Tool change location relative to limit switch

Hi, all;

I've been working on tweaking the location LinuxCNC moves the Z axis to for tool change on my mill. I actually also just re-did the limit and home switches on the Z axis.

The issue I'm working with is this: The mill needs the Z to be nearly at the top of its range in order for the power drawbar wrench (it's pneumatic) to get a good grip on the hex end of the drawbar.

I've put my new limit switches closer to the + end of the Z than the old, trying to make sure the drawbar can reach. Part of the reason I had to do this is that I repaired the Z axis ball screw and mount, and the replacement ball screw needed an adapter attached to the Z quill. The adapter takes up about 1cm of vertical space, reducing the Z travel and causing this issue.

Even after putting the home switch (Z MAX/tool change location) as close to the limit switch (which actually depowers the axis) as possible I'm just barely able to use the power wrench to unlock tool holders. Tonight I'm going to tell LinuxCNC that Z(MAX) is *below* the tool change/home location by 0.08" to get the last little bit of grip I can.

My questions at this point are:

1) Is telling LinuxCNC that the end of the Z axis (and therefore the tool change location) is above home but below the limit switch a kosher thing to do? Will it get confused?

2) Other than replacing the Z ball screw again (which I will do eventually) and re-doing the quill attachment for a better fit, what can I do to make this work better, replace the socket on the impact wrench? If this will work, is there something special about those sockets, or can I just modify an ordinary socket?


Thanks for any suggestions,

Erik

Hi

1) Is telling LinuxCNC that the end of the Z axis (and therefore the tool change location) is above home but below the limit switch a kosher thing to do? Will it get confused?

Linuxcnc does not know where the limit switches are, only where the soft limits are set.

Some machines do not home at the end of an axis travel, so that position can be anywhere, quite often with some gantry type machines it is in the middle of X and Y axes.

So long as your MAX_LIMIT allows movement above the home position, it should be fine

regards

Checked the code in src/emc/rs274/interp_convert.cc

This is what executes the tool_change_quill_up or tool_change_at_G30.
It only uses the STRAIGHT_TRAVERSE( ), so it is subject to exactly the same restrictions as any other move.

Its movement would be governed by being able to carry out the move within the soft limits envelope.

regards

Thanks!

I'll plan on trying my adjustment tonight then once I re-set the soft limits to the new locations.

Probably I'll need to replace the socket or extend my drawbar, but at least I can try this first without thinking I'm doing something unusual.

Erik