# using linuxcnc for laser fiber marking

06 Oct 2021 08:17 #222337
Hi
I want to create a fiber laser marking with linuxcnc and galvo with xy2-100
I could run and use this setup .
But when I want to mark, for example, a square, because of the high speed, the square turns into a circle!
I used g64 for solve this problem.
But my next problem is the increase in speed along the line, and when it approaches the vertex of the square, its speed decreases
There is no problem if the spindle is used, but if the laser is stopped for a long time, it will damage the part.
and finally four points remain from the square

Does anyone have a solution to this problem?

06 Oct 2021 09:16 #222340 by rodw
There is not much you can do to circumvent the laws of physics.
But define high velocity.
What is cutting velocity?
What is maximum velocity?
What is your maximum acceleration? This is probably the most important parameter.

The size of the rounded corner and velocity reduction is determined by the machine's acceleration. I can;t be specific without the specifics requested.
I would explore reducing the laser power when cut velocity falls below the commanded velocity using a custom component.

06 Oct 2021 10:40 #222345
In fact my speed is not very high(for my work)
my normal speed is 200 mm/s
but because linuxcnc is for milling machine have some laws that not means in fiber marking
for example move shouldnt have acceleration(or should be very high). this in hardware is possible But I do not know how to do this in software(linuxcnc)
and about the reducting laser power should say that impossible because I want to marking on a plate not cutting .

06 Oct 2021 13:28 #222357 by andypugh
Your INI file defines max velocity and acceleration for each axis.
If you are using a galvanometer then those numbers should be very high.

So, turn off G64 and edit the INI limits instead.

06 Oct 2021 13:29 #222358 by andypugh
As an aside the velocity limit for a galvanometer (in terms of spot velocity) can be faster than the speed of light.

06 Oct 2021 15:43 #222374
I increased speed , but my main problem is acceleration i set that to very high , but when pointer close to the shape cornel the speed is decreased .

this is my G code

G00 X0 Y0
G01 X1 Y0
G01 X1 Y1
G01 X0 Y1

This photo may help me convey the message

Where the line is thicker the speed decreases and where the line is thinner the speed increases
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06 Oct 2021 15:52 #222375 by andypugh
I think that the slowing in the corners is probably due to you having G64 Pn active still.

Do you still get this with G64 P0 ? (I would expect a corner rounding instead)

06 Oct 2021 16:06 #222377
It works but it does not benefit me.
However at the beginning of the shape and the end of the shape, the increase and decrease of speed still happens.

06 Oct 2021 17:47 #222385 by PCW
I think your acceleration is still set _way_ too low

12 Oct 2021 12:04 #222927

I think your acceleration is still set _way_ too low

you are right.
I set the acceleration to the maximum value and it was solved

But now there is another problem
When the cursor moves at high speed,The square location on the screen shifts
I think that's why I use velocity mode for pid , But I do not know how to solve it.