584,829 active members*
4,868 visitors online*
Register for free
Login
Results 1 to 9 of 9
  1. #1
    Join Date
    Aug 2015
    Posts
    11

    Stepper motor grinding

    Hey everyone, been using cnc zone for years. But this is my first time posting. Hoping to get a little help if possible. I'm on my second cnc build, in which I downsized from a larger cutting area to smaller more rigid setup. The machine is already built and has been used on a v-inlay project, and milling small brass parts. But I was having trouble losing steps when running at higher speeds. I walked away from it for some months, was just very busy with stuff, and didn't need it for a while. So I'm getting back to needing to run some projects and I wanted to figure out what was going on, so I don't waste material and so I can be more confident in walking away with out having to be concerned about missing steps.

    So getting back to the issue, I'm running nema 23's 425oz and my issue is anything over 50 ipm the motor stops turning, skips, and makes an aweful grinding noise.
    I have checked connections, removed motors from the machine to make sure nothing is binding. Which I was able to turn all ballscrews easily by hand on all axis and for the entire length of travel both ways. Iv tried adjusting microsteps, along with trying different motor tuning in mach3, and every time once I hit between 70-80 ipm is stops, skips and that aweful grinding sound. The machines rigidity is to the point where I'd like to be running 100 plus ipm for woodworking projects, and a bit faster for non ferrous milling. Along with being able to rapid more quickly.

    Here is a like to the electronics packa ge I bought 5 years ago.

    https://www.automationtechnologiesinc.com/products-page/stepper-nema23-3-axis-kits/3-axis-nema23-cnc-kit-36v9-7a425-oz-inkl-4030/

    If anyone has any suggestions as to helping to figure this out it would be greatly appreciated.

    Thanks !

  2. #2
    Join Date
    Dec 2003
    Posts
    24216

    Re: Stepper motor grinding

    That is the motor going in to torque limit and can be the source of a few reasons, overloaded, miss-match of drive and power supply, low voltage DC etc.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  3. #3
    Join Date
    Aug 2015
    Posts
    11
    Quote Originally Posted by Al_The_Man View Post
    That is the motor going in to torque limit and can be the source of a few reasons, overloaded, miss-match of drive and power supply, low voltage DC etc.
    Al.
    Thanks Al for the quick feedback, I was hoping you might be able to direct me toward some material that helps explain those conditions and the steps taken to test each scenario.

    Thanks again!

  4. #4
    Join Date
    Jul 2005
    Posts
    2415

    Re: Stepper motor grinding

    Its all about RPM of the motor and the amount of torque you need to accelerate, and move th eload using a given tool. At some RPM all steppers "stall" (which is the symptoms you describe). Spin a steeper fast enough and it will stall with little or no load. You are simply asking the motor(s) to move a load too fast and the motor hits its RPM /torque curve. Motor RPM is a function of applied voltage. You need to look at the physics (math) of the drive train and calculate the motor RPM needed to hit the speeds you want to cut at. The goal is to keep the Motor RPM at about 50% max RPM while cutting to have some reserve torque.

    The final drive ratios predict things like top speeds and torque and the anout of ft-lbs of linear force you can expect at a given speed.

    So to give you further help you need to post:
    Power supply voltage
    Linear drive type (if leadscrew, then the leadscrew TPI, if R & P or Belt the diameter of the final drive gear and any belt reduction)

    Of less importance but stillpart is the weight of the gantry and the type of tools and media you are trying to cut.
    . .

  5. #5
    Join Date
    Aug 2015
    Posts
    11
    Quote Originally Posted by Torchhead View Post
    Its all about RPM of the motor and the amount of torque you need to accelerate, and move th eload using a given tool. At some RPM all steppers "stall" (which is the symptoms you describe). Spin a steeper fast enough and it will stall with little or no load. You are simply asking the motor(s) to move a load too fast and the motor hits its RPM /torque curve. Motor RPM is a function of applied voltage. You need to look at the physics (math) of the drive train and calculate the motor RPM needed to hit the speeds you want to cut at. The goal is to keep the Motor RPM at about 50% max RPM while cutting to have some reserve torque.

    The final drive ratios predict things like top speeds and torque and the anout of ft-lbs of linear force you can expect at a given speed.

