Re: Re: Learning BDI Emc - Outputs

["Ian Wright" <Ian-at-iw63.freeserve.co.uk>]

Hi Ray,

Perhaps I'm being a bit dim (its been a bad morning as I left my machine
downloading the latest BDI image overnight and somehow it crashed and
managed to delete bot the download program I was using together with all the
previously downloaded files and my mail program - its taken me a couple of
hours to get this bit functioning again!!) but I can't see how a centre home
switch could be catered for. Say you have the home switch in the centre of
the x-axis, then this would logically make the centre of travel the zero
position. So, any movement to the left would be a negative movement and
would therefore need a positive direction of travel to home but any movement
to the right would be a positive movement and would need a negative
direction of travel to home. As soon as the  table passes over the home
switch, the direction of travel in the .ini file would have to change
from -1 to 1 or vice versa?
Surely, unless the home switch is at one end of the axis, the .ini file
can't predict to required direction of homing.

Ian
--
Ian W. Wright
Sheffield  UK
www.iw63.freeserve.co.uk
----- Original Message -----
From: "Ray" <rehenry-at-up.net>
To: "Multiple recipients of list" <emc-at-nist.gov>
Sent: 10 January 2002 01:43
Subject: Re: Re: Learning BDI Emc - Outputs


>
>
> Ian
>
> I've no doubt but that intuitive logic is on your side.  It would be
possible
> however to center the switch and apply a home offset that shifts the axis
in
> the opposite direction to that taken when the home sequence is initiated.
> Then you have only to be certain that you home out the machine each time
> before shutting it down.  Of course it would also be wise to look before
you
> press the home siwtch and to be ready to press abort.
>
> Ray
>
>
> On Wednesday 09 January 2002 03:52 pm, Ian wrote:
> > HI,
> >
> > Ray, I think the clue is in the original question - our friend is
wanting
> > to site his home switch near the centre of the axes travel distance
which I
> > think is a no-no with EMC. With the switch at mid distance it will not
be
> > possible to preset a homing direction as this will depend on which side
of
> > the switch the travelling part is. The only way to get the machine to
> > 'home' to the centre of its travel would be to site the home switch at
one
> > end of the travel and set the 'home offset' to half the travel distance
so
> > that the carriage runs right to one end of the machine and then returns
to
> > the half way point. Unless the machine is to be used purely for
engraving
> > on circular disks or something similar, I cannot see the purpose of
homing
> > to the centre and I would favour putting the home switches on the left
hand
> > end of the x-axis and the back of the y-axis so that the cutter finishes
up
> > hovering over the 'bottom left-hand corner' of a workpiece fixed to the
> > table.
> >
> > Ian
>
>
>