Problem Stalling at high speed


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    Member thomasks's Avatar
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    Default Stalling at high speed

    I just completed upgrading my desktop cnc router to a large size shop cnc router. The ball screws and bearing slides are 1500 mm (or about 59") and is built from 80/20 and aluminum stock. The workable area now is 48" x 48" and I have put down a MDF spoilboard that I have been struggling to surface. The surfacing bit I have is a 2" 4 flute with a 1/2" shank. It is required to spin about 18000 rpm and cut at 200-600 ipm. I cant get my axis to move that fast without stalling. I am using Stepper Online motors and drivers. The motors are Nema 23 hi torque 3.0Nm(425oz.in) 200 steps per rev. 4.2A
    I have a 1000W 48VDC power supply dedicated to the drivers. The stepper drivers are DM542T model (V4.0) the microstepping is set to 6400 steps per rev, and I was thinking this may have something to do with it. I cannot get over 100ipm with out stalling.
    Any ideas?

    Thanks

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    Quote Originally Posted by thomasks View Post
    I just completed upgrading my desktop cnc router to a large size shop cnc router. The ball screws and bearing slides are 1500 mm (or about 59") and is built from 80/20 and aluminum stock. The workable area now is 48" x 48" and I have put down a MDF spoilboard that I have been struggling to surface. The surfacing bit I have is a 2" 4 flute with a 1/2" shank. It is required to spin about 18000 rpm and cut at 200-600 ipm. I cant get my axis to move that fast without stalling. I am using Stepper Online motors and drivers. The motors are Nema 23 hi torque 3.0Nm(425oz.in) 200 steps per rev. 4.2A
    I have a 1000W 48VDC power supply dedicated to the drivers. The stepper drivers are DM542T model (V4.0) the microstepping is set to 6400 steps per rev, and I was thinking this may have something to do with it. I cannot get over 100ipm with out stalling.
    Any ideas?
    Thanks
    That sounds about right for 48v.
    Those motors aren't great, they have an inductance value above 3mh. That causes what you describe at those kind of speeds, they can't get the power they ask the drive for.
    To overcome the inductance you need to run higher voltage drives and at least 60v.
    Voltage = speed.
    Amps = torque.
    Or buy some AC servos.

    High inductance in steppers is the enemy.


    I had same issue. Swapped stepper drives to DM860T (110vdc/80ac). Have 2 motors on 60vdc and 1 on 80vdc.
    Solved it immediately.
    In fact, they could all do with running on the 80v, it flies!.



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    Default Re: Stalling at high speed

    Going back to my previous post.
    You could try halving your steps per rev and steps per unit but it's unlikely to get much more benefit.
    Voltage is where it's at.

    The best stepperonline motors are their P series 5.0A, 495oz. Their DM860T drivers are good, and paired together on 80vdc or higher pack a punch. But, steppers are only rated to 1000rpm max. They never really hit that, and you need steppers below 2mh.
    If you have 5mm screws fitted the max you can get is 5000m/min (197ipm).
    You need at least 80vdc for that. (more with your existing motors).

    For anything above 200ipm you need either 10mm pitch screws or an AC servo on the axis (or both). Delta servos are good quality for the price.
    If a high encoder count is not required then Lichuan servos are a decent option too.


    Don't piss about, pay attention to this info.
    I've been there.
    Do a fair bit of research and math.

    Last edited by dazp1976; 05-06-2022 at 05:21 PM.


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    Default Re: Stalling at high speed

    That seems to be a high rpm for a large diameter bit. Normally those large surfacing bit are limited to about 8000 rp



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    Default Re: Stalling at high speed

    Quote Originally Posted by thomasks View Post
    I just completed upgrading my desktop cnc router to a large size shop cnc router. The ball screws and bearing slides are 1500 mm (or about 59") and is built from 80/20 and aluminum stock. The workable area now is 48" x 48" and I have put down a MDF spoilboard that I have been struggling to surface. The surfacing bit I have is a 2" 4 flute with a 1/2" shank. It is required to spin about 18000 rpm and cut at 200-600 ipm. I cant get my axis to move that fast without stalling. I am using Stepper Online motors and drivers. The motors are Nema 23 hi torque 3.0Nm(425oz.in) 200 steps per rev. 4.2A
    I have a 1000W 48VDC power supply dedicated to the drivers. The stepper drivers are DM542T model (V4.0) the microstepping is set to 6400 steps per rev, and I was thinking this may have something to do with it. I cannot get over 100ipm with out stalling.
    Any ideas?

    Thanks
    What is stalling the spindle or the axis drive motor, and what size spindle do you have that's a big cutter and need Hp to drive it.

    Mactec54


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    Default Re: Stalling at high speed

    Thanks for the replies.
    I have a 2.2KW spindle air cooled 220VAC that will turn up to 24000 rpm.
    I tried reducing the spindle speed down to 8000 so that I may be able to get away with a slower feedrate and still have enough chip load that I don't have another wood burning experiment in my shop. I burned up a 1-1/4 surfacing bit when the motors stalled out during cutting and I had left the room.
    Anyway, I changed my pulses per step to 1600 and still have the problem. Also I misstated the driveers I am using it is actually a Sainsmart ST-M5045 . I was thinking of upgrading to another brand that is American made if there are any.
    Any suggestions?



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    Default Re: Stalling at high speed

    I have ordered 4 DM860H drives and a 1000W 12A 80VDC power supply. Hopefully this will help.
    Thanks for the advice guys.



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