Stringing after clogged nozzle  

RE: Stringing after clogged nozzle

Did you follow the E3D instructions for replacing the nozzle?  If not, you should probably look them up and reassemble the hot end correctly.

RE: Stringing after clogged nozzle

Posted by: Visitor247

[...] Anyway, the printer finished the task but some of the layers were not printed properly. Also the nozzle was completely clogged.

With the help of the Prusa page and some YT Videos I was able to unscrew the nozzle and get the filament out, using pliers and a lot more force than I wanted to.

Exactly how did you go about cleaning the nozzle? If you were inserting anything into the aperture opening and using a bit of force, it's entirely possible the nozzle opening is damaged, which can certainly explain the stringing and possibly other quality issues. It's always a good idea to keep a spare nozzle around to swap in if you're uncertain. Read up on properly doing a swap, and it only takes a few minutes.

Considering the amount of banging about it sounds like you did, I'd definitely re-calibrate Live-Z and XYZ as well, just to be safe. If you put a bit of force on anything, it's very likely to come out of calibration.

RE: Stringing after clogged nozzle

Thanks for the fast answers. I finally found some time to try a few things:

First, I unscrewed the nozzle as was described in a Prusa YT Video. As far as I remember I didn't insert anything into the aperture opening.

I unscrewed the nozzle today again, to look at it again but found nothing. I reattached the nozzle and than did a XYZ Calibration (with includes Live-Z). I then did this (see image) 1st layer print.

As you can see the nozzle stopped giving enough filament at the end and left a string again after finishing.

I found, that when I let filament flow out of the nozzle that it often curls around the nozzle instead of flowing downwards. Maybe that is what happens when the extruder moves to another place, hence the stringing? So maybe there's a tiny invisible dent in the nozzle?

I guess my next step is changing the nozzle (luckily two came with the printer), right?

RE: Stringing after clogged nozzle

Posted by: Visitor247

Thanks for the fast answers. I finally found some time to try a few things:

First, I unscrewed the nozzle as was described in a Prusa YT Video. As far as I remember I didn't insert anything into the aperture opening.

I unscrewed the nozzle today again, to look at it again but found nothing. I reattached the nozzle and than did a XYZ Calibration (with includes Live-Z). I then did this (see image) 1st layer print.

As you can see the nozzle stopped giving enough filament at the end and left a string again after finishing.

I found, that when I let filament flow out of the nozzle that it often curls around the nozzle instead of flowing downwards. Maybe that is what happens when the extruder moves to another place, hence the stringing? So maybe there's a tiny invisible dent in the nozzle?

I guess my next step is changing the nozzle (luckily two came with the printer), right?

Consider yourself lucky, my printer did not come with spare nozzles. Should it have? PR doesn't have a "what's in the box" description of kits/printers; there have been differences like this before where, e.g. assembled ones get a spatula tool and kits do not.

RE: Stringing after clogged nozzle

Posted by: vintagepc
Consider yourself lucky, my printer did not come with spare nozzles. Should it have? PR doesn't have a "what's in the box" description of kits/printers; there have been differences like this before where, e.g. assembled ones get a spatula tool and kits do not.

Mine did not. Fortunately, I'd purchased a couple of spares as part of my "first aid kit" and had it on hand when needed. Finding a 6in/15cm X 1.5mm rod was a fluke and turned out to be one of my most important diagnostic and repair tools. Fortunately, I had avoided ordering any of the "3D printer starter kits" you find on eBay and Amazon as nearly 1/3 of the contents seem NA for a Prusa printer (spatulas and the like).

RE: Stringing after clogged nozzle

Posted by: Visitor247

[...] As you can see the nozzle stopped giving enough filament at the end and left a string again after finishing.

I believe what is happening is that you're so low at the end that the nozzle is having trouble extruding filament and it peters out right at the end of the little box. Notice how rough the surface is on the bit of box above those lines. That's usually due to the nozzle literally dragging into the surface of the print.

I found, that when I let filament flow out of the nozzle that it often curls around the nozzle instead of flowing downwards. Maybe that is what happens when the extruder moves to another place, hence the stringing? So maybe there's a tiny invisible dent in the nozzle?

If you raise Z and extrude filament, it should come out smoothly and evenly and form a natural coil on the bed beneath. If it's off to one side, irregular or bubbling, you likely have a partial clog. Try doing some cold pulls. If that fails, replace the nozzle.

