Help: How to run X and A axis with different feed rates simultaneously?

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20 Nov 2024 11:04 #314894 by sk_linuxcnc
Hello All, I am at a beginner level in linuxcnc and cnc programming.

I have to build a simple winding machine, as depicted in the attached image. (I wish to perform side by side winding of the mateial without any gaps or overlaps)

the X axis is supposed to control the layup slide back and forth.
the A axis is supposed to rotate at a constant speed in the same direction until multiple layers are wound.

here is a simple working example of the gcode i prepared.
g91
o100 repeat [5]
g1 x80 a3600 f360
g1 a720 f10000
g1 x-80 a3600 f360
g1 a720 f10000
o100 endrepeat
m2

*please note that this is just a representative code, which performs the desired motion for me.*
however, since the feedrate is calucated in a compound manner, giving priority to the x-axis, adjusting the rotational speed so as to have a side-by-side layup of material is difficult.

secondly, since the A axis isnt rotating conitnously, it generates a momentary pause (due to deaccelartion and re-accelartion when a line of code ends)

Q: I am looking to eliminate both of these problems, but i dont know how to make it possible in the gcode.
I wish that A axis would keep rotating indefinietly without any pause at a given certain feed rate. and the X axis to keep moving back and forth independently at a different given feedrate.


i can use a spindle setting instead of A axis, the example gcode for it looks something like this:
s100 m3
o100 repeat [5]
g91 g0 x80 f360
g91 g0 x-80 f360
o100 endrepeat
m2

However, i wish to know if this is possible to with X and A axis, what would the gcode look like.

Any help is much appreciated. :)
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20 Nov 2024 12:06 - 20 Nov 2024 12:07 #314897 by timo
Seems to be very similar to a lathe.
When the a axis gets an encoder and the x axis is "slaved" to this.
Pitch should be adjustable.

Leaves the back and forth movement to be taken care of.

Is it a dedicated winding machine? Or you need to solve it just with G-code for a standard x-y-z a Machine?
Greetings Timo
Last edit: 20 Nov 2024 12:07 by timo.
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20 Nov 2024 12:32 #314900 by sk_linuxcnc
yes it is a dedicated winding machine. I could go with just X and Z lathe config. However, the problem still remains. the Z axis would then take feed in mm/min right? and not be a rotary axis.
nevertheless, can you help further?

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20 Nov 2024 23:28 #314954 by tommylight
Do you maybe have some set speeds for one or the other?
On my rotary plasma machines i make separate configs for every diameter tube, so speeds and distances are set accordingly.
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21 Nov 2024 02:15 #314960 by Masiwood123
hello, the question is interesting but the fact should be taken into account, the feedrate for the linear axis is understood by the configuration as mm/min, but for the rotary axis it is understood as deg/min. so depending on the transmission on the A axis the example shows that the same feed is for both x and A, mechanically the two speeds should be matched. of course it also depends on the thickness of the wire you are winding, so I would personally try to solve the problem by exporting gcode from a program that supports constant rotary operation, I know it can be done in ``deskproto'' and maybe I would try to define a stepover via the definition processing tools (for example, the endmill 1mm tool replaces a 1mm wire in practice, stepover 1mm as well), I would subsequently edit such a gcode to support cycle repetition. it is essential that the CAM program outputs adequate A and X feedrates to synchronize the movement.
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21 Nov 2024 02:27 #314962 by Masiwood123
that is, I would try it with a configuration for 4 axes, it can probably be done as a lathe config with ``spindle synchronized motion'', but I have no experience on that topic.
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21 Nov 2024 09:43 #314975 by sk_linuxcnc
diameter of the mandrel = 100mm
length of the tube to be wound = 300mm
material speed (to be wound per second) = 100mm/s
material width = 6.35mm
material thickness = 0.14mm (lets ignore it at the moment for a simple program)
requirement = side-by-side layup of material without any gaps and overlaps

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21 Nov 2024 09:48 #314976 by sk_linuxcnc
yes, to match the feedrates when two axis are called simultaneously within a single line of code, the gcode calculates a compound feedrate, with the X axis as master, and the A axis as slave. so basically the X axis dictates how fast the A axis would rotate. i do not want this.

i want the A axis to be rotating continously at a given feedrate.
and X to perform back and forth motion (based on the material width that i have, so that i can acheive a side-by-side layup of the material) the material parameters are mentioned on the above reply of mine.

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21 Nov 2024 10:22 #314977 by Aciera
Sounds like you should maybe run it as a spindle instead of axis A.
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21 Nov 2024 10:28 #314978 by sk_linuxcnc
Yes i think that is the way to go. but I am curious to find out if it is also possible to do it while configured as an A Axis?

secondly, i have a parallel thread on going the discussion of a spindle, where i am not able to attain the max rotational speed when my motor is configured as a spindle compared to as an A axis (where i get more rpm).

forum.linuxcnc.org/16-stepconf-wizard/54...-par-port-stepconfig

help is much appreciated :)

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