current axis position

[cxevalo]

are there machine variables that have the current axis positions that i can access from gcode? #5061 #5062 ---etc give the probe impact value but i want the value at program start and after a move.
I have some irregular stock (reclaimed machinable wax) i want to machine it to a standard thickness. so i am trying to write a program that starts with the z axis zeroed to the bottom of the stock and the tool setting at the z-max of the stock. i want to run a surfacing pattern in a loop stepping z until i get to the pre set thickness.
this is simple to do if i can read the current position in the gcode.
where in the documentation would i likely find this information?

[Big John T]

For looping look in the O code section of the manual.

http://www.linuxcnc.org/docview/deve...ml#cha:O-Codes

If your stock is different heights can you adjust your number of loops or something like that...

Are you using 2.3 or 2.2.x?

John

[cxevalo]

Thanks John.
i understand about writing loops and using variables. I can get the job done by measuring the thickness of the wax and entering that in the program, and that works fine. What i want to do is mount the hunk of wax with the z axis zeroed to the bottom of the piece/top of the fixture, and with the z step down set in the program start from where ever the machine is setting and make surfacing passes to my predefined thickness. I am trying to get around editing the program for each hunk of wax, because i am a klutz and i don't trust my typing all that much. so in use i would mount the wax run the tool to the highest point and start the program. taking off the z step thickness or fraction of for the last pass.
i am not sure which version of emc2 i have. I downloaded the live cd for hardy heron, it came with axis 2.2.7 if that helps.

[Big John T]

If you don't mind using a beta version you can upgrade to 2.3 beta and use G28.1 or G30.1 to store your current locations then do the math in your loop to figure out how many passes you need.

http://www.linuxcnc.org/docview/deve...sec:G30,-G30.1

and to upgrade

http://wiki.linuxcnc.org/cgi-bin/emc...?UpdatingTo2.3

John

[cxevalo]

thanks again BigJohn g30.1 is exactly what i want. I will have to think about upgrading to 2.3beta.
I am just getting started with cnc milling and i don't know if i want the extra anxiety of unstable software. Ill have to do some reading about 2.3

[Big John T]

So far 2.3 seems to be bug free... I have it on two computers now and have been using the pre 2.3 on my plasma cutter for quite some time (a year maybe). It doesn't look like much of a pain to revert back to 2.2.x should you want.

John

[cxevalo]

the upgrade seems simple enough. i think you talked me into it. i have some things to run this morning, but should enough time to do it this afternoon.

[Big John T]

When you get your code worked out if you don't mind sharing post it here or send it to me. It sounds like some useful reusable code.

John

[cxevalo]

i upgraded. mostly going ok. i had trouble getting the x axis to home. no matter where i set it when i hit home axis it set x to -.5499

i greped the machine config directory for 5499 and found that in emc.var 5221 was -0.549925. changed the entry to 0.00000 and i can now home x ok

while i was editing emc.var i noticed that 5223 is set to -0.00000. is that meaningful ?

now to go see if g30.1 and g28.1 work

[Big John T]

Not that I know of. There is a menu item under Machine to clear offsets... Don't know what all it will clear off the top of my head. Sounds like your making progress now. IMHO 2.3 is WAY better from every aspect.

Keep us posted or pop in on the IRC and chat with the rest of the EMC group. Just click on the embedded java client if your not savvy with the IRC on this page.

http://www.linuxcnc.org/content/view/4/8/lang,en/

John

[cxevalo]

i got to work on the program for a while this morning and have a subroutine doing one pass correctly.
now i have to write write a subroutine to do the inverse pass machining back to the start.
then add a z step loop and it will be soup.

there are a few nasty things going on with the conditionals when you put then in a while statement. It took me some time to hack around the problem. it makes the program klunky but i think its a real bug.
what happens is if you use a GE in a while as in:
o100 while [ # GE #]
and then put an 'if' statement inside the 'while' loop emc goes into an infinite loop trying to calculate a tool path. with no conditionals inside the loop GE is fine LE does the same thing.

i will have to play with it some more to be sure of all the conditions that make it crash.

[samco]

could you post the program that doesn't work?

thanks
sam