Re: Help a confused newbie out please

--- In CAD_CAM_EDM_DRO@y..., Jim Brown <jagco1998@y...> wrote:

>
> Caudlet.Im more confused than you.
> But on a serious note..I should set up the axis with 2 limit

switches on both ends near the end of travel(depending on rate of
decelleration), and at the end of travel on the axis I should put 2
limit switches that will create an Estop if hit.

> Is this about right??
> Just how many switches can a gecko g201 handle?
> Thanks
> Regards,
> Jim

Well, not exactly. The limit switches should be connected back
through the parallel port to let the Controller software get the
signal. While you can turn off a Gecko, the Controller program just
keeps pumping out signal cause it doesn't know you hit limits. You
need for the program to control stopping the machine.

The e-stop should be a big red button that is mounted in a location
that would allow you to stop the machine when you are running or
jogging. I have two. One on the machine itself for when I am doing
a setup and test and another on the console. They are wired in
an "OR" (actually NOR) configuration so that either being turned on
grounds the e-stop line.

There are two ways to go about this. One school of though makes the
e-stop button instantly kill all power to the motors (some include a
dump resistor to quickly dissipate the back EMF from the motors).
You can do that by making the button open the main power contactor to
the DC supply. The other approach is to pick a defined input pin on
the parallel port and let the controller software sense an e-stop
condition. No matter which way you choose to go (or both ways) the e-
stop is NOT part of your table limit switches.

IMHO the limit switches are there to keep your machine from ending
it's own short life by driving past the physical limits of the
machine. I use them as the last resort for something like servo run
away (ugly thing) or dumb rapid jogs by a stupid operator (me) or
defective g-code. Some systems have separate home switches that are
positioned at 0,0,0. Machine zero should be some offset from the
table limits. Several controller programs let you use the - limit
switches as both limit and home. Other controller programs allow you
to define 0,0,0 as some offset in mm or inches from the limits. The
sequence then is to tell the machine to "zero from the limits"
meaning it will run back to the limits (a known place) then move an
absolute distance from there and zero itself.

To comment on Alan's observations. I normally layout a piece to cut
on an oversized chunk of material. I will run the table to some
point that "looks like zero" and zero my DRO/Controller indicator. I
have a broken carbide mill that is exactly .249 inch in diameter. I
put the mill/feeler in the chuck and move the head down so it's lower
than the surface of the piece I need to cut. I gently slide the
material against the "feeler" so the Y edge of the material touches
it and lightly tighen the hold downs. I then jog the machine with
the head retracted to the other end of the same Y edge and once again
lower the feeler and touch it with the edge. Now I recheck the
original stop and make any slight adjustments. At this point I have
established two reference points paralle to the X axis travel. All
you have to do then is raise the head, move more than the diameter of
the feeler up the Y axis and use one last pint to establish the
x "0". Now take your machine back to zero, zero and then move each
axis exactly 1/2D of the feeler; in my case .1245". The center of
the tool is now over the material zero. Reset your machine to 0,0
and you can start your program. (set the z by putting in the tool you
will use to cut with and moving the head down until a piece of thin
paper placed on the material under the cutting tool has resistance
from being pulled out. If you ever loose zero during a cut you can
repeat the procedure to get things back in register. This works on a
piece of material that has at least one staight edge.

This looks more complicated than it really is. I can do the whole
manouver in 5 minutes.