On Wednesday 10 April 2019 13:29:54 Gene Heskett wrote:

> On Wednesday 10 April 2019 12:47:23 John Dammeyer wrote:
> > Hi Andy,
> > See below.
> > [...] 
> > > > The question then is whether or not the system, when starting
> > > > can/will
> > > recognize an input which is a unit present signal.
> > >
> > > This is a solved problem :-) (I have exactly the same 4th axis as
> > > you)
> > >
> > > I have a loop of wire on two spare pins on the connector where the
> > > 4th axis plugs in to the machine:
> > > This drives an input on the STMBL. The STMBL HV enable is only set
> > > (HAL Logic) if this input indicates motor-present.
> >
> > My HP_UHU drives have that feature built in.  The encoder connector
> > has to have a jumper to show the encoder is connected.  Probably to
> > avoid a runaway condition.
> >
> > > I just accept having an A axis display even when the axis isn't
> > > connected. And the machine will f-error if you try to move or jog
> > > it.

I could tolerate that.

> > I'm testing with both MACH3 and LinuxCNC so I can write up a neat
> > little conversion document that takes a parallel port BoB based
> > system from MACH3 into LinuxCNC with minimal pain.  In the MACH3
> > system, on my CNC router, when I tell the open loop stepper
> > controlled axis to home all that MACH3 does is zero out the DRO.
> >
> > But Gene has a home switch on his rotary indexer.  Now thinking
> > about it I think the solution might be simple. When he pulls the
> > indexer off the mill he has to unplug the encoder cable.  If he's
> > using safe type limits then the switch is normally closed and a home
> > (or limit) happens when it opens.
>
> Exactly what I'm doing.  Except no endoder, stepper driven and likely
> needs a bigger motor, and more speed reduction to improve the holding
> power.  Thats a downright puny motor on it now, and I have a 270 oz/in
> currently holding down a stepladder step. 8 wire so slower top speed
> but easy on the psu. In fact I think I'll check and see if its shaft
> is compatible yet today.

It was, and its been installed. Not tested yet, I need a male GS-16-4 or 
5 to hook up the home switch, AND send a signal back to hal that tells 
it its plugged in. I haven't figured out yet what to do with the signal 
though. But from what I can find on fleabay, it looks like I'll have to 
make a backshell and strain relief, the males I've found are all panel 
mount.  Nothing but a 16mm panel nut for a back end.  Sigh. I was born 
either 40 years early, or 40 years too late. I'd flip a quarter but it 
stands a measurable chance of not coming back down. :)

> > So run the home switch circuit through the encoder connector and
> > wire the mating encoder connector to have the connection closed. 
> > From the CNC controller perspective the system is already homed.
>
> Thats not how lcnc homes. In fact if the switch is closed, it jogs
> away till it opens, THEN goes into the normal home search routine. I
> use that to advantage on the Sheldon to assure it actually searches
> for the switch closure.  By sensing the front gib, which is NOW a
> solid bar the width of the carriage, once it has approached the
> spindle and closes, it stays closed, At homing, it will back away to
> the right till it opens before the normal search begins.
>
> I found this undocumented behavior when I put home switches on TLM.
> Putting in on the back of the bed because the screw is in the way on
> the front, and set the switch roller to touch the tapered gib holders
> bottom as it goes by. In fact I had to do a minor rebuild because I
> added the gibs.


Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>



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