Re: EMC: Spindle drive options ?

--- In CAD_CAM_EDM_DRO@y..., Jon Elson <elson@p...> wrote:

> awemawson wrote:
> > The spindle motor is three phase 240 /440v (ie star or delta)

0.37KW

> > which on the original machine was driven by a VFD (1985 vintage)

that

> > has been 'hacked' to interface it. I expect that I'll have to
> > buy a new VFD but what are the options for speed control &

direction

> > with EMC? Any pitfalls to avoid ? Anyone got a suitable VFD ?
>
> The best ones are quite flexible. I have a Magnetek, I think they

are

> made by Yaskawa. It can take one contact closure for run/stop and

one

> for forward/reverse, or one for forward and one for reverse (none

is stop,

> both is fault). These are pretty standard functions. Speed

control is

> usually by an external pot (although some really basic ones are
> keyboard only). Most have an option for external voltage or current
> loop speed command. The 0-10 V speed control is what you want
> if you were going with analog-input servo amps. Since geckos use
> step/direction commands, you won't have any hardware that could
> send analog speed control to the VFD. Some, like my Magnetek, can
> be set up for auxilliary speed control, where contact closures set

it

> for 25, 50 75 and 100% speed, or some similar combination.
> Most modern VFD's have the features, but the problem is getting the
> signals out of the PC. You might find one that can take serial

ASCII

> commands on a current loop port. Or put a CAN-bus or DeviceNet
> interface in your PC.
>
> Jon

Would it be an option to use a quasi fourth axis driving a bit of
electronics? Taking step and direction it would be relatively simple
to produce a 0-10v signal, and maybe use a tacho circuit to provide
feedback emulating an encoder disk.

Has anyone been down this path before?

Andrew