Re:Home Switches

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "industrialhobbies"
<admin@i...> wrote:

> First, opticals are the way to go, hands down.
>
> The problem you're experiencing is more than likely because the

home

> is referenced durring the back off phase of the home. So although
> the contact is repeatable the "unclick" is not. One way to deal

with

> this is to put a "one shot" on the home switch. It allows you to
> give a percise pulse on the click. It would incorporate the

function

> of a de-bounce and an auto back off in one $2 circuit.
>
> Just somthing to think about.
>
> Thanks
> Aaron Moss
> www.IndustrialHobbies.com
>
>

I was not saying that I had a problem with homing from the limit
switches, I was stating how to achieve very accurate limit switch
homing even at high return rates. The idea that a spring-operated
switch is more accurate when springing on to the switch then
springing off the switch is only a perceived problem. The main
problem is ramping onto a mechanical switch at high speed and
thinking the instant the switch is contacted actually means
something. With the servos seeking to maintain position at high speed
and the mechanical spring delay of the switch .010" repeatability
would seem excellent, where high speed homing to the switch and a
slow exit can easily achieve .0002" repeatability

Jeff

> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Dave Fisher" <dave@d...>
> wrote:
> > On fitting home switches to our router table, I notice that each
> time
> > I home the table - the X and Y readings differ greatly, some

times

> upto + -
> > 0.5 mm. Seldom never going to zero. Slowing the home traverse

speed

> seems to
> > make little difference.
> >
> > I would have expected there to be some differnces caused by
> backlash etc but
> > not as much as I am getting.
> >
> > I have used good quality lever type micro switches, but wonder if

I

> am
> > suffering from switch bounce or just the mechanical properties of

a

> micro
> > switch. Would I be better using a slotted opto coupler to

eliminate

> > mechanical tolerences or any other method ?
> >
> > The table is being driven with Rutex Amps and The Desk CNC

sofware

> and
> > controller.
> >
> > Any advice would be appreciated
> >
> > Rgds to all
> >
> > Dave Fisher