Is this the right lead screw?

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This topic contains 10 replies, has 3 voices, and was last updated by  John 1 month ago.

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  • #46359

    John
    Participant

    I just bought this “8mm T8x2 Threaded Rod for Trapezoidal ACME Lead Screw“.  Is this the right one to replace my threaded rod on my MPCNC with?  I know I probably should’ve asked first before buying it but either way, no biggie.

    Running DIV268N drivers at 1/16 steps.  Can anyone tell me what the steps per mm is that I would need to enter/change in Marlin?

     

    Thanks

    #46360

    Ryan
    Keymaster

    You should be fine just use my firmware for the rambo mini and change the board to whatever board you have.

    #46363

    John
    Participant

    Oh OK.  I’m using your firmware now, but for ramps T8 threaded rod.  So I’m guessing it would be easier to do it the way you said rather than changing the values needed to make it right

    #46370

    Ryan
    Keymaster

    Just cut the Z value in half on the ramps version, either way only one edit (I’m 99% sure).

    #46373

    John
    Participant

    I think on mine might have to be much less than half.  My steps per mm on Z right now is 2600.  It is a fine thread 8mm rod.

    When you said to reduce it by half, did you mean from default 400?  I think default was 400??  Could be wrong

    #46376

    Martin S
    Participant

    Hi John. If this math is correct, then your steps per mm should be 1600.

    You are using a TR8*2, which has:

    1 Start

    2mm pitch

    2mm lead.

     

    (motor step angle x driver microsteps) / (thread pitch x starts) = steps/mm

    For a 1.8º motor: (200 x 16) / (2 x 1) = 1600 steps/mm

    For a 0.9º motor: (400 x 16) / (2 x 1) = 3200 steps/mm

     

    Please someone correct me if wrong.

    Hope it helps, Martin.

    #46377

    Martin S
    Participant

    Forgot to mention, if you have EEPROM enabled you will need to update your steps/mm there too (or just there :P).

    #46378

    Ryan
    Keymaster

    Im not at a computer to check but that doesn’t sound right. You can verify by matching the minirambo z steps.

    The t8’s should be 4 start.

    #46379

    John
    Participant

    OK thanks guys,

    I’ll have a look at the rambo config.h.  I also think this is a 4 start thread

    #46381

    Martin S
    Participant
    I just bought this “8mm T8x2 Threaded Rod for Trapezoidal ACME Lead Screw“. Is this the right one to replace my threaded rod on my MPCNC with? I know I probably should’ve asked first before buying it but either way, no biggie. Running DIV268N drivers at 1/16 steps. Can anyone tell me what the steps per mm is that I would need to enter/change in Marlin? Thanks

    uhmmm, that’s a TR8*2, or you are using TR8*8 like stock MPCNC? (https://shop.vicious1.com/collections/parts/products/300mm-leadscrew-and-nut)

    TR8*8 has 4 starts and a 2mm pitch, so 8mm lead. But for a TR8*2 is like I said earlier.

     

    If you do have a TR8*8 then your steps/mm should be 400. (x16 microsteps, 1.8º motor)

    #46383

    John
    Participant

    I can only go by what it is sold to me as, and indeed it is TR8X2

    Thanks Martin

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