Weird extrusion issue

I have a Taz5. I’ve put well over 1500-2500 hours on it. It has open beam X, stock z and y.

I’m currently printing on hatchbox abs at 230/90 with no fan. I’ve used about 10lbs of this plastic with no issues. I’m also printing 3mm shells and 75% infill and printing slow at 35mms, .3mm layers.

When I noticed the problem I rotated the part 90 degrees to try and narrow it down to a single axis. It seams to effect both.

I measured the stepper temps they range from 130-150f.

It looks like an odd over extrusion issue. Prints were perfect prior to a couple days ago. Same slicer settings.

I pulled the extruder carriage to inspect, no obvious issues. Swapped to a fresh roll of filament no difference.

Also the extruder does grind on top of the over extruded part but not on the smooth part.


Any help is appreciated

Can we see the STL? Is it all parts or just that one? What does a calibration cube look like on it?

It definitly looks like overextrusion that starts mid part. The first layers might be a small bit off, but not enough to produce that effect. the motion segment looks fine, it’s tracking like an Openbuilds X equipped machine should… 90 is a bit low for the bed, but it doesn’t look like you have any lifting at all. I’d be inclined to look at the extruder wire harness as a starting point, or the bearing on the idler arm. It looks almost like the motor is exerting a constant force, hits the midpoint and starts extruding more, then backs off again. A short could do that if it has a short, goes into full contact and then moves away, but that would be a very rare issue. usually seen with extended wire harness segments. Since position doesn’t matter though, that almost makes me want to think it’s something in the model itself. A thin outer shell that looks connected to the main structure with a void behind it would produce that effect.

It starts into the issue on the top layer when it starts making the longer straight segments, but the curved perimiter doesn’t seem affected. Issues on longer runs can be due to overcooling of the bore, or a failing heater carriage, but I would expect to see the same issue on the longer perimiter run unless its just running it enough slower that the fillament is able to completely melt.

If it were me, i’d probably verify the temperature on the hotend with a point and shoot thermometer first, if that comes back ok, maybe spring for a second refurb hotend and swap it out to eliminate electrical on the hotend, and maybe even go so far as to run a temporary extruder wire harness to route around the existing one.

is this in an enclosure at all? If so, how is the electrical board vented?

Are you running any of the new experemental firmware variants?

enclosure yes, has fresh air intake from the exterior of the enclosure.

no experimental firmwares.

here is the stl
C-Combo.stl (1.5 MB)
there are also parts a b and d. they are all exactly the same except for tooth layout of the gear.

a printed with no issues, b with slight issues c I have stopped 1-2 hours after start.

after extended inspection the main extruder gear (large) has a huge amount of play in the bearings. the bearings are actually loose in the housing. im still not terrible sure that is the cause but it is definitely going to be fixed.

That could definitely contribute, the bolt can move and pinch filament that way. The model looks fine, that’s going to be a challenging print though. You might be running into too thin areas with that side hole and getting overheating and lifting that is compounding to later layers. Its right about that area where the issue starts. Is that hole present on the other parts?

Yeah they are all the same, except for the gear. First one printed perfect, no lifting at all. Second is where the over extrusion started. It completed as well. No problems with lifting at least on there parts.

I’m going to fix the issues with the gear and go from there.

Any thing else that you think could contribute?

The only other things I can think of would be very u usual. If it were a nozzle tip blowout it would be affecting the corners, a software issue would be more random or more consistent, not just concentrated in the middle. I’m not ruling out a haunting.

that is exactly what im thinking, ive been using 3d printers for over a decade, and I havnt ran in to an issue I didnt know the fix in a while. so a haunting sounds quite possible.

Ill update once there is no play in the extruder bearings whether it works or not.

Printed an extruder body with no issues, but I also didn’t fix anything… maybe it is the stl…

Which direction was that sitting on the bed? You’ve got some ringing going on after the Idler latch screw holes in what I’m guessing was your Y axis. You may want to check the bearings for debris and contact pattern on the rods when you get a chance.

you would be right the ringing is on the y axis, those igus bearings fit a little loose, and it has goeetn worse since I got the printer, I will be doing your open rail system as the fix, eventually. Ill probably fo the z at the same time.

As a temporariy fix, try sliding the Y bearing holders closer together on the bed plate if you have any room and then tighten them back down. that should help.

Cool I will attempt, thanks man

What’s ringing? Is it that vertical wavy pattern?

Yup, Ringing gets its name from the easiest way to detect it, a faint circle shape just after a hole in an object. What happens is that for a given layer containing a cylendrical hole, it basically shows up in a given layer as a rectangular void in the layer. Printing that hole starts with an X axis movement transitioning to Y, or vice versa. When that movement starts, if the rod is gummed up it will start to move and be pulled along by the bearing, but friction from the rod will slow it enough that you get one or more faint buildup areas in that perimiter. Think of it like pushing something heavy or stuck. it’s difficcult at first, but once you get it going it’s ok as long as it doesn’t stop again. if it stops you have to use more force to get it moving agian.

The friction usually doesn’t go away in subsequent layers, and its usually about the same amount of friction so you end up with a similar blob in the perimiter exactly the same distance from the start of the hole. Since each following layer gets closer to closing the hole, the position of the blob follows the hole. The distance is the same, the starting point isn’t.

Thats why ringing can be frustrating. It sometimes occurs lower down and then magically dissappears at the next identical hole because the gum in the bearing worked its way out. Or a piece of depbris will fall into a bearing mid print, screw up one hole, then work its way out for the rest of them, etc.

There are things that look like ringing that aren’t. Really thin walls right after a hole can tend to ripple due to heat and look like ringing sometimes. Majorly excess belt tension can also produce a ringing effect, though in my oppinion if your belt tension can make it do that, you need to redesign your axis to take stronger belt tension.

Nice explanation, thanks. Not suffered from that yet but it’s good to know in case it ever happens.


while the extruder is still being used, it is printing flawlessly. It seams that it was a weird error in the stl. the parts all printed they just dont look great, but since they are just part of an internal flywheel for a bb8 it shall be fine.