Current turning capabilities status

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13 years 1 week ago #40108 by andypugh

emcPT wrote: Can someone please inform if G41 G42 is really working as stated on several linuxcnc documentation for lathes?


Yes, definitely and absolutely.

Is it possible that you are not in the XZ plane?

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13 years 1 week ago #40115 by andypugh
Discussion on IRC just brought up the issue that we don't actually know what a G10 rotation does to G41/G42. It may be the case that they switch meaning. It might even be the case that they _should_ switch meaning. It maybe that they should, but don't.

However, for radius compensation to work, the took orientation needs to be correct for the axis directions on the diagram. You have rotated the sense of X, not the tool.

This genuinely confusing, hence me not knowing what is "correct"

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13 years 1 week ago #40116 by andypugh
There is a hack you can put in a .axisrc file in your home directory here:
wiki.linuxcnc.org/cgi-bin/wiki.pl?BackToolLathe

It might suit you better than the coordinate rotation. Reading back the rotation idea was for someone with tools on both sides.
The following user(s) said Thank You: emcPT

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13 years 1 week ago - 13 years 1 week ago #40119 by emcPT
Thank you for your feedback. G18 on my code will force to be in XZ plane.
I will cover (test) this issue during today so that I can reply properly.
Last edit: 13 years 1 week ago by emcPT.

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13 years 1 week ago - 13 years 1 week ago #40123 by emcPT
So I tested the best I could:

a) The backtool script change: It works good (X and Z are properly displayed), BUT the tool representation disappears. This is something that I can live with, but of course it would be better to have the tool displayed. Any ideas in where in the code (source code) this is handled?

b) the tool compensation is also not affected by the geometry rotation. The issue here is the tool tip direction that in linuxcnc is different from all others controllers that I worked with (Fanuc, Okuma, Mitsubishi, Syntec). 3 and 2 (and possible others are swapped).

Using like this, it displays correctly.

This is a edit to my original post, where I figured out that changing the tooltip direction would correct the issue (although I still think that the tip direction should be corrected and be equal to all other machines).
Last edit: 13 years 1 week ago by emcPT. Reason: Further tests leaded to different conclusions

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13 years 1 week ago #40124 by andypugh
When I have used G42 on my lathe it has definitely worked correctly. I don't normally bother, as you have said, it makes no difference on straight facing or diameter cuts.

I need to spend some time with a LinuxCNC machine in front of me to see what does what. (currently I am at my day-job with a Windows machine).

Are you using the Rogge patch? I see that you are not using G43 after a tool change to load the geometry. This is normally required.

I think that the problem is that you are using Tool orientation 3 when you should be using 2. If you look at
www.linuxcnc.org/docs/html/lathe/lathe-user.html
You will see that Orientation 2 is the direction that points in the -Z and -X direction. You need to flip the picture if you flip X.
(Somewhere I have seen a document, Possibly the Fadal manual, that had different diagrams for front-tool and back-tool cases.).

I think if you set the tool as a type-2 and reload it (G43) you should see the correct behaviour.

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