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Cutting going off path.

Discussion in 'CNC Mills/Routers' started by slade2000, Jul 1, 2019.

  1. slade2000

    slade2000 New
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    HI All.

    I have an issue where my machine will go off path at random times during a gut but mostly at the same spot.

    Machine is a GRBL with Arduino. I have tried different speeds and feeds and same issue. I have also checked all belt tensions and pulley's and all good. What can cause this issue as seen in the pictures?

    All of the cuts you see was one job and then started going off. Sometimes it does happen earlier on as well.

    20190701_193710.jpg 20190701_193701.jpg
     
  2. Gary Caruso

    Gary Caruso OpenBuilds Team
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    Hi Slade,
    Loosing steps? Did you check all your wiring? Maybe motor connection, is it always in Y? What drivers are you using? are you cooling them enough (fan)? You said you tried different feeds? let us know the details, what speeds, rpm's, looks like pine, is it a down cut bit?
    Post the file, and your grbl settings.
    Thanks
    Gary
     
  3. slade2000

    slade2000 New
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    My head is going towards thermal cutoff, as I do not have fans over the drivers. The drivers are A4988. Why also did check the wiring and did look all okay.

    Feed rates: 900, 1000, 1100, 1300, 1600, 2000. I think I might have just found an issue with my speeds, I never checked the actual RPM on my Makita and it turns out that it is 12000 - 30000 RPM and I ran it on setting 5 which is 25000rpm (WOOPS), no wonder I run trough bits like nothing.

    Yes it is pine and down cut 1/4 bit and run it at 3mm per pass. Will get the file tonight and post it.

    It is basically doing it always in the X direction even if the motion is towards Y
     
  4. Alex Chambers

    Alex Chambers Master
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    Another possibility is EMI - are your mains wires well away from any low voltage cables? You often get away with wires crossing, but parallel to each other is not good.
    Alex.
     
    GrayUK likes this.
  5. slade2000

    slade2000 New
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    Okay I will need to fix that. My power for my router runs with the stepper cables in the same track.
     
  6. David the swarfer

    David the swarfer OpenBuilds Team
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    Please make sure that your $1 setting is 255 so that the drivers do not shutdown in hte middle of a cut.

    Those drivers are a little small for that size machine, I think a Blackbox would be a much better bet (or DQ542 external drivers at 24 volts)

    What voltage power supply?

    in the meantime,
    1. point a fan at those drivers, one may be shutting down due to overheating (in any group is identical electronic things, one will always fail first, like the weak link in a chain).
    2. reduce depth of cut. use the calculated feedrate and lower RPM and adjust depth to make the machine happy.
    3. assuming you are doing a conventional cut (anticlockwise around the outside) then it looks like X is slipping due to cutter forces. Can you increase the current on X and test? If you switch to a climb cut then at least the bit will move away from the part.
    4. what bit? 2 flute? straight or spiral? spiral is better, you must absolutely never recut the chips. Short is better.
    5. I have that Makita (the 0701) and run pretty much everything at speed setting 2 which my table tells me is 12000rpm. from that the tooth count and the chipload per tooth we want, we can calculate the feedrate. for a 2 flute at 12000rpm. In pine I would aim for 0.025mm per tooth, which is 600mm/min feedrate. This gives a starting point with known values, I would then mess with the speed override during some test cuts and see what happens at 10 and 20% slower and faster. LISTEN to the machine. Look at the chips, they need to be chips not powder. Powder is from too slow feedrate and too high rpm and causes a LOT of heat and wears the tool extra fast. if the chips are too big (too fast feed for the rpm) then they will pack up and jam the bit.
     
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  7. Gary Caruso

    Gary Caruso OpenBuilds Team
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    Yes thermal is probably the issue, now that we know the drivers used.
    Could tell from the nice fuzz free edge that it's a down-cut, which is great but on such a deep slot you will run into problems with the chips packing in and not enough power to push through them.
    Gary
     
  8. slade2000

    slade2000 New
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    HI All. I fixed a few of the issues you all raised and I could immediately see and hear a difference in the machine.

    Changes made:
    1. Fitted up-cut 2 flute spiral.
    2. Added 2 fans on top of the drivers.
    3. Now running correct RPM.

    Still need to change:
    1. Remove power from running next to low voltage.
    2. Think I am going to upgrade to BlackBox

    I will do a full cut tonight again that will take around 3 hours and see how it goes.

    These were the chips from all the changes above. How does it look?

    chips.jpeg
     
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  9. David the swarfer

    David the swarfer OpenBuilds Team
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    good chips!
     
  10. Alex Chambers

    Alex Chambers Master
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    Good to see things are now running smoothly.
    EMI from mains cables can run to 100's of volts though. The likelyhood of it damaging your electronics is low, but if it does the switch to a blackbox will become urgent. I'd get that mains cabling away from the low voltage stuff as soon as possible.
    Alex. :D:eek::thumbsup:
     
  11. Gary Caruso

    Gary Caruso OpenBuilds Team
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    With the Makita router it's very easy to replace the included cable with shielded 2 conductor, then you can keep it in the drag chains, only needs to be 18awg (I've even gotten by with 20awg).
    Cheers
    Gary
     
  12. Alex Chambers

    Alex Chambers Master
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    I just routed my mains cable for the router above the machine - one day I'm going to arrange a more sophisticated support for it. :D:p:) The mains cables for my power supply are at the front of the machine, and the controller at the back.

