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Thread: Z axis skipping

  1. #1
    Join Date
    Mar 2010
    Posts
    3

    Default Z axis skipping

    I am having a problem with the Z axis skipping during 3D contouring. It doesn't lose count but doesn't keep up with the motion of the X and Y axis. I am using V3.5.1 software with NC code generated from MasterCAM. The machine is a newer PRS Standard. I have tried taking the feedrate down to 40IPM/.66IPS and still have problems. If I run a contouring routine where I am stepping down and running just the X and Y axis it makes a perfect cut at speeds up to 3IPS. The slides on the machine are clean and there doesn't seem to be any binding or roughness.

    Any Ideas?

  2. #2
    Join Date
    Jan 2004
    Location
    iBILD Solutions - Southern NJ
    Posts
    7,964

    Default

    Type in VR to SB3. Post a pic of the values you are currently running. Also, tell me what the Move Speeds are for this file - EG MS,2,1

    You can easily get a snapshot of the VR screen by holding down the Alt key + Pressing 'PrintScreen' key. Then open up your favorite photo editing software (or MSPaint) and paste it in as a new image.

    -B
    Last edited by Brady Watson; 03-11-2010 at 06:29 PM.
    High Definition 3D Laser Scanning Services - Advanced ShopBot CNC Training and Consultation - Vectric Custom Video Training IBILD.com

  3. #3
    Join Date
    Mar 2010
    Posts
    3

    Default

    I am running the G-Code directly as a .nc file.

    Here is the screen shot of the setup. Standard as I haven't played with it.

    SB_Setup.jpg

  4. #4
    Join Date
    Mar 2010
    Posts
    3

    Default

    Bump. Anyone have any ideas

  5. #5
    Join Date
    Jan 2004
    Location
    iBILD Solutions - Southern NJ
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    7,964

    Default

    Frank,
    The relation between the XY speed and the Z speed is important when cutting 3D reliefs. The intricacy of the design & level of detail you need to pick up, will ultimately set the 'speed limit' of the tool when cutting. Smaller and more intricate designs (that maybe have a background texture etc) require slower speeds than larger smooth/undulating moves. If nothing else, it is a matter of physics as to how fast the Z axis can move up & down - carrying the weight of the spindle/router.

    Here are a few XY,Z speeds that I have found helpful for cutting most 3D parts:
    1,0.5
    1,1
    2,1
    3,2
    5,3

    It is important that you be realistic about the speeds you select, as you must consider what you are asking the tool to do. A speed of 5,3 is not going to be good on a 3D relief that is only 3" in diameter.

    In regards to your VR settings, try adjusting the following, which should give you a smoother running tool under all conditions:

    Change the 3D Threshold to 150 - This will reduce slowing/ramping in 3D
    Change Slow Corner Speed to 45
    Change Min Distance to Check to .08
    Change Fast Stop Threshold to .8
    Change KeyPad Ramp Rate to .2

    The last 2 settings only apply to keyboard mode. Drive the tool around in Keyboard mode - Note how much more responsive & smoother it is.

    Try messing with the speeds listed above for 3D cutting. One of these combos will get you in the range for what you are cutting.

    -B
    High Definition 3D Laser Scanning Services - Advanced ShopBot CNC Training and Consultation - Vectric Custom Video Training IBILD.com

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