Homing procedure for axis with multiple slaves

Hey, thank you all for the replies!

As suggested, I'm trying to upgrade to version 2.8, but I'm encountering some issues.
I added the repo "buildbot.linuxcnc.org/ wheezy 2.8-rt", the updates are found but linuxcnc-dev won't be installed as:
"Depends on python-serial but it is not installable"

Any advises?

It may be because Wheeay is EOL. When a release reaches end of life, Debian moves all of their repositories to archives. If you have not changed apt to point to the Debian archived repositories you will have the same problem installing or updating almost any app. Edit your /etc/apt/sources.list by commenting out all of the old Debian Wheezy repository lines (but not the Linuxcnc ones) and add these.

Clive S wrote:

The only thing I found homing at high speed is that the joints need room to almost coast to a stop during homing for maximum accuracy so you need to allow for this when setting your home switch position so you don't hit any limits.

Rod I think I have to disagree. I have used gantry homing on several machines. the HOME_SEARCH_VEL is there for that reason.
so you don't try to home at max speed..
.

Also once triggered, a home switch must stay triggered all the way to the limits so that if the machine is homed with limit switches triggered, Linuxcnc knows which way to move off the limits before the homing sequence commences.

The HOME_LATCH_VEL with the correct sign will back off the switch and thus be triggered but not active. I don't use any long slides to keep it active
.
I actually started a post in 2013 forum.linuxcnc.org/forum/49-basic-config...with-x-axis-2-joints before this all came into linuxcnc When I look back on it a lot has changed with linuxcnc :)

Clive, I did not say home at maximum speed but on a larger table, you don't want to wait forever for it to home. I don't. I do it with a high HOME_SEARCH_VEL. But there is a tradeoff between speed and the distance it coasts.

You are wrong about the keeping active part 100%. If there is an isolated home switch on the axis and you travel left to right when homing everything works fine while you start homing on the left hand side of the switch. If you start homing positioned on the right side of the switch, Linuxcnc will still move left to right and crash into the limits. If the home switch remains active on the right hand side, Linuxcnc knows which way to go to get back to the home switch triggering edge before the homing sequence commences.. There are a number of posts about this on the forum where people have got into grief with this.

You are wrong about the keeping active part 100%. If there is an isolated home switch on the axis and you travel left to right when homing everything works fine while you start homing on the left hand side of the switch. If you start homing positioned on the right side of the switch, Linuxcnc will still move left to right and crash into the limits. If the home switch remains active on the right hand side, Linuxcnc knows which way to go to get back to the home switch triggering edge before the homing sequence commences.. There are a number of posts about this on the forum where people have got into grief with this.

We may be both correct with this. I don't use travelling sensors mine are fixed at each end of travel so the homing routine always knows which direction to go.

I have a feeling you do.

Clive S wrote:

You are wrong about the keeping active part 100%. If there is an isolated home switch on the axis and you travel left to right when homing everything works fine while you start homing on the left hand side of the switch. If you start homing positioned on the right side of the switch, Linuxcnc will still move left to right and crash into the limits. If the home switch remains active on the right hand side, Linuxcnc knows which way to go to get back to the home switch triggering edge before the homing sequence commences.. There are a number of posts about this on the forum where people have got into grief with this.

We may be both correct with this. I don't use travelling sensors mine are fixed at each end of travel so the homing routine always knows which direction to go.

I have a feeling you do.

Yes, your machine still complies with my rule so I win

I made the decision to implement every sensor available on all axes and only use a shared home/limit switch on the Z axis due to lack of room. I'm certain you could not use a HOME_SEARCH_VEL of 6000 mm/min with shared home and limits. Something would break. I wanted to make it faster but the tradeoff with coasting to a stop came into play. I probably coast about 50mm after the home edge is first triggered. It took me a lot of playing to come up with this as when I built my machine 2.8 had just been released and hardly anyone was using it for joint axes at the time so I was on my own.

rodw wrote: ............. as when I built my machine 2.8 had just been released and hardly anyone was using it for joint axes at the time so I was on my own.

Yes he was, i still feel his pain !