RE: [CAD_CAM_EDM_DRO] Re: Big servo motors drive recommendations

Gecko's are cheap, they have their design limitations, issues like fixed I,
though that becomes a problem for smaller low voltage rather than bigger hi
voltage motors.

For my servo's the issue again will be dynamic range, with the Tek cards, if
I hardwire out the false current trip, I am down to an unreliable
25mm/sec/sec acceleration, and 100mm/min speed on my Y with the way the PID
goes direct to PWM rather than torque/current, and regular 12 bit errors.
For Gecko's the volt drop I could live with since full rapid speed is
frightening and I will only run to half that, but I don't think Mariss's
cards will be much better here, I need cutting speed of at least 400mm/min,
and the machine should easily accelerate at 500mm/sec/sec with rapids at 8
to 16m/min.

The DIY cards are just too slow for me and lack viable dynamic range, so
some of us get away with it, and some (me) do not. I also still have the
original analogue cards 18 years old and fully operational so I am going to
try and get some pixie cards to drive them when Skyco come back from the
hols.



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 vrsculptor
Sent: 26 May 2007 21:26
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: Big servo motors drive recommendations



I used Gecko 320's to retrofit my big mill with a large (4.5" dia, 11"
long) 160 volt DC brush motors. The Machine is big with a 12X26
cutting area but fairly efficient with ballscrews and turcite ways.
I'm running at close to 80 volts with a 10 amp home made power supply
with BIG caps.

The Gecko's are costing me a bit on accileration and I can only get
around 120 ipm rapids.

This setup is not optimal but has proved to be very reliable and works
fine for me. I won't dispute the fact that more powerful analog or
digital AMPs would work better but the Gecko's are less than $150
which is about a quarter of what a better AMP might cost. I use Mach3.

There is some big iron on this group running Gecko's.

Roger





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