Any G code for acc/dec override ?

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23 Apr 2013 21:11 - 24 Apr 2013 00:28 #33062 by bigalex
Hi people.
Is there any G code or parameter into the G code programming for override the acc/dec value (in %) for the axis movements.
In case I need to move one or more axis in G0 and I need to reduce the machine shaking as well .
I remember that on some CNCs this feature is present but I did not find it in LCNC (maybe I'm wrong).
I attach a couple of pages from the Fagor 8070 CNC programming manual as per example.


bigalex :blink:

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Last edit: 24 Apr 2013 00:28 by bigalex.

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24 Apr 2013 09:14 - 24 Apr 2013 09:16 #33112 by jaredts
What about just lowering your max acceleration?
edit: are you running step/direction?
Last edit: 24 Apr 2013 09:16 by jaredts.

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24 Apr 2013 13:29 - 24 Apr 2013 14:21 #33117 by bigalex
Hi jaredts.
I'm talking about override the acc/dec value setted into the .ini file during an .ngc program execution.
In case of an heavy machine with a big inertia I would like to change the percentage of the acc/dec for a particular
movement normally during a G0 without decrease the entire machine acc/dec performance during the working
program execution .
If you read the attached document you can clearly understand what I'm talking about.
Here is a link to a discussion (into another forum site) for the same feature for Mach3 .

bigalex :blink:
Last edit: 24 Apr 2013 14:21 by bigalex.

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24 Apr 2013 15:42 - 24 Apr 2013 15:43 #33120 by ArcEye

If you read the attached document you can clearly understand what I'm talking about.
Here is a link to a discussion (into another forum site) for the same feature for Mach3 .


Unfortunately this is a Visual Basic script which uses Machs completely different data structures to change values through a M Code macro.

The MAX_ACCELERATION figure from the .ini file is written to a structure in NML, one entry per axis, from whence it is accessed in an AXIS_MAX_ACCELERATION[axis_num] fashion
It is possible to set the axis acceleration using the function emcAxisSetMaxAcceleration(axis, maxAcceleration)

You would require a good knowledge of C & C++ and the linuxcnc internals, to write the code necessary so that it could be called from a user M Code.

IMHO The problem is caused by your acceleration figures being too high.

If your machine is unstable at high acceleration in G00 moves due to inertia and momentum, you need lower figures.
It is only in G00 moves that the MAX_ACCELERATION has much bearing, in G01/2/3 moves the speed is much lower, so takes little or no time to get to it, so acceleration plays a much smaller part.

regards
Last edit: 24 Apr 2013 15:43 by ArcEye.

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24 Apr 2013 16:51 - 24 Apr 2013 16:52 #33125 by bigalex
Hi ArcEye.
I clearly understand that LinuxCNC is not Mach3 . :)
I was only asking if it is possible to do it in some way.
And now it is clear that it is not possible for a "normal LinuxCNC user" as I am.
I'm not talking about a machine tool but a sort of cartesian (and/or different architecture) manipulator that have to handle fuse aluminum (about 800°C temperature).
So change only the speed or the AXIS_MAX_ACCELERATION decrease the overall performances and not only during specific
movements with the fuse aluminum handling.
For this kind of stuff I was using General Purpose CNC (with a sort of meta-language motion oriented), Machine tool CNC and now I'm using a PLC based Motion Controller (up to 6 axis) .
At the moment I'm still training on LinuxCNC to explore the performances, limitations and possibilities for a real application.
I bought a Mesa card configuration to use for the tests.

Thank you for your support.

bigalex :blink:
Last edit: 24 Apr 2013 16:52 by bigalex.

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