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  1. #1
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    Apr 2013
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    6

    multiple start thread mach3

    hello folks,

    i've been trying to get multiple thread to work (mach3)

    so far, i've tried two methods (Z offset method, spindle angle method)

    this is the common method and the code

    3-start thread

    G0 G40 G18 G21 G80 G50 G90 <-G40~G90 absolutely required??
    G00 G53 X0 Z0 <-G53 absolutely required??
    T101M6
    G00 X0.025
    G00 Z0
    G00 X0
    M03 S120
    M08
    G76 X-0.5 Z-5 Q1 P2.1 J0.006 L0 H0.25 I29 C0.025 B0.0001 T0
    G00 Z0.7 (offset 1)
    G00 X0
    G76 X-0.5 Z-5 Q1 P2.1 J0.006 L0 H0.25 I29 C0.025 B0.0001 T0
    G00 Z1.4 (offset 2)
    G00 X0
    G76 X-0.5 Z-5 Q1 P2.1 J0.006 L0 H0.25 I29 C0.025 B0.0001 T0
    M9
    M5
    M30

    what's happening is, somehow the Z offset is ignored by mach3

    i think mach3 tries to repeat the prior thread, regardless of the Z offset position

    which means mach3 is somehow set to remember the prior position?

    has anyone experience with this problem

    share of knowledge or experience is greately appreciated

  2. #2
    Junior Member
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    Jun 2010
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    3755

    Re: multiple start thread mach3

    Interesting. Imho, that code should work.
    I assume that you are working in metric (yes, g21) and cutting soft aluminium?

    Have you tried starting several turns out to let the system synchronise? That is, start at (say) X5.0, X5.7, X6.4.

    Cheers
    Roger

  3. #3
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    Join Date
    Jun 2015
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    2729

    Re: multiple start thread mach3

    what's happening is, somehow the Z offset is ignored by mach3

    i think mach3 tries to repeat the prior thread, regardless of the Z offset position

    which means mach3 is somehow set to remember the prior position?
    hy dovidu i am not sure, but you don't seem to be certain about how the controller behaves, so let's check it :
    ... cut a thread ( preferably simple, no custom infeed paterns, unless you are sure that your cnc syncs beween different infeed paterns )
    ... shift start_Z with +pitch/2, and recut only a few passes, with total doc = a few tens ( same rpm and same X_start as before )

    if all ok, 2nd operation should deliver a small spiral ( small cut ), equidistant between the spirals of the 1st operation / kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  4. #4
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    Re: multiple start thread mach3

    Quote Originally Posted by deadlykitten View Post
    hy dovidu i am not sure, but you don't seem to be certain about how the controller behaves, so let's check it :
    ... cut a thread ( preferably simple, no custom infeed paterns, unless you are sure that your cnc syncs beween different infeed paterns )
    ... shift start_Z with +pitch/2, and recut only a few passes, with total doc = a few tens ( same rpm and same X_start as before )

    if all ok, 2nd operation should deliver a small spiral ( small cut ), equidistant between the spirals of the 1st operation / kindly
    hello deadlykitten!
    i've no problem with simple threading, and have used it extensively,
    i will give it a go one more time,

    i will use P1.5 for double start (original single thread P=0.75)
    and offset +Z0.75

    so
    1) P1.5 Z=1
    2) P1.5 Z=1.75

    i will post result
    wish me luck

  5. #5
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    Re: multiple start thread mach3

    Quote Originally Posted by RCaffin View Post
    Interesting. Imho, that code should work.
    I assume that you are working in metric (yes, g21) and cutting soft aluminium?

    Have you tried starting several turns out to let the system synchronise? That is, start at (say) X5.0, X5.7, X6.4.

    Cheers
    Roger
    i am actually machining ebonite material (kinda similar to plastic)
    and yes, i am metric (G21)

    "That is, start at (say) X5.0, X5.7, X6.4" <-- so let the machine run several air cuts? this helps with synchro?

  6. #6
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    Jun 2015
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    2729

    Re: multiple start thread mach3

    i will use P1.5 for double start (original single thread P=0.75)
    and offset +Z0.75

    so
    1) P1.5 Z=1
    2) P1.5 Z=1.75
    hy, if original thread pitch is 0.75, and inserts are for pitch0.75, then try p0.75 z2.5 and p0.75 z2.5+0.75/2

    thus, don't use pitch1.5 if insert is for pitch0.75

    you may cut with small doc, for example p0.75 z2.5 doc0.1 and p0.75 z2.5+0.75/2 doc0.1, and check if cuts are equidisant; thus you can check cnc behaviour, without cutting full thread depth

    also, about z_start :

    1) P1.5 Z=1
    2) P1.5 Z=1.75
    1.5[pitch]*850[rpm]*0.9/1000 = 1.1475, so z start should be >=1.15, considering 0.9/1000 to be a cnc specific constant, which delivers the minimal distance required for the rotary&linear axis to get in sync; i used 0.9/1000 only for an example, it may not be suitable for your machine

    wish me luck
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  7. #7
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    Re: multiple start thread mach3

    Quote Originally Posted by deadlykitten View Post
    hy, if original thread pitch is 0.75, and inserts are for pitch0.75, then try p0.75 z2.5 and p0.75 z2.5+0.75/2

    thus, don't use pitch1.5 if insert is for pitch0.75

    you may cut with small doc, for example p0.75 z2.5 doc0.1 and p0.75 z2.5+0.75/2 doc0.1, and check if cuts are equidisant; thus you can check cnc behaviour, without cutting full thread depth

    also, about z_start :



    1.5[pitch]*850[rpm]*0.9/1000 = 1.1475, so z start should be >=1.15, considering 0.9/1000 to be a cnc specific constant, which delivers the minimal distance required for the rotary&linear axis to get in sync; i used 0.9/1000 only for an example, it may not be suitable for your machine



    1) don't use pitch1.5 <----- i am trying to make double start version of P0.75 thread, therefore doubling the lead
    i am making a pen body. i used P0.75, it simply takes too many turns to open the cap.
    so i am trying to double the lead.
    shouldn't i be using P1.5?
    or it is possible to use P0.75 but double start? (to double the lead??)
    i am confused lol

    2) i will try to use thread with,
    1)Z1.15
    2)Z1.15 + ??? (i have no idea lol)

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