Movement Stutter

[Micael]

Hi, I'm having a strange issue, my printer seems to stutter when doing certain moves, I recorded a video of it https://www.youtube.com/watch?v=LIQ_ZDB ... e=youtu.be" onclick="window.open(this.href);return false; not sure how well it can be seen on the video, but it can easily be heard, in this case the move that the machine is making is:

G28
G1 Z10 X100 Y-65 F10000

It also happens if I change direction and do a X-100 Y60, it even happens on lower speeds, for example if I do a:

G28
G1 Z10 F5000
G1 Z10 X100 Y-60 F5000

although in this case I don't notice the skip on the the G1 Z10 F5000, just on the last command.

The skipping is extremely repeatable, since I currently have a FSR attached to the hotend, and if I repeat the same command 10 times with a G30 (probing) at the end of each I will get the same distance every time (0.01mm or less).

Do all printers do this? If not does anyone know what the problem is?

Thank you.

[Tincho85]

Yes, it seems to be normal.
http://forum.seemecnc.com/viewtopic.php ... 723#p71723

They all do it, it's an issue in the firmware, that is triggered by very long linear moves, so Slicer can be a contributor, basically AFAICS the code that breaks the move into parts for the delta calculation has a very small buffer and it ends up getting starved/can't keep up with the motion.

[youtube]http://www.youtube.com/watch?v=LGb9PChLzwA[/youtube]

It always happens to me when doing the calibration, right after the G28.
If there is a pause between G28 and the next command it doesn't do that.

[Micael]

Hi, thanks for answering, and that is in fact the issue, although as pointed out in the topic it doesn't create any issues, I tried with and without pauses and I got the same movements.

Which is almost a shame was hoping this would be the problem that I'm having, since I have been trying to use this software http://forum.seemecnc.com/viewtopic.php?f=36&t=8698" onclick="window.open(this.href);return false; and was able to calibrate with it, however something is probably wrong with my printer, if I go to the same spot but use different means of getting there, for example going directly there vs going to some other spot and only then going there, I end up being at significantly different heights from the heatbed, with differences as high as 0.09mm, this is the code I use to test this (requires a probe to test ofc):

G28
G1 Z10 X0 Y0 F5000
G1 Z10 X-110 Y-65 F5000
G30
G1 Z10 X0 Y0 F5000
G1 Z10 X110 Y65 F5000
G30
G1 Z10 X0 Y0 F5000
G1 Z10 X110 Y-65 F5000
G30
G1 Z10 X0 Y0 F5000
G1 Z10 X-110 Y65 F5000
G30
G1 Z10 X0 Y0 F5000
G1 Z10 X0 Y130 F5000
G30
G1 Z10 X0 Y0 F5000
G1 Z10 X0 Y-130 F5000
G30


G28
G1 Z10 X-110 Y-65 F5000
G30
G28
G1 Z10 X110 Y65 F5000
G30
G28
G1 Z10 X110 Y-65 F5000
G30
G28
G1 Z10 X-110 Y65 F5000
G30
G28
G1 Z10 X0 Y130 F5000
G30
G28
G1 Z10 X0 Y-130 F5000
G30

At this point I have spent over 20 hours testing things, have disassembled and reassembled the cheapskates 3 or 4 times (and adjusted them every time), have completely removed the belts to check for damage, have disassembled the arms and reassembled them, have even put some rubber bands on them to see if it solved the issue, have adjusted the belt tension several times, have checked tower alignment also several times and they are all at 90º (give or take 0.1º). So far the only thing I can spot that is probably not correct with the printer, is that I get black crumbs from the belts even at the top, which probably means that the belt is rubbing on the tower, but no idea if that's normal or not, and also no idea on how to fix it if it isn't.

[KAS]

You can use a file to chamfer the inside edges of the extruded tower. If the belt isn't aligned exactly parallel and center to the bottom, the belt can rub the edge causing the black specs you're seeing.

You can try to align the top pulley to center the belt over the bearing by changing the angle of the screws. It's difficult to juggle everything for alignment and tension. It usually takes a bit of trial and error.