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GCode instructions getting skipped or re-arranged while being executed

NakshatraAichNakshatraAich
in General
Hello. I am using Repetier-Host for passing a series of gcode instructions for a custom dispensing task using a Ender 3 Pro (Creality V4.2.2 board). My task requires high-speed movement and extrusion. Unfortunately, as I increase the overall speed of the printer (Feed or F instructions), it seems to skip steps or re-arrange them by itself. This happens at lower speeds as well, though not at the same frequency than when in high speed.
My G-code consists of repeated instructions that trace a specific profile and execute a sequence of tasks. Below is one such code block.
; --- Move to (-87.00, -125.00) ---
G1 X-87.00 Y-125.00 F1500 ; Move to point
G1 Z-10.00 F600 ; Lower to dispense height
G1 E122.00 F60 ; Extrude
G4 P300 ; Wait
G1 E118.00 F60 ;Retract
G4 P300 ; Wait
G1 Z0 F600 ; Lift nozzle before move
While executing, the nozzle often goes lowers and instantaneously lifts up to its previous position and then extrudes. This action is unintended and inconsistent.

Since my code is generated through a python script I am mostly sure the error does not lie in the GCode. Please let me know if you have encountered anything similar.

Comments

  • RepetierRepetier
    There is no code to rearrange order of execution. Some commands might get executed out of order (emergency commands) but none of them is one. You can see this also when you enable logging.

    Skipped steps can become a problem especially if the happen at the start of an acceleration they might continue until the end of the move. Reason is always that force required for set jerk/acceleration/speed it not high enough. For extrusion F60 is not really fast but for dosing application you might need lower jerk compared to extruders. If you use Repetier-Firmware (since you posted in this forum also ender uses marlin I think) you should also know that minimum jerk also depends on acceleration, so check firmware output at startup. Lower acceleration allows lower jerk.
  • NakshatraAichNakshatraAich
    Understood. Thank you for the help. 
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