Under Extrusion problems

[Nylocke]

My machine runs very well mechanically. TL arms, cheapskates adjusted properly, etc, but I've been having problems with extrusion/plastic flow.

I have an E3d Kraken with custom nozzles, but I get the same issue with or without the custom nozzles. I'm not around for most of the prints that I do, but for the ones I am I don't hear any clicking extruder or see anything weird or unusual. Some prints (generally more complex prints) come out awesome, no extrusion issues that I can see, but the more simple ones (e.g. a circle with the center cut out and several circles revolving around the center) have issues.

I know I'm over extruding, I haven't had the time to really carefully tune the extruder to get exactly the amount I need, so I just resolved to over extruding, since its easier to subtract material for holes and things than to add.

Ignoring that and the issues caused by that (I know how to and can fix that when I have more time), I'm getting some other problems that seem really backwards. Its only noticeable on the top and bottom layers (those are the only solid infill places you can see after all), but I get this:

Isolated pockets of under extrusion

In other places I get the exact opposite (since I am over extruding), too much material and the nozzle is moving it to the side, resulting in some extra material creating "burrs". I can fix that of course, its pretty easy.

I'm running around the 250C range, so Ive got plenty of heat (I like to run a little hot, get better layer adhesion), so I can't really figure out whats causing this. The EZstruder seems fine, the gear doesn't have any plastic stuck in the teeth, its tight on the axle, etc.

[JFettig]

I see that you have only one perimeter, how many top and bottom layers are you using? I usually see something like this in the 2nd top layer, I have been running 3 or 4 to get a good solid part.

[Nylocke]

Its actually 2 perimeters and 3 top and bottom solid layers. Or in Cura setting lingo, Nozzle diameter .4, Shell thickness .8, Top/Bottom thickness .6, layer height .25 (rounds up to 3 top/bottom layers)

[Nylocke]

I think I found the problem. Apparently there was a gap between the nozzle and the heat break. I took the nozzle off to swap it out and there was a bunch of carbon in between the two. I thought I got it pretty goodntight. As my lathe instructor says, german torque!

doing a PLA print now, turning out fine. I need to clean out the other nozzle and make sure the depth of the hole is correct.

[bot]

Did you have any more thoughts on resolving this? I found I had the same problem, and even after tightening the loose nozzle, there is some under extrusion. Do I need to stick a guitar string up there?

[Nylocke]

Are you using the V5 nozzle? I'm thinking its due to 3 things, the bore length of the nozzle, the temp, and the coloring in the plastic (mainly issues with certain ABS colors).

Ive noticed that certain coloring (mainly the non primary colors, but it depends on the manufacturer) has a weird effect on how the plastic prints. I have some Red Octave ABS that doesn't have any extrusion issues, but the Silver SeeMe and even the Ultimachine ABS seems to be more "brittle" do to the coloring or something. Brittle isn't quite the right word, but it can affect extrusion, specifically after retracts.

I got 3 new V6 nozzles and heater blocks and the issues have been decreased significantly, the back pressure is way less. This was discussed in the V5 thread in the V1 MAX sub forum.

Ive noticed too high of temps, specifically with the weird ABS coloring, can do this as well. Printing at 250C will result in bad things with my Silver ABS.

[bot]

I'm using the stock hot end at the moment, but I have a v6 waiting to be installed. I just need to decided on the mounting method.

I think I kind of figured out my under-extrusion. It wasn't really the extruder but it was actually because one of the cheapskates was TOO tight, so tiny movements wouldn't actually register. The pulley would move, but the carriage wouldn't. The vibration damper would flex instead. After loosening all the cheapskates off I haven't noticed the issue yet. (Though I'm currently experiencing banding due to temp fluctuation... gonna wrap the hot end with kapton and do some more PID fiddling.

Thanks for your thoughts.