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  1. #1
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    Mach 3, g28 safe travels height

    Hi everyone, relatively new CNC guy here. I’m using a Chinese 6040 machine, Mach 3, and fusion 360. My issue is I’ve designed a milling toolpath in fusion 360, I’ve set all My clearance heights correctly in Fusion 360... but when I initiate the program in Mach 3, at the start of the command the router travels exactly on the Z0 on its way to the initial cut. I believe this is related to the g28 command? I just can’t for the life of me figure out how to change this travel height in mach 3. Is of course like it to start, raise to z2 or z3... travel to initial cut area and then begin. The fusion 360 forums have all directed me to a Mach 3 settings issue.

    Anyways, thanks so much for any help. I’ll post the g code below.

    Cheers, Al

  2. #2
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    Jan 2005
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    10680

    Re: Mach 3, g28 safe travels height

    Quote Originally Posted by WoodLover View Post
    Hi everyone, relatively new CNC guy here. I’m using a Chinese 6040 machine, Mach 3, and fusion 360. My issue is I’ve designed a milling toolpath in fusion 360, I’ve set all My clearance heights correctly in Fusion 360... but when I initiate the program in Mach 3, at the start of the command the router travels exactly on the Z0 on its way to the initial cut. I believe this is related to the g28 command? I just can’t for the life of me figure out how to change this travel height in mach 3. Is of course like it to start, raise to z2 or z3... travel to initial cut area and then begin. The fusion 360 forums have all directed me to a Mach 3 settings issue.

    Anyways, thanks so much for any help. I’ll post the g code below.

    Cheers, Al
    No code attached Just Cut Paste the code, a G28 can be a problem You don't need to use a G28 in any program
    Mactec54

  3. #3
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    Quote Originally Posted by mactec54 View Post
    No code attached Just Cut Paste the code, a G28 can be a problem You don't need to use a G28 in any program
    G90 G94 G91.1 G40 G49 G17
    G21
    G28 G91 Z0.
    G90

  4. #4
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    Quote Originally Posted by mactec54 View Post
    No code attached Just Cut Paste the code, a G28 can be a problem You don't need to use a G28 in any program
    For the life of me I can’t attach an image. The site won’t let me, but here’s the first few lines of code

  5. #5
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    Re: Mach 3, g28 safe travels height

    Wrap in code tags ? It's in the 'advanced' post options. There's probably other ways as well.
    Code:
    G90
    G20
    G17 G64 P0.001 M3 S3000 
    F75.00
    G0 Z0.2500
    G0 X-8.5865 Y-0.7747
    G1 Z-0.0300 F50.00
    G1 X-8.5865 Y-0.7747F75.00
    G1 Y0.7710
    G1 X-8.5850 Y0.8052
    G1 X-8.5786 Y0.8454
    G1 X-8.5703 Y0.8717
    G1 X-8.5592 Y0.8946
    G1 X-8.5398 Y0.9200
    G1 X-8.5219 Y0.9351
    G1 X-8.5084 Y0.9433
    G1 X-8.4935 Y0.9500
    G1 X-8.4688 Y0.9573
    G1 X-8.4314 Y0.9618
    G1 X-7.6572 Y0.9617
    G1 X-7.6354 Y0.9596
    G1 X-7.6049 Y0.9527
    G1 X-7.5860 Y0.9454
    G1 X-7.5682 Y0.9361
    G1 X-7.5515 Y0.9248
    G1 X-7.5360 Y0.9114
    G1 X-7.5217 Y0.8959
    G1 X-7.5097 Y0.8782
    G1 X-7.4992 Y0.8601
    G1 X-7.4832 Y0.8224
    G1 X-7.4735 Y0.7830
    G1 X-7.4711 Y0.7625
    G1 X-7.4704 Y0.7282
    I agree with the idea of removing G28 from post process, works fine as long as you're aware of tool position before hitting cycle start.
    I'm assuming you change tools manually.
    Anyone who says "It only goes together one way" has no imagination.

  6. #6
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    Re: Mach 3, g28 safe travels height

    Quote Originally Posted by WoodLover View Post
    G90 G94 G91.1 G40 G49 G17
    G21
    G28 G91 Z0.
    G90
    Just remove the G28G91 This has no place at the beginning of any program

    And try it like this G0Z0. this should go to your machine Home Zero

    Do you Home the Machine Before you setup your work offsets G54 and Tool height G43

    To post your program just save it as text in MS word or Notepad then you can just paste it here into a post
    Mactec54

  7. #7
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    Re: Mach 3, g28 safe travels height

    WoodLover
    I see now it's a 6040 so no tool changer
    Are you using a tool setter or do you measure by touching each tool to the top of the stock ?
    Anyone who says "It only goes together one way" has no imagination.

  8. #8
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    Re: Mach 3, g28 safe travels height

    Hi all, sorry for the late reply.

