CNC MILL?

Thanks Gary.

Rich
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2c. Re: CNC Mill?
Posted by: "Gary Click" garyclick@... nitewatchman5
Date: Tue Oct 4, 2011 9:09 am ((PDT))

I was a Fagor reseller for several years and retrofitted several machine
with
8000 series control. Machines ranged from Bridgeport size mills to a 52'
planer
mill with a 110' bed nd two 50HP Spindles. Controls are easy to install,
well
documented and extremely reliable.


First programs can be easily loaded up and down through the RS-232 port
using
Fagor's DNC Software. Early controls are picky about the header characters
of
the file but it works, biggest limitations on the 8020/8024/8025 is file
size
since as I remember this is an 8-bit control. We would hit a stone wall on
some
machines we modified to drill tube sheets somewhere around 3500 holes and
usually move to the 16-bit 8050 series controls. Fagor did have Drip-feed
option
but it had problems of its own.

As to the z axis creeping down, normaly these were closed loop machine
with the
in-position and following error values set via parameters stored in the
control.
In this case as soon as the machine drifted to the limit of the
in-position
parameter the control will atttempt to drive it back with in bounds by
powering
the servos (+/-10V), if the machine could not regain control and restore
position it will e-stop locking all axis by dropping the Control OK signal
which
is normally connected to the Servo Drive Enable Input. This will take the
all
drives off line and motion will stop on the machine at a rate depending on
how
the servos are configured. On a machine with a heavy Z-Axis however the
ball-screw will freewheel and the axis will literally fall from the sky if
the
drive is suddenly taken off line. To prevent this we add a relay
controlling a
Brake on the Servo Motor or Ball Screw if there as a reduction between the
motor
and screw that is controlled by the Drive Ok Signal which normally connects
to
an input on the control and will go low when the Drive Enable signal is
dropped.


I beleive however there was an option to run an axis open without encoder
feedback, we never used it. This was used for position axes like column
cross
travel on Horizontal Boring Mills where the axis was positioned clamped
and left
in place during machining operation. If this is the case and the machine
z-axis
parameter is set to open it ignore position errors and on an axis with an
unbalanced servo drive it will likely drift until it hits an end stop.


This was 15 years ago and details are fuzy but I do have the documentation
still
somewhere.

nitewatchman






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