1. #1
    So I finally have Lucy set up and read to go.

    Yesterday i was doing some test cuts on some 10mm foam board i had readily available.

    I quickly drew up a file with 6 circles that sit within each other, and for the CNC to cut various steps into the foam board, then finally cut the circle out of the board.

    Circle Depth Radius
    Circle 6 8mm 20mm
    Circle 5 6mm 40mm
    Circle 4 4mm 60mm
    Circle 3 2mm 80mm
    Circle 2 1mm 100mm
    Circle 1 11mm 120mm

    Should look like this:
    Click image for larger version. 

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    Click image for larger version. 

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    See the attached Aspire file, dxf and file for Mach3 txt file: CNC Test-20170304.zip

    I set the feed rate to 100 mm/sec and 8,000 RPM

    Anyway, everything looked file until it got to the outer circle (circle 1), when it did this (I set it to do 11mm, so all the way through)!

    Click image for larger version. 

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    Does anyone have any ideas why it did such a crazy thing?

    EDIT: Uploaded correct Mach3 file: CNC Test-20170304.txt

    Just as a reminder,
    I have a 1m x 1m,
    Dimension: 3 + 1 (mirrored)
    Drive type: Belt
    Last edited by CrazeUK; 04-03-2017 at 02:18 PM.

  2. #2
    Gcode looks odd - is that to cut just the outer circle? However, apart from a few rapid moves, it just looks like a set of circles. Used properly, Aspire is pretty solid so unlikely to generate wild code like that. Personally, my guess is that a coupling slipped or there was a similar mechanical issue. 100mm/sec is 6m/min which is pretty fast; depending on things like max acceleration this is going to put a fair load on the machine. But without more data, this is a guess!

  3. #3
    What machine is this exactly.? You say 1m x 1m with drive belt but this tells us very little really.!! Give detailed info on mechanical and electrical setup.
    Also please explain exactly what happened in relation to the pic. Did machine go in all directions like pic shows or is some of that from prevoius cuts.? Did material move.?

    Like Neale says 6mtr/min is going a little but it is correct for this type of material and decent setup machine should easily handle that. However that doesn't mean your machine can handle that speed. So it could be that you have been losing position because pushing too hard for it's capabiltys.

    When this happened did you hit the E-stop.? And when E-stop occurs does it drop power to the Drives.?
    If so then it's possible one of your drives faulted but you didn't see because E-stop reset the drive when dropped power. However looking at the pic I'm not sure this was the case.!

    Often these things nearly always boil down to 2 reasons. Pushing too hard or Mechanical / electrical issue.
    90% of time it's mechanical with either lose coupler or binding bearings etc. Occasionally lose wires at the drives can cause loss of position.

  4. #4
    Quote Originally Posted by Neale View Post
    Gcode looks odd - !
    Same here - when I load it in Mach3 all the cuts are at one Z height
    You think that's too expensive? You're not a Model Engineer are you? :D

  5. #5
    Maybe used Aspire to generate separate gcode files for each circle? There's quite a small stepover as well, from what I can see, which is probably not needed for cutting this material. Not how I would have done it, but not the issue here, I think. It does take a while to get the hang of all the different settings once you start using any CAM package. I still favour mechanical overload causing something to slip, having had exactly this problem setting up my own new machine a week or two back

  6. #6
    Hey guys.

    Thanks for the responses:
    Apologies, looks like i uploaded an incorrect file, i have now edited the original post with the correct file: CNC Test-20170304.txt

    The machine ran from the centre circle 6, outwards until circle 2.
    I noticed everytime the machine was doing a circle it moved to the centre and worked its way out - I know i set the design up wrong.
    At circle 1, The machine lifted off the Z axis zero about 2 inches, then went to start the Outer circle (which was a full through cut (with 1mm extra). At that point it went off on a tangent, which looked random, i would describe it as jumping.

    Judging by what you guys have said about feed rate, do you think it was:
    1. It went from foam board into MDF so was a bit tougher
    2. The feed rate was way to high for the depth it was cutting at, so it jumped.

    I know the machine definitely lost position, because it didnt go to the correct home position after.

  7. #7
    Machine Setup:

    Not sure what other info you need:

    The bit: End mill 3x6x15x57 (Shank x Bit Radius x Shank length x Bit length)

    Dimensions: 1000 x 1000mm
    Cutting D: X: 720 x Y: 800 x Z: 400 (i think)
    Axis: 4 (3+1)
    Drive: X & Y - Belt, Z - Ball screw
    Driver board: CNC4x45A Via Parallel
    Limits: X, Y, Z Home, X, Y, Z Limit + EStop
    Software: Mach3, LazyCam, Aspire, Autodesk, Google Sketchup Pro

  8. #8
    had a look at the new file, it seems fine to me, apart from the feed which is set at 12000mm/minute, very fast but depends on how good your machine is. Personally I would say that is the cause of your problems but that is just my thought

  9. #9
    Quote Originally Posted by johngoodrich View Post
    had a look at the new file, it seems fine to me, apart from the feed which is set at 12000mm/minute, very fast but depends on how good your machine is. Personally I would say that is the cause of your problems but that is just my thought
    My machine definitely isn't great. I have a huge list of upgrades that are needed. Primarily around driving the various axis.

    Sent from my SM-N930F using Tapatalk

  10. #10
    @Johngoodrich i think you where right. I was pushing the machine way too fast.
    I have slowed it right down to between 5 and 15 mm/sec dependent on the material.

    I am also doing numerous passes depending on the thickness, so no errors as yet.


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