oscillation during welding

I intend to weld with a 3-axis kinematics, but it must oscillate. How can I realize this with linuxcnc?

Weave is the term used for that type of welding, and it is done in CAM software.
LinuxCNC is a machine controller, it takes the gcode outputted from CAM and uses that to control and move the machine.
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There are several ways of doing this, from writing gcode directly with a text editor, to using Inkscape with the included path2gcode plugin, to writing a bit of code that would use "external offsets" to do the waving and adjustments of the amplitude and frequency in real time while the machine is working.
If it is an industrial machine, i would choose the last option as it would be the most flexible and versatile of them all al would not require any other software. Also, the ability to have all the required parameters adjustable and settable on the main screen makes for enjoyable machine use.
linuxcnc.org/docs/stable/html/motion/external-offsets.html

thank you for the quick reply, even if I did not fully understand.
I have also been programming robots for 30 years and here I only specify the movement type and the pendulum parameters.
But if I have now understood correctly, I must specify each point on the pendulum path individually. I can't imagine that, that would be stone age.

Its not really necessary to do the weave in cam.
You could use external offsets and calculate an appropriately scaled sine wave with siggen and apply it as an external offset.
the external offset is applied outside the motion controller so a straight line in CAM can be made to weave. (a Sine wave oscillates from -1 to 1)
Linuxcnc is really just designed for normal CNC machines .Welding is  special case. The tools are there, you just need to implement it.
Good luck!

Lindi wrote:

I have also been programming robots for 30 years and here I only specify the movement type and the pendulum parameters.

I was sure it is for something like robots, plenty of experience with those, also, mostly Kuka, they use the term "weave" for that.

Lindi wrote:

But if I have now understood correctly, I must specify each point on the pendulum path individually. I can't imagine that, that would be stone age.

Yes, one of the methods is exactly that, writing every move in gcode using a text editor. For short stuff, this is sometimes the fastest thing, especially while testing.
The second method is to use Inkscape, it is a vector drawing software that outputs directly gcode usable in LinuxCNC. It is easy to use and there are no other steps involved.
The third method is using external offsets, it is a feature included in LinuxCNC allowing to move the axis in real time from external effectors, be it siggen as Rod mentioned or a slider on the GUI or an external button.
This is by far the best method, it does require a bit of coding/editing, but would enable changing all the parameter even while the machine is working.
Basically, you give it a straight line to move, then the external offsets take over and do the weaving across that line based on the set parameters, and those parameters and be changed and adjusted while the machine is working.

For 3 axis welding, External offsets and siggen ( linuxcnc.org/docs/devel/html/man/man9/hm...FACE%20CONFIGURATION ) are pretty easy and for x and Y  directions, it would just involve some hal components and a couple of variables on the console for frequency and amplitude. Travelling diagonally would be harder as the weave needs to be apportioned between the X & Y axes. Linuxcnc lacks a heading value which tells you the angle of travel.