Re: [CAD_CAM_EDM_DRO] EMC: Spindle drive options ?

awemawson wrote:

> Hi,
>
> I'm now committed to converting my Denford TRIAC mill to EMC - I'll
> be using the exisiting steppers via Gecko 210's but what are my
> options for spindle speed control?
>
> 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