Re: [CAD_CAM_EDM_DRO] New question about limit and home switches

jguenther@... wrote:

> Hi everybody,
>
> I have a question about home and limit switches, and EMC. Let's say I
> have a machine with a 12 x 15 table. I want home to be the center if
> the table. The machine has limit switches on each axis and a home
> switch on the x and y axis positioned so that the table is centered
> when the home switches are tripped. The question is, what does EMC do
> if a home switch is tripped during a movement such that x would move
> from -4 to +4 and trip the home switch when it passes 0? The
> following code may help explain this:
>
> g0 x0 Machines is at home.
> g0 x-4
> g1 x4 Machine being directed to move 8 units from -4 to +4
>
> The g1 x4 movement will pass through the home postion and trip the
> home switch. Will this cause problems with EMC?

Of course not. the home switch is only looked at when an axis
in in homing mode. When homing, EMC must be in manual mode,
and the homing action is under a special case of computer control,
where it moves in the homing direction until it sees the switch
trip. If it is open-loop or the encoder has no index channel,
then it accepts the switch trip as home. if it has encoders with
an index channel, it continues past the trip of the home switch
until it detects the index pulse, and that is the home position.
When not homing, the home switches are ignored, and are
always ignored in auto or MDI mode.

Jon