    So to give you further help you need to post:
    Power supply voltage
    Linear drive type (if leadscrew, then the leadscrew TPI, if R & P or Belt the diameter of the final drive gear and any belt reduction)

    Of less importance but stillpart is the weight of the gantry and the type of tools and media you are trying to cut.
    . .
    I was running them with just the weight of the gantry and axis it was moving. When I started to try and increase speed is when I removed the steppers, so zero load. My power supply is 36v, with a separate 5v supply for my b.o.b.
    I checked the voltages at each of the drivers for pulse and direction. Which were at 2.63v, then checked voltage at power input to the drivers which were all at 38.5v. And the voltage at phase A and phase B alternate from what I understand, so one phase reads 2.5v and the other reads 0.0v

    That's all I went through and tested for, as I can't seem to find any documentation on what the drivers are suppose to output.

    As for my linear drive, I'm using 16mm ballscrews for all 3 axis. The lead is 5mm and they all have dual fixed end supported by bearing blocks. The y axis which carries the moving gantry is around 50 lbs. The weight is fully supported by 20mm sbr linear rails. The x axis is only carrying the z axis which is around 12lbs. And the z axis carrying the router, is around 7-8 lbs.

    Also there is no gear reduction, the motors are coupled directly to each ballscrews.

    I hope this information helps as to trying to figure out if I can gain more speed or if I am topped out.

    Thanks for the help!

  6. #6
    Join Date
    Jul 2005
    Posts
    2415

    Re: Stepper motor grinding

    Okay: At 38 volts, top RPM is in the range of 600 RPM . At 500 RPM you have virtually NO torque left. Your ballscrew provides a 5:1 speed reduction so at 500 RPM the TOP speed would be 100 IPM. (virtually no load) so I would expect the motors to run out of torque to move the gantry at the 70 - 80 IPM. Cutting speeds will be even lower at 45 to 50 IPM as you load the linear motion.with the cutting forces.

    You can't read voltage across the coils without a scope...they are a pulsed DC . Step is also a wave form so you just see and average Or worse . It too needs a scope to see the waveform. Direction will be either high or low and shoulld be about 3Volts and close to zero on a direction change. Even if you had a scope it would not tell you much. You need the see the CURRENT wave form to make any sense of torque .

    So: To get more cutting speeds you can:
    1. Raise the DC volts to 48VDC of your drivers will take it.
    2. Make sure your current setting on the drivers is at the motor spec or slightly higher
    3. Do a 1.5 : 1 pulley step up (larger pulley on the motor) so your motors are operating in a lower RPM range with more torque That should get you to the 100 IPM range.at least with not cutting loads
    4 Get motors with more torque and lower inductance that have a longer torque curve. Combine with 1 and 2 (and 3)

    As it is you have proven it won't go any faster

  7. #7
    Join Date
    Jul 2005
    Posts
    2415

    Re: Stepper motor grinding

    The other fact you are fighting is a 16mm ballscrew has RPM limitations. The longer it is and the looser the mounts, the lower the max RPM . So even if you could spin the leadscrews to 1000 RPM to get 200 IPM they probably won't take it .

  8. #8
    Join Date
    Aug 2015
    Posts
    11

    Re: Stepper motor grinding

    Thanks torch for all the feedback, I really appreciate it^

    It took me some time yesterday but I have everything tuned back in and with keeping everything 50ipm and below it's running very smooth. My workable area is also not very big so I think for a good long while I'll be fine with the speed limitations. My machinable area is 18x23. I also work in a machine shop where I'm normally used large vmcs in which we try to adapt hsm into many of the things we do. So I ran a program last night and it was plenty fast enough at 30ipm.

    I also did try to figure out some of the math you were throwing my way, looked at a bunch of different resources, but unfortunately I'm not really grasping it. I'll have to do some more reading up for future instances.

    Thanks again for all your help!

  9. #9
    Join Date
    Apr 2015
    Posts
    113

    Re: Stepper motor grinding

    take the coupler off and see what the raw motor is able to do. I can get 1000 rpm out of my 425ozin motors on 48V WITH LOAD. 2010 ballscrews.
    Luthier/Woodworker/Machinist in NS, Canada.

Similar Threads

  1. Connect an 8 wire stepper motor to a TB6560 Stepper motor driver
    By muldoon22 in forum Stepper Motors / Drives
    Replies: 2
    Last Post: 12-31-2016, 07:26 AM
  2. Stepper motor noise and grinding
    By motion86 in forum Stepper Motors / Drives
    Replies: 3
    Last Post: 01-23-2014, 10:31 AM
  3. Replies: 0
    Last Post: 02-26-2013, 08:37 AM
  4. Integrated stepper motor? with built-in stepper motor driver
    By uirobot in forum News Announcements
    Replies: 0
    Last Post: 06-07-2010, 09:59 AM
  5. Motor Grinding And Binding
    By pzzamakr1980 in forum Uncategorised MetalWorking Machines
    Replies: 1
    Last Post: 08-13-2007, 03:31 AM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •