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  1. #1
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    May 2017
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    57

    Time to change it up.

    Hello all,
    I have a home built (?) machine that I am thinking of upgrading the drivers and BOB. I have had an intermittent issue with one side of the "Z", It stops randomly while moving from one cut to another. There are no "rapids" as I am a hobby user of f360 (no rapids). It most recently happened while in a move from one cut to the next. It is a new Nema 23 motor but from some older posts, I understand the drivers are not very good. I have SainSmart drivers and a ST-V3 interface board.
    Any recommendations on something fairly straightforward to switch to? I'm not that great with the mechanics of these machines but am willing to give it a go.
    If you have a recommendation, please advise why you recommend a particular product. I am looking for something basically "plug and play" so I can get back into playing!
    Any help would be great!
    This machine was made by a guy in SOCal trying to start a business. The company name was "lightening cnc". The machine needed a lot of work when I got it second hand. I was able to get a ton of information from this forum to get her up and running. But now I have this random issue. 4080 table, spindle...
    Ask for more information if needed please...
    rockaukum
    Attachment 482894
    Attachment 482896
    Attachment 482898

  2. #2
    Member
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    Nov 2013
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    2021

    Re: Time to change it up.

    Hi,
    what inductance are the steppers? Inductance is a good measure of how fast the machine will go before it starts missing steps. These cheap
    machines tend to have high inductance steppers and are let down by them.

    You may need to replace the steppers with low inductance ones, 1mH-2mH, 1mH preferred and reject anything over 2mH.

    The second let down with cheap machines is the wimpy power supply, commonly 36VDC. To make your machine sit up and take notice you'd want at least 60VDC or 80VDC preferred,
    but your drivers probably would not handle that, so you'd have to replace them as well.

    Craig

  3. #3
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    May 2017
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    57

    Re: Time to change it up.

    The inductance for the Nema 23 is 3.7mH
    This is what was on the machine when I got it. I have been using the machine for more than a several years, so I am baffled as to why this gremlins come up randomly.
    ra

  4. #4
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    Apr 2004
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    5539

    Re: Time to change it up.

    If you want to keep those motors and plan to change out the drivers and power supply, look for drivers that can tolerate 60 volts of DC, and give it a power supply that puts that out. This will give the motors enough juice to perform their best at high speeds.
    Andrew Werby
    Website

  5. #5
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    2021

    Re: Time to change it up.

    Hi,
    all steppers lose torque the faster they go, and eventually all will lose steps no matter how low the torque load.

    For instance a 1mH inductance stepper may have about 45% of its torque at 1000rpm, whereas your 3.7mH inductance steppers may have less than 10% at 1000rpm.
    Rather than the absolute best highspeed the lower inductance stepper will have increased torque authority at any given speed.

    I have been using the machine for more than a several years, so I am baffled as to why this gremlins come up randomly.
    I would suggest that your steppers are marginally overloaded and randomly miss steps. The only way to avoid that is to reduce the speed and thereby increase the torque that the
    stepper can apply and so avoid missing steps. Most find that slowing the machine even more is unpalatable. The choices are:
    1) Replace the steppers with low inductance types
    2) Increase the drive voltage.

    I agree with awerby, that to increase the drive voltage to 60VDC would be a big step forward, but even better step up to 80VDC. That would require both a supply and new drivers
    but may well be sufficient that your existing steppers perform adequately.

    Craig

  6. #6
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    1475
    Quote Originally Posted by awerby View Post
    If you want to keep those motors and plan to change out the drivers and power supply, look for drivers that can tolerate 60 volts of DC, and give it a power supply that puts that out. This will give the motors enough juice to perform their best at high speeds.

    I had similar problems years ago when I started out.
    Losing steps and stalling at moderate rapids.
    So:
    My motors are 3mh.
    I swapped out the drivers to DM860T.
    Swapped power supply to 60vdc.
    No more problems.
    Tried them with 80vdc too (the T version driver can go to 110vdc). Better still.

  7. #7
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    May 2017
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    57

    Re: Time to change it up.

    Thanks for the information!
    I think the "Rapid" was about 50 or 75ipm. I have run the machine at much faster speeds in the past. When this last happened, it was moving form one location to the next (not cutting) but at the same speed as the cut speed.
    With the recommendations presented, it seems to me the best approach would be at a minimum to change out the power supply as well as the drivers. If I went this route, Would I be able to replace the motors in the future without compromising the new drivers and power supply? This is hobby based but I certainly don't want to say speed is not an issue, however, reliability is.
    What are the thoughts not he BOB?
    Would you care to point me in the direction of which drivers and power supply would be sufficient for this upgrade?
    Thanks a lot!
    rockaukukm

  8. #8
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    Nov 2013
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    2021

    Re: Time to change it up.

    Hi,

    When this last happened, it was moving form one location to the next (not cutting) but at the same speed as the cut speed.
    That tends to suggest that the occasional fault may not be about the motors at all. If the motors were marginally overloaded then the problem would get worse as the
    speed increases....which does not fit your description.

