How do you set zero coordinates?

Can you guys tell me where the 'Zero Coordinates' is in LinuxCNC? In Mach my workflow was like this:

- Move bit to lower left corner of work piece where I want cut to start and lower bit so it touches the top corner of the material
- Hit 'Zero Coordinates' button
- Raise the Z-Axis and turn on my spindle
- Hit 'Go To Zero' button
- Start file

I do not see in LinuxCNC where you can duplicate this workflow, am I missing something? Surely there is a way to place the bit where you want the print to start and then make that your 0 point right?

Did you tested touch off?

gnipsel.com/linuxcnc/g-code/gen05.html

wiki.linuxcnc.org/cgi-bin/wiki.pl?CoordinateSystems#Touch_Off

wiki.linuxcnc.org/cgi-bin/wiki.pl?CoordinateSystems

Rick G

So what am I doing wrong here?
1. I home the machine to machine 0,0,0
2. I jog the machine to where I want to start cutting on my workpiece
3. I hit the 'Touch Off' button while selecing the Z-Axis (bit is sitting on top corner of workpiece), leave the form value at 0.0 and hit okay.
4. I repeat #3 for X and Y (bit still at top corner of workpiece where I want it to start)
5. I hit play, it runs the program and then errors with this line: "N365 G53 Z0." The error says:

"Linear Move on Line 75 would exceed joint 2's positive limit"

In my .ini file Z-Axis which is joint 2 I believe is set with MIN_LIMIT = -6.0 and MAX_LIMIT = 0

Because your home position (machine Z0) is = to your Z max soft limit, it is setting the alarm. Try to adjust your soft limits so they home position is within them. Maybe make your Z MAX_LIMIT = 0.1. If you don't have enough free travel to do that, you could adjust your homing position to give you the needed space. Typically I home to a limit switch, then set the home and home offests so that the home position (X0,Y0,Z0) is a half inch or more away from the home/limit switches. This gives you enough wiggle room to set the soft limits so they don't get in the way.

Todd, look at this post to see the problem I was having with my soft limits: forum.linuxcnc.org/forum/38-general-linu...t-limits-with-homing

So your HOME = 0, your HOME_OFFSET = to half inch inside the MAX_LIMIT? If so, then you can jog right into your limit switch and forego the benefit of the soft limit where you do not have to click override in order to get off the switch

If I am misunderstanding, can you tell me what your HOME, HOME_OFFSET, and MAX_LIMIT values are and maybe that will help?

Thanks.

In my config, I have the Z HOME=0, HOME_OFFSET=0.5 and the MAX_LIMIT=0.3. I can then jog the machine up, 0.3 before it hits the soft limit, the hard limit is an additional .02 further up.

Do you have an entry HOME_IGNORE_LIMITS for each axis in your ini file? Is it set to YES or NO? If you're homing to a limit switch this needs to be set to YES for each axis that uses a combined home/limit switch.

Yes, it is is set to HOME_IGNORE_LIMITS = YES but what is happening is since the MAX_LIMIT is reached before the hard limit switch it throws a soft limit error and will not move to homing the next axis. Do you not have that problem with your soft limit being before your limit switch when you hit "Home All"?

I do not have this problem. Before homing there should be no soft limits, since Linuxcnc does not know where it is to even begin to calculate them. Maybe you should post copies of your ini and hal files so we can see what your working with.