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Start G-code being ignored?


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Posted · Start G-code being ignored?

Our UM2+ where I work has been out of calibration by about -2.5% (20mm cube prints as 19.5mm) in the y direction since day one. Scaling each and every part in Cura is a pain. So, I tried putting "M92 Y82.05" in the "Start Gcode" field to scale it up using 80 steps/mm as the baseline. I'm actually not sure that 80 steps/mm is the proper baseline so please correct me if i"m wrong. In any case, it seems to be ignored. The print comes out exactly the same size as without. I also tried using Cura via USB and sending the gcode directly to the printer. Upon pressing "send gcode", the printer display blinks out for a second as if the code is being received. Is this normal? This also has no effect on the print size.


Any thoughts would be greatly appreciated as this issue has wasted a considerable amount of our time. Thanks!

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    Posted · Start G-code being ignored?

    What gcode flavour do you use? The default gcode flavour for the UM2+ is Ultigcode (mislabeled as Ultimaker 2 in Machine Settings). Ultigcode does not use start g-code afaik.

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    Posted · Start G-code being ignored?

    Thanks for the quick reply. I left the default which was Ultimaker 2 since I am not too familiar with the subject. Can I use a different flavor that will use the start gcode without affecting other functions? Marlin, RepRap?

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    Posted (edited) · Start G-code being ignored?
    2 hours ago, tps2000 said:

    So, I tried putting "M92 Y82.05" in the "Start Gcode" field to scale it up using 80 steps/mm as the baseline.


    The easiest way would be to write this line in a plain text editor, followed by a line with M500, save the file with the *.gcode" extension to the sdcard and "print" it.

    This sets the steps/unit and saves it to the printers EEPROM. The benefits: no other things are affected and no need to change start gcodes or GCode-flavor.



    M501         ;read current parameters from EEPROM
    M92 Y82.05   ;set steps/unit for Y
    M500         ;save changed value back to EEPROM


    Edit: a different deviation of x and y is usually a good sign that there is something else wrong with the hardware.

    I would check for any mechanical issues. Perhaps are the axis not longer perpendicular to each other, or a sliding block or linear bearing is damaged, a loose pulley, or the belts have slack and needs to be replaced... such things...

    Edited by tinkergnome
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    Posted · Start G-code being ignored?

    I tried "printing" the gcode file as you suggested and once again there was no change in the scaling. Mechanically there seems to be nothing wrong and this scaling problem has existed since the machine was new. It is unfortunate that the firmware doesn't allow for scaling. I have an inexpensive Creality CR-7 that has scaling parameters and it works perfectly. 


    I also tried changing the g-code flavor to marlin and added the start g-code and the results were the same, no change. I guess for now we are stuck with scaling the model in Cura each time. 

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