Extruder Position at startup

I am having a very strange problem that just started happening. When I power up the printer, the E position will be at very large negative number, -5,143,673.50 mm. When I try to home the printer or move the x, y, or z axis individually, the extruder will turn in the negative direction without being commanded to do so. If I try to move the extruder (after preheat), it does not move. For every 1mm of position change, positive or negative, the "filament printed" decreases by 5,143m.

Sometimes, if I issue a G92 E0.0 command either through Repetier Host or by gcode on the sd card, this behavior stops and the printer begins to work normally again.    


  • Never seen this and makes not much sense. Sounds like you are somehow overwriting the ram position of E since extruder position starts with 0. This can happen if you have not enough free ram for the stack. Especially on 8 bit systems with only 8 kb and delta printers. Make sure you have at least nearly 1000 bytes free ram - when you compile firmware you normally see it near bottom. 
  • Repetier, 
    Thanks for responding. 
    Here is what Arduino 1.8.13 says after the compile.

    "Sketch uses 165392 bytes (65%) of program storage space. Maximum is 253952 bytes.
    Global variables use 4843 bytes (59%) of dynamic memory, leaving 3349 bytes for local variables. Maximum is 8192 bytes."

    I recently rewired this entire printer and replaced the motherboard and all motor drivers because it was acting strange. Could this be caused by a short in one of the electrical components? what other information can I provide that might help in sorting this out? 

    The printer was originally a Cultivate3D Beast V1, but I have made some modifications to it the extruder etc. 

    Like I said before, this problem didn't start immediately, and once I zero the E things seem to work normally. 
    I am going to investigate further, but it may be that I have to connect to the board with usb and zero through repetier host before things will work.

  • Free ram should be enough, so not the reason.

    In configuration there is a start gcode. You can put G92 E0 into it when you say that it helps if you send it via host. That is more or less the same just earlier in startup process.

    Short will not selectively only change E. They might crash firmware in total due to voltage drop or have no effect repeatable.

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