RE: [CAD_CAM_EDM_DRO] High Voltage servo cards

Thanks Wayne

I heard the bigger tek drives have been having problems poping fets. All
claimed to be due to wrong inductance, but sort of sounds like joining
another Rutex list.

It's also a case of how much current the others will take, most are listing
15 or 20 amps at 200V, my servo's can pull 40 amps, which is what the Rutex
is rated for. We know the Rutex can't handle this much current, 20A is more
like it, because it can't throttle back the pwm fast enough when a rapid
load change occurs, their 40A rating was based on a publication by Mariss.
If these others have used the same rating to get to their 15 and 20 amps
figures, they won't be big enough.



Too many unknowns really, and too many damn sales engineers stuck in the
middle.



There are also some Canadian cards, nice processor, lots of optical
isolation, big heatsink panel, serially programmable, some nice soft load
features, but the card looks really DIY. These are the Viper drives from
LarkenCNC. No one seems to have used any yet, perhaps I can scrounge a
freeby to trial and publish the results here!!.



I still have the analogue cards that came with my mill, at least I assume
analogue, stepper signals went to the main computer control, only resolver
signals to the cards. They are old, and thus I assumed unreliable, but who
knows. If however I buy interface cards to run them as step direction, I may
be back stuck with others encoder problems.



Those Rutex cards I have working, once you have the noise under control work
very well. The follow up error is very small, I can do 16m/minute with a
follow up count that doesn't go above 39 and is normally around 20 counts.
When one count is 0.64 micron, that is acceptable. At machining speeds up to
a couple of meters per second it doesn't really top more than 4 to 6 counts
with quite hi accelerations which again is quite acceptable. I will probably
buy another Rutex card just to get it up and running again, but have to
think what alterantive I am going for if it failes again. In the past I have
had three failures, one unknown, blew a hole in the encoder chip, two that
were my fault/G100 went nuts, but not Rutex's fault and esily repairable.
The last one the card works, but it gains steps and the G0 moves sound
horrible.



Thanks for your input Wayne

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 Wayne Weedon
Sent: 01 April 2007 12:05
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] High Voltage servo cards



Mark Vaughan wrote:

> I've just lost another Rutex which has gone noisy, grunchy motor control,
> and gaining steps, change the card and it's OK so must be a bad card.

Oh dear, I'm sort of glad I became rather cynical about the Rutex's and
didn't buy their drives.

>
> The PID control on the Rutex is brilliant, but they suffer from noise,

which

> I've just about got a handle on, and seems have a few other weaknesses.
>
> Time I thought about what alternatives there are.
>
> Any suggestion please, good or bad, together with your experiences.

Well I have been evaluating the CNC Teknix drives here albeit only the
80v 25A drives (tek10) their Tek20 drive 200v 15A CONT is currently off
their website, but if you speak to the Designer there, he may be able to
advice.

Email me offlist and I'll pass on his direct contact details.

Other than that there's a whole range of more industrial analogue input
drives out there which you could use with something like the Pixie
interface. Like Axor, Elmo, etc etc. Very unlikely to be in the same
price range though! But sometimes you have to do what you have to do eh!

Wayne.....

--
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Wayne M Weedon Email: wayne@fdos-design. <mailto:wayne%40fdos-design.com>
com
Fdos Design Poole UK
Tel +44-1202-677025 Fax +44-1202-770515 Mobile: 07774 439915

Specialists in small batch & Production Mechanical/Electrical Engineering
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