Format Error , Wrong Checksum , Extrusion Stops

I keep getting a repeated message throughout the logs with no obvious pattern or predictability.
Error: Wrong Checksum
Resend ....
Error: Format Error
Resend ...

I can run the same print twice off the same slice and the errors occur on different lines

The errors occur on different objects sliced on slic3r and cura

On about half the prints this error repeating eventually results in a momentary pause and the extruder will swap from 1 to 2 or 2 to 1 ( you can watch the offset change) and motion continues with no printing. Heat stays on but nothing extrudes. 

I re-downloaded both the Host and the Firmware newest versions, no change.

Error occurs in both Windows 8.1 and Windows 10 on the same notebook.

Custom Build printer no kit or premade
relevant hardware: 
 -Ramps 1.4
 -reprap discount LCD
 -fan extender
 -shielded USB cable
Baud rate 250000 

Short of removing/replacing hardware I can't seem to find any pattern or problem location.
Any help is greatly appreciated.


  • Resends occur These errors come from communication errors and get normally fixed. They do not depend on slicers. If you get only a few per hour you can normally neglect it. If you are using Marlin and get much more you should think about fixing the source.

    What often helps is:
    - Other/shorter shielded usb cable, some say even with ferrit block also it normally works without.
    - Other baudrate
    - Check that extruder/bed/motor cables are not in big contact with usb.
  • I'm using repetier firmware, not marlin.

    I ran the usb cable under the printer to avoid interference. There is about 50 mm and a 8mm thick sheet of uhmw between the usb and all components.

    The errors themselves are not really a problem, it's the extruder switch and ruined prints.

    I toyed around with cura host and could not reproduce the error with the same firmware, baudrate, and usb cable after a dozen test prints.

    I'll attempt running a lower baud rate tonight.
    I'll skeptical though. I've been running the same hardware for months minus the fan extender. The failed prints started in the last 2 weeks
  • When was the last firmware update? Some users had problems with switching extruders as well, but that suddenly stopped with newer firmware.
  • I reinstalled the newest firmware lastnight at a lower baud rate (115200) and so far 3 prints and no log errors or failed prints. 
    last firmware update prior to this was about 4 days while troubleshooting then a couple weeks prior to that. 
    I am by no means a programmer, but I'm not a novice either. 
    Its strange a firmware reinstall and a lower baud rate may have fixed the issue on this firmware but the error didn't occur on another host.

  • Yes, it is strange like the error it self. I never had it and for others having it, it disappeared before finding the cause just like it happened with you.
  • Well, the change in baud rate has removed all log errors, but the problems with the extruder switch and no extrusion is still happening.
    Part way through the print, there is a momentary pause and a quick offset of the extruder postion, then the host ran through the remaining 6hrs of Gcode in about 4mins. Then it displays print completed

    I vaguely remember reading something similar on this forum but I can't seem to locate it again, any suggestions?

  • Sounds like it executed the commands
    M111 S16

    The 16 debug field makes com test only which is very fast and does not move printer head. Or did it move in these 4 minutes? 

    The problem is why does the firmware think it should do this. I'm sure your code did not contain this. A communication error misinterpreted as this is one thing, but in binary mode without normal errors unlikely.
    You could add a print command where extruder switches get send and where executed to see if one of them gets called. It should then show in log. I think about a memory access at wrong position, but then the extruders would not swap. So this is quite mysterious.
  • After, dozens of test prints, taking apart the ramps and mega, straightening out and separating every cable, I finally got desperate and purchased a new ramps and mega clone. (I had not read the last reply here)
    While taking everything apart I noticed a slightly abnormal smell, that smell you get from heavily used electronics that are failing. 
    Seems to have been a hardware issue, as I am no longer getting any errors after a few dozen prints
    Thank you for the help.
  • Hello guys :) I'm making a CNC machine( 2D printing Only) as a graduation Project ....I'm using Ramps , ARDUINO MEGA , Marlin Software V1.1 and Repetier program ...when I upload a G-Code File the Repetier program starts but at a certain point the machine stops and gives me this error .

    Error:No Checksum with line number, Last Line: 29 Recv: Resend: 30

     What should I do to avoid it ????(i use inkscape and Makercam to upload the design to Repetier ) thanks :)
  • Check in log what that command was. Some commands like M117 get send without checksum as some versions had interpreted the checksum as part of the text to output. In Host you can change config to not send M117 to solve the problem.

    If it was just a communication error host would resend the line and it would continue.

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