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Problem with multipass inside cut tool

Discussion in 'SketchUcam Bugs' started by Forrest Dietrich, Oct 12, 2014.

  1. Forrest Dietrich

    Forrest Dietrich New Member

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    Appreciate all the good workon SketchUcam and find it very useful!

    I think there is a bug in the inside cut tool only when Z zero is at top of material in the a Z0.000 instruction is inside the multipass loop and results in a wedge of material not being cut as the cutting head moves from first to second XY position and also goes each pass from Z0.000 to correct Z depth.

    This is not a problem for code generated if Z=0 is TableTop.

    See following to demo this:
    %

    (Generated by SketchUcam {1.2})

    (File: Test01a.skp)

    (Bit diameter: 1/8")

    (Feed rate: 50"/min)

    (Plunge Feed rate: 10"/min)

    (Material Thickness: 3/4")

    (Material length: 24" X width: 12")

    (Overhead Gantry: true)

    (Retract feed rate NOT limited to plunge feed rate)

    (Multipass enabled, Depth = 1/4")

    (Optimization is ON)

    (www.PhlatBoyz.com)

    G90 G20 G49

    M3 S15000

    G0 Z1.0000

    (Pass: 1)

    X0.4802 Y0.0625

    G1 Z0.0000 F10

    X0.4333 Y0.4375 Z-0.2500 F50


    X0.6667

    X0.6198 Y0.0625

    X0.4802

    (Pass: 2)

    Z0.0000 F10

    X0.4333 Y0.4375 Z-0.5000 F50


    X0.6667

    X0.6198 Y0.0625

    X0.4802

    (Pass: 3)

    Z0.0000 F10

    X0.4333 Y0.4375 Z-0.7500 F50


    X0.6667

    X0.6198 Y0.0625

    X0.4802

    G0 Z1.0000

    G0 X0 Y0 (home)

    M05

    M30

    %
     
  2. swarfer

    swarfer Moderator Staff Member

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    someone posted this last week too and I'm looking at it.
    however, none of my 4 installs of Sketchup (v7 8 2013 and 2014) actually do this so I am failing to have a test case to work with thus far.
    very hard to debug something that works (-:

    one idea though is that something went wrong in the install so maybe if you can reinstall sketchucam 1.2, close and restart sketchup and then retest and let me know if that made any difference I'd appreciate it.

    also make absolutely sure you have z0 turned off (-:
    ie turn it off and close and restart sketchup

    if that does not fix it then please make a zip file of your plugins folder and send it to me so I can use 'your' actual installed code for testing.
     
  3. swarfer

    swarfer Moderator Staff Member

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    solved. you have you min_z and max_z set incorrectly.
    to quote the help for options setting... menu at
    tools|phlatboyz|options|machine options
     
  4. Forrest Dietrich

    Forrest Dietrich New Member

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    Thanks a lot ... something simple it figures ...
    Actually I am a bit confused now ... as a few lines later the g-code did have negative Z value.
    Suggest safe min, safe max and max travel set in one place? Also for X and Y.
     
    Last edited: Oct 13, 2014
  5. swarfer

    swarfer Moderator Staff Member

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    That was a bug in the code, it was checking for Z < minZ in the move command but not doing anything about it.
    From the next release, this will be fixed. :)
    However, the real issue is that you did not read the help and follow the instructions.
    You cannot blame the software for doing the wrong thing when you set it up incorrectly.
    they ARE all in one place (-: (for setting the defaults anyway).
    then you can set the material size for Safe Length and Safe Width in the parameters dialog so you can lay out your parts on a scale drawing of the material. After initial setup, you never need to change min and max Z.

    The way that the internal code uses the max_z and min_z is historical and very difficult to change, and does not allow for the user setting 0 at any level between the table and the max_z up travel. it also does not know how long the toolbit is.
    ie, the software does not know where you have set 0, so cannot limit travel purely based on what it does know. We do not want any more settings (for users to get wrong! :) so will not try to introduce another setting/s to facilitate this kind of smart limiting, preferring to let users do some thinking instead (-:

    Thus the help says to set the min_z to -(distance z can travel) and max_z to +(distance z can travel). this is the best we can do with what we have got without introducing a lot more complexity in setting up jobs.

    One alternative if you are really set on having the machine do your thinking for you is to always use 'table top as Z zero',
    and set min_z to '0', max_z to (max Z travel - longest toolbit).
    now it will never generate Gcode that cuts into the table top, but material thickness is restricted to (max_Z travel - the longest toolbit length).
    Note that once you set it up like this you cannot use "material top as Z zero", ever.

    happy cutting
     
  6. Forrest Dietrich

    Forrest Dietrich New Member

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    Thanks for your long explanation, and again, I really like and appreciate your work and this software.
    Actually the Z travel is set in the parameters and the min and max Z elsewhere in the options, not in the same place at all, and I did not think of the Z max and min due the negative Z that was showing up a few lines later .... happy you are so familiar with this that you thought of it!
    My goal it not to have the machine do the thinking for me, but to understand its limits and how to best use it. You have made a very good and flexible extension to Sketchup, but as I am a novice to this it takes me some time to understand benefits and limitations ... please do not think I am complaining about anything and take any suggestions as you will to use or discard. Thanks again for increasing my understanding of how this works.
     

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