Repeated movement with no extrusion

itisnot_me

I am printing a good 15 hr'ish print (currently 4 hours in) and I have noticed something a little odd. Every now and then it started to go over a part that it just printed and didn't extrude anything. Almost like it was nozzle sanding. It looks like it would get stuck for a little bit going over this area the. After about 1-3 minutes it would continue to print.

Samuel Pinches

I assume you're printing from USB? that sounds like communication glitches between the LCD and motherboard. I would guess that if you try printing from a computer / raspberry pi, you won't have this issue.

itisnot_me

I am printing from the USB stick. I have tried to print from the computer and leave the laptop sitting there on but I had multiple cases where the print just stopped mid print and had to restart the printer and lost what was already printed.

Firmware for both the mother board and the LCD are updated so I am not sure why that would be the case.

Samuel Pinches

You can see what is going on - print via usb stick, while connected to pronterface, and with debug mode turned on: 

M111 S1
Then you can compare the log of what the main motherboard prints out (what it recieved) with the commands that it should be printing in the original gcode files. No doubt you will see two things happening

• Errors that the motherboard detected due to incorrect checksum, so it asked for the line again
• Errors where the checksum and command were so corrupted, that the checksum actually was correct, so the printer executes the command without asking for it again (I think this is those random movements you see)

Anyway, that's my theory. I don't have a lot of confidence in the LCD module, its been flakey in about every single way possible from what I've seen people experience. Could also be electrical noise from other cables (stepper drivers make a lot of electrical noise) making its way onto the serial communication lines between the LCD and motherboard. Difficult to troubleshoot that though without a good oscilloscope.