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Thread: VFD on a 25HP Rolling Mill

  1. #21
    Member 8sigma's Avatar
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    Default Re: VFD on a 25HP Rolling Mill

    Quote Originally Posted by Al_The_Man View Post
    Running at present at 63rpm and wishing to stop within 0.125" could be done probably with a VFD with a encoder option., I did a similar thing on a machining centre.
    I forgot to mention the motor has a brake so that should help. Maybe I should try stopping it with that and see how consistent it is.



  2. #22
    Community Moderator Al_The_Man's Avatar
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    Default Re: VFD on a 25HP Rolling Mill

    It certainly would help, I assume there is some degree of reduction from the motor to the final positioning?
    26:1 gear ratio?

    CNC, Mechatronics Integration and Custom Machine Design

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  3. #23
    Community Moderator Jim Dawson's Avatar
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    Default Re: VFD on a 25HP Rolling Mill

    Quote Originally Posted by 8sigma View Post
    I forgot to mention the motor has a brake so that should help. Maybe I should try stopping it with that and see how consistent it is.
    Consider a vehicle analogy. You are in a car idling up to a stop sign, maybe going 10 MPH. You reach the target stop point and slam on the brakes to stop. Conversely, you start applying brakes 15 or 20 feet from the target stop point and roll smoothly to a stop. In other words you lengthen the deceleration time to blead off stored kinetic energy over time so you are not over stressing the mechanics. Just something to think about.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: VFD on a 25HP Rolling Mill

    Quote Originally Posted by Al_The_Man View Post
    It certainly would help, I assume there is some degree of reduction from the motor to the final positioning?
    26:1 gear ratio?
    Yes, 26:1 gear reduction. However even at that I'm calculating the linear speed (surface speed) at 1700 IPM based on the size of the rolls.
    I'd like to decelerate as I get close to the end. I'm planning on using a linear scale to keep track of the end of the part. As the material is reduced it's going to get longer. A lot longer, like 50%. The part has an unrolled section at each end, so I can't just pass it through.



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    Default Re: VFD on a 25HP Rolling Mill

    Quote Originally Posted by Jim Dawson View Post
    Consider a vehicle analogy. You are in a car idling up to a stop sign, maybe going 10 MPH. You reach the target stop point and slam on the brakes to stop. Conversely, you start applying brakes 15 or 20 feet from the target stop point and roll smoothly to a stop. In other words you lengthen the deceleration time to blead off stored kinetic energy over time so you are not over stressing the mechanics. Just something to think about.
    Thanks Jim, I'm planning on decelerating the motor as I get close to the target length based on scale feedback. If it's tuned correctly it'll come to a smooth stop and perhaps engage the brake at the desired location. That's why I think I need a VFD. I'm also pulling on each end to keep the workpiece in tension so the brake might help prevent overtravel until the linear actuators de-energize.



  6. #26
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    Default Re: VFD on a 25HP Rolling Mill

    Quote Originally Posted by 8sigma View Post
    Thanks Jim, I'm planning on decelerating the motor as I get close to the target length based on scale feedback. If it's tuned correctly it'll come to a smooth stop and perhaps engage the brake at the desired location. That's why I think I need a VFD. I'm also pulling on each end to keep the workpiece in tension so the brake might help prevent overtravel until the linear actuators de-energize.
    I agree.

    Since the material grows in length as the cross section is reduced and the leading edge is therefore variable, I wonder if it would make more sense to use a photo eye to sense the trailing edge position and use that as the stop trigger point. At least you know where that edge is. The actual stop point could be some number of encoder pulses from the photo eye position. I have done this in a number of applications where I have variable length material.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: VFD on a 25HP Rolling Mill

    Quote Originally Posted by Jim Dawson View Post
    I agree.

    Since the material grows in length as the cross section is reduced and the leading edge is therefore variable, I wonder if it would make more sense to use a photo eye to sense the trailing edge position and use that as the stop trigger point. At least you know where that edge is. The actual stop point could be some number of encoder pulses from the photo eye position. I have done this in a number of applications where I have variable length material.
    I like that idea for the simplicity vs. some sort of linear scale. The various parts that we are running have different lengths from the end. I guess that distance can be loaded into a parameter table for the different part numbers and use an algorithm to calculate the stopping point.



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    Default Re: VFD on a 25HP Rolling Mill

    Quote Originally Posted by 8sigma View Post
    I like that idea for the simplicity vs. some sort of linear scale. The various parts that we are running have different lengths from the end. I guess that distance can be loaded into a parameter table for the different part numbers and use an algorithm to calculate the stopping point.
    A vision system may do a better job and may be easier to setup

    Mactec54


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    Default Re: VFD on a 25HP Rolling Mill

    I'm now the proud owner of a 25HP rolling mill soon to be converted to CNC/PLC control!
    VFD on a 25HP Rolling Mill-img_2036-jpg



  10. #30
    Community Moderator Jim Dawson's Avatar
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    Default Re: VFD on a 25HP Rolling Mill

    Looks like a beefy machine. Careful of your fingers

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: VFD on a 25HP Rolling Mill

    Quote Originally Posted by Jim Dawson View Post
    Looks like a beefy machine. Careful of your fingers
    285,000 pounds of separating force!



  12. #32
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    Default Re: VFD on a 25HP Rolling Mill

    The one I retro fitted looked similar to this.
    Four rollers.

    Attached Thumbnails Attached Thumbnails VFD on a 25HP Rolling Mill-rollingmc-jpg  
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VFD on a 25HP Rolling Mill

VFD on a 25HP Rolling Mill