Re: Constant Velocity unwinder

Thanks Mariss,
Not that proficient in electronics, but I will look into it.
I will let you know.
Regards and thanks a lot
Fernando.
--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mariss Freimanis"
<mariss92705@...> wrote:

>
> A simple analog method is have a tach (tiny DC motor) attached to a
> capstan wheel. Form a summing node of the tach feedback (- voltage)
> with a velocity command (+ voltage). Use an op-amp to PID amplify the
> difference voltage (error signal) and drive the VFD analog speed
> input with the output. You should be able to regulate the feedrate to
> within 1% that way. A quad op-amp and a dozen resistors/capacitors
> should do it. About $0.99 of parts.:-)
>
> Mariss
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Fernando" <fer_mayrl@>
> wrote:
> >
> > Hello,
> > I think this would be off topic, dont know so if you think it is,
> > please add the OT on the subject on your replies.
> >
> > I have a client that has an unwinder, it unwinds flatstock
> about .25"
> > thick, it has a 5HP motor with a reducer, and a VFD. The client has
> it
> > right now as to supply the max amount of material it can, but
> > obviously, as the diameter of the roll gets smaller the less
> material
> > is being delivered. What would be a good way to supply constant
> > material flow? I was kind of thinking of replacing the motor and
> VFD,
> > with a servo operating in velocity mode, and attaching the encoder
> to
> > a following wheel that is in contact with the material being
> > delivered. Does anyone know if there are VFD that can accept a
> signal
> > that regulates the speed, that signal being an encoder or tach
> > attached to the advancing material?
> > Any suggestions would be greatly appreciated.
> > Regards
> > Fernando
> >
>