Auto Z Position with EMC2 and Axis?

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10 Oct 2009 10:11 #937 by NeilR
Hi,
Ive just come across this thread on CNC zone and since it addresses a common issue that I have of getting Z depth consistant EVERY time, especially during tool changes with my router, I was wondering how to get something like this working with EMC/AXIS. pyVCP? The CNCzone thread is speaking about Mach3 which I dont have, nor want to.
Look forward to your comments and assistance.

Regards
Neil
www.cnczone.com/forums/showthread.php?t=36099

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10 Oct 2009 11:12 #938 by BigJohnT
Finding the material top is easy if you have a probe... is that what your trying to ask? I didn't read the whole thread...

John

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10 Oct 2009 11:25 #939 by NeilR
Hi John,
well, yes and no. From my reading of it and from what I have learned from the mach3 guys who use it, its an automatic process. Lots of gcode in behind the buttons though I think. Essentially, at tool change or job start, you hit the button and the machine does the rest. Yes, a probe must be involved of course.
Neil

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10 Oct 2009 11:47 #940 by BigJohnT
Are you trying to find the top of the material with a probe? That is just a couple of lines of code...

John

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10 Oct 2009 16:45 #943 by cmorley
Here is one approach:
wiki.linuxcnc.org/cgi-bin/emcinfo.pl?Cla...utton_probe_touchoff
unfortunately it relies on using g92 .

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10 Oct 2009 20:52 #944 by NeilR
Yes John. As you know, im green at this so what "couple of lines of code" do you mean exactly. Thanks.

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10 Oct 2009 20:53 #945 by NeilR
cmorley wrote:

Here is one approach:
wiki.linuxcnc.org/cgi-bin/emcinfo.pl?Cla...utton_probe_touchoff
unfortunately it relies on using g92 .


Thank you. Having some trouble following it though

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10 Oct 2009 22:18 #946 by BigJohnT
NeilR wrote:

Yes John. As you know, im green at this so what "couple of lines of code" do you mean exactly. Thanks.


Ok. ASSUMING your probe is connected correctly and it is on your Z axis.

Move the probe into the XY position you wish to probe.
G38.2 Z-2 (Do a probe move with a limit of Z-2)

When the probe is tripped it will stop the axis. At that point I issue a

G91 (incremental move)

Then move my Z axis up the amout of travel it takes to trip from the time of contact. This puts my torch at Z0 Then I do a:

G92 Z0 (Set the Z coordinate offset so it is at Z0)

Lots of sparks for me, in your case lots of wood chips.

G0 Z to my safe position
G92.1 (cancel offsets and set zero)

In my case I have a floating torch head with a micro switch. Unless you have tooling that can be removed and replaced without changing the Z offset of that tool you can't do what I do exactly.

It would be a big help if you just spilled the beans and told what exactly you have/plan to do so we can stop guessing which solution you are seeking. :S

Regards
John

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10 Oct 2009 22:25 #947 by BigJohnT
NeilR wrote:

Hi,
issue that I have of getting Z depth consistant EVERY time, especially during tool changes with my router,
Neil
www.cnczone.com/forums/showthread.php?t=36099


Neil,

How consistant does a router need to be in the Z?

The simple way to set tools that look like endmills is to have a known diameter pin. Place the pin next to the tool and move the tool low enough so the pin will not roll under the bit. move the bit up using .001" jog moves until the pin just rolls under the bit. You know know exactly within .001 the distance from the bit to the work. Just do a tool offset at that point and enter in the diameter of the pin in the offset box. Takes a couple of seconds... once you do it a time or three and no chance for damaging your bit.

John

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11 Oct 2009 00:49 #949 by NeilR
OK John. Thank you for your time. Sorry I was vague but the CNCzone link pretty well explained it.
To answer your question. I liked the "auto Z" concept described and would like to go to this one day. The Z depth is critical on some of the work I do with the router. Especially when there are 2 or 3 manual tool changes per job and the tools are of differing length. I hadnt thought of the pin. Thats a great idea.
Thanks again for your assistance and explaining the lines of gcode to achieve the depth. This gives me a lot of ammo to work with.
Neil

Neil

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