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IndustryArena Forum > GENERAL MANUFACTURING PROCESSES > MILLING > expertise needed for toolpath problem
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  1. #1
    Member
    Join Date
    Nov 2013
    Posts
    8

    expertise needed for toolpath problem

    Hello everyone,

    Look at the pics to see the problem...

    The first is surfacing 20lb foam with a 1/4" cutter (70% overlap) in the y axis direction.
    You can see the difference in height every time it changes direction.
    About 10 thou ???

    The second pic is a 1/8" ballnose with a 30 thou pass in hdp foam.
    Again, same problem.
    Its like the z axis is somehow changing height when the machine changes direction ?

    I would post the gcode but it shows static height.
    Mach 3 wouldn't do that I dont think.
    10HP high frequency spindle runs smooth.
    Rhinocam cut speed is 80ipm.
    30 for approach and engage.

    Any thoughts ?

  2. #2

    Join Date
    Aug 2019
    Posts
    295

    Re: expertise needed for toolpath problem

    Pics aside, for anyone to really be able to help, we'd need to see your program code (gcode) bud
    If the gcode is standard/validated toolpath and you are getting something else then something hardware/mechanical might be at fault :/
    Problem occurs only on this part/toolpath?

  3. #3
    Registered
    Join Date
    Dec 2003
    Posts
    427

    Re: expertise needed for toolpath problem

    If the code doesn't show a change of Z,you might have some play in the machine.If it is showing on something as easy to cut as 20lb foam it needs fixing.Additionally I would regard a 70% stepover as a high value for a surfacing operation if a good finish is sought.For a fairly good finish I would be using something like 10%.

  4. #4
    Member
    Join Date
    Jul 2018
    Posts
    920

    Re: expertise needed for toolpath problem

    Hi Brant - Its not software or controller. This is a mechanical issue with the machine. Backlash, joint looseness, gantry walking, tramming many mechanical reasons that need to be checked out. Peter

  5. #5
    Member
    Join Date
    Nov 2013
    Posts
    8

    Re: expertise needed for toolpath problem

    OK,
    Here is the gcode.
    I am wondering if there is an antibacklash for the z axis. Or if a contaminant could be between the nut and the ball screw.
    It is very precise in its error.

    G00 G49 G40.1 G17 G80 G50 G90
    G20
    (Parallel Finishing)
    M6 T4
    M03 S18000
    G00 G43 H0 Z0.2493
    G00
    X10.2756 Y-1.0432
    G01 Z0.0243 F33.0
    Z-0.0007
    Y0.1248 F88.0
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X10.0831
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X9.8906
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X9.6981
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X9.5056
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X9.3131
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X9.1206
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X8.9281
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X8.7356
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X8.5431
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X8.3506
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X8.1581
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X7.9656
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X7.7731
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X7.5806
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X7.3881
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X7.1956
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X7.0031
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X6.8106
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X6.6181
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X6.4256
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X6.2331
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X6.0406
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X5.8481
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X5.6556
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X5.4631
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X5.2706
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X5.0781
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X4.8856
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X4.6931
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X4.5006
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X4.3081
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X4.1156
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X3.9231
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X3.7306
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X3.5381
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X3.3456
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X3.1531
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X2.9606
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X2.7681
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X2.5756
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X2.3831
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X2.1906
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X1.9981
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X1.8056
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X1.6131
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X1.4206
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X1.2281
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X1.0356
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X0.8431
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X0.6506
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X0.4581
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X0.2656
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    X0.0731
    Y18.5760
    Y18.5750 Z-0.1139
    Y0.1258
    Y0.1248 Z-0.0007
    Y-1.0432
    X0.0000
    Y0.1248
    Y0.1257 Z-0.1139
    Y18.5750
    Y18.5759 Z-0.0007
    Y19.7440
    Z0.0243 F33.0
    G00 Z0.2493
    M5 M9
    M30

  6. #6
    Registered
    Join Date
    Jul 2010
    Posts
    139

    Re: expertise needed for toolpath problem

    What are you talking about? Your Z height is alternating between -0.1139 and 0.0007 constantly.

    What Cam are you using? Simulation will show you this.

  7. #7
    Member
    Join Date
    Nov 2013
    Posts
    8

    Re: expertise needed for toolpath problem

    Yes, that is correct but if you look at the second pic you can see those two heights clearly.
    The .007 has a slightly different height in the cut depending on which way the y axis is travelling.

  8. #8
    Registered
    Join Date
    Dec 2003
    Posts
    427

    Re: expertise needed for toolpath problem

    Quote Originally Posted by Brantcnc View Post
    Yes, that is correct but if you look at the second pic you can see those two heights clearly.
    The .007 has a slightly different height in the cut depending on which way the y axis is travelling.
    Indeed it does. Guess what that causes on the workpiece? The machine seems to be doing exactly what it is told and the question is why the instruction has been generated by the CAM system

  9. #9
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    Join Date
    Nov 2013
    Posts
    8

    Re: expertise needed for toolpath problem

    thanks Peter,
    I think so too
    It's not tramming and not sure what gantry walking is ?
    I know there is backlash on the x and y but not sure for z (that could explain it though)
    Maybe contaminant in the nut on the ballscrew....

  10. #10
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    Dec 2003
    Posts
    427

    Re: expertise needed for toolpath problem

    You seem to have missed the point described in post #6.The program is telling the tool to go from one Z height to another-which it does and the apparent gouging is the result.

  11. #11
    Member
    Join Date
    Jul 2018
    Posts
    920

    Re: expertise needed for toolpath problem

    Hi Brant - walking is when one side of the gantry moves ahead of the other side then the other side catches up and then again and again. Its a form of stick slip action. Peter

  12. #12
    Registered
    Join Date
    May 2006
    Posts
    130

    Re: expertise needed for toolpath problem

    do not zig zag the toolpath. instead go with a 1 way feed. the action of going from climb cut to conventional makes the material suck up into the cutter. make sure the cutter is climbing on the 1 way . that should keep the pressure pushing the material away.

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