Have you checked to make sure there is nothing weird with the .stl(have you rotated it to see if the anomaly moves?) and is all your motion lubricated and moving freely?
Assuming “yes” to the above, take a look at my visual aid.
Where there is a red X, an axis is switching directions.
If that is where the anomaly is then you want to check that axis. Is there any play anywhere? Is the belt tight? Is the belt too tight(this can cause it to vibrate like a guitar string on a direction change)? Have you done any mods to that axis that would make the moving parts heavier?
Where there is a blue O, both axis are moving at equal speed.
If the anomaly happens here it’s a little more tricky. When any axis moves it causes vibration. When both are moving at the same speed they can cause resonance and significantly amplify the vibration(this is more common than you might think). You should be able to feel it by lightly laying a hand on the machine. Let me know if this is the case and I can help you troubleshoot further.
Hope that helps!
-Jesse
In your S3D settings are you printing inside to outside, or outside to inside? Try reversing and report back. This may be very similar to the ringing effect you see on sharp corners. But in this case it could be the print head transitioning from the inside of the shell to the outside for the next layer and the “ringing” after effect as the mass of the print head settles down. You could also try adjusting the S3D setting that indicates a random start point for each layer.
@Mindfull has good info here. People always wonder why I tell them to print at 73mm/s!
There is a strong indication that your resonance can match stepper movements, etc. I had this exact situation on some extruded text on a print. I kept getting slower and slower on the print… First 60mm/s, then 30mm/s, then 15mm/s. All that happened was the ringing changed. It actually almost went away at 73mm/s. I have been printing at 73mm/s a lot after that (xy print speed).
Yes, and it makes some sense because I can see that it does the inner loop then hits the outer and reverses direction so there is momentum from direction change and lateral position change.
Before changing speeds I am going to try a print (just top part) with random and also with most efficient start-stop and see what I can see. Just for fun.
Interesting. I was told recently that a full step on the Z is 40 microns to make layer heights a multiple such as 1.2 instead of 1. Another thing I pick up is this for better resolution prints and save some time is drop to 1.6 layer height and print the infill at 3.2 every other layer. Seemed to work out ok.
Ok, test 1, slowed non print X-Y movement down from 4200 to 1000 and no difference.
Now running at reduced print of base 1000mm/min and 50% outer shell. Almost done.
Watching the preview while printing it is the direction change doing it I am convinced. It goes from the inside ring to the outer with a direction change at the seam and then the outer to the inner with a direction change again at the seam and I can see a similar effect on the inside in the opposite direction from the seam.
This thread is dealing with vertical ringing along the x/y, so I dont want you to come to the wrong conclusions when you apply that to layer height, which has a slightly different effect.
As far as infill at every other layer, this can be good if you are printing under certain circumstances, and at a small enough layer height. When your height to width ratio gets too high, printing every other layer of infill, you can get infill that does not adhere well, making your part weak, or it can become so wispy it does not hold your top layers up well.
But yeah, printing infill at every other layer, and support at every other layer, when it works, is GREAT! (really increases printer time), and I do it for my personal printing sometimes, but not for my professional printing.
So at 1000mm/min it is good, at 1500mm/min it is definitely passable but the ringing is starting.
Slowing the non print XY speed didn’t do anything and I think because it is simply reversing direction and going from inner shell to outer shell (2 shells) so the movement is small but abrupt.
I can try really setting the non print speed to extremely slow and see!
Also I learned about the ratio and I think 1.6 and infill at 3.2 every other is about the limit maybe 1.8 and 3.6.
Yeah, the common wisdom seems to be that you should keep your layer height at 80% or less of nozzle diameter. I personally never go above 50%, even on infill, for reasons above.