    The fault could be the parallel port stuttering. The parallel port is very subject to timing jitter faults which in turn relates to the parallel port competing for CPU service with the operating system,
    typically Windows. Can you tell us about the PC, the software you are using and the motion controller.

    Craig

  9. #9
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    May 2017
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    57

    Re: Time to change it up.

    Okay, Thanks for staying with me with an open mind and patience...
    The computer came with the machine and is a Dell Optiplex GX620.
    Not sure about the motion controller. someone will have to direct me on getting that information.
    I am using Mach3 software.
    Again, Thanks for sticking with this.
    rockaukum

  10. #10
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    Nov 2013
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    2021

    Re: Time to change it up.

    Hi,
    looking at your original pics the system is Mach3/Mach parallel port as evidenced by the parallel input breakout board in your control box.

    In the early days of hobby CNC Mach3 and Mach's parallel port were very popular because they were cheap but they were always fairly slow and very prone
    to stuttering and/or stalling. This comes about because the PC is the motion controller, ie the gadget that generates accurate pulse streams for the motors,
    but has to compete with Windows and any other services running on the PC. Windows PCs are not very good in that type of service.

    In more recent years we have switched to external motion controllers like an Ethernet SmoothStepper ($190) or a UC300 ($160). These relieve the PC of having to generate
    pulse streams. With the old parallel port the PC had to be a desktop 32bit and Windows7 or WindowsXP, with an external motion controller now you can use just about
    any PC you want, including laptops, 64 bit up to Windows 11. The smoothness and accuracy of motion are the standout improvements over a parallel port.

    From your description of the random fault I'm coming to believe you are seeing an increase in jitter, or timing error, from your PC. If that's the case either new steppers or new
    drives wont fix it.

    You might be advised to get a UC100, its an external motion controller that plugs into the USB port of your PC but has a DB25 output socket that would plug straight into
    your breakout board. Beware the Chinese made rip-offs on EBay or Amazon, they are not a patch on the real UC100 by CNCDrive, buy genuine or don't buy. A UC100
    is about $120. It will certainly benefit the smoothness of your machine whether it solves the missing steps or not, and not a huge sum spent to try it out.

    A UC100 has the equivalent of one parallel port of output (17 inputs and outputs) whereas the more expensive UC300 has 85 and an Ethernet SmoothStepper has 51
    and both these boards are faster. If you are thinking about bigger/better/faster in years to come then one of these bigger boards is a good investment.

    Craig

  11. #11
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    Jul 2018
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    4200

    Re: Time to change it up.

    Hi Rock - There's nothing "random' in machine behavior. I suggest you work it through more before you buy anything. So 1) check the Z axis is mechanically correct 2) check the code and see if it is consistent in behavior when the same code is run (but seems not in your case so this eliminates the code and some electronics) If it has been running fine for some time and now there is an issue it should be able to be put back to working fine. 3) check all mechanical parts to ensure all good. Then start checking the electrical stuff. It will be something simple....Once this is fixed you can assess the components and upgrade as you see fit. . Peter

    eg over time any cable that is moving fatigues and its terminations may come loose. So check all cabling continuity on your Z axis connections and their terminations. Loose/frayed wires is a common fault on old machines.

  12. #12
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    May 2017
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    57

    Re: Time to change it up.

    JA, thanks for the follow up. good information as I was not aware of the additional benefits of an external control.
    Peter, thanks for the advice. It makes sence that there can be wear in the cabling with the machine in constant movement.
    I'll try to trace out the wiring and determine if there are any breaks as well as the connections at the terminals.
    That said, I know my computer is old and the thought that I can use my laptop (newer and portable) for the design as well as running the cnc, makes me think that external motion controller would be a great advancement to the operation.
    rockaukum

  13. #13
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    May 2017
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    57

    Re: Time to change it up.

    Went to the shop the other day and took a look at the electrical connections. I did find a few connections that I was able to get another twist on the recurring screws. I traced the wires to the motor in question and did not find anything of concern. So I set to work on doing another cut. This cut was basically the same as the last one in which the "Z" stalled / skipped or what ever it was doing. The cut went from start to finish without issue! very please with that. I hope to do a few more before I celebrate too much.
    Thanks to all who helped with this.
    rocakukum

  14. #14
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    May 2017
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    Re: Time to change it up.

    Aw crap!
    Back to square one with this. I tried yet again on a carve and had the machine mess up again.
    I removed the wood and ran the gantry manually to see if it would do it again. Fortunately (unfortunately) it did happen without any load on the machine. So. I got the camera and recorded what it was doing so some of you could see just how bad it is. My first thought now was that the acceleration should be turned down but watching the video, I see it happening at high speed as well as regular speed. I am using a playstation or xbox to maneuver the gantry around and I can boost the speed via the controller. Please take a look at the video hosted on YouTube and give me your thoughts on this.
    rockaukum
    https://www.youtube.com/watch?v=77ZmnRY5uP0

  15. #15
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    Jul 2018
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    Re: Time to change it up.

    Hi Rock - Its the RHS and LHS having a difference of opinion. I suspect its something mechanical on the side thats jamming. Peter

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