RE: [CAD_CAM_EDM_DRO] Big servo motors drive recommendations

I tried Tek 20's and Tek10's

Peter who designed them looked at the DIYers that were building servo
controls for smaller motors and getting by. He designed his PID circuit
which is limited but adequate, he took the PID output and directly converted
it to a PWM width. The trouble is as the motor gets bigger a fixed PWM will
result in significantly different torques at different speeds. At low RPM
you will get lots of current and massive torque, at hi RPM you don't get
enough torque. He should have taken the PID output and sent that to a
current controlled PWM loop so it calls up current or torque. Without is you
just don't have any dynamic range. He also has a badly designed current trip
that dues to bad PCB grounding design and some poor assumptions, his current
circuit reads significantly in error and will keep tripping when the true
current is mush lower. I tried dropping the voltage and using Tek10's
because they can run with twice the current but they were no good either.
Ended up with a machine with snails acceleration and speed. He did refund
me, which was good of him, and he explained some of it's problems before I
tried them.

As you probably know I also tried Rutex, also no go.



I have gone back to the old analogue cards made by Norwin which seem bullet
proof by comparison, and will run them with Pixies. My Pixies arrived last
week, I am presently building the logic level interfaces for them, got a
mixture of 5V, 12V, 24V logic that all needs to talk to each other.



You could look at www.granitedevices.fi <http://www.granitedevices.fi/> ,
Toro that designed these has a much better firm understanding of what is
needed, I've had a lot of discussions with him, tried to trip him up
technically a couple of times, and put my own foot in it, his replies were
always correct, gives one confidence in his work, though servo design isn't
really my field.. Hs drives will run AC or DC servos with the same drive. DC
servo control is easy, AC is a lot more complex to pull off. His drives will
go up to 200V, but they were a little short on current for me to take the
risk again, it's not the parts price anymore, it's hundreds if not thousands
of hours to rewire the machine to try yet another controller.



Hope that helps, for a medium big DC servo I would go for Granite Devices,
for a big DC servo it has to be commercial analogue control cards and
pixies. To the hobby boys our motors are big, to the commercial analogue
cards they are everyday run of the mill. Big servos to these guy's is
absolutely massive.



Regs Mark



Dr. Mark Vaughan Ph'D. B.Eng. M0VAU

Managing Director

Vaughan Industries Ltd, reg in UK no 2561068

Water Care Technology Ltd, reg in UK no 4129351

Addr Unit3, Sydney House, Blackwater, Truro, Cornwall, TR4 8HH, UK.
Phone/Fax 44 1872 561288

RSGB DRM111(Cornwall)

_____

From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Polaraligned
Sent: 06 July 2007 18:02
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Big servo motors drive recommendations



It is now July Mark.
Just wondering if you have had any more success with
drives.

I have a series 2 BP that is near ready for drives.
My Series 1 uses Gecko's and I am not totally thrilled
with them. I have Baldor motors for the mill and I don't
mind running them at 80v or so. I can still get almost
200 IPM rapids at that voltage.
It is kind of pathetic that there is such a void in the market.
Was it just the Tek 20's that you have had problems with?
I was wondering if the Tek 10's were any better.

Scott

> I have worked with Rutex to identify many of their problems,

similarly I am

> working with CNC Teknix to improve theirs, and the problems we presently
> have can be overcome, but I don't feel there is anything at this time
> adequate on the market. My mill now has been in rebuild for over 12

months,

> it has to be operating by July or I will have to go out and buy a

new one

> and I hate giving those big CNC guys the satisfaction they have

beaten me.

>
>
>
> Dr. Mark Vaughan Ph'D. B.Eng. M0VAU
>
> Managing Director
>
> Vaughan Industries Ltd, reg in UK no 2561068
>
> Water Care Technology Ltd, reg in UK no 4129351
>
> Addr Unit3, Sydney House, Blackwater, Truro, Cornwall, TR4 8HH, UK.
> Phone/Fax 44 1872 561288
>
> RSGB DRM111(Cornwall)
>

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