Newbie CAM model to level sacrificial bed

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Thread: CAM model to level sacrificial bed

  1. #1
    Join Date
    Oct 2016
    New Zealand

    Default CAM model to level sacrificial bed

    Hi All

    I'd very much like some advice on what is happening with my model and subsequent Gcode.

    I want to face a new sacrificial board on my Chinese 3040 router. The model I've created allows for the four corners on the sacrificial board not to be machined as I have four bolts located at each corner. I'll machine those areas as a secondary function.

    The model when running in Fusion looks good and simulates as designed. However when I generate the Gcode and run it on mach3, it adds a significant Z axis command that sends the spindle into the stratosphere, across then back down to begin the machining.

    Any ideas why this would occur? I haven't added a command for the z axis to rise.

    I do wonder if it is related to G28 G91 Z0 in line 5 and setting a home position.

    I'd really like at attach the .tap file but cannot. Hope it's ok to post the Gcode below.

    Thanks in advance. Apologies for any misuse of terms...I'm very much learning my way around Fusion 360 and Mach 3.

    (T1 D=10. CR=0. - ZMIN=0. - FLAT END MILL)
    G90 G94 G91.1 G40 G49 G17
    G28 G91 Z0.

    (2D POCKET2)
    T1 M6
    S5000 M3
    G0 X78.694 Y-0.5
    G43 Z20. H1
    G1 Z12.5 F1000.
    X84.25 Z9.909 F333.
    G3 Y0.5 I0. J0.5
    G1 X75.75 Z5.945
    G3 Y-0.5 I0. J-0.5
    G1 X84.25 Z1.982
    G3 Y0.5 I0. J0.5
    G1 X80. Z0.
    G3 Y-3.015 I0. J-1.758
    G1 X82.696 F1000.
    G3 X83.015 Y-2.696 I0. J0.319
    G1 Y2.696
    G3 X82.696 Y3.015 I-0.319 J0.
    G1 X-82.696
    G3 X-83.015 Y2.696 I0. J-0.319
    G1 Y-2.696
    G3 X-82.696 Y-3.015 I0.319 J0.
    G1 X80.
    G2 X85.448 Y-5.754 I0. J-6.789
    G3 X91.237 Y-3.837 I2.577 J1.916
    G1 Y10.918
    G3 X90.918 Y11.237 I-0.319 J0.
    G1 X-90.918
    G3 X-91.237 Y10.918 I0. J-0.319
    G1 Y-10.918
    G3 X-90.918 Y-11.237 I0.319 J0.
    G1 X90.918
    G3 X91.237 Y-10.918 I0. J0.319
    G1 Y-3.837
    G2 X95.348 Y2.329 I6.68 J0.
    G3 X99.459 Y8.496 I-2.569 J6.167
    G1 Y18.274
    G3 X99.211 Y18.936 I-1.007 J0.
    G1 X99.068 Y19.1
    G3 X98.281 Y19.459 I-0.788 J-0.684
    G1 X-98.281
    G3 X-99.068 Y19.1 I0. J-1.043
    G1 X-99.211 Y18.936
    G3 X-99.459 Y18.274 I0.759 J-0.662
    G1 Y-18.274
    G3 X-99.211 Y-18.936 I1.007 J0.
    G1 X-99.068 Y-19.1
    G3 X-98.281 Y-19.459 I0.788 J0.684
    G1 X98.281
    G3 X99.068 Y-19.1 I0. J1.043
    G1 X99.211 Y-18.936
    G3 X99.459 Y-18.274 I-0.759 J0.662
    G1 Y8.496
    G2 X104.668 Y15.548 I7.379 J0.
    G3 X107.011 Y23.997 I-1.53 J4.973
    G2 X103.385 Y28.297 I67.989 J61.003
    G3 X102.646 Y28.655 I-0.739 J-0.585
    G1 X-102.646
    G3 X-103.385 Y28.297 I0. J-0.942
    G2 X-108.292 Y22.598 I-71.615 J56.703
    G3 X-108.655 Y21.679 I0.982 J-0.919
    G1 Y-21.679
    G3 X-108.292 Y-22.598 I1.345 J0.
    G2 X-103.385 Y-28.297 I-66.708 J-62.402
    G3 X-102.646 Y-28.655 I0.739 J0.585
    G1 X102.646
    G3 X103.385 Y-28.297 I0. J0.942
    G2 X108.292 Y-22.598 I71.615 J-56.703
    G3 X108.655 Y-21.679 I-0.982 J0.919
    G1 Y21.679
    G3 X108.292 Y22.598 I-1.345 J0.
    G2 X107.011 Y23.997 I66.708 J62.402
