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G-Code from Fusion 360 RPM's fluctuating with ramping, lead in & lead out

Discussion in 'CNC Mills/Routers' started by Paul Mitchener, Dec 17, 2021.

  1. Paul Mitchener

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    Hi Brains trust,

    Working with my new CNC router and doing some testing with aluminium.

    I am trying to cut some brackets out of 5083 aluminium to fix my router frame to the bench. When cutting the spindle RPM is fluctuating depending on the profile being cut if I set the spindle speed above 10000 RPM. Ideally I am trying to cut at 24000.

    Attached is the G-Code and below is a sample video of the job running at an elevated Z home point to demonstrate the change in RPM. Ignore the broken bit and the spindle bearing noise (warranty issue being pursued). First attempt at cutting aluminium with this G-Code.

    I have been cutting ply with no problems at all, but I am cutting ply at 10000RPM.

    The machine is using a xPro v5 controller and CNC.js. The VFD is a Follin connected via 0-10V.

     

    Attached Files:

  2. David the swarfer

    David the swarfer OpenBuilds Team
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  3. Paul Mitchener

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    Thanks for the response @David the swarfer .

    Looking at the G-Code, that was my gut feeling too. It's odd, as the RPM's fluctuate depending on the toolpath. Slows for the tight radius, then ramps up for the straight cut, then slows for the ramp.

    In relation to the post processor. I have followed the Documentation you have referenced and linked that CPS file to my machine profile in Fusion. The screenshots in the documentation don't really match the current build of Fusion360. Either that, or I am looking in the wrong spot.

    This is what my post setup looks like.
    upload_2021-12-18_0-1-49.png

    This is what the machine setup looks like

    upload_2021-12-18_0-2-56.png
     
  4. sharmstr

    sharmstr OpenBuilds Team
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    Its in your machine setup, but its not selected in your nc program settings.

    upload_2021-12-17_6-50-54.png


    Keep in mind that once you start using the OB post, you have to make sure you home your machine.
     
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  5. David the swarfer

    David the swarfer OpenBuilds Team
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    it looks correctly setup but is not being used to generate the gcode (the Gcode contains a T4 command, which the OB post will never do), so, check carefully the entire toolchain, somewhere some other post is selected, maybe in the NC Program area?

    as for the speed changes, maybe laser mode is selected? or maybe your PWM frequency is too fast for the processor to keep up with when it is doing arcs? maybe you can post all your xPro settings so we can have a look at the details.
     
  6. Paul Mitchener

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    @David the swarfer I worked out getting the post processor to generate the gcode.

    In relation to the spindle speed issue. Below are my initialisation macro for the xPro v5 and the gcode settings ($$)

    Code:
    $Homing/Cycle0=Z
    $Homing/Cycle1=X
    $Homing/Cycle2=Y
    $Stepper/Pulse=5
    $Stepper/IdleTime=255
    $Stepper/DirInvert=Y
    $Stepper/EnableInvert=Off
    $Limits/Invert=On
    $Probe/Invert=On
    $Report/Status=1
    $Limits/Hard=On
    $Homing/Enable=On
    $Homing/DirInvert=X
    $Homing/Squared=Y
    $Homing/Feed=100.000
    $Homing/Seek=1500.000
    $Homing/Pulloff=2.500
    $X/StepsPerMm=200.002
    $Y/StepsPerMm=199.823
    $Z/StepsPerMm=200.400
    $A/StepsPerMm=199.823
    $X/MaxRate=3000.000
    $Y/MaxRate=3000.000
    $Z/MaxRate=2500.000
    $A/MaxRate=3000.000
    $X/Acceleration=150.000
    $Y/Acceleration=150.000
    $Z/Acceleration=150.000
    $A/Acceleration=150.000
    $X/MaxTravel=1232.50
    $Y/MaxTravel=830.00
    $Z/MaxTravel=210.00
    $A/MaxTravel=810.00
    $X/Current/Run=1.950
    $Y/Current/Run=1.950
    $Z/Current/Run=1.950
    $A/Current/Run=1.950
    $X/Current/Hold=1.250
    $Y/Current/Hold=1.250
    $Z/Current/Hold=1.250
    $A/Current/Hold=1.250
    $X/Microsteps=8
    $Y/Microsteps=8
    $Z/Microsteps=8
    $A/Microsteps=8
    $Spindle/Type=PWM
    $GCode/MaxS=24000
    $GCode/MinS=8000
    Code:
    client> $$
    $0=5 (Step pulse time, microseconds)
    $1=255 (Step idle delay, milliseconds)
    $2=0 (Step pulse invert, mask)
    $3=2 (Step direction invert, mask)
    $4=0 (Invert step enable pin, boolean)
    $5=1 (Invert limit pins, boolean)
    $6=1 (Invert probe pin, boolean)
    $10=1 (Status report options, mask)
    $11=0.010 (Junction deviation, millimeters)
    $12=0.002 (Arc tolerance, millimeters)
    $13=0 (Report in inches, boolean)
    $20=0 (Soft limits enable, boolean)
    $21=1 (Hard limits enable, boolean)
    $22=1 (Homing cycle enable, boolean)
    $23=1 (Homing direction invert, mask)
    $24=100.000 (Homing locate feed rate, mm/min)
    $25=1500.000 (Homing search seek rate, mm/min)
    $26=250.000 (Homing switch debounce delay, milliseconds)
    $27=2.500 (Homing switch pull-off distance, millimeters)
    $30=24000.000 (Maximum spindle speed, RPM)
    $31=8000.000 (Minimum spindle speed, RPM)
    $32=0 (Laser-mode enable, boolean)
    $100=200.002 (X-axis travel resolution, step/mm)
    $101=199.823 (Y-axis travel resolution, step/mm)
    $102=200.400 (Z-axis travel resolution, step/mm)
    $103=199.823
    $104=100.000
    $105=100.000
    $110=3000.000 (X-axis maximum rate, mm/min)
    $111=3000.000 (Y-axis maximum rate, mm/min)
    $112=2500.000 (Z-axis maximum rate, mm/min)
    $113=3000.000
    $114=1000.000
    $115=1000.000
    $120=150.000 (X-axis acceleration, mm/sec^2)
    $121=150.000 (Y-axis acceleration, mm/sec^2)
    $122=150.000 (Z-axis acceleration, mm/sec^2)
    $123=150.000
    $124=200.000
    $125=200.000
    $130=1232.500 (X-axis maximum travel, millimeters)
    $131=830.000 (Y-axis maximum travel, millimeters)
    $132=210.000 (Z-axis maximum travel, millimeters)
    $133=810.000
    $134=300.000
    $135=300.000
    ok
    Looking at the readout on my VFD, it looks like the rpm is dropping by 15% in most situations. There are a couple of motions where it drops even more.
     
  7. David the swarfer

    David the swarfer OpenBuilds Team
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    surely $133 must be the same as $131 so the Y and A move exactly the same?
    other than that I cannot see an issue with the settings.
    Without physical access to the machine I am some what stumped now (-:
    At this point you need to talk to the xPro v5 experts ,Spark Concepts
     
  8. Paul Mitchener

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    Darned EMI. Spark Concepts replied to my Github issue and it turns out that it's EMI on the 0-10V signal line. The quick addition of a 22uF capacitor on the input to the VFD has solved the issue.
     
    sharmstr and David the swarfer like this.

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