    When i use mach 3, I manually direct the tip of the bit to the top of the stock, then I zero everything out, to include "reference all to home"... When everything is completely zeroed, I regenerate the toolpath, start my spindle and hit start. With this code, however, it moves along the stop of the stock until it gets to the initial starting/entry point. from there, it raises in the air to what should have been the safe travel height, and then it initiates a plunge and begins the code.
    .
    Fusion 360 forums have all said that I have a G28 "safe setting" set to 0. I dont know enough about g code to comfortably mess with the actual notepad code file. Here's the intro code and first few lines. Thanks so much!

    Al
    1001)
    (MACHINE)
    ( VENDOR AUTODESK)
    ( DESCRIPTION GENERIC 3-AXIS)
    (T1 D=6.35 CR=3.175 - ZMIN=-42. - BALL END MILL)
    G90 G94 G91.1 G40 G49 G17
    G21
    G28 G91 Z0.
    G90


    (ADAPTIVE2)
    M5
    T1 M6
    S5000 M3
    G54
    G0 X-27.525 Y324.991
    G43 Z5. H1
    Z3.
    Z1.5
    G3 X-25.816 Y324.674 Z0.429 I1.078 J1.043 F500.
    X-24.955 Y326.185 Z-0.642 I-0.632 J1.36
    X-27.94 Y325.884 Z-3.362 I-1.492 J-0.151
    X-27.625 Y325.105 Z-3.854 I1.492 J0.151
    X-25.955 Y324.618 Z-4.925 I1.177 J0.93

  9. #9
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    Re: Mach 3, g28 safe travels height

    deleted
    Anyone who says "It only goes together one way" has no imagination.

  10. #10
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    Re: Mach 3, g28 safe travels height

    deleted
    btw: learning at least basic g-code should go on your to-do list
    Anyone who says "It only goes together one way" has no imagination.

  11. #11
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    Re: Mach 3, g28 safe travels height

    I don't use Mach3 so would be better of staying out of this, sorry. If G28 doesn't raise the spindle something is off in the machine absolute reference positions.
    My preference would be stripping out the G28 line completly and simply make sure the spindle is directly above the the part a few inches before hitting cycle start.
    In fact I've stripped G28 and G53 and even G43 out of Fusion post process .cps file. Without repeatable tool lengths G43 is a nuisance and a possible crash.

    Edit/ You are homing the machine at start up ? It almost reads like you set home at the work piece coordinates but then the spindle shouldn't rise much or at all due to upper travel limit. (unless reference points are messed)
    My lack of Mach3 terminology knowledge shines through, apologies.
    Anyone who says "It only goes together one way" has no imagination.

  12. #12
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    10680

    Re: Mach 3, g28 safe travels height

    Quote Originally Posted by WoodLover View Post
    Hi all, sorry for the late reply.

    When i use mach 3, I manually direct the tip of the bit to the top of the stock, then I zero everything out, to include "reference all to home"... When everything is completely zeroed, I regenerate the toolpath, start my spindle and hit start. With this code, however, it moves along the stop of the stock until it gets to the initial starting/entry point. from there, it raises in the air to what should have been the safe travel height, and then it initiates a plunge and begins the code.
    .
    Fusion 360 forums have all said that I have a G28 "safe setting" set to 0. I don't know enough about g code to comfortably mess with the actual notepad code file. Here's the intro code and first few lines. Thanks so much!

    Al
    1001)
    (MACHINE)
    ( VENDOR AUTODESK)
    ( DESCRIPTION GENERIC 3-AXIS)
    (T1 D=6.35 CR=3.175 - ZMIN=-42. - BALL END MILL)
    G90 G94 G91.1 G40 G49 G17
    G21
    G28 G91 Z0.
    G90


    (ADAPTIVE2)
    M5
    T1 M6
    S5000 M3
    G54
    G0 X-27.525 Y324.991
    G43 Z5. H1
    Z3.
    Z1.5
    G3 X-25.816 Y324.674 Z0.429 I1.078 J1.043 F500.
    X-24.955 Y326.185 Z-0.642 I-0.632 J1.36
    X-27.94 Y325.884 Z-3.362 I-1.492 J-0.151
    X-27.625 Y325.105 Z-3.854 I1.492 J0.151
    X-25.955 Y324.618 Z-4.925 I1.177 J0.93
    So in your Program Drawing where is your Z0. the top of the part or the bottom of the part

    It looks by what you have done here is you have your Z0 at the bottom of your part, this can be a trap for new users, set up you work piece in your Cad / Cam with the Z0 at the Top of your part then your code will look a lot different

    You will see a Z-1.5 for the Z axes move, you also have to set your tool to the Top of the part then it will all work as it should

    Unless you have your machine Axes setup incorrect Z axes up is a positive number Z axis Down is a negative number check this to see if your machine is work correct, just zero out the dro and jog the Z axes up and down to check
    Mactec54

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