Tool offsets

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07 Oct 2019 21:42 #147369 by Scot
Tool offsets was created by Scot
I've been reading up on the processes that LinuxCNC uses for tool setting and selection and I'm not sure if they fit with the configuration of my machine.

I use a gang-tool lathe. The gangtool lathe is a very simple machine in comparison to a classic turret-style tool changing lathe. The tools are held in a tool block on the XZ slide which travels in front of the spindle. They're in a straight line, in line with the X axis for fast access between each one. It's a superior way to make small parts in a rapid manner, which is what I do. Tools which are close means fast chip-to-chip times and it leaves an output open. Tool turrets need to be actuated. Gang tool lathes don't need that. The tools are connected to the AXES directly and don't spin into position. The axes move the tools to where they need to be

The tools are programmed into a tool offset table, similar to the LinuxCNC tool table. But I'm unsure how the setting of the tools works as well as how the controller sees the offsets and how it treats them in coordination with the XZ slide.

When I learned how to program my lathe, before it's controller died and I chose LinuxCNC, it was very simple. I would call the tool number up through the interface, set the X and Z according to the diameter of the material I was using to touch the tool off, to. Then when I would program it. When the system saw the tool number in the code, it would move the tool to the prescribed position according to the part it was set to.

There was no tool change command. The control would simply see T1 with a certain position in comparison to the machine coordinates, then move the XZ slide according to where that position was put into the table.

Linux CNC is very complex in comparison due to it's multiple configuration capability, being able to be any number of machines. Gang tool lathes are very simple, in comparison.

Is there anyone out there who could help me understand this more clearly than the information in the document pages before I go and start programming tools?

Thanks,

Scot

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07 Oct 2019 22:00 #147371 by cmorley
Replied by cmorley on topic Tool offsets
Have you read this:
linuxcnc.org/docs/2.7/html/lathe/lathe-user.html

Linuxcnc can indeed be made to use just the T command to change tools.
It requires remap python code and is an advanced modification.
sim/axis/lathe-fanucy is a sample that uses this technique.

other wise linuxcnc requires g43 to add the tool offset and m6 to 'index' the tool, even if there is no tool changer.

Chris
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07 Oct 2019 22:38 #147374 by Scot
Replied by Scot on topic Tool offsets
I've been reading that link. But that's what threw me. I was used to such a simple programming process, that seeing all the extra code, such as the G43 and M6 just didn't make much sense. Perhaps it's because I don't program mills just yet. But that's going to come soon. I have an old chinese mill I want to convert.

I don't mind the advanced configuration in this case if it helps with the ease of programming, but I'm sure I can figure out how to run the code without a problem. It's just more time consuming than I'm used to.

The syntax of the extra code makes programming a bit confusing and round-about. Rather than direct.

So when you program with the G43 and M6, what's the typical syntax for calling up a tool? And I can't seem to find the path you laid out in my system. Is there a directory above sim or is this located in the sim.axis file in my home/linuxcnc/ path/

Thanks in advance.

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07 Oct 2019 23:03 #147380 by BigJohnT
Replied by BigJohnT on topic Tool offsets
If you have each tool in the gang tool holder offsets in the tool table you simply need to use G43 with the H option to specify which tool your going to use next.

linuxcnc.org/docs/2.7/html/gcode/g-code.html#gcode:g43

JT
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07 Oct 2019 23:52 #147396 by OT-CNC
Replied by OT-CNC on topic Tool offsets
Hey Scot, I run my hardinge with a gang slide and changing tool positions is real easy using M6 T# and G43. You'll get used to it once you play around a bit.
One thing to look at is G30
linuxcnc.org/docs/html/gcode/g-code.html#gcode:g30-g30.1
I don't use it but some posts (fusion tormach) will output a g30. If that's not set in the ini, your machine may rapid to undesirable location.
Also, from your other posts, your spindle isn't setup yet correct? Will you be reading in a spindle encoder? Just bringing that up in case there is a spindle at speed signal needed and you try to run a test program, the axis may not move at all while looking for a spindle at speed to be true.I forget already how that's setup on the pico. It would run with no speed programmed for testing cutting air. Just trying to save you some frustration as I have been there.....
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08 Oct 2019 04:02 #147419 by Scot
Replied by Scot on topic Tool offsets
So when the tool position is stored, then you can use both a T-word and an H word to call up a tool, using G43? One way is to use the M6 Txx G43 and the other is just G43 Hxx?

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08 Oct 2019 16:38 #147470 by BigJohnT
Replied by BigJohnT on topic Tool offsets
Yep

JT
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09 Oct 2019 05:30 #147533 by Scot
Replied by Scot on topic Tool offsets
Simple enough. Setting tools tomorrow while waiting on the DAC to run my spindle. Cutting air til it gets here, I guess. Worse things have happened to better people than me.

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18 Oct 2019 12:23 #148185 by andypugh
Replied by andypugh on topic Tool offsets
I find that my fingers just type "G43" automatically after an "M6 Tn" but I realise that isn't conventional on a lathe.

You can probably just open "lathe-fanucy", which will copy the sim to your configs folder, then just copy the remap files across to your real config.

Tormach have the T-only behaviour hard-coded, I can see an argument for it being a simple INI switch rather than a remap.

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