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Losing position when moving from one vector to the next - Workbee w/ blackbox

Discussion in 'CNC Mills/Routers' started by Alex Ahrens, May 26, 2020.

  1. Alex Ahrens

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    Hi all. I've been using my screw-driven Workbee 1010 for a few months but have recently been having an issue. I'm cutting 3/4" baltic birch plywood in 5 passes + a reverse finishing pass. The parts cut well, all of the passes line up perfectly, but when the machine finishes a part and raises to move to the next one, it makes a low grumbling sound and moves toward the direction of the next vector but not as far as it should. Then, it cuts the next part flawlessly (but overlapping and cutting into the previous part).

    Checking the control, the software shows that it is at the correct programmed position, but it's sometimes several inches off. Any ideas as to what could be causing it to lose position, but only when moving between vectors? I have checked the wheels and re-done the motor couplings and bearings. The code is the same as I was using before this started.

    Before this started happening, I had a couple of instances of some bad design/code causing the the router bit to gouge into parts on the last pass that had not been cleared by previous passes which caused some jolts to the machine, but this is the only thing that happened that I feel may be contributing.
     
  2. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Rapid feed set too high? Show us your grbl settings? (Send "$$" and copy the output here)
     
  3. Alex Ahrens

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    [14:02:24] [ $$ ] $0=10 ;Step pulse time, microseconds

    [14:02:24] [ $$ ] $1=255 ;Step idle delay, milliseconds

    [14:02:24] [ $$ ] $2=0 ;Step pulse invert, mask

    [14:02:24] [ $$ ] $3=3 ;Step direction invert, mask

    [14:02:24] [ $$ ] $4=1 ;Invert step enable pin, boolean

    [14:02:24] [ $$ ] $5=0 ;Invert limit pins, boolean

    [14:02:24] [ $$ ] $6=0 ;Invert probe pin, boolean

    [14:02:24] [ $$ ] $10=1 ;Status report options, mask

    [14:02:24] [ $$ ] $11=0.020 ;Junction deviation, millimeters

    [14:02:24] [ $$ ] $12=0.002 ;Arc tolerance, millimeters

    [14:02:24] [ $$ ] $13=0 ;Report in inches, boolean

    [14:02:24] [ $$ ] $20=0 ;Soft limits enable, boolean

    [14:02:24] [ $$ ] $21=1 ;Hard limits enable, boolean

    [14:02:24] [ $$ ] $22=1 ;Homing cycle enable, boolean

    [14:02:24] [ $$ ] $23=3 ;Homing direction invert, mask

    [14:02:24] [ $$ ] $24=100.000 ;Homing locate feed rate, mm/min

    [14:02:24] [ $$ ] $25=1000.000 ;Homing search seek rate, mm/min

    [14:02:24] [ $$ ] $26=250 ;Homing switch debounce delay, milliseconds

    [14:02:24] [ $$ ] $27=5.000 ;Homing switch pull-off distance, millimeters

    [14:02:24] [ $$ ] $30=1000 ;Maximum spindle speed, RPM

    [14:02:24] [ $$ ] $31=0 ;Minimum spindle speed, RPM

    [14:02:24] [ $$ ] $32=0 ;Laser-mode enable, boolean

    [14:02:24] [ $$ ] $100=196.416 ;X-axis steps per millimeter

    [14:02:24] [ $$ ] $101=195.580 ;Y-axis steps per millimeter

    [14:02:24] [ $$ ] $102=195.000 ;Z-axis steps per millimeter

    [14:02:24] [ $$ ] $110=2500.000 ;X-axis maximum rate, mm/min

    [14:02:24] [ $$ ] $111=2500.000 ;Y-axis maximum rate, mm/min

    [14:02:24] [ $$ ] $112=2500.000 ;Z-axis maximum rate, mm/min

    [14:02:24] [ $$ ] $120=150.000 ;X-axis acceleration, mm/sec^2

    [14:02:24] [ $$ ] $121=150.000 ;Y-axis acceleration, mm/sec^2

    [14:02:24] [ $$ ] $122=150.000 ;Z-axis acceleration, mm/sec^2

    [14:02:24] [ $$ ] $130=824.000 ;X-axis maximum travel, millimeters

    [14:02:24] [ $$ ] $131=780.000 ;Y-axis maximum travel, millimeters

    [14:02:24] [ $$ ] $132=122.000 ;Z-axis maximum travel, millimeters
     
  4. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Actually feeds look good. Not what I was expecting


    Any chance you can that sound on video? Might bring up some ideas
     
  5. Rob Taylor

    Rob Taylor Master
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    Settings look pretty good, though the accelerations look pretty slow.

    The G-code section where the issue happens could also be useful.
     
  6. Alex Ahrens

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    Interesting. Is there a negative side effect to having a slow acceleration? Just curious. I haven't changed any settings from the default except for steps/mm.

    I think I spoke too soon when I said I'd checked all the wheels - after posting I noticed one on the bottom of the x-beam was pretty tight. I adjusted the eccentric nuts so that none was too tight, which left some loose but there was no left-to-right play in the z-assembly so I ran a few jobs (after also slowing the rapids feed rate) and did not have this issue happen again.

    The wheel may have been the issue. But, even after loosening all the eccentric nuts, there was still a bit of pressure on it (a wheel in the middle), while the wheels on the left and right were not making contact at all... This afternoon I kind of compromised between looseness and tightness, but I'm wondering if there some other adjustment that can be made to get even pressure on all wheels.
     
    Peter Van Der Walt likes this.
  7. David the swarfer

    David the swarfer OpenBuilds Team
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    check for dirt in the leadscrews and leadnuts.
    if it was working and now is not, then something has changed, and that something is usually dirt in something. (that is a lot of somethings! :) )

    losing steps during rapid motion is a quick indicator that there is some interference with smooth movement.
     

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