    X106.851 Y31.246 I4.143 J3.717
    G3 X103.752 Y37.801 I-3.1 J2.545
    G1 X-107.266
    G3 X-107.953 Y37.446 I0. J-0.842
    G2 X-117.439 Y26.318 I-67.047 J47.554
    G3 X-117.801 Y25.458 I0.844 J-0.86
    G1 Y-25.458
    G3 X-117.439 Y-26.318 I1.205 J0.
    G2 X-107.953 Y-37.446 I-57.561 J-58.682
    G3 X-107.266 Y-37.801 I0.687 J0.487
    G1 X107.266
    G3 X107.953 Y-37.446 I0. J0.842
    G2 X117.439 Y-26.318 I67.047 J-47.554
    G3 X117.801 Y-25.458 I-0.844 J0.86
    G1 Y25.458
    G3 X117.439 Y26.318 I-1.205 J0.
    G2 X107.953 Y37.446 I57.561 J58.682
    G3 X107.266 Y37.801 I-0.687 J-0.487
    G1 X103.752
    G2 X96.939 Y42.343 I0. J7.381
    G3 X90.126 Y46.885 I-6.813 J-2.839
    G1 X-112.19
    G3 X-112.822 Y46.533 I0. J-0.743
    G2 X-126.526 Y30.263 I-62.178 J38.467
    G3 X-126.885 Y29.466 I0.706 J-0.798
    G1 Y-29.466
    G3 X-126.526 Y-30.263 I1.065 J0.
    G2 X-112.822 Y-46.533 I-48.474 J-54.737
    G3 X-112.19 Y-46.885 I0.632 J0.391
    G1 X112.19
    G3 X112.822 Y-46.533 I0. J0.743
    G2 X126.526 Y-30.263 I62.178 J-38.467
    G3 X126.885 Y-29.466 I-0.706 J0.798
    G1 Y29.466
    G3 X126.526 Y30.263 I-1.065 J0.
    G2 X112.822 Y46.533 I48.474 J54.737
    G3 X112.19 Y46.885 I-0.632 J-0.391
    G1 X90.126
    G2 X83.372 Y51.387 I0. J7.317
    G3 X76.618 Y55.89 I-6.754 J-2.814
    G1 X-117.487
    G3 X-118.059 Y55.542 I0. J-0.644
    G2 X-135.533 Y34.478 I-56.941 J29.458
    G3 X-135.89 Y33.747 I0.571 J-0.731
    G1 Y-33.747
    G3 X-135.533 Y-34.478 I0.927 J0.
    G2 X-118.059 Y-55.542 I-39.467 J-50.522
    G3 X-117.487 Y-55.89 I0.572 J0.296
    G1 X117.487
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    G2 X118.059 Y55.542 I39.467 J50.522
    G3 X117.487 Y55.89 I-0.572 J-0.296
    G1 X76.618
    G2 X69.938 Y60.343 I0. J7.236
    G3 X63.258 Y64.796 I-6.68 J-2.783
    G1 X-123.256
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    G2 X-144.443 Y39.024 I-51.238 J20.546
    G3 X-144.796 Y38.366 I0.437 J-0.658
    G1 Y-38.366
    G3 X-144.443 Y-39.024 I0.79 J0.
    G2 X-123.762 Y-64.454 I-30.557 J-45.976
    G3 X-123.256 Y-64.796 I0.507 J0.203
    G1 X123.256
    G3 X123.762 Y-64.454 I0. J0.546
    G2 X144.443 Y-39.024 I51.238 J-20.546
    G3 X144.796 Y-38.366 I-0.437 J0.658
    G1 Y38.366
    G3 X144.443 Y39.024 I-0.79 J0.
    G2 X123.762 Y64.454 I30.557 J45.976
    G3 X123.256 Y64.796 I-0.507 J-0.203
    G1 X63.258
    G2 X56.688 Y69.177 I0. J7.118
    G3 X50.117 Y73.557 I-6.571 J-2.738
    G1 X-129.641
    G3 X-130.075 Y73.222 I0. J-0.449
    G2 X-153.209 Y43.987 I-44.925 J11.778
    G3 X-153.557 Y43.408 I0.308 J-0.579
    G1 Y-43.408
    G3 X-153.209 Y-43.987 I0.655 J0.
    G2 X-130.075 Y-73.222 I-21.791 J-41.013
    G3 X-129.641 Y-73.557 I0.434 J0.114
    G1 X129.641
    G3 X130.075 Y-73.222 I0. J0.449
    G2 X153.209 Y-43.987 I44.925 J-11.778
    G3 X153.557 Y-43.408 I-0.308 J0.579
    G1 Y43.408
    G3 X153.209 Y43.987 I-0.655 J0.
    G2 X130.075 Y73.222 I21.791 J41.013
    G3 X129.641 Y73.557 I-0.434 J-0.114
    G1 X50.117
    G2 X43.705 Y77.832 I0. J6.947
    G3 X37.292 Y82.107 I-6.412 J-2.672
    G1 X-136.891
    G3 X-137.244 Y81.783 I0. J-0.354
    G2 X-161.766 Y49.493 I-37.756 J3.217
    G3 X-162.107 Y49.002 I0.183 J-0.49
    G1 Y-49.002
    G3 X-161.766 Y-49.493 I0.523 J0.
    G2 X-137.244 Y-81.783 I-13.234 J-35.507
