4th axis tangent to path XY
15 Apr 2012 11:24 #19218
by andypugh
Replied by andypugh on topic Re:4th axis tangent to path XY
molotow wrote:
Sorry, I have been away.
This will happen if your A axis can't move fast enough to keep up with a change in direction. You will either need to write G-code where all corners are slow arcs, and there are no reversals of direction, or "short-circuit" the position feedback in the HAL file so that LinuxCNC doesn't realise that the A-axis can't keep up.
Tangentkins isn't really the ideal way to do the job, it is just an easy way. The correct way would be to have the trajectory planner output the current motion direction. However that would need significant changes to critical code, and almost nobody needs it.
My problem is that i alway get the following error:
37403: ERROR: joint 3 following error
Am I doing something wrong?
Sorry, I have been away.
This will happen if your A axis can't move fast enough to keep up with a change in direction. You will either need to write G-code where all corners are slow arcs, and there are no reversals of direction, or "short-circuit" the position feedback in the HAL file so that LinuxCNC doesn't realise that the A-axis can't keep up.
Tangentkins isn't really the ideal way to do the job, it is just an easy way. The correct way would be to have the trajectory planner output the current motion direction. However that would need significant changes to critical code, and almost nobody needs it.
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15 Apr 2012 15:29 #19220
by molotow
Replied by molotow on topic Re:4th axis tangent to path XY
Hi,
thanks for your reply.
We've decided to use another software for that, but it's not as cool as EMC.
So I am still interested in cutting with EMC.
However I've tried to "short-cicuit" the position feedback this way:
net apos-cmd axis.3.motor-pos-cmd => stepgen.3.position-cmd
net apos-cmd => axis.3.motor-pos-fb
I simply set axis.3.motor-pos-fb to the input of axis.3.motor-pos-cmd.
This did not work, i got FOLLOWING ERRORS for all other axes. So i tried to do this for all other axes as well.
This worked ok, but now i get a new error:
Exceeded soft limit
This error appears, when axis position is out of range.
Have you any better idea, how to do that?
And it couldn't be that hard to implement.
Thanks
thanks for your reply.
We've decided to use another software for that, but it's not as cool as EMC.
So I am still interested in cutting with EMC.
However I've tried to "short-cicuit" the position feedback this way:
net apos-cmd axis.3.motor-pos-cmd => stepgen.3.position-cmd
net apos-cmd => axis.3.motor-pos-fb
I simply set axis.3.motor-pos-fb to the input of axis.3.motor-pos-cmd.
This did not work, i got FOLLOWING ERRORS for all other axes. So i tried to do this for all other axes as well.
This worked ok, but now i get a new error:
Exceeded soft limit
This error appears, when axis position is out of range.
Have you any better idea, how to do that?
I don't think so. Even Mach3 has a tangential controller.and almost nobody needs it.
And it couldn't be that hard to implement.
Thanks
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15 Apr 2012 17:00 #19221
by andypugh
Replied by andypugh on topic Re:4th axis tangent to path XY
molotow wrote:
Any idea how Mach does it?
I think that the best way to do it is in the G-code, with a pre-processor that inserts an A-axis move prior to each linear XY move. (and adds an A-move to all arcs too)
As you can probably tell, I have rather gone of "tangentkins" as a solution, for the reasons you have found.
I don't think so. Even Mach3 has a tangential controller.and almost nobody needs it.
And it couldn't be that hard to implement.
Any idea how Mach does it?
I think that the best way to do it is in the G-code, with a pre-processor that inserts an A-axis move prior to each linear XY move. (and adds an A-move to all arcs too)
As you can probably tell, I have rather gone of "tangentkins" as a solution, for the reasons you have found.
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16 Apr 2012 22:59 #19256
by Dimitrios
Replied by Dimitrios on topic Re:4th axis tangent to path XY
Hi all,
I installed a 4th axis to make cuts with tangent knife (using a circular blade) and got very good results with Gcodetools. Nick, the principal developer, is very friendly and helpful. In the last stable version (1.7) you have to change the 4th axis scale from 1 to 180/pi to have it generate the angles in degrees. I already tested it and works very well.
