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Thread: CNC Router - Z-Axis Issue - Please Help!!

  1. #1
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    CNC Router - Z-Axis Issue - Please Help!!

    Hi Community,

    I was wondering if anyone could shed some light on an ongoing Issue I've been having with my CNC Router.

    I'm not sure the exact manufacturer of my CNC as I purchased it used and it is a Chinese made machine. It is a 600mm x 900mm machine with a water cooled spindle (see attached photo). It's connected to my computer via a driver plugged into a slot in the back of my computer with a serial port attached. I use Artcam to create G code and export "multicam new .plt" files which I then use ncstudio to send the G-code to my machine. There are photo of my ncstudio settings below for reference.

    The issue I'm having is that my machine randomly seems to forget where the Z home is, this can happen after I've restarted the machine, in between cuts, but most frequently it seems to reset in the middle of a cut. The X and Y axis seem to be fine, but the Z axis will drill straight through the material and MDF (see attached photo). This happens on average 1-3 times a week, and I typically run my machine about 6-8 hours a day. My first step, I suppose, is to narrow it down to either a Machine issue or a driver issue. I believe it's a machine issue as I can set the home position one day and come back the next morning and the home will still be saved, then another day the X and Y will be fine, but the Z home will drill through the MDF again. Initially I believed I may have had an issue with losing power for a split second so I purchased a battery backup which made no difference. My machine is 220V so I'm using a step up converter, which has a max of 1500W, my current assumption is that's not enough, so I have a 5000W step up on its way from Amazon. Lastly, My stepper motor parameter settings are weird. As you can see in the below photo of my settings, the X and Y motor parameters are set to .00625 and the Z axis is set to .003125. I don't know if this is common, I assumed not... When I purchased the machine I was having an issue with the Z axis cutting too deep, then with some messing around I changed the Z from .00625 to .003125 and solved that issue. My guess is that at some point the Z motor was changed...

    I would really appreciate input from anyone who thinks they can help. Thank for taking time out of your day to read this.

    1.jpgcnc2.jpgcnc1.jpgCapture.PNGCapture1.jpg

  2. #2
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    I do not recognize the control software, maybe someone else will. I would start with some simple stuff and as electrician who made a good income by fixing things. I would check ALL the connections inside the control box, with the power off of course, looking does not count and saying ok I did that does not count either. Take a screw driver and check each point and make sure its tight.Look for something that may not look right, burnt connection or Grounds.

    Is the machine grounded? Does it feed back to a grounded outlet or power source? I am assuming your running a 3 phase spindle off a VFD. Is that cable or cables ground? The shield grounded? The electrical noise or EMI or RFI can feed back into your controller and cause weird things to happen. If the steps per mm was off, it would be wrong all the time, not just once in a while.
    Its sounds like what I have outlined above. Loose connection, broken wire or grounding issue.
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

  3. #3
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    Bill,

    Thanks so much for the input. I did check all connections wit ha screwdriver and seemed to be fine, however I didn't have a chance to look for a short anywhere. I will look tonight, thanks for the advise. As an electrician, do you think my step up converter only being 1500W would be causing this issue?

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    Quote Originally Posted by Ryan Murphy View Post
    Bill,

    Thanks so much for the input. I did check all connections wit ha screwdriver and seemed to be fine, however I didn't have a chance to look for a short anywhere. I will look tonight, thanks for the advise. As an electrician, do you think my step up converter only being 1500W would be causing this issue?
    You do not have 220/240 volts in your shop?
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

  5. #5
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    Unfortunately I do not.

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    Quote Originally Posted by Ryan Murphy View Post
    Unfortunately I do not.
    How hard would it be to install as running off a transformer is really not a good option. Your going to be drawing a lot of amps on your 120 volt line. What does the nameplate on your machine say? Heck my spindle alone is at least 2000 watts. Yours could be less Hp but still 1000 watts.
    Last edited by Bill George; 02-27-2019 at 8:13 AM.
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

  7. #7
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    I had a similar issue last year with my z Axis, it ended up being a bad wire. I could not see any damage to the wire, but when I jumped it with a new wire, problem was solved. Not sure if that could be your issue, but worth a check.

  8. #8
    Are any of your stepper motors or stepper motor drivers overheating? I would think it would happen with more consistently if it was the case, but it's worth a quick glance. Some electronics will briefly shut down to save themselves if they get too hot, and during that period it'll miss steps. So if it misses the command to raise the z-axis, but catches the command to lower it, you'll be plowing right into your material. On one of my first machines, I had the current set too high for my motor drivers and periodically I'd miss steps and ruin a job.
    Last edited by Matt Schrum; 02-27-2019 at 4:45 PM. Reason: Typo
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  9. #9
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    It would be hard to install 220V, is that's the case I'm hoping upgrading my Converter to 5000W will do the trick!

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    I will definitely look for a bad wire, thanks for the input!

  11. #11
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    My motor seem to be fine, but I haven't taken a look at it directly after the issue occurred. I can't believe I didn't think of that... It could very well be what's going on. Do you think the best troubleshooting method would be to check the temp of the z motor next time I experience the Issue?

  12. #12
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    Why don't you post a picture of your machine nameplate. A lot of those Chinese machines are dual voltage. A switch on the DC power supply can be flipped to 120 volts and a lot of the VFD's can take either 240 or 120 volt input. I had a smaller Chinese CNC the VFD was 120 volts but the spindle was 240 volt 3 phase of course. If your transformer is only 1500 watts, then your voltage could be lower under load, causing the motor or driver to overheat. If the Z motor stopped getting power the weight and bit torque would pull it down.

    Generally its not that expensive to run a 240 volt line.
    Last edited by Bill George; 02-27-2019 at 10:54 AM.
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

  13. #13
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    Quote Originally Posted by Ryan Murphy View Post
    It would be hard to install 220V, is that's the case I'm hoping upgrading my Converter to 5000W will do the trick!
    You have a 40A 120V circuit? The converter doesn't create power. Make sure the entire circuit back to the breaker is appropriately wired.
    Colorado Woodworkers Guild
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  14. #14
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    Quote Originally Posted by Richard Gonzalez View Post
    You have a 40A 120V circuit? The converter doesn't create power. Make sure the entire circuit back to the breaker is appropriately wired.
    Good point Richard and I missed that. Yes 5000 watts / 120 volts is 42 amps. Thats at least a 45 amp breaker on #8 or #6 wire. A lot more expensive than a 20 amp 240 volt one. I would need to see the nameplate.

    My machine has 120 volts for the control panel and the stepper drives/motors and a 240 volt one for the VFD and Spindle.
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

  15. #15
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    I'll start by asking about the plt output you're choosing. Why are you using the multicam output? Multicam uses a proprietary controller specific to their machines.

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