3DPrinting

In what can only be described as "perfect timing", the 3d printing channel teaching tech uploaded a video about just this problem literally a day ago: https://youtu.be/vl0FT339jfc

Is the bad side of the seam where it stops or where it starts printing the outer wall? I assume it's where it stops and then it cross the wall to form the infill?

To add to the PA questions, are you sure that your PA setting actually are changing anything?

What printer is this and what firmware?

Does a spiral mode print work fine?

What if you print the part significantly slower (to rule out rigidity/acceleration issues)

What printer do you use. This is a mechanical issue. It's something binding as the one x or y is traveling could be a bearing or the stepper motor it self. It prevents the arc from being fully formed even though the machine thinks it is key point you made is that randomized z seam leaves the same mess, but if notice it's not all the layers are cut short only some.

Take the belt off and move the axis by hand slow and easy do you feel anything that isn't smooth like silk? That would be it. Feel the stepper is the drive gear tight any slip ?? Any play in the shaft side?

Edit

Looking at the pictures again I'd bet that if you went taller and printed faster, it would be even worse because the bad part got hotter and more bound up more Alternatively printing faster might make it better because you have the inertia to push past the binding spot.

I have one just like that on my scrotum and was told it's normal so I wouldn't worry about it too much.

So I stared at this for a while, particularly the pattern of the seam, I have a few questions. What type of infill are you using? how many outer wall loops? How much infill overlap (or whatever it is called)?

Also what happens if you rotate the part on the bed 90 degrees so the seam is on a different axis? Or maybe 45 degrees? This will make sure it’s not some sort of mechanical issue in one direct that shows up in this specific situation.

I know that all seems random but those are what I would check hah.

Duct tape.

Most probably PA. You should try adjusting it while printing using some g-code console. This way you get immediate feedback. What they often don't tell you is that pressure advance is not something you can calibrate once and forget, it's dependent on material, temperature, nozzle diameter and also a lot on feed rate and extrusion rate.

The need for PA and precise tuning is more pronounced the higher changes in extrusion rate you have eg, you print very fast or with wide or high layers.

Just play around with it a bit and I'm sure that you'll find a better value after some layers.

There are even macros that try to remove the feed rate dependency by effectively replacing every g-code that adjusts feed-rate by a combination of the original g-code pre-ceded by an adjustment of PA. I haven't tried them out yet though.

What's weird is the differences of the effect between the layers. Is the every layer the same or is the path different for different layers? Maybe post some images of the inside of the model.

_ I’m not using .... “retract on layer change”_

There's your problem.

Have you tried checking the belts and all the bearings/rails for tightness and smoothness? It almost seems like layer shift at the seam, and if you compare both seams side by side, layer by layer, it almost seems like the print head shifts equally on both prints for any given layer (e.g. left print looks over-extruded while right print is under-extruded, next layer up, it flips and right print looks over-extruded while left print looks under-extruded).

If not the belts or other hardware, perhaps it's a flow issue. Do you know if the gross looking seams are the start or the end of the layer?