Steppers, crown test and first use

New Home Forum Mostly Printed CNC – MPCNC Troubleshooting – MPCNC Steppers, crown test and first use

This topic contains 6 replies, has 2 voices, and was last updated by  Alex 2 weeks ago.

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  • #103227

    Alex
    Participant

    Hi,

    I have finished my MPCNC everything is square and correctly mount (I think). I first had some issues with the steppers that were just rattling but not moving. It happened to be a wiring issue, that I fixed after some research thanks to this video : https://www.youtube.com/watch?v=bR3853iNaW8

    Now everyhting moves but the steppers still doing that rattling noise but as soon as I remove the belt it’s fine. It’s like they are not powerful enough to move everything. I tried the crown test anyway but the drawing is really bad and not precise at all (almost square instead of round).

    I am using Nema 17 1.5A 2.4V 1.8°420mN.m with A4988 drivers on a Mega 2560 and a Ramps 1.4 but do you think it’s enough or should I switch to DV8825 and more powerful steppers?

    Also, to run the crown test, first I place the gantry on the corner and then I set the Z with a sheet of paper. I hit start, the tool goes up move to go in place and then go down, but way to down so the pen is pushed up.
    Do I miss something? I believe it’s a tool setting in ESTLCAM but I don’t really understand all the settings of the tool. Can somebody help me about it?

    Thank you for your help.

    Alex

    #103231

    Ryan
    Keymaster

    Did you set the pots on your drivers to match your steppers?

    #103350

    Alex
    Participant

    Thank you for your reply, I forgot to write that but yeah I did. I set 0.7 and I tried a bit lower but nothing better.

    And I don’t really know how to calculate the current tbh. I found some things that explains how to do it but I did not really understood it.
    I have read the page and the text about the stepper driver current here many times : https://www.v1engineering.com/assembly/ramps-wiring/ but I still don’t understand ^^’

    #103368

    Ryan
    Keymaster

    0.7V is for DRV8825, the setting and equations are different for A49’s.

    #103450

    Alex
    Participant

    Yes that’s what I thought, but I still don’t understand how to calculate it and I don’t find anything clear enough for me.

    Guess I will continue my research. Thank you anyway for your replies.

    #103470

    Ryan
    Keymaster

    The equations depend on one resistor, https://www.pololu.com/product/1182

    but if you are using the standard cheap imports there are thousands of youtube videos about it. These used to be the most common drivers in the world for many years. Typically the current you want divided by 2.5

    1 user thanked author for this post.
    #111728

    Alex
    Participant

    Hi, sorry for my late reply. I had to pause the CNC project for some times and I forgot to reply. Sorry again.
    I will try to understand that again to adjust the drivers. Thank you for the link.

    Best

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