Situation - Occasionally I lose the 0,0,0 position when I am working on a piece. I have a gantry style machine and I can actually move the head (mainly on the Y axis) if I put too much pressure on it. Also, if I accidentally run the head into a clamp or some other unintended head crash (I know everyone is in shock that anything like this could ever happen  ).

I have added DROs to show the machine position on the program run screen. My normal mode is to put the 0,0,0 point in the middle of the work piece and reset the zero point to this place. Once I zero out the piece I write down the machine work coordinates so if something happens I can move back to this position after rehoming the machine. Usually I do this with expensive stock.

What I would like is a way of capturing the machine coordinates once I have set the 0,0,0 point on the work piece. Also, I would like a way to automatically move back to this place once I have rehomed the machine.

Thoughts on the best way to do this?

Thanks,
Peter

When you zero to the center of the workpiece, you are actually setting G54 offsets.
If you save your offsets after zeroing, after you home your machine, goto zero should take you back to the middle of your piece.

This assumes that you have accurate home switches.

I found the G54 offsets - it is all there. A couple of questions - how do I save the offsets? Do I need a script on a button? Not very good with scripts (yet)...

When I home the machine it wipes out the G54 offset. Is there an easy way to put this back?

My home switches are manual switches so they are not real accurate; however, they are better than trying to guess the 0,0,0 point. Should be within a few 100ths. Probably good enough for my uses.

Have a look at G10.  But as Gerry says, it depends on accurate homing.

G10 L2 P1 X_ Y_ Z_

The L word/address specifies the type of offset.  L2 for fixture offsets.
The P word/address specifies the fixture offset to set.  P1 for G54, P2 for G55, etc..

Steve

Smurph - The problem I have is the G54 coordinates are reset to 0 in M4 when you home the axis. I was looking for an easy way to capture the G54 data when I set an axis to 0,0,0 on the work piece. I would then like any easy way to reinsert the G54 data after I rehomed the machine.

I was thinking it would be something like a DRO box that captured G54 when the machine was zeroed to the work piece. I could then hit a button to make it go back to the position once I rehomed the machine. Of course I have no idea how to do this - it is just a thought...

When you home the machine, move the the axes to the part zero.  Zero out the DROs.  Now the G54 fixture offset is in place.  Click on the "machine coordinates".  This is how far you are from the home position.  Write down the X and Y values.  Say X machine pos is -12 and Y machine pos is -8.  (Just generalizing)

Then, modify your G code program.  Add

G10 L2 P1 X-12 X-8

after your program initialization lines and before any movement. 

Done.  Now all you have to do is home the machine and run the program.  This assumes that the vise or fixture is always in the same place on the table and the part zero never changes. 

That is how you set a fixture offset in a program.

Now...  one question I have is why is your G54 fixture offset getting cleared when you home your machine?  Mine doesn't.  I can home my machine, move to and set part zero, home my machine, and then press "goto zero" and I'm right back at part zero.  Try it with Sim.  Works every time with the default profile.  Nothing in Mach is clearing the G54 offset.  Maybe the motion plugin is not setting the home position to machine 0?

Steve

In fact, the fixture offsets are saved across Mach sessions.  If I set a G54 offset, all I have to do is restart Mach, home the machine, and hit "Goto Zero".  I'm right back at part zero.

So I'm not sure why your G54 offsets are cleared at all unless they are manually cleared (zeroing the DROs at the home position).

Steve

I think Pedio is using a PMDX SmartBOB. If so, clearing the offsets on homing is a
known bug and has been fixed in our upcoming plug-in release. That release should
go out this weekend.

Steve Stallings
PMDX

As a quick way of doing things cant you use the buttons on the stock screen (Remember Position and Return to Position)

Daz

The PMDX SmartBOB plugin release (0.33.159) that fixed the problem with homing causing
the fixture offset tables to be overwritten is now available. It can be downloaded here:

http://www.pmdx.com/PMDX-SmartBOB-USB-Plug-In

Regards,
Steve Stallings
PMDX