gangtool setup / backtools

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06 Oct 2012 19:26 - 06 Oct 2012 19:31 #25075 by gmouer
U[date: I caught mhaberler on IRC (he did the remap code). He looked at my code and didn't see a problem, when he tried the code himself he discovered a bug in his code. It would not take the G68 remap, G68.1 would work. He has since pushed a fix for this to master.

ALSO! Being all remaps are modalgroup 1, axis parameters are normally required. BUT !!!!! He also made a change to the remap code to accomidate this!!! Now, if its a remapped G code, axis parameters are no longer needed. This was a second fix, pushed to master.

So........... G68 and G69 can now be remapped to the approporiate G10 L2 P0 Rx code in a subroutine.

I never dreamed it was a bug in the remap code, as always, linuxcnc support was beyond outstanding !!!

I think this makes this pretty much a case-closed with the exception of me writing some info for the docs to give to John. I will wait a bit to do that so I can test a bit further and become more familiar with the whole process.
Last edit: 06 Oct 2012 19:31 by gmouer.

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06 Oct 2012 19:38 #25076 by BigJohnT
That is why this is in master and not in a released version. Testing testing testing...

Sounds like your on the way.

John

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31 Dec 2020 12:26 #193638 by strantor
Replied by strantor on topic gangtool setup / backtools
Has there been any progress made on G68/G69 since 2012? Or some other officially supported method for swapping from traditional to back cutting? This seems like a pretty common lathe operation and I'm surprised to find it so challenging to accomplish. I felt like I must be missing something but after reading through this thread it seems maybe not.

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31 Dec 2020 15:56 #193662 by andypugh
Replied by andypugh on topic gangtool setup / backtools
I am not sure that anything in particular is needed, if you are prepared to use negative X coordinates for the back tool.

Do you have a CAM post-processor that inserts G68 / G69 for the back tool? Is the remap not usable for your situation?

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31 Dec 2020 18:52 #193677 by strantor
Replied by strantor on topic gangtool setup / backtools
I am in the process of figuring how to set up my post processor to do back cutting. Right now it isn't putting any G68/G69 in the g-code. It looks correct when simulated in Fusion 360, but when I get it into LinuxCNC both turning and part-off tool are on the same side and turning tool goes the wrong way on arcs. Since (I think) my post processor already needs modifications, I was going to figure out what it takes to make it put G68/G69 in, but maybe that's the wrong answer. Looks like I need to figure out how to make it put in negative X-values.

I have never tried to use remap.

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31 Dec 2020 19:57 - 31 Dec 2020 19:57 #193678 by andypugh
Replied by andypugh on topic gangtool setup / backtools
Remap is easy, and would allow you to use G68 / G69.

In effect all you want to do is have "G69" actually execute "G10 L2 P0 R180" and "G68" execute "G10 L2 P0 R0"

It's pretty easy, look for the "minimal example" here:
linuxcnc.org/docs/2.8/html/remap/remap.h...xample_remapped_code

Your requirement is even easier

Create a file called "g68" and another called "g69" and put them in your ngc-files folder.

The first file:
O<g68> SUB
G10 L2 P0 R180
O<g68> ENDSUB

The second file:
O<g69> SUB
G10 L2 P0 R0
O<g69> ENDSUB

Then, in the [RS274NGC] section of your INI file:
REMAP=G68 ngc=g68
REMAP=G79 ngc=g69

That should do it. Note that I haven't tested this.
Last edit: 31 Dec 2020 19:57 by andypugh.
The following user(s) said Thank You: strantor

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01 Jan 2021 03:49 #193697 by strantor
Replied by strantor on topic gangtool setup / backtools
Thanks! I'll give it a shot.

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17 Jul 2021 12:22 #215131 by harindugamlath
Hi, does anyone have a update on g68 and g69. Thanks Andy for posting remapping. that's pretty nice. Does fusion 360 output g68 and g69 now or does anyone has a post processor that do that?

I'm trying to figure out how to retrofit this okuma lathe with front and back tooling. Seems like i'm going to face the same situation with front and back tooling.

forum.linuxcnc.org/38-general-linuxcnc-q...-retrofit-servo-help

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18 Jul 2021 02:59 #215197 by cmorley
Replied by cmorley on topic gangtool setup / backtools
I know you'll need to make an XYZ config to use G10 l2 p0 r180 if using 2.8 or master.
make the Y home in place and then always use 'all home'

After that ignore the Y axis.

The remapped g68 does not take care of the spindle direction.

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24 Jul 2021 12:02 #215767 by andypugh
Replied by andypugh on topic gangtool setup / backtools


The remapped g68 does not take care of the spindle direction.


But probably could, fairly easily.
Does it need to simply reverse the motor or does LinuxCNC need to "know"?

It could also be done in the PP (M3 or M4 depending on tool. I think F360 has this)

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