Re: [CAD_CAM_EDM_DRO] Question on stepper control

Jeff Goldberg wrote:

>I'm still trying to figure out the direction to take on the BP miller with
>antique NC controller. I came across to FET-3 controller on
>www.stepperworld.com . Does this take the place of a Geko 210 (or 3)? Is it
>big enough to handle Superior Slo-Syn NEMA 42 steppers. The other thing I
>came up with was called a BTR (Behind the Tape Reader). This seems to allow
>retaining the current controller and being able to insert a serial signal
>from a PC instead of from the paper tape reader. Seems to keep a large,
>awkward controller, but all the wiring in side is already done. What are
>the drawbacks to this approach?
>
>

I built my own BTR contraption to use with an Allen-Bradley 7320 CNC
control that at least had a
CRT display. I really don't think I'd want to use anything that didn't
have a CRT display. The
7320 showed all the modal command functions (things that stayed in
effect for more than one
block) such as spindle on, absolute/relative coordinates, etc. It could
show commanded position,
actual position, distance to end of move or following error in the axis
area by hitting a key.
It also showed the last 2 blocks, the current block, and the next block
to execute. There was also
other info on the screen. But, it had a number of deficiencies. One
was it was not reliable, and
it had a VERY slow servo update rate, leading to sluggish performace and
a lot of following
error. But, when it worked, it was pretty good.

So, in general, I would go for the upgrade. You will almost certainly
get more reliability,
faster performance (with steppers, you don't have to worry about
following error), MUCH
easier editing and monitoring of the program as it executes, etc.

Jon