    G3 X-136.891 Y-82.107 I0.353 J0.03
    G1 X136.891
    G3 X137.244 Y-81.783 I0. J0.354
    G2 X161.766 Y-49.493 I37.756 J-3.217
    G3 X162.107 Y-49.002 I-0.183 J0.49
    G1 Y49.002
    G3 X161.766 Y49.493 I-0.523 J0.
    G2 X137.244 Y81.783 I13.234 J35.507
    G3 X136.891 Y82.107 I-0.353 J-0.03
    G1 X37.292
    G2 X31.126 Y86.218 I0. J6.68
    G3 X24.96 Y90.329 I-6.166 J-2.569
    G1 X-145.009
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    X-145.306 Y87.505 I139.412 J0.
    G2 X-145.284 Y85. I-139.39 J-2.505
    X-169.999 Y55.753 I-29.662 J0.
    G3 X-170.329 Y55.363 I0.067 J-0.39
    G1 Y-55.363
    G3 X-169.999 Y-55.753 I0.396 J0.
    G2 X-145.284 Y-85. I-5.01 J-29.3
    X-145.306 Y-87.505 I-139.412 J0.
    G3 X-145.329 Y-90.009 I139.39 J-2.505
    X-145.009 Y-90.329 I0.319 J0.
    G1 X145.009
    G3 X145.329 Y-90.009 I0. J0.319
    X145.306 Y-87.505 I-139.412 J0.
    G2 X145.284 Y-85. I139.39 J2.505
    X169.999 Y-55.753 I29.662 J0.
    G3 X170.329 Y-55.363 I-0.067 J0.39
    G1 Y55.363
    G3 X169.999 Y55.753 I-0.396 J0.
    G2 X145.284 Y85. I5.01 J29.3
    X145.306 Y87.505 I139.412 J0.
    G3 X145.329 Y90.009 I-139.39 J2.505
    X145.009 Y90.329 I-0.319 J0.
    G1 X24.96
    G2 X18.793 Y94.44 I0. J6.68
    G3 X12.627 Y98.551 I-6.167 J-2.569
    G1 X-153.231
    G3 X-153.551 Y98.231 I0. J-0.319
    G1 X-153.506 Y85.
    G2 X-175. Y63.506 I-21.494 J0.
    X-176.616 Y63.528 I0. J58.021
    G3 X-178.231 Y63.551 I-1.616 J-57.998
    X-178.551 Y63.231 I0. J-0.319
    G1 Y-63.231
    G3 X-178.231 Y-63.551 I0.319 J0.
    X-176.616 Y-63.528 I0. J58.021
    G2 X-175. Y-63.506 I1.616 J-57.998
    X-153.506 Y-85. I0. J-21.494
    G1 X-153.551 Y-98.231
    G3 X-153.231 Y-98.551 I0.319 J0.
    G1 X153.231
    G3 X153.551 Y-98.231 I0. J0.319
    G1 X153.506 Y-85.
    G2 X175. Y-63.506 I21.494 J0.
    X176.616 Y-63.528 I0. J-58.021
    G3 X178.231 Y-63.551 I1.616 J57.998
    X178.551 Y-63.231 I0. J0.319
    G1 Y63.231
    G3 X178.231 Y63.551 I-0.319 J0.
    X176.616 Y63.528 I0. J-58.021
    G2 X175. Y63.506 I-1.616 J57.998
    X153.506 Y85. I0. J21.494
    G1 X153.551 Y98.231
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    G1 X-161.454
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    G1 X-161.728 Y85.
    G2 X-175. Y71.728 I-13.272 J0.
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    G2 X-161.728 Y-85. I0. J-13.272
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    G1 X161.454
    G3 X161.773 Y-106.454 I0. J0.319
    G1 X161.728 Y-85.
    G2 X175. Y-71.728 I13.272 J0.
    G1 X186.454 Y-71.773
    G3 X186.773 Y-71.454 I0. J0.319
    G1 Y71.454
    G3 X186.454 Y71.773 I-0.319 J0.
    G1 X175. Y71.728
    G2 X161.728 Y85. I0. J13.272
    G1 X161.773 Y106.454
    G3 X161.454 Y106.773 I-0.319 J0.
    G1 X0.293
    G2 X-5.877 Y110.886 I0. J6.685
    G3 X-12.047 Y115. I-6.17 J-2.571
    G1 X-170.
    G2 X-175. Y80. I-5. J0.
    G1 X-195.
    G2 X-170. Y-85. I0. J-5.
    G1 Y-115.
    G2 X175. Y-80. I5. J0.
    G1 X195.
    G2 X170. Y85. I0. J5.
    G1 Y115.
    G3 X-12.303 Y114.967 Z0.034 I0. J-1.
    G1 X-12.418 Y114.929 Z0.084
    X-12.527 Y114.878 Z0.134
    X-12.615 Y114.823 Z0.213
    X-12.697 Y114.76 Z0.293
    X-12.755 Y114.706 Z0.396
    X-12.809 Y114.648 Z0.5
    X-12.87 Y114.569 Z0.741
    X-12.889 Y114.54 Z1.
    G0 Z20.

