Change default set-up home from 0,0,1 to 0,0,0.25

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3 years 8 months ago #264640 by jferguson
When I fire up Linuxcnc to run the mill, after I've engaged the E-Switch and the second switch I must home each axis before starting the run.  LinuxCNC then sets the home to 0,0,1.0.  The height gage I use is 1/4 inch in thickness (for a good reason). I now have to do some manual fussing to get what I want.
How can I change this default to X=0, Y=0, and Z=0.250?
 

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3 years 8 months ago #264687 by tommylight
Edit the ini file in the config folder with the machine name, set
Home = 0 or whatever you need for each axis and joint
Home_offset = 0 or whatever you need after homing is finished.
Normaly Home is 0, while Home_offset is set to something small so the machine backs off of the limit switches, or if you need the machine to position itself somewhere else to easier load material.
Be aware that using Home_offset will show 0 after homing, and using Home values will show those values.

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3 years 8 months ago #264700 by jferguson
thanks much.
btw, My installation of a Debian 2.8.4 linuxcnc instance on my multi boot machine is a roaring success. 2tricks, one was to use ethernet (no driver for my wifi card in this Debioan ISO, if Grub loader refuses to install, use the one you already had.
john

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3 years 8 months ago #264704 by jferguson

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I was hoping that somehow, I could get the homing setup which is shown on this screen to indicate the Z Home to be .250. I just cannot find anywhere in the INI where this can be changed.  Is it hard-coded somewhere?

I suppose an alternative way to get the result I want it is to put a line sending the machine to Z0.25 (instead of 1.0000) before the first stop for a tool change.

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3 years 8 months ago #264705 by Aciera
As already suggested:
Change the HOME_OFFSET value in the relevant JOINT_n section of the ini file (where 'n' is the joint number for your z axis)
linuxcnc.org/docs/html/config/ini-config.html#sec:joint-section

edit:
If unsure please post your ini file.

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3 years 8 months ago #264711 by jferguson
Worked exactly as I wanted. Thank you both so much for helping me with this.

John

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3 years 8 months ago #264723 by pippin88
The safest home position is with Z all the way up.

If the 0.25 is just for a tool change, think hard about all possible machine movement scenarios.
E.g clamps, workholding, tall work piece.

You don't want some g code to tell the machine to go to home (e.g. G53 X0Y0Z0) and smash into clamps etc.

The most common way to setup a machine is for Z0 to be at the top of the Z travel, and for all Z travel to be negative.

If you are not already familiar with the difference between
G53 / machine coordinates
G54-G59 / work coordinates
Then I suggest you read about them as it's very important to understand

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3 years 8 months ago #264728 by jferguson
hi Pippin, I do tiny stuff on a Sherline 2000 with very small bits. I've found the best way to set the height is to roll a piece of .250 drill rod back and forth under the bit until the bit just clears. If I set Z to .250, All I need to do is start linuxcnc, home all axes and then turn everything on. It may seem clunky, but this is not a production environment and I can take the time needed to not destroy bits and gouge workpieces.

I picked up this method routing PCB;s where the depth of cut is critical.

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3 years 8 months ago #264742 by rodw
you can still home at top of travel but use g54 offsets and touch off the Z axis to 0.0 at the height you want.

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