I guess my next step is changing the nozzle (luckily two came with the printer), right?

Hmm. Mine ... did not!

RE: Stringing after clogged nozzle

Well…, I was looking for the second nozzle I mentioned but wasn't able to find it. It's somewhat embarrassing, but I think I confused the 0.25 nozzle I ordered on top with a spare 0.4 nozzle, sorry.

Anyway, thanks a lot for the tip on Jeff Jordan's "Life Adjust". I found I had to raise the nozzle from -.750 to -.670. Unfortunately the stringing problem is still there. As soon as the head goes from one place to another it leaves a spider silk thin string.

And, is this normal? When I take away a bit of filament rest which pokes out of the nozzle by hand (say 0.5 cm), it also leaves a very thin string, easily a meter long before stopping.

I then tried to print some stringing towers. That was just a mess and didn't work out at all. 

I now ordered new nozzles and will let you know if they were the reason behind all this.

RE: Stringing after clogged nozzle

I forgot to mention: I did do two cold pulls but there was nothing from the old filament on those.

RE: Stringing after clogged nozzle

Posted by: Visitor247

Well…, I was looking for the second nozzle I mentioned but wasn't able to find it. It's somewhat embarrassing, but I think I confused the 0.25 nozzle I ordered on top with a spare 0.4 nozzle, sorry.

Not a problem. All sorts of goodies in the box. At least you didn't eat the nozzle with the gummi bears... or did you?

Anyway, thanks a lot for the tip on Jeff Jordan's "Life Adjust". I found I had to raise the nozzle from -.750 to -.670. Unfortunately the stringing problem is still there. As soon as the head goes from one place to another it leaves a spider silk thin string.

Jeff's procedure helps get the all-so-important Live-Z set correctly. It won't help with stringing, but is important for a good solid print.

And, is this normal? When I take away a bit of filament rest which pokes out of the nozzle by hand (say 0.5 cm), it also leaves a very thin string, easily a meter long before stopping.

I find that varies by filament and sometimes whether the filament has been exposed to high humidity or moisture. Temperatures can tie into it as well. Have you printed with different filaments from different manufacturers?

I then tried to print some stringing towers. That was just a mess and didn't work out at all. 

I've done a lot of testing and found that I tend to get worse stringing on those test towers than I do in actual prints. I've settled for getting stringing down, and just live with a little of the fine spiderweb stringing that I can easily get rid of with a pass of the heat gun.

I now ordered new nozzles and will let you know if they were the reason behind all this.

Try a new nozzle of the same size. At one point, I realized my original 0.40mm nozzle was making my life miserable, and I finally tossed it. Keep a few spares on hand so you don't suffer needlessly. The cost of filament from lost prints will far exceed the cost of a nozzle!

RE: Stringing after clogged nozzle

Back again, and a lot happened.

The new nozzle made a difference, but not completely. 

So I disassembled the extruder body. One thing that could have caused the problem may or may not have been the PTFE tube, so I changed it.

Unfortunately, and I don't know how it happened but one of the long screws stuck in the nut. The nut overwound. Luckily the screw was already so far out that I could grab the nut with pliers. I was able to turn the screw in a way that it broke. Otherwise I wouldn't have been able to get it out.

I glued in a new nut, reassembled the extruder body parts and did a full calibration using the wizard.

After z-calibration I printed a temp tower but something in the script seems to be wrong because the temperature did not change where it should.

The part that I printed does not look bad, but again (as you can see on the right side) some layers were not printed properly, which is just what happened first after the clogging. Stringing looks good, though ( I think it can count as "within the scope").

RE: Stringing after clogged nozzle

Small update: I changed the additional gcode from == to >= && <. Now it did work. The temp tower was printed really good until 200°C. Then the filament stuck in the extruder again.

My guess is that the filament is cooling so fast in the heatbrake that at 200°C it stucks in there. Luckily there was no problem with unloading it this time.

I cannot really see differences between 220°C and 205°C, even the bridging looks the same to me, so I should be fine with 215°C.

One day I will have to try the cheaper Prusa PLA that shipped with the printer again, although I'm a little bit afraid, but we'll see.

I'm also thinking about getting a straight original E3D v6 heatbrake (all these new terms I didn't now before starting this thread :-)).