    G28 G91 Z0.
    G28 G91 X0. Y0.

    Similar Threads:

  2. #2
    Join Date
    Feb 2012

    Default Re: CAM model to level sacrificial bed

    [QUOTE=ShaneMinnear;2313240]Hi All

    Try removing "G28 G91 Z0" and run again.

  3. #3
    Join Date
    Feb 2004
    Philadelphia, PA

    Default Re: CAM model to level sacrificial bed

    Yes, remove all the G28 lines, and add manually any moves of your own for the Z. I ran into the same issue and this fixed it for me. Note, I’m a beginner at Fusion and Mach 3 so don’t take what I wrote as gospel

    Edit: for me fusion also ads the two g28 lines you have at the end of your program, every time. I edit those out also.

  4. #4
    Member The Engine Guy's Avatar
    Join Date
    Jun 2008

    Default Re: CAM model to level sacrificial bed

    The whole reason for having the G28 G91 Z0 line is for SAFETY, but it only works if the user has correctly setup their machine and it has been correctly "Homed".

    Regardless of where the machine is at when it starts up the first move must be to a safe place particularly on the Z axis which should go to it`s highest level so that regardless of what moves the machine might make in the X and Y directions the head has been moved up so it will then miss any fixtures, clamps etc, etc.
    That is why the Post processors are configured to output the G28 lines.

    However if the actual machine has not been setup correctly then yes, as others have said the G28 G91 Z0 lines and any other G28 lines will need to be removed that`s for sure.
    Not the best way to use a machine but people do "get by" doing it but it is what is commonly called the "half-assed" method !!


  5. #5
    Join Date
    Oct 2016
    New Zealand

    Default Re: CAM model to level sacrificial bed

    Quote Originally Posted by ShaneMinnear View Post
    Hi All

    Try removing "G28 G91 Z0" and run again.

    Thanks, that was what I also thought to try. Reading through I will try and rehome my machine and get it working that way.

  6. #6
    Join Date
    Oct 2016
    New Zealand

    Default Re: CAM model to level sacrificial bed

    Thanks for your reply daytrader. I'll try homing my machine then if that doesn't help I'll remove the g28 lines.

  7. #7
    Join Date
    Oct 2016
    New Zealand

    Default Re: CAM model to level sacrificial bed

    Thanks for your reply Rob. I'll try and get the machine homed correctly as you advise.

  8. #8
    Join Date
    Mar 2016

    Default Re: CAM model to level sacrificial bed

    When generating your post in Fusion you can turn G28 off in the parameter box in the lower right of post dialog window. Just scroll down and about half way down is the G28 parameter.

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