture above were flipped around. This is the 1st few layers of printing)


I am not sure what to do... I would greatly appreciate any help or advice...

5)

6)
6)

7)


Thanks

[TommyDee]

Wow! Looks like a feature. I can think of applications

I take it that this is with your recent success in increasing the PLA temperature to make the clear stuff work?

See if there is a melt bulb that has crept under the Teflon tube and extruded with some thickness to the stainless steel tube.

That can minimize the melt bulb and leave a very small orifice.

The clicks you hear are "pressure reliefs" which can continue (one tooth jump) but the effective extrusion pressure is suddenly released.
Which translates to a thin print. However, this is only a consequence from the restricted nozzle.

Easy enough to fix. Just rebuilt the nozzle... meaning clear out the old gunk and check the nozzle build for excess tube clearance.
Have you found the wire cleaning references?

At worst, there could be carbon buildup. Although some argue vehemently, I know this stuff burns if it gets too hot. Therefore, I, me, my opinion says that PLA and ABS nozzles should not be interchanged. This of course complicates significantly when you throw in temperature modifiers and exotic materials. Filled materials, for instance, can accelerate nozzle wear significantly. Just remember the "value" of one silly little part. I haven't worn one out yet (enlarging aperture), but I have burned one tip. And then sectioned it to find carbon blockage at the final cone once I got the zoom power I needed. Carbon is tough to remove! For the filament, it's like trying to walk directly through blackberry bushes.

Just a word of caution

[KHMusicMan]

SOLUTION!!!

Thank you TommyDee. I appreciate your through response. It was the stupid little plastic tube in the print head/nozzle. Apparently, the plastic tube wasn't in the nozzle far enough, so the filament was touching the metal before it was supposed to, causing the filament to pre-heat, and expand. the metal ring that wraps around the tubing in the print head fell off, so i guess without it, the plastic tube shifted.


Thanks =]

Wow! Looks like a feature. I can think of applications

I take it that this is with your recent success in increasing the PLA temperature to make the clear stuff work?

See if there is a melt bulb that has crept under the Teflon tube and extruded with some thickness to the stainless steel tube.

That can minimize the melt bulb and leave a very small orifice.

The clicks you hear are "pressure reliefs" which can continue (one tooth jump) but the effective extrusion pressure is suddenly released.
Which translates to a thin print. However, this is only a consequence from the restricted nozzle.

Easy enough to fix. Just rebuilt the nozzle... meaning clear out the old gunk and check the nozzle build for excess tube clearance.
Have you found the wire cleaning references?

At worst, there could be carbon buildup. Although some argue vehemently, I know this stuff burns if it gets too hot. Therefore, I, me, my opinion says that PLA and ABS nozzles should not be interchanged. This of course complicates significantly when you throw in temperature modifiers and exotic materials. Filled materials, for instance, can accelerate nozzle wear significantly. Just remember the "value" of one silly little part. I haven't worn one out yet (enlarging aperture), but I have burned one tip. And then sectioned it to find carbon blockage at the final cone once I got the zoom power I needed. Carbon is tough to remove! For the filament, it's like trying to walk directly through blackberry bushes.

Just a word of caution

[TommyDee]

Oh, yea, that was the first thought in my reply.

You are using a modified stock nozzle housing, right?

We like pix!

[slx612]

[QUOTE = TommyDee; 44389] Oh, sí, ese fue el primer pensamiento en mi respuesta.

Está utilizando una carcasa de boquilla de stock modificada, ¿no?

Nos gusta pix! [/CITAR]

¿que marca de filamento usas?

[TommyDee]

I prefer PrintrBot for their transparent filament and 3D Solutech for solid PLA colors.

Welcome to the forum, slx612

[slx612]

gracias

[KHMusicMan]

I keep getting this issue... I dont think there is anything I can do...

[slx612]

check the melting temperature of the filament, it must be the same as the cube3

[TommyDee]

I keep getting this issue... I dont think there is anything I can do...

I am an advocate of cleaning your nozzle from time to time.
I have found some really funny globs in the nozzle from various sources.
It doesn't take much.

Cleaning the nozzle entails a careful use of a butane lighter and some strands of copper electrical wire salvaged from a spare power cord or something.

The idea is that you get yourself about a 6-8" length of a single strand of copper wire that fits within the nozzle aperture -and- is strong enough to push without bending.
Warm the tip with the lighter sufficiently to push the wire through from the exit side; meaning, not the side the filament feeds from.
If not warm enough, the wire will not feed into the aperture. Add more heat. Be careful though, the tip does melt with a butane torch.

When you push the wire through, you will get a blob and some stringiness. If you inspect the blob, you might see some contaminants... maybe not.
Check that you can see through the aperture with light. If not, repeat.

The other reason this happens is if there is extra clearance within the nozzle between the aluminum tip and the Teflon tube inside.
Ideally, you want the tube touching the aluminum inside. A gap of 1/2mm is about the tolerable limit.
If the gap is say 1 to 2mm, it can fill with plastic making a 3mm donut that will not melt completely.
It is the center of this donut that now creates the aperture size rather than the aluminum tip.
The aperture in this blob will only be as big as the melt allows. Meaning that flow is restricted before it ever gets to the heat.