> -----Original Message-----
> From: Mark Johnsen [mailto:[email protected]]
> Sent: March-07-21 10:22 AM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] isolcpus?
>
> On Sun, Mar 7, 2021 at 7:25 AM Gene Heskett <[email protected]> wrote:
>
> > On Sunday 07 March 2021 06:58:01 Gene Heskett wrote:
> >
> >
> > > > It takes at least 5 seconds for it to get up to search speed, and
> > > > another 5 seconds to get back to a stop after the home switch has
> > > > been found, coasting 20-25 degrees getting stopped, then it goes
> > > > into latch speed and takes another minute to get back to the switch
> > > > edge. And theres a random offset being applied to the home position
> > > > in the linuxcnc dro that does not exist
> >
>
> I don't know the inner workings of the LinuxCNC home switch routine as my
> machine doesn't have a home switch (someday hopefully). However, it sounds
> like an acceleration/deceleration setting for the homing routine is too
> low. At least that's what I would look at with an off-the-shelf motion
> system.
>
> This isn't related in terms of code to LinuxCNC, but in general
> motion control practice:
> For an old Parker compumotor 6k2 motion controller, the homing routines had
> their own Accel, decel, home to index (was it John D w/ the 2 mechanical
> switches), and other routines such as approach from CW or CCW, go past and
> slew back slowly, etc... I would look at that rather than the linux setup
> (isolcpus, latency, etc). But, I'm not an expert on this..
>
> Mark
>
I share the home and limit switch for each axis. The other end of each axis
has a limit switch in series with the other two axis. Total inputs used is 4
then. The Z always homes first by itself to clear tools. Then XY happen at
the same time.
I've also got soft limits set up so loading a G-Code program tells me if I'm
outside my work envelope regardless of G54, G55 etc.
I think I used this document to determine what to set and how and it's pretty
comprehensive.
http://linuxcnc.org/docs/2.8/html/config/ini-homing.html
I don't have a home or limit switch on my rotary A axis.
This is Z and notice the sign of the OFFSET verses final velocity. The knee
moves away from the spindle towards the home/limit switch. The Z value gets
smaller (more negative) as we move closer to the spindle just like on a lathe.
HOME_OFFSET = 0.2
HOME_SEARCH_VEL = 0.8
HOME_LATCH_VEL = 0.01
HOME_FINAL_VEL = -0.2
HOME_IGNORE_LIMITS = YES
HOME_USE_INDEX = 0
HOME_SEQUENCE = 0
Compare that with Y axis which moves the table towards the column and
home/limit switch. That puts the Y=0 location on the table just like an XY
graph where the Y axis value increases as it we move up the axis.
HOME_OFFSET = -0.1
HOME_SEARCH_VEL = -0.8
HOME_LATCH_VEL = 0.01
HOME_FINAL_VEL = 0.2
HOME_IGNORE_LIMITS = YES
HOME_VOLATILE = 1
HOME_SEQUENCE = 1
If you get those signs wrong it behaves very funny.
John Dammeyer
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