    Workbee.JPG

    Alex.
     
  13. slade2000

    slade2000 New
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    @Alex Chambers that is an idea. I will have to make a plan as my machine is enclosed for sound damping as I am in a very tight residential area. I might build an elbow arm to run the cable on.

    I am also happy to report back that I did a full 3hour cut last night with he same code and had no issues.
     
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  14. sharmstr

    sharmstr Master
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    I basically did the same thing "just to see if it would work" about 8 months ago. I finally swapped out the scrap piece of wood with some 20x20 extrusion today.
     
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  15. slade2000

    slade2000 New
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    So did the same cut over the weekend and failed again at exactly the same spot. So I will now need to remove the power en then see how it goes.
     
  16. GrayUK

    GrayUK Openbuilds Team Elder
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    Error in exactly the same place doesn't sound like EMI. Probably not mechanical per se, but sounds like an event happening in that position.
    i.e. Cable bend causing an EMI event at that point, a mechanical stress point, etc. An error in the Code. :rolleyes:
     
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  17. Alex Chambers

    Alex Chambers Master
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    Can't see how it could be the code if it works sometimes, but if you post your G code here I'll have a look at it.
    Looking at the cut that went wrong I can't think of a mechanical cause either - that would usually result in the machine trying to follow the correct path, but offset from where it should be.
    Let us know how you get on when you have extracted your power lead from the drag chain.
    Alex. :confused:
     
  18. Alex Chambers

    Alex Chambers Master
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    Just had another look at the cut that went wrong - it does look (as @David the swarfer and @Gary Caruso were suggesting) as though the X axis stepper driver has shut down - something like a blackbox may well be a good solution in the long term.
    Alex.
     
  19. slade2000

    slade2000 New
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    Hi All

    I eventually got to remove the power away from the low voltage, and now it has gone down hill completely. Could not even get 1 good cut. it will go okay for a few laps and then just go nuts. No errors reported on the machine. The very last cut (bottom of picture) was even 500mm/min and 3mil depth and it still happened.

    I immediately jumped online to order the black box and with my luck can't find stock anywhere.

    [​IMG]
     
  20. slade2000

    slade2000 New
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    Here is the gcode
     

    Attached Files:

  21. Alex Chambers

    Alex Chambers Master
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    Hi @slade2000, as @Gary Caruso and @David the swarfer said earlier - it definitely looks as though the X axis stepper driver is shutting down if only momentarily. Good luck on getting your hands on a blackbox - they do sell out very quickly.
    Alex.
     
  22. slade2000

    slade2000 New
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    Okay I got hold of one in the UK so might take a while to get to Australia.
     
  23. slade2000

    slade2000 New
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    Okay blackbox arrived. Busy testing but having an issue. Both my Y axis nema 23's are making a squeal sound. X and Z is fine. When I plug x or z into y plug they are fine and when I plug y into z or x they still squeal. When I adjust the current the pitch just changes. If I ignore the noise they do work correctly but obviously something not right. I double checked the connection and they are fine.

    Any suggestions?
     
  24. Gary Caruso

    Gary Caruso OpenBuilds Team
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    Hi Slade, Please post your $$ settings, probably something different between Y and X and Z, too fast acceleration or max speed can cause the squeal.
    Cheers
    Gary
     
    #24 Gary Caruso, Aug 2, 2019
    Last edited: Aug 2, 2019
  25. Alex Chambers

    Alex Chambers Master
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    Hi @slade2000, if you take both Y steppers off the machine do they still squeal? - in other words are they squealing when not under load?
    Alex.
    PS: I just noticed you also have an issue with your blackbox, which may complicate dealing with this problem. Also I don't think you ever said whether your machine is leadscrew or belt drive?
    Let us know how things go.
    Alex.
     
    #25 Alex Chambers, Aug 3, 2019
    Last edited: Aug 3, 2019
  26. slade2000

    slade2000 New
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    @Gary Caruso not sure how I can pull the clean settings off the black box. Tried to copy it from the grbl settings but then it does not include the values.

    @Alex Chambers yes OpenBuilds replaced it very quickly. I received it today and installed. The stepper noise was still there but quite less than before. I removed the steppers off load like you suggested, however the noise did not change.

    I am in the process of doing a cut and will see how it goes. Must say the black box is a dream to work with.

    Again thx for everyone's help.
     
  27. Alex Chambers

    Alex Chambers Master
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    Well that would seem to rule out any mechanical component to the problem. Still puzzling that the Y motors squeal when connected to the X and Z outputs of the blackbox but the X and Z motors don't.
    Alex.
     
  28. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    @Alex Chambers - well past that: see Blackbox driver warning indicator stay on. - his got replaced

    and from

    I'd say he's happy now (;
     
  29. slade2000

    slade2000 New
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    @Peter Van Der Walt the squeal is still there even with the new box but much less.

    The machine has now been running for 2hours and so far so good.
     
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