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My Z-axis is sagging

Discussion in 'CNC Mills/Routers' started by Gaccus, Mar 4, 2017.

  1. Gaccus

    Gaccus Well-Known
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    I was going get finnished calibrating my OX today. But when I came to the z-axis I ran into problems. When I drive the z-axis up, it just sag down to my base again. What I have on there is a Makita 700W router fasten with a litle wooden jig. Nothing especially heavy. The wheels are also pretty tight. I use a nema 17 there. Is that the problem? What shall I do?
     
  2. Joe Santarsiero

    Joe Santarsiero OB addict
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    The 17 may not be sufficient, but check to see if your driver is holding at full current when stopped. Some controllers have this option and if it's off then you may be holding at half current. Regardless, It'll still drop when you turn everything off.
    You could try counter weighing it with springs to help that little nema out.
    May want to look at installing a 23.

    Joe
     
  3. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    You could also go with a screw with a shallower pitch. The TR8*8 is considerably more aggressive than a Z-axis really needs. A TR8*2 is a bit more appropriate for the task and it won't spin under the weight of the router.
     
  4. Gaccus

    Gaccus Well-Known
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    How do I check if the driver holds the current? I have connected a multimeter to the motor. It only shows current when the motor moves.

    I'm verry new at this. Could you please give me a link to this TR8*2 screw?

    Thank's for the respons. It's some frustrations every day with this cnc.

    I'll probably invest in a new 23. Need some dustcollector on this thing to. And that will make it even heavyer.
     
  5. David the swarfer

    David the swarfer OpenBuilds Team
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    What controller are you using?
    It is the controller that controls the power to the motors so that is where we need to change a setting.
     
  6. Gaccus

    Gaccus Well-Known
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    It's CNC shield/adruino uno combo.
     
  7. David the swarfer

    David the swarfer OpenBuilds Team
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    ah, then you need to set GRBL to keep the stepper drivers enabled.
    Grbl v1.1 Configuration · gnea/grbl Wiki · GitHub

    basically, set $1=255 to keep the drivers enabled.
     
  8. Gaccus

    Gaccus Well-Known
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    That trick worked. But the powerdraw like this is very high. The psu's fan went in overdrive and the drivers became very hot, fast. A fan blowing on the drivers is a must like this. But can the cnc shield handle full power on all the drivers all the time?
     
  9. Giarc

    Giarc Master
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    I had the same issue with the Z dropping. Then after switching to the 255 setting, my cnc shield started getting hot. I had to install better heat sinks and a fan. Occasionally I would still lose steps. It is the reason I upgraded to the DQ542MA drivers. Those small stepper drivers work well for light weight hobby grade cnc and 3d printers. Mine is quite a bit more robust than a shapeoko. More of a heavy duty hobby grade, and I felt the DRV8825 drivers I was using in my cnc shield just weren't up to the task. My z stepper used to get hot too. I have not had this issue with the new drivers.
     
    Joe Santarsiero likes this.
  10. Gaccus

    Gaccus Well-Known
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    Thanks for your reply.
    Yes, it's more and more clear that I have to upgrade the controller/driver system even before I have begun using the thing :p
    Not a great loss. It was the first thing I bought, and didn't know anything. I want a Mach-compatible controller for eas of use. And now heavyer drivers. Just trying to figure out what to buy.
     
  11. Joe Santarsiero

    Joe Santarsiero OB addict
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    Mach systems can get pricey. There are ways to use an Arduino and seperate drivers to take advantage of the freeware available.

    Joe
     
  12. Gaccus

    Gaccus Well-Known
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    Is there freeware out there that can use auto z-zero/edge finders?
     
  13. David the swarfer

    David the swarfer OpenBuilds Team
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    yes, GRBL can do it. bCNC has, I think, the best implementation of edge finding for GRBL.
    Candle has a Z probe function as well.
     
  14. Giarc

    Giarc Master
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    I have only used GRBL panel, but it works for z-probing. I have not tried any other probing like edge detection.
     
  15. Gaccus

    Gaccus Well-Known
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    I'll try those programs then. So for now I have just ordered some new drivers. Thanks for all your responses.
     

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