If you need, I can elaborate better how I did it.
Regards,
Dimitrios
I installed a 4th axis to make cuts with tangent knife (using a circular blade) and got very good results with Gcodetools. Nick, the principal developer, is very friendly and helpful. In the last stable version (1.7) you have to change the 4th axis scale from 1 to 180/pi to have it generate the angles in degrees. I already tested it and works very well.
If you need, I can elaborate better how I did it.
Regards,
Dimitrios
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18 Apr 2012 07:22 #19335
by molotow
Replied by molotow on topic Re:4th axis tangent to path XY
Hello Dimitrios,
thanks for your reply. Do you mean the inkscape extension gcodetools?
Sorry but this is no option for me. I want to be independent of any CAM software.
When I've time I'll try to write a preprocessor for that, this is probably the best solution.
thanks for your reply. Do you mean the inkscape extension gcodetools?
Sorry but this is no option for me. I want to be independent of any CAM software.
When I've time I'll try to write a preprocessor for that, this is probably the best solution.
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18 Apr 2012 20:28 #19362
by Dimitrios
Replied by Dimitrios on topic Re:4th axis tangent to path XY
Hi Molotow,
I understand what you want, I thought about doing it too, but my programming skills fall short for this task
I am still learning to use inkscape, but the more I use, more I like it, and the Gcodetools interface is very simple, once you go through the learning curve. for now and for me, it is a good fit in the workflow.
I'd rather use inkscape and gcodetools to load it to LinuxCNC than using any other controller.
I will try to use the tangentkins soon, keep us informed of your progress.
Regards,
Dimitrios
I understand what you want, I thought about doing it too, but my programming skills fall short for this task
I am still learning to use inkscape, but the more I use, more I like it, and the Gcodetools interface is very simple, once you go through the learning curve. for now and for me, it is a good fit in the workflow.
I'd rather use inkscape and gcodetools to load it to LinuxCNC than using any other controller.
I will try to use the tangentkins soon, keep us informed of your progress.
Regards,
Dimitrios
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26 May 2012 21:04 #20430
by billykid
Replied by billykid on topic Re:4th axis tangent to path XY
hi all
I tried tangentkins. and seems to work, only that I have the button touch off inactive (gray)
you know it can be?
thanks
Mauro
I tried tangentkins. and seems to work, only that I have the button touch off inactive (gray)
you know it can be?
thanks
Mauro
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26 May 2012 23:28 #20432
by andypugh
Replied by andypugh on topic Re:4th axis tangent to path XY
billykid wrote:
Sorry, no, I have no idea. I doubt it is related to the kinematics, I assume there is something about the machine state in Axis that means that touch-off isn't likely.
Do you need to switch to World Mode? (xyz positions, not 123 joints). There is a menu option, or use $
hi all
I tried tangentkins. and seems to work, only that I have the button touch off inactive (gray)
you know it can be?
Sorry, no, I have no idea. I doubt it is related to the kinematics, I assume there is something about the machine state in Axis that means that touch-off isn't likely.
Do you need to switch to World Mode? (xyz positions, not 123 joints). There is a menu option, or use $
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27 May 2012 00:41 #20437
by BigJohnT
Replied by BigJohnT on topic Re:4th axis tangent to path XY
In Axis you can only touch off when E-Stop is out, Power is On and you are in World Mode. F1, F2, $ is the shortcut keys.
John
John
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27 May 2012 16:43 #20450
by billykid
Replied by billykid on topic Re:4th axis tangent to path XY
Many thanks Andy, John ! touch off work properly but axes in world mode are noisy, I think perhaps excessive gain.
in mode 0 1 2 3 the movement is fluid.
I will try the next version of tangentkins so that it can be enabled only when needed.
regards
mauro
in mode 0 1 2 3 the movement is fluid.
I will try the next version of tangentkins so that it can be enabled only when needed.
